Northern Powergrid will now only supply 80A on a single phase supply. I contacted them recently after buying a house to notify them that there was a heat pump, air con and a hot tub connected to the installation. Along with Solar PV and now an EV charger. The previous owner had just installed what he liked. They came to inspect the main cutout and actually downgraded me from 100A to 80! I wasn't particularly happy and the bloke doing the work even commented that I should have kept quiet. Although 80A is just enough, and the EV charger will ramp down if I get close to it, I thought I'd enquire about 3 phase for the future. They did a desktop survey and came back with a figure of £9k to dig a trench over to the other side of the (quiet) road - about 10m I would guess. So I won't be doing that any time soon.
Northern Power grid is getting very twitchy about EV's and the potential for larger loads affecting their dodgy circuits. I have noticed they are making a lot of "Grid Reinforcements" upgrades in my area as the electrical loads are ramping up and they are paranoid about everyone moving en-masse to EV's and Heat Pumps.
I spoke to Northern Powergrid about this and they said there was no such global policy in place to downgrade to 80A supplies on single dwellings. They do have situations where the local network is no longer capable of 100A due to changes and additions, particularly with respect to how the phases have been divided up or if supplies have been looped or extended. They also explained that they do take a view on the potential loads for a given dwelling - the' single-bed granny bungalows behind me tend to get a 40A cut-out. On my own property the DNO approval from Northern Powergrid for an 8kW MEC with a 100A cut-out went through the approval process in Feb 2024 - so very recent. It only took a few days for them to come back with: "We have reviewed our existing network and, in this case and based upon the information you have provided, have found that the existing connection arrangement (the “Connection”) is sufficient to allow the connection of the generator to take place at the Premises. As no work is required to be undertaken by us, there is no associated cost but our agreement to the connection of the generator is subject to a new connection agreement for the ongoing use of the Connection being put in place." The DNO service was fast, free and permissive. What's not to like? (Clearly I am aware of more challenging DNO permissions than this but I don't think they are out to be difficult for the fun of it.)
@@ascot4000 Yeah I can certainly say they've been nothing but helpful and efficient when I've contacted them. When I was downgraded from 100 to 80A. there didn't seem to be much in the way of checks. He just saw the 100A and immediately said he'd have to reduce it as 'that's what we do now'. When I spoke with the pleasant chap on the phone about the costs for 3 phase, I asked if 80A was the max on 1P now. He said it was, but that exceeding 80A would be 'fine' for 'a while'. Not something I'd like to test out although I do understand that these fuses won't blow the moment you exceed their rating. Maybe if I went back to them and argued that 80A isn't enough for all my green/renewable tech, they'd look closer and actually check if my local network could cope with me having 100A.
We used to have a phrase that went ‘Regulation is 2 steps behind the cutting edge of bad practice’ this has never been more true than for PV & Battery installs…
It's also worth bearing in mind that the onsite guide says it's important to ensure that distribution boards and consumer units are of sufficient rating to take the total load connected without applying diversity.
I was thinking back to this video the other day. If you've got a 100 service fuse, plus solar and/or battery then one solution is to fit a second, small consumer unit upstream of the existing one. 100A service comes into the new one, the existing one gets fed from it through a 63A MCB. PV/battery also goes to the new one. You could also potentially put one heavy-hitter such as an EV charger on the new one. You've now got a maximum house demand of 63A, plus an EV of 32A, so you're within the specs of the board and 63A for the house board should be plenty, especially with the EV shifted off it (and at least you're only playing Buckaroo with an MCB, not the DNO's fuse). If you have battery storage integrated with the PV then there's the potential for a demand of 63A plus 32A plus the battery doing an off-peak top-up, but then you've still got the 100A DNO fuse protecting the board so - as long as the PV and battery share an MCB, otherwise move the battery back to the house board - you'd still be covered. EDIT: Unfortunately the regs don't appear to take the downstream protection into consideration, so the small one's still got to be 125A rated, such as a Schneider SE125A6.
Informative video Joe. Just 1 point to pickup on. Main cut shows 100 amp as a max and not what the fuse inside is rated to. They are meant to put a sticker over the top for the rating of the actual fuse as apparently it is illegal to cut the seals to check the fuse rating.
Beat me to it, plus with grid CTs on all generating sets this seems null and void to me. Also, 116A load?? 😂 no chance. The most I’ve seen is 90A and that was with the customer trying to get to 100A with a Tesla power wall, Tesla charger, tapeo electric boiler and other heating elements in the house.
Yes, but the rating on the fuse carrier is therefore the maximum current for the installation, so if you select the current rating for the consumer unit based on that figure rather than the actual fuse rating inside, then you are 100% sure that the CU has been rated safely. (not withstanding the calculation to include current from the generating set). So you don't actually need to break the seal on the main fuse and inspect the rating of the fuse inside. The only adverse impact to this technique is where the fuse rating is lower than the fuse carrier maximum current rating, eg.60 amp main fuse in a 100amp carrier, you end up over specifying the current handling rating for the CU, so you spend more money than is necessary. The benefit of doing it this way, is obvious: if the fuse is ever upgraded from 60 to 100 you don't need to upgrade the CU as it has already been selected based on that 100 amp rating .
@@bradleyarcher9840Grid CT's are irrelevant. We are talking here about having a fundamentally safe installation. And that means sizing all parts appropriately. CT's and measuring currents don't help in that.
Interesting that 551.7.2 says you CAN install your genset on the supply side of the overcurrent protective devices. In your example this effectively makes a 116A supply available to your 100A rated CU Main switch before the 100A supply fuse even starts getting warm. Many G99 solar installations are far bigger than 16A...
DNO specification for single-occupied domestic properties specifies an 80A main fuse is fitted to a 100A-rated cut-out AND the maximum continuous load is 20kVA at unity power factor (so 20kW). At a nominal 230V then, the max continuous load is 87A. Add on the potential 16A from your PV system and the total is 103A. I'm not sure when the max continuous load for single-phase supplies increased to 20kW; the breakpoint for upgrading to a 3P+N supply used to be 17kW.
@@efixx that's difficult to say. Supply spec - particularly the use of diversity factors in network design - has been evolving for more than 10 years; firstly due to heat pumps and more recently (say last five years) due to EV adoption. My own experience of the 17kW breakpoint goes back to the early 90s, when I did a two year stint in distribution network design. Back then the large domestic loads were almost universally due to electric storage heating.
If you are pulling 100 amps from the grid and the inverter starts up and out puts 16amp of current the installation would be using 84amps from the grid with 16 amps from solar . Even if the system had a battery and you set it to max export ,the export would go to demand in the home .
@@persona250 As a practical person, I would think that. But the addition wouldn't be type approved, no more then people whinging about Make A breaker in Make B CU...
Absolutely agree Northern Power downgraded my main fuse without telling me while I had a replacement smart meter fitted (my 3rd in 5yrs) . Previously I had asked 2 years prior to this for upgrade to 100amps which was done no query at all. As you say certainly Northern Power are downgrading every main fuse to 80amps on every visit for any reason and do not tell you.As you say with heat pumps, large arrays, batteries, car chargers and water heaters 80 amps is very minimal. My system trips about once a year and I put that down to load issues.
You're gonna hate me for this: I live in an E7 heated home with (What _should_ be) a 100A DNO fuse. But since the energy crisis, it's been rare for my total household load to ever exceed *ONE* amp... 🎸💸😳
@@davepusey I said _rare_ , and that's generally when the kettle isn't going. It's a 700w travel kettle, so a smaller element than the usual. 🫖 (I also use it for heating bathing water, as that works out considerably cheaper - If not less convenient - Than running the HW cylinder on my super-discounted income. 🌻🇬🇧🏚💸)
However, the regulation is clear that Ig(s) is the rated output current of the generating set or sets, NOT the rating of whatever overcurrent protection that is installed on the generating set or sets. Which means, the PV fuse is not what sets the limit, but what the PV set is capable of outputting if no fuse were to be installed and any current settings are set to unlimited. Ergo, the output rating of the inverter and/or the solar panels. Meaning, that if you install a "beefier" inverter and/or solar panels to cope with periods of low sun, and then set the inverter to never output more than 16 A, and then install a 16 A fuse, then you would fall short of this regulation if the generating set are *capable* of outputting more than 20 A if the incoming fuse supply is 80 A (even if this would trip the PV fuse or generator fuse). I guess its a fault of the wording of the regulation, and it should have said something in the like: Ig(s) is the rated output current of the generating set/sets, or the rated current/current setting of the generator circuit overcurrent protective device either incororated within the low voltage switchgear and controlgear or upstream of it, whichever is lowest.
The 100A cut out would normally protect the consumer unit where it to take more than 100A if everything was turned on at once which is possible but unlikely. Adding 16A from PV and bypassing the cut out is only a 16% difference which even if it was passing through the 100A cut out would not cause it ti blow anyway - so every CU can exceed 100A by 16A even without PV just by turning lots of things on. It'll be well within the design envelope. It's not a practical concern just a pedantic regulation point. People install 10kW showers on 32A breakers with 43A going through which don't trip and when the regulations allow diversity they are acknowledging probability - how long is this 16% theoretical overload going to last?
Thanks for that, interesting video. In the real world, I think the risk is more theoretical than probable. My PV system only delivers full output in high summer, so there is zero chance that I would want another 100 amps of heating load is zero. I doubt if I could get to 100 amps if I turned everything electrical on at the same time, let alone 116 amps. It wouldn't be sustained for any length of time either - the breakers in my consumer unit only add up to 92 amps (I suspect that the ring main breaker would be first to trip, as the lighting circuits are grossly underloaded with the advent of LED lights.
It does seem to be a rather academic discussion as it's hard to see any real situation that this would become an issue. The solar input is offsetting the incoming current so generally reducing the load. And the incoming fuse, mcbs etc don't suddenly fuse/ trip when the current reached the number written on then. You'd probably need twice the rated current for a conventional fuse to fail instantly. And mcb's etc are designed to mimic conventional fuses, hence the two trips mechanisms.
@@efixx Thing about those loads (hobs, ovens, showers) etc is that they are not continuous loads. A typical oven may well take upto 32A to get up to temperature but it sure doesn't sit at that rating for the total duration is is on. The overload case here is a thermal overload and I^2R for 116A vs 100A is 34% increase in resistive losses, which means 34% more heat, and as things get hotter their thermal impedance falls so 34% more heat flux is not 34% more temperature. Without a complex precision thermal simulation you'd be hard pressed to objectively define the time constant for this increase ime. Just turning on a toaster say, for an extra 10A for 3min is not going to cause a thermal runaway when you consider the specific heat capacity of the system. far far more likely ime, is a thermal event in the CU at high currents that sit WITHIN the fusing thermal limits (which of course are much higher than 100Arms) due to a poor joint, ie an low clamp load or corroded joint in the system. In the area i work in (electric vehicles) we have moved to active pyrotechnic fuses to allow much better control of fusing currents across a far wider range of conditions. As you mention, most PV systems now are explicitly set to OFFSET grid load, ie the 16A it supplies is used to reduce grid load by 16A (using a CT around in the incomer). 116Arms at 240Vrms is a faintly ridiculous 27.8kW which with most high current loads now including APFC is an absolutely enormous amount of power to continuously pull for any private domestic properly really. This reg is probably aimed at commercial properties where the overal power requirements are much higher than a typical single phase private household?
It might not be that unlikely to see higher rated consumer panels in the UK at some point. In the USA some years back a few panels started to be offered with a standard 200 Amp main breaker and an upsized 225 Amp bus. I have one of those in my basement that was installed back in 2019. I assumed it was due to solar, but I never saw any marketing material that said so.
Ah, i think I get it now. The supply potential is considered to be upped to 116a if solar is installed. Does this increase if a battery storage unit is also fitted? An extra 20 amps can be provided by those.
Pretty much. It’s not so much about actually having it, rather the capability to have it. You could (for some bonkers reason) be drawing 116A total, that being 100a from grid and 16a from solar/battery in a 100a rated CU. Most I’ve ever used at any one time is 37A.
No as the battery is usually installed on the DC side of the inverter, and would share the PV current. Meaning, if the solar panels suppy 20A, then 16A would go to the house and 4A would go to charge the battery. In many cases, the inverter could during low solar periods and cheap electricity, "suck" electricity from the PV input to charge the battery, to be able to supply battery power during expensive period.
@@damiendye6623 Yeah thats another thing and would add to the "generating set". Its however a inefficient thing to do, as the inverter converting between AC/DC and the different voltages for battery and supply, does consume a LOT of efficiency. So if you have a PV installation, installing a Tesla Power Wall isn't the brighest idea (since you would invert the PV electricity to AC, then recitify it into the batteries, which wastes lot of power). Its better to install some batteries on the DC side of the solar installation, and then install a smart inverter that can both consume and supply power. Or keep the old inverter and just have the batteries as storage for solar power.
It must have been another quiet day in the regulations office when they came up with that nonsense reg. They can add it to all the other nonsense regs that no one takes any notice of! 🤦♂️
Whilst most configurations are DNO Fuse -> Meter -> Main CU not all of them are. In my own personal property the path is DNO Fuse - Meter - Electronic Isolator / Generator / Battery Backup / switching Interface -> Main CU. This switching interface controls what power comes from where, as well as providing protection from back-feeding the grid during a grid outage. Is this magic box enough to meet the protection required by the regulations and, if so, does it give us a hint of the future by allowing active monitoring and direct control?
Personally, if solar panels are there, I like Schneider industrial distribution boards rated at 125 amp they do make two way ones which are single phase which are a good way to add soda in without changing the existing shimmer unit as some models have each way rated at 100 amp so it will allow you to have a breaker for the main consumer unit and one for the solar and that shouldn’t be much of an issuethey also offer quite a few benefits when adding solar to the ability to get higher than 100 A but I think this is standard with industrial boards
Would it not be sensible to have all sources of power (including solar inverter, battery storage and future V2G equipment) to first come together with the meter tails before they go into the consumer unit? Obviously each unit would then need its own protection devices. I'm thinking that added cost, number of enclosures and time of installation would be considerations but since I'm not a qualified person, just an average member of the public, can someone enlighten me as to where my thinking is wrong. Cheers.
I'm in the same position as you (Not a qualified Spark, and not PV experienced either ⚡) but I'm going to guess it's mainly to do with cost, plus tricky issues about system zoning between the intake point and the consumer unit/CU. 📜 In this video it appears that the PV installation feeds its output directly into the load side of the CU as if it was any other regular load circuit, even if current flow is going in the opposite direction to traditional. In this way all of the consumer equipment (loads and otherwise) is south of the CU and protected by the main breaker - The PV inverter monitors voltage phase and synch's its output to match, so you don't have two out-of-phase AC supplies feeding the same circuit 💥 - And it may save the supplier/DNO installing costlier equipment to monitor and handle exports to the network. 😇
In principal that doesn't stop excess current through the original CU, as you could still have eg 100A through the cutout and then 16A from your solar heading in through the main switch in the original CU. I guess this reg doesn't specifically apply, but you'd be in breach of another surely as now the overall CU is undersized for the feed to it...
Can you pleae comment on the following please: Let's assume we have a single DB with a 100amp isolator and a 100amp fuse in the cut out. Unless the solar generation is injected upstream of the DB how can any component, including any part of the busbar in the DB exceed 100amp? OR have I misunderstood? As experts in the field, your input to this would be much appreciated.
I don't understand this - what happened to diversity? I have a twin stacked main CU - on the lower busbar there are 6 circuits that, if you just blindly added all the CB ratings together, comes to a total of 176 amps. Great Scott, I could melt the house with that and worse, this busbar 'only' has a 63 amp RCD on it - begad! The upper busbar has my lights/smoke/alarm circuits on a 63 amp RCD plus a 32 amp RCBO for the garage sockets and (gulp) the dreaded PV circuit feed that can shift 32 amps / 8 kWh when sunny. Quick maths when I have somehow loaded the lighting, smoke detectors and alarm circuits all to 6 amps each = 54 + 32 + 32 = 118 amps! Clearly I can melt the house, or something. Think of the children. Meanwhile, all my circuits are protected at the correct value, no busbar is overloaded and the DNO 100 amp fuse is untroubled. The maximum load I have ever pulled from the grid for all the domestic circuits is 32A / 8kWh (multiple ovens etc, near to Christmas). To that I could add 8kWh from my inverter to potentially add up to 64 amps but that would still be split across the 2 busbars and, in this example, would be the PV/Battery doing all the work and not the grid. I guess I could charge the battery from the grid (at 5kWh) plus do multiple ovens etc, to pull 13kWh / 53 amps from the grid but again, this troubles nothing. Oh and since when did we add incoming amps to outgoing amps? We used to think of current flow. Yes, you could transfix yourself with the idea that 100 amps incoming when combined with 16 amps of solar could enable a household to exceed the 100 amp rated limit of their CU. But guess what, you can do that right now as the 100 amp fuse will quite happily supply you with 116 or even 132 amps for a very very long time... This is all a distraction as the main issues we face with domestic electrics are poor workmanship or undetected failures. We are way past the era of simple circuits on aluminium wiring feeding multiple 3-bar fires under the glow of multiple 60 or 100 watt bulbs. We live in an era of LED lights, efficient heating systems and a plethora of low-current devices spread liberally around the house. Our real-world issues involve things like switch-mode power supplies, DC leakage, nuisance tripping et al. When you see how much current an illegal grow-house can pull without anyone noticing I doubt this PV concern is of any actual concern.
In terms of diversity, the DNO considers a 3-bed semi with, say, a 6kW heat pump and a 7.2kW EV charger as having an after-diversity-maximum-demand (ADMD) of .... 9.5kW, so just over 40A! Of course, diversity factors for the DNO are higher than those of BS7671 as they are looking at dozens of installations simultaneously, not just one.
@@efixx That is true but ensuring safety and compliance is through training, application, trade skills and inspection. We don't usually see failures due to sustained loads alone, only that sustained loads tend to reveal failures in training, application, skills and inspection. A busbar that has missed the CU clamp may indeed survive years of use when all it does is supply a few LED bedside lights and PED chargers. However, when that same circuit plays host to a load of IT systems, big TVs, portable AC units and alike the situation changes and latent failures spring into life. The problem is not the heavy sustained loads but the original poor installation and inspection process. The industry keeps tripping itself up on the basics, not the installation of heavy loads.
hm... how do we fare if all mcb's inside the board only come to say 78 or 80 amps. Say a 16amp for solar pv and 2 x 32amp circuits. What if you have several boards? Do we need to fit an external fused switch after the cutout If no board has over 80 amps of mcb's? Can the installation actually draw 100amps even with solar (other than a fault condition)? Just thinking of need for bi directional rcds / mcb's and type b rcd for heat pumps. you could end up with a board for heat pump and say home battery, board for ev's and solar and then another board for everthing else. or at least 2 board supplied buy you own fused switches (x2) after the main cut out. In the very near future the potential of 2x ev's, home battery and solar pv could actually generate over 20kw on its own! Having a home battery and DC solar instead of AC solar will help a bit, but directional charging / discharging of ev's is going to throw a spanner in the works..
I haven't done any PV installs but are people connecting them directly into the DB through a breaker like that? The only ones I've looked at are connected into something like the Hendy blocks with the mains which then feeds into the DB. This way isolation is still through the 100A isolator in the board, just make sure the tails are rated properly. Also the DB is completely dead when the isolator is off rather than having a second supply into it. Anyone out there who does PV want to chip in with how they do it?
How many installations have you ever seen drawing the 100A - 23kw ?? - that would be costing £6.90 hour £165.60 day £1159.20 per week ? Yet again the regulatory framework continuues its never ending upward spiral - the regulations will shortly look like the old Encylopia Brittanica full set. The lunatics have left the assylum and are currently housed at the NICEIC headquarters with "jobs for life" and "gold plated pensions".
All at once at full power ?? You could include 20 x 3kw fan heaters in every socket if you wanted plus a patio heater 2x Electric showers, hot tub, swimming pool and sauna if you wanted.@@efixx
I'm planning on having our place fitted out with infrared ceiling panels. I'm concerned about how the system will be able to cope if I have about seven or eight IR panels wired in. How do I know a competent sparky to employ? What qualifications or certs should I look for can you tell me please? My only thoughts are recommendations on our local fb group at the moment. Or would I be better off having the panels fitted by the uk company i plan to buy them from? Hoping you dont mind me crashing your video, Joe, I'm only an interested bystander, eager to get things right, proper and safe electrically speaking in my property. Love watching your very informative videos and often try to guess the words in your news reviews, never been right yet!
@@edc1569well with the system I have in mind it's not going to give quite that effect. However if it did I wouldn't mind feeling something similar to the warmth of the sun on me as I'm mostly housebound.
One thing worth noting is this video is the first place I've heard about the 16A export limitation for domestic solar PV installations. Thinking of the number of people I've heard going on about filling whole tracts of land they don't use with PV arrays for the *$£€s* I can see a lot of unqualified PV planners becoming rather disappointed! 😥🌦😉 As for me? I live in a home that faces north, where PV panels would be about as much use as a fuse in a teacup. Who needs a 16A export limitation? I'd be lucky if I ever produced 16 *mA!* 🤣
16A is the max export without requiring explicit DNO permission or them having to make upgrades which you would need to pay for which is essentially what solar farms would need to do to get a grid connection…
So hundreds if not thousands of legacy PV installs that were done in the days of the feed-in-tariff up until they conjured up this reg are technically non-compliant much like all those that don’t have type A RCDs because it wasn’t a “thing” 10 years ago? 🤔🙄 I see the logic but in practical terms it’s creating a solution for a very unlikely problem
@@efixxthat's true but I wouldn't describe this situation as an "advance" since PV installs have been around for decades now - working out that a house *could" potentially draw 116A is more like an after thought ;) - if anything new PV installs are oversized to say 5 or 6kW maybe 10kW and the inverter has G100 export limitation to 16A - in those circumstances the PV inverter could happily push out 20A+ if the house demanded it AND the mains could supply a further 100A - why not upgrade the mains isolator and have a suitably robust bus-bar to suit (a lump of copper like that will happily take the load) Dropping the DNO fuse from 100A to 80A is a rather crude approach and wouldn't necessarily fix the issue anyway as in reality will the DNO fuse blow at exactly 80A - unlikely! It also means that then when there is no PV generation, the house is limited to the lower value which in time will create yet another "problem" to resolve when there are car chargers and heat pumps all wanting to run...
British installations are so far behind. Where I'm living we all have 3 phase supply with 35A main fuses and it works without any problems and you are not overloading the switchboard. And yes 35A main fuse sounds small but you don't need 32A in front of your sockets.
Hi there. I designed, built and opened a zero-emission B&B down here in Rye, East Sussex. Along with a 34-panel solar array, 12kw ASHP, Smart Mixergy Tanks, 10x Air to Air Heat Pumps, underfloor heating and heater skirting boards, 4x 7kw EV chargers (and more)...and you're invited to come and stay with us :-) Hope you catch this comment....and keep up the good work! Javed, Magnolia House Rye
The reality is inverters are used to facilitate the interconnection of sources of electrical energy with the DNO network. ENA Engineering Recommendation G98, which governs the majority of domestic generation interconnections, defines a Micro-generator as - _A source of electrical energy and all associated interface equipment able to be connected to an electric circuit in a Low Voltage electrical installation and designed to operate in parallel with a public Low Voltage Distribution Network with nominal currents up to and including 16 A per phase._ So an inverter is effectively a generator.
@@efixx it could be a problem if V2G becomes the norm with EV adoption growing at a steady rate and everyone thinks they can export into the DNO network. Voltage rise will be the first symptom.
Seems to me you need a current limiting device on the solar to stop it ramping up under full load conditions in the installation. Or obviously down grading the main fuse to take account off the additional supply but I’m sure there’s lots of installs out there that are not compliant. It’s not good enough to hide this in BS7671 waffle well done for highlighting this!🥵
Upu should see the shocking installs I come across unfortunately you can put all the regs you want but people dont give a damn 😮😢. Gets me abit down as we teaun and read and keep upto date but alot of cowboys just lash it all in and dont care. Need more strict electrical work carried out with procedures to stamp out poor craftsmanship. Thoughts people ???
The elephant in the room that no-one is talking about: PV inverters export by generating a voltage about 5V higher than the incoming mains and can go as high as 265Vac. So what happens to the property voltage if the mains is already the maximum tolerance of 253Vac? What happens if two neighbouring properties export at the same time? Has anybody thought this through?
I guess the inverter is running as a current source when grid connected as the grid is a voltage source (ie low impedance). So the apparent rise in voltage is the current output from the inverter times the mains impedance. So 16 amps into say 0.5R would result in a rise in voltage of 8V. So yes, one could easily exceed to 253v by quite a lot, especially if on the end of a long LV line with higher impedance.
@@ratherbewindsurfing With the G83 lower overvoltage limit set at 262.2Vac this means that an inverter will tripping and not exporting anything like what would be expected, if anything, when the supply voltage is high and appliances in the property may be damaged. This information is not revealed in all the sales hype and I have found inverter manufacturers to be evasive when asked directly.
@@hintoninstruments2369 The amount of power you can export will be. limited by the Impedance and the open circuit voltage of your supply. If you are hitting the over voltage limit your supply needs to be upgraded by reducing its impedance or reducing the supply voltage (altering transformer taps).
Good video but thats not how its done in the real world. 551 who actually know this as all.mcs installers have not got a clue lol. Thousands of systems have been fitted. So now they should not really be fitting solar to certain properties no
@@efixx so we need a day with full sunshine and run enough stuff in the house flat out to draw 116A all at the same time. That scenario is far far less likely to happen compared to the diversity factor BS7671 allows for a cooker circuit. A simple setting in the solar system to stop exporting in that situation would solve the non issue.
Fit your own garage board every time with a 40amp mcb ready for a ev charger problem solved,but as usual can whoever dreamt this up while they had nothing else better to do explain how a energy supply from solar generation #clue right there becomes a load oh unless it’s the 4w standby overnight usage while on standby,so on that logic the 60/80/100 amp supply should be a load too.
@@efixx a g98 3.68kw inverter will very rarely generate full capacity of 16a which you would need around 6kw of dc power to get it there in the summer which will get absorbed into the system anyway,and the fact if you look at the average house board with diversity applied your still well over 100a. Then look at the thousands that are already installed safely producing electricity,this is just pure drivel.
![Interconnected Electrical Power Production Sources, Supply-Side Source Connections,NEC 2020 [705.11]](/img/n.gif)
Northern Powergrid will now only supply 80A on a single phase supply. I contacted them recently after buying a house to notify them that there was a heat pump, air con and a hot tub connected to the installation. Along with Solar PV and now an EV charger. The previous owner had just installed what he liked. They came to inspect the main cutout and actually downgraded me from 100A to 80! I wasn't particularly happy and the bloke doing the work even commented that I should have kept quiet.
Although 80A is just enough, and the EV charger will ramp down if I get close to it, I thought I'd enquire about 3 phase for the future. They did a desktop survey and came back with a figure of £9k to dig a trench over to the other side of the (quiet) road - about 10m I would guess. So I won't be doing that any time soon.
Northern Power grid is getting very twitchy about EV's and the potential for larger loads affecting their dodgy circuits.
I have noticed they are making a lot of "Grid Reinforcements" upgrades in my area as the electrical loads are ramping up and they are paranoid about everyone moving en-masse to EV's and Heat Pumps.
Thanks for sharing your experience. 😊
I spoke to Northern Powergrid about this and they said there was no such global policy in place to downgrade to 80A supplies on single dwellings. They do have situations where the local network is no longer capable of 100A due to changes and additions, particularly with respect to how the phases have been divided up or if supplies have been looped or extended. They also explained that they do take a view on the potential loads for a given dwelling - the' single-bed granny bungalows behind me tend to get a 40A cut-out.
On my own property the DNO approval from Northern Powergrid for an 8kW MEC with a 100A cut-out went through the approval process in Feb 2024 - so very recent. It only took a few days for them to come back with:
"We have reviewed our existing network and, in this case and based upon the information you have
provided, have found that the existing connection arrangement (the “Connection”) is sufficient to
allow the connection of the generator to take place at the Premises. As no work is required to be
undertaken by us, there is no associated cost but our agreement to the connection of the generator
is subject to a new connection agreement for the ongoing use of the Connection being put in place."
The DNO service was fast, free and permissive. What's not to like?
(Clearly I am aware of more challenging DNO permissions than this but I don't think they are out to be difficult for the fun of it.)
@@ascot4000 Yeah I can certainly say they've been nothing but helpful and efficient when I've contacted them. When I was downgraded from 100 to 80A. there didn't seem to be much in the way of checks. He just saw the 100A and immediately said he'd have to reduce it as 'that's what we do now'.
When I spoke with the pleasant chap on the phone about the costs for 3 phase, I asked if 80A was the max on 1P now. He said it was, but that exceeding 80A would be 'fine' for 'a while'. Not something I'd like to test out although I do understand that these fuses won't blow the moment you exceed their rating.
Maybe if I went back to them and argued that 80A isn't enough for all my green/renewable tech, they'd look closer and actually check if my local network could cope with me having 100A.
We used to have a phrase that went ‘Regulation is 2 steps behind the cutting edge of bad practice’ this has never been more true than for PV & Battery installs…
It's also worth bearing in mind that the onsite guide says it's important to ensure that distribution boards and consumer units are of sufficient rating to take the total load connected without applying diversity.
Excellent point, thanks James. 👍
I was thinking back to this video the other day. If you've got a 100 service fuse, plus solar and/or battery then one solution is to fit a second, small consumer unit upstream of the existing one. 100A service comes into the new one, the existing one gets fed from it through a 63A MCB. PV/battery also goes to the new one. You could also potentially put one heavy-hitter such as an EV charger on the new one. You've now got a maximum house demand of 63A, plus an EV of 32A, so you're within the specs of the board and 63A for the house board should be plenty, especially with the EV shifted off it (and at least you're only playing Buckaroo with an MCB, not the DNO's fuse). If you have battery storage integrated with the PV then there's the potential for a demand of 63A plus 32A plus the battery doing an off-peak top-up, but then you've still got the 100A DNO fuse protecting the board so - as long as the PV and battery share an MCB, otherwise move the battery back to the house board - you'd still be covered. EDIT: Unfortunately the regs don't appear to take the downstream protection into consideration, so the small one's still got to be 125A rated, such as a Schneider SE125A6.
Hager were talking about this at their recent tech talk at Elex
What was their guidance on it? 🤔
@@efixx silence Dave Savery?
Informative video Joe. Just 1 point to pickup on. Main cut shows 100 amp as a max and not what the fuse inside is rated to. They are meant to put a sticker over the top for the rating of the actual fuse as apparently it is illegal to cut the seals to check the fuse rating.
Beat me to it, plus with grid CTs on all generating sets this seems null and void to me.
Also, 116A load?? 😂 no chance. The most I’ve seen is 90A and that was with the customer trying to get to 100A with a Tesla power wall, Tesla charger, tapeo electric boiler and other heating elements in the house.
Yes, but the rating on the fuse carrier is therefore the maximum current for the installation, so if you select the current rating for the consumer unit based on that figure rather than the actual fuse rating inside, then you are 100% sure that the CU has been rated safely.
(not withstanding the calculation to include current from the generating set).
So you don't actually need to break the seal on the main fuse and inspect the rating of the fuse inside.
The only adverse impact to this technique is where the fuse rating is lower than the fuse carrier maximum current rating, eg.60 amp main fuse in a 100amp carrier, you end up over specifying the current handling rating for the CU, so you spend more money than is necessary.
The benefit of doing it this way, is obvious: if the fuse is ever upgraded from 60 to 100 you don't need to upgrade the CU as it has already been selected based on that 100 amp rating .
@@bradleyarcher9840Grid CT's are irrelevant.
We are talking here about having a fundamentally safe installation. And that means sizing all parts appropriately. CT's and measuring currents don't help in that.
Nice point thanks Sergio. 👍
Yup. Many old installs are 60A or 80A. Its the rating of the carrier, but the fuse that is inside.
Interesting that 551.7.2 says you CAN install your genset on the supply side of the overcurrent protective devices. In your example this effectively makes a 116A supply available to your 100A rated CU Main switch before the 100A supply fuse even starts getting warm. Many G99 solar installations are far bigger than 16A...
DNO specification for single-occupied domestic properties specifies an 80A main fuse is fitted to a 100A-rated cut-out AND the maximum continuous load is 20kVA at unity power factor (so 20kW). At a nominal 230V then, the max continuous load is 87A. Add on the potential 16A from your PV system and the total is 103A. I'm not sure when the max continuous load for single-phase supplies increased to 20kW; the breakpoint for upgrading to a 3P+N supply used to be 17kW.
Was it with the rise of EV charge points and heat pumps? 🤔
@@efixx that's difficult to say. Supply spec - particularly the use of diversity factors in network design - has been evolving for more than 10 years; firstly due to heat pumps and more recently (say last five years) due to EV adoption. My own experience of the 17kW breakpoint goes back to the early 90s, when I did a two year stint in distribution network design. Back then the large domestic loads were almost universally due to electric storage heating.
If you are pulling 100 amps from the grid and the inverter starts up and out puts 16amp of current the installation would be using 84amps from the grid with 16 amps from solar . Even if the system had a battery and you set it to max export ,the export would go to demand in the home .
yeah but the problem is if you start up your dryer or vacuum cleaner or stove, and now your demand is over 100 A.
Yes but the solar supplying 16A allows the installation to pull 116A without blowing the cutout.
@@alikirk4034a simple fix is to double up the busbar . It’s flowing through the busbar not the cutout
@@sebastiannielsen this would be more of a problem without solar as you would be pulling 116 amps plus the vacuum or stove etc
@@persona250 As a practical person, I would think that. But the addition wouldn't be type approved, no more then people whinging about Make A breaker in Make B CU...
Absolutely agree Northern Power downgraded my main fuse without telling me while I had a replacement smart meter fitted (my 3rd in 5yrs) . Previously I had asked 2 years prior to this for upgrade to 100amps which was done no query at all. As you say certainly Northern Power are downgrading every main fuse to 80amps on every visit for any reason and do not tell you.As you say with heat pumps, large arrays, batteries, car chargers and water heaters 80 amps is very minimal. My system trips about once a year and I put that down to load issues.
You're gonna hate me for this: I live in an E7 heated home with (What _should_ be) a 100A DNO fuse. But since the energy crisis, it's been rare for my total household load to ever exceed *ONE* amp... 🎸💸😳
Thanks for sharing your experience. 👍
@@dieseldragon6756You never pull more than 240W? Do you not have a kettle, microwave, heater?
@@davepusey I said _rare_ , and that's generally when the kettle isn't going. It's a 700w travel kettle, so a smaller element than the usual. 🫖
(I also use it for heating bathing water, as that works out considerably cheaper - If not less convenient - Than running the HW cylinder on my super-discounted income. 🌻🇬🇧🏚💸)
However, the regulation is clear that Ig(s) is the rated output current of the generating set or sets, NOT the rating of whatever overcurrent protection that is installed on the generating set or sets. Which means, the PV fuse is not what sets the limit, but what the PV set is capable of outputting if no fuse were to be installed and any current settings are set to unlimited. Ergo, the output rating of the inverter and/or the solar panels. Meaning, that if you install a "beefier" inverter and/or solar panels to cope with periods of low sun, and then set the inverter to never output more than 16 A, and then install a 16 A fuse, then you would fall short of this regulation if the generating set are *capable* of outputting more than 20 A if the incoming fuse supply is 80 A (even if this would trip the PV fuse or generator fuse).
I guess its a fault of the wording of the regulation, and it should have said something in the like:
Ig(s) is the rated output current of the generating set/sets, or the rated current/current setting of the generator circuit overcurrent protective device either incororated within the low voltage switchgear and controlgear or upstream of it, whichever is lowest.
Maybe it'll get tweaked in AMD3... 🤔
The 100A cut out would normally protect the consumer unit where it to take more than 100A if everything was turned on at once which is possible but unlikely.
Adding 16A from PV and bypassing the cut out is only a 16% difference which even if it was passing through the 100A cut out would not cause it ti blow anyway - so every CU can exceed 100A by 16A even without PV just by turning lots of things on. It'll be well within the design envelope. It's not a practical concern just a pedantic regulation point.
People install 10kW showers on 32A breakers with 43A going through which don't trip and when the regulations allow diversity they are acknowledging probability - how long is this 16% theoretical overload going to last?
Thanks for that, interesting video. In the real world, I think the risk is more theoretical than probable. My PV system only delivers full output in high summer, so there is zero chance that I would want another 100 amps of heating load is zero. I doubt if I could get to 100 amps if I turned everything electrical on at the same time, let alone 116 amps. It wouldn't be sustained for any length of time either - the breakers in my consumer unit only add up to 92 amps (I suspect that the ring main breaker would be first to trip, as the lighting circuits are grossly underloaded with the advent of LED lights.
Electric shower say 40A, induction hob on boost 32A and EV charger another 32A, that's me over 100A right there.
Heating load could include hobs, oven, showers, unlikely but not impossible. 🤷
It does seem to be a rather academic discussion as it's hard to see any real situation that this would become an issue. The solar input is offsetting the incoming current so generally reducing the load.
And the incoming fuse, mcbs etc don't suddenly fuse/ trip when the current reached the number written on then. You'd probably need twice the rated current for a conventional fuse to fail instantly. And mcb's etc are designed to mimic conventional fuses, hence the two trips mechanisms.
@@efixx Thing about those loads (hobs, ovens, showers) etc is that they are not continuous loads. A typical oven may well take upto 32A to get up to temperature but it sure doesn't sit at that rating for the total duration is is on. The overload case here is a thermal overload and I^2R for 116A vs 100A is 34% increase in resistive losses, which means 34% more heat, and as things get hotter their thermal impedance falls so 34% more heat flux is not 34% more temperature. Without a complex precision thermal simulation you'd be hard pressed to objectively define the time constant for this increase ime. Just turning on a toaster say, for an extra 10A for 3min is not going to cause a thermal runaway when you consider the specific heat capacity of the system.
far far more likely ime, is a thermal event in the CU at high currents that sit WITHIN the fusing thermal limits (which of course are much higher than 100Arms) due to a poor joint, ie an low clamp load or corroded joint in the system. In the area i work in (electric vehicles) we have moved to active pyrotechnic fuses to allow much better control of fusing currents across a far wider range of conditions.
As you mention, most PV systems now are explicitly set to OFFSET grid load, ie the 16A it supplies is used to reduce grid load by 16A (using a CT around in the incomer). 116Arms at 240Vrms is a faintly ridiculous 27.8kW which with most high current loads now including APFC is an absolutely enormous amount of power to continuously pull for any private domestic properly really.
This reg is probably aimed at commercial properties where the overal power requirements are much higher than a typical single phase private household?
Thanks. More videos on this area would be good.
It might not be that unlikely to see higher rated consumer panels in the UK at some point. In the USA some years back a few panels started to be offered with a standard 200 Amp main breaker and an upsized 225 Amp bus. I have one of those in my basement that was installed back in 2019. I assumed it was due to solar, but I never saw any marketing material that said so.
Ah, i think I get it now. The supply potential is considered to be upped to 116a if solar is installed.
Does this increase if a battery storage unit is also fitted? An extra 20 amps can be provided by those.
Pretty much. It’s not so much about actually having it, rather the capability to have it. You could (for some bonkers reason) be drawing 116A total, that being 100a from grid and 16a from solar/battery in a 100a rated CU. Most I’ve ever used at any one time is 37A.
And yes battery will add extra as it is considered both a load and a generator. I believe it is detailed better in the guidance note.
No as the battery is usually installed on the DC side of the inverter, and would share the PV current. Meaning, if the solar panels suppy 20A, then 16A would go to the house and 4A would go to charge the battery.
In many cases, the inverter could during low solar periods and cheap electricity, "suck" electricity from the PV input to charge the battery, to be able to supply battery power during expensive period.
@@sebastiannielsenplenty of AC coupled batteries. Tesla power wall being one example of such
@@damiendye6623 Yeah thats another thing and would add to the "generating set". Its however a inefficient thing to do, as the inverter converting between AC/DC and the different voltages for battery and supply, does consume a LOT of efficiency. So if you have a PV installation, installing a Tesla Power Wall isn't the brighest idea (since you would invert the PV electricity to AC, then recitify it into the batteries, which wastes lot of power).
Its better to install some batteries on the DC side of the solar installation, and then install a smart inverter that can both consume and supply power. Or keep the old inverter and just have the batteries as storage for solar power.
It must have been another quiet day in the regulations office when they came up with that nonsense reg. They can add it to all the other nonsense regs that no one takes any notice of! 🤦♂️
I think the logic behind it is flawless to be honest. 🤔
@@efixx the logic is fine, but the likeness of occurrence is extremely low.
Gets really fun when you have a 10kW hybrid inverter with 20kWh of storage. It is both a parallel supply and a load.
Whilst most configurations are DNO Fuse -> Meter -> Main CU not all of them are. In my own personal property the path is DNO Fuse - Meter - Electronic Isolator / Generator / Battery Backup / switching Interface -> Main CU. This switching interface controls what power comes from where, as well as providing protection from back-feeding the grid during a grid outage. Is this magic box enough to meet the protection required by the regulations and, if so, does it give us a hint of the future by allowing active monitoring and direct control?
Personally, if solar panels are there, I like Schneider industrial distribution boards rated at 125 amp they do make two way ones which are single phase which are a good way to add soda in without changing the existing shimmer unit as some models have each way rated at 100 amp so it will allow you to have a breaker for the main consumer unit and one for the solar and that shouldn’t be much of an issuethey also offer quite a few benefits when adding solar to the ability to get higher than 100 A but I think this is standard with industrial boards
Would it not be sensible to have all sources of power (including solar inverter, battery storage and future V2G equipment) to first come together with the meter tails before they go into the consumer unit? Obviously each unit would then need its own protection devices. I'm thinking that added cost, number of enclosures and time of installation would be considerations but since I'm not a qualified person, just an average member of the public, can someone enlighten me as to where my thinking is wrong. Cheers.
I'm in the same position as you (Not a qualified Spark, and not PV experienced either ⚡) but I'm going to guess it's mainly to do with cost, plus tricky issues about system zoning between the intake point and the consumer unit/CU. 📜
In this video it appears that the PV installation feeds its output directly into the load side of the CU as if it was any other regular load circuit, even if current flow is going in the opposite direction to traditional. In this way all of the consumer equipment (loads and otherwise) is south of the CU and protected by the main breaker - The PV inverter monitors voltage phase and synch's its output to match, so you don't have two out-of-phase AC supplies feeding the same circuit 💥 - And it may save the supplier/DNO installing costlier equipment to monitor and handle exports to the network. 😇
Interesting thought. 👍
So someone else made a good comment about maybe coming off henly blocks to its own cu. Good subject
My EV charger comes directly off the Henly blocks to an IP65 CU - its common sense to use this method and very neat to boot.
In principal that doesn't stop excess current through the original CU, as you could still have eg 100A through the cutout and then 16A from your solar heading in through the main switch in the original CU. I guess this reg doesn't specifically apply, but you'd be in breach of another surely as now the overall CU is undersized for the feed to it...
Western power are fitting 80A cutout fuses as standard according to there engineers when i've needed an upgraded supply
Good to know. 👍
Why not connect the PV invertor output to the supply side of the consumer unit main fuse?
How that will make any difference the potential of more then 100 amp is still there
For many properties that would be the suppliers cut out fuse. 🤔
Two CUs is a perfectly valid installation process.
Can you pleae comment on the following please: Let's assume we have a single DB with a 100amp isolator and a 100amp fuse in the cut out. Unless the solar generation is injected upstream of the DB how can any component, including any part of the busbar in the DB exceed 100amp? OR have I misunderstood? As experts in the field, your input to this would be much appreciated.
I don't understand this - what happened to diversity?
I have a twin stacked main CU - on the lower busbar there are 6 circuits that, if you just blindly added all the CB ratings together, comes to a total of 176 amps. Great Scott, I could melt the house with that and worse, this busbar 'only' has a 63 amp RCD on it - begad! The upper busbar has my lights/smoke/alarm circuits on a 63 amp RCD plus a 32 amp RCBO for the garage sockets and (gulp) the dreaded PV circuit feed that can shift 32 amps / 8 kWh when sunny. Quick maths when I have somehow loaded the lighting, smoke detectors and alarm circuits all to 6 amps each = 54 + 32 + 32 = 118 amps! Clearly I can melt the house, or something. Think of the children.
Meanwhile, all my circuits are protected at the correct value, no busbar is overloaded and the DNO 100 amp fuse is untroubled. The maximum load I have ever pulled from the grid for all the domestic circuits is 32A / 8kWh (multiple ovens etc, near to Christmas). To that I could add 8kWh from my inverter to potentially add up to 64 amps but that would still be split across the 2 busbars and, in this example, would be the PV/Battery doing all the work and not the grid. I guess I could charge the battery from the grid (at 5kWh) plus do multiple ovens etc, to pull 13kWh / 53 amps from the grid but again, this troubles nothing.
Oh and since when did we add incoming amps to outgoing amps? We used to think of current flow. Yes, you could transfix yourself with the idea that 100 amps incoming when combined with 16 amps of solar could enable a household to exceed the 100 amp rated limit of their CU. But guess what, you can do that right now as the 100 amp fuse will quite happily supply you with 116 or even 132 amps for a very very long time...
This is all a distraction as the main issues we face with domestic electrics are poor workmanship or undetected failures. We are way past the era of simple circuits on aluminium wiring feeding multiple 3-bar fires under the glow of multiple 60 or 100 watt bulbs. We live in an era of LED lights, efficient heating systems and a plethora of low-current devices spread liberally around the house. Our real-world issues involve things like switch-mode power supplies, DC leakage, nuisance tripping et al. When you see how much current an illegal grow-house can pull without anyone noticing I doubt this PV concern is of any actual concern.
But we also live in a world of heavy sustained loads, EVs, heat pumps etc...
In terms of diversity, the DNO considers a 3-bed semi with, say, a 6kW heat pump and a 7.2kW EV charger as having an after-diversity-maximum-demand (ADMD) of .... 9.5kW, so just over 40A! Of course, diversity factors for the DNO are higher than those of BS7671 as they are looking at dozens of installations simultaneously, not just one.
@@efixx That is true but ensuring safety and compliance is through training, application, trade skills and inspection. We don't usually see failures due to sustained loads alone, only that sustained loads tend to reveal failures in training, application, skills and inspection.
A busbar that has missed the CU clamp may indeed survive years of use when all it does is supply a few LED bedside lights and PED chargers. However, when that same circuit plays host to a load of IT systems, big TVs, portable AC units and alike the situation changes and latent failures spring into life. The problem is not the heavy sustained loads but the original poor installation and inspection process.
The industry keeps tripping itself up on the basics, not the installation of heavy loads.
hm...
how do we fare if all mcb's inside the board only come to say 78 or 80 amps. Say a 16amp for solar pv and 2 x 32amp circuits. What if you have several boards? Do we need to fit an external fused switch after the cutout If no board has over 80 amps of mcb's? Can the installation actually draw 100amps even with solar (other than a fault condition)?
Just thinking of need for bi directional rcds / mcb's and type b rcd for heat pumps. you could end up with a board for heat pump and say home battery, board for ev's and solar and then another board for everthing else. or at least 2 board supplied buy you own fused switches (x2) after the main cut out.
In the very near future the potential of 2x ev's, home battery and solar pv could actually generate over 20kw on its own!
Having a home battery and DC solar instead of AC solar will help a bit, but directional charging / discharging of ev's is going to throw a spanner in the works..
I haven't done any PV installs but are people connecting them directly into the DB through a breaker like that? The only ones I've looked at are connected into something like the Hendy blocks with the mains which then feeds into the DB. This way isolation is still through the 100A isolator in the board, just make sure the tails are rated properly. Also the DB is completely dead when the isolator is off rather than having a second supply into it. Anyone out there who does PV want to chip in with how they do it?
How many installations have you ever seen drawing the 100A - 23kw ?? - that would be costing £6.90 hour £165.60 day £1159.20 per week ?
Yet again the regulatory framework continuues its never ending upward spiral - the regulations will shortly look like the old Encylopia Brittanica full set.
The lunatics have left the assylum and are currently housed at the NICEIC headquarters with "jobs for life" and "gold plated pensions".
It's not that far removed from reality, electric shower, hob, oven, EV charger and heat pump would soon be up there.
All at once at full power ??
You could include 20 x 3kw fan heaters in every socket if you wanted plus a patio heater 2x Electric showers, hot tub, swimming pool and sauna if you wanted.@@efixx
I'm planning on having our place fitted out with infrared ceiling panels. I'm concerned about how the system will be able to cope if I have about seven or eight IR panels wired in. How do I know a competent sparky to employ? What qualifications or certs should I look for can you tell me please? My only thoughts are recommendations on our local fb group at the moment. Or would I be better off having the panels fitted by the uk company i plan to buy them from?
Hoping you dont mind me crashing your video, Joe, I'm only an interested bystander, eager to get things right, proper and safe electrically speaking in my property. Love watching your very informative videos and often try to guess the words in your news reviews, never been right yet!
Where does this fascination with infra-red panels come from, people want toasty heads? Simulate the feeling of sitting outside under a patio heater?
@@edc1569well with the system I have in mind it's not going to give quite that effect. However if it did I wouldn't mind feeling something similar to the warmth of the sun on me as I'm mostly housebound.
One thing worth noting is this video is the first place I've heard about the 16A export limitation for domestic solar PV installations. Thinking of the number of people I've heard going on about filling whole tracts of land they don't use with PV arrays for the *$£€s* I can see a lot of unqualified PV planners becoming rather disappointed! 😥🌦😉
As for me? I live in a home that faces north, where PV panels would be about as much use as a fuse in a teacup. Who needs a 16A export limitation? I'd be lucky if I ever produced 16 *mA!* 🤣
16A is the max export without requiring explicit DNO permission or them having to make upgrades which you would need to pay for which is essentially what solar farms would need to do to get a grid connection…
Hopefully those installations are applying for permission to export more... 😃
look at north facing pv panel performance videos on youtube, at the cheap price now they are worth installing on north facing roofs...
Take into account weather conditions, when the sun shines you don’t use a lot of power
does an MCB in a consumer unit used for solar power have to be bi-directional and double pole?
AC power is bi directional anyway .. 😀
So hundreds if not thousands of legacy PV installs that were done in the days of the feed-in-tariff up until they conjured up this reg are technically non-compliant much like all those that don’t have type A RCDs because it wasn’t a “thing” 10 years ago? 🤔🙄 I see the logic but in practical terms it’s creating a solution for a very unlikely problem
Yur, but that's the nature of the regs, if they didn't develop alongside advances in the industry we'd still be using rewirabke fuses everywhere. 🤔
@@efixxthat's true but I wouldn't describe this situation as an "advance" since PV installs have been around for decades now - working out that a house *could" potentially draw 116A is more like an after thought ;) - if anything new PV installs are oversized to say 5 or 6kW maybe 10kW and the inverter has G100 export limitation to 16A - in those circumstances the PV inverter could happily push out 20A+ if the house demanded it AND the mains could supply a further 100A - why not upgrade the mains isolator and have a suitably robust bus-bar to suit (a lump of copper like that will happily take the load) Dropping the DNO fuse from 100A to 80A is a rather crude approach and wouldn't necessarily fix the issue anyway as in reality will the DNO fuse blow at exactly 80A - unlikely! It also means that then when there is no PV generation, the house is limited to the lower value which in time will create yet another "problem" to resolve when there are car chargers and heat pumps all wanting to run...
British installations are so far behind. Where I'm living we all have 3 phase supply with 35A main fuses and it works without any problems and you are not overloading the switchboard. And yes 35A main fuse sounds small but you don't need 32A in front of your sockets.
3 phase domestics where they exist are thankfully a lot higher than 35 A. 22 kW EVSE ahoy ;)
Where are you in the world? 😃
I can honestly say that the last thing I want as an electrician is the homeowner/DIY expert having access to 415V 3-phase electricity. 😱
@@intercity125 Not many ev's can charge with 22KW most is only 11KW
@@efixx Denmark
You mention the 100A main fuse, but what if the main switch in the CU itself is rated 63A. That would mean 63+16=79 so ok then?
If you think that then you probably shouldn't be touching anything electrical tbh.
The main switch isn't a protective device so this would be a problem. 🤔
Hi there. I designed, built and opened a zero-emission B&B down here in Rye, East Sussex. Along with a 34-panel solar array, 12kw ASHP, Smart Mixergy Tanks, 10x Air to Air Heat Pumps, underfloor heating and heater skirting boards, 4x 7kw EV chargers (and more)...and you're invited to come and stay with us :-) Hope you catch this comment....and keep up the good work! Javed, Magnolia House Rye
I have a 125a three phase dB in my house kindly source from work
Do you have a matching supply? 😃🤔
@@efixx nope there's a piece of buz bar linking the phases in the main switch
An inverter is not a generator. An inverter is an inverter. The regs just don’t meet with reality.
The reality is inverters are used to facilitate the interconnection of sources of electrical energy with the DNO network. ENA Engineering Recommendation G98, which governs the majority of domestic generation interconnections, defines a Micro-generator as -
_A source of electrical energy and all associated interface equipment able to be connected to an electric circuit in a Low Voltage electrical installation and designed to operate in parallel with a public Low Voltage Distribution Network with nominal currents up to and including 16 A per phase._
So an inverter is effectively a generator.
Well a PV array and an inverter will "generate" electricity to be fair. 🤔
V2G is going to be a problem then.
Let's call it an opportunity... 😂
@@efixx it could be a problem if V2G becomes the norm with EV adoption growing at a steady rate and everyone thinks they can export into the DNO network. Voltage rise will be the first symptom.
Seems to me you need a current limiting device on the solar to stop it ramping up under full load conditions in the installation. Or obviously down grading the main fuse to take account off the additional supply but I’m sure there’s lots of installs out there that are not compliant. It’s not good enough to hide this in BS7671 waffle well done for highlighting this!🥵
Great
Upu should see the shocking installs I come across unfortunately you can put all the regs you want but people dont give a damn 😮😢.
Gets me abit down as we teaun and read and keep upto date but alot of cowboys just lash it all in and dont care.
Need more strict electrical work carried out with procedures to stamp out poor craftsmanship.
Thoughts people ???
The elephant in the room that no-one is talking about: PV inverters export by generating a voltage about 5V higher than the incoming mains and can go as high as 265Vac. So what happens to the property voltage if the mains is already the maximum tolerance of 253Vac? What happens if two neighbouring properties export at the same time? Has anybody thought this through?
I believe they typically use a phase-leading output, rather than a higher voltage.
I guess the inverter is running as a current source when grid connected as the grid is a voltage source (ie low impedance). So the apparent rise in voltage is the current output from the inverter times the mains impedance. So 16 amps into say 0.5R would result in a rise in voltage of 8V. So yes, one could easily exceed to 253v by quite a lot, especially if on the end of a long LV line with higher impedance.
Yes this has been thought through. Compliance with G83 ensures inverters disconnect when the voltage exceeds the overvoltage limits.
@@ratherbewindsurfing With the G83 lower overvoltage limit set at 262.2Vac this means that an inverter will tripping and not exporting anything like what would be expected, if anything, when the supply voltage is high and appliances in the property may be damaged. This information is not revealed in all the sales hype and I have found inverter manufacturers to be evasive when asked directly.
@@hintoninstruments2369 The amount of power you can export will be. limited by the Impedance and the open circuit voltage of your supply. If you are hitting the over voltage limit your supply needs to be upgraded by reducing its impedance or reducing the supply voltage (altering transformer taps).
Good video but thats not how its done in the real world. 551 who actually know this as all.mcs installers have not got a clue lol. Thousands of systems have been fitted. So now they should not really be fitting solar to certain properties no
Hence the video! 😃
Sounds like something else to put in the pile of reasons to try and justify a whole new set of books.
It's more about preventing the current from exceeding the rating of the CU.
@@efixx so we need a day with full sunshine and run enough stuff in the house flat out to draw 116A all at the same time. That scenario is far far less likely to happen compared to the diversity factor BS7671 allows for a cooker circuit. A simple setting in the solar system to stop exporting in that situation would solve the non issue.
Fit your own garage board every time with a 40amp mcb ready for a ev charger problem solved,but as usual can whoever dreamt this up while they had nothing else better to do explain how a energy supply from solar generation #clue right there becomes a load oh unless it’s the 4w standby overnight usage while on standby,so on that logic the 60/80/100 amp supply should be a load too.
It's not about it being a load it's about the current it generates passing through the board. 🤔
@@efixx a g98 3.68kw inverter will very rarely generate full capacity of 16a which you would need around 6kw of dc power to get it there in the summer which will get absorbed into the system anyway,and the fact if you look at the average house board with diversity applied your still well over 100a.
Then look at the thousands that are already installed safely producing electricity,this is just pure drivel.