Hot Tub Supply, Which earth Arrangement? Exotic life of an Electrician
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- เผยแพร่เมื่อ 28 ก.ย. 2024
- Installing armoured cable to rotary isolator for a hot tub
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Napit technical said on this job with what i explained about the job running a PME supply to the hot tub is fine,
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Did a hot tub supply about a month ago. PME supply. 40A rcbo to isolator. Isolator to Wiska box fed In 6mm 3c swa. Hot tub company connected hot tub to wiska and was happy with that. Some sparkys priced TT install, some didn't. In my head a pme will disconnect quicker than a TT if the RCD fails. If there was extraneous pipes etc near hot tub then I would of quoted TT. Seams to be quite a mixed bag opinions, same with supplies to sheds etc etc
The problem with PME is the (very unlikely) PEN fault that leaves the water up at 230V which is why it is safer (in theory) to use TT
I’ve got a hot tub coming up in the spring so this saved me a call. Cheers
Nick, hot tubs are not "all plastic", specifically the heater element is often inside a metal tube which is earthed and in contact with the water which is high in salt/chlorine. If you use PME and have a PEN fault the water can rise to 230V. I would run a sub-main to the shed, put a TT board in the shed with as many earth rods as you need to get a decent Ze and then run 3-core SWA or if its a protected run NYY-J to the tub. I had to use 3 rods 3m apart to get Ze down to 39 ohms on a recent install of a sub-board for a hot tub.
Around here in the states we don’t get called for hot tub installs unless it’s at least 85 degrees (F).
PME is fine.Be interesting to see what the manufacturers recommend on their installation instructions. PS neat work
A hot tub is like a small outdoor pool, even though it is double insulated the problem is when you're wet your resistant lowers and makes you more susceptible to electrical shock from other sources such as class 1 lights and fittings, hence the 'no PME'
Steve Jordan Tang it’s more to do with the whole hot tub becoming live if you lose the PEN conductor... you step out and make contact between live water and ground... assuming it’s not class 2 hot tub
@@Dontmindme__ Exactly, they are effectively Class-1 devices as the heating elements are in a metal tube that is in direct contact with the (high salt/chorine) water.
Only this week I was given a non Conformity on my annual CPS assessment for a hot tub installation😭.
I installed a sub main with RCD protection in the adjacent shed which was supplied from a PME consumer unit in the house. Shed or hot tub had no incoming metallic parts which were in contact with the ground, hot tub was all plastic construction and sat on paving slabs.
I was told that I must have an earth rod installed with a resistance lower than 20 ohms! I told my assessor I couldn't find it in the regs book and he said it wasn't in there... it is in fact in The Electricians Guide to the Building Regulations! (can't remember which page of the top of my head).
I was totally gutted I got a non-Conformity for my installation work but hey you learn from your mistakes and it makes you a better electrician for it. Haven't had time to watch the video yet but thought I'd add my two pence worth... Will catch up with it tomorrow.
Have a look at Page 2 of this
myenergi.com/wp-content/uploads/2019/09/Protection-against-damaged-PEN-Conductor-r1_0.pdf
It seems to say that your earth electrode impedance needs to be less than 20 ohms if you're adding it to the network earth by joining it at the MET. If you keep your earth rod separate as a straight TT job, then the usual 200 ohms applies, as do other requirements like an RCD main switch.
Killing it with the uploads. Keep up the good work :)
Great video as always Nick. Drives my missus nuts when I watch your vids back to back 🤷🏼♂️. Having sold and installed 1,000’s of hot tubs and swim spas in the southwest since 1999, I can honesty say I can count on one hand the amount of times a sparks has used a earth rod.
Using the wrong sparks lol, get in touch with us mate at CJC electrical
Okay so I'll summarize, going back a few years now a decade maybe, reminded at college every time I go back for reg updates. Metal Bath was bonded yet had plastic pipework supplying it, electric shower cpc/earth wasn't as good as the bath's bonding, so killed the girl when there was a fault. Basically if you're dealing with a double insulated hot tub you're better off leaving out the extra TT stake and just trusting the RCD.
This whole put a TT stake in to cover the electrical distributors lack of motivation to maintain their network at risk of lowering profits has to stop. If the cable breaks down we all know it's not just one house in a street effected, they're risking many of them. Sadly like most things in this country until it causes a massive incident they wont be held accountable.
The dno has no responsibility to provide a earth unless it’s a new supply the consumer has paid for, it is the customers responsibility to make sure the earthing arrangement is suitable. (Eqsc regs)
Agree. I also would not trust the physical ground near the hot tub (where people might be standing/dripping) -- you can't count on the Earth to have a better earth than your TN-C-S earth so you should install your hot tub either on a large metal platform that you earth, don't let people walk on the ground barefoot, or install the hot hub inside. I've gotten shocks between real earth (through wet concrete) and PME earthed surfaces when neighbors were leaking current from their unearthed fountain into the wet ground.
Broom handles can barely support the weight of the broom head. I'm surprised you weren't limping. Still you can sweep around corners a treat now.
I do lightning protection and its possible to get that reading off a 2.4m rod all depends on soil conditions I work in london so normally not great
Hi Nick. Great video, good to see other methods people use. I wanted to ask, why do you choose to drill into the mortar line as oppose to the brick, esp for a heavier cable. And what is the drill bit you used when screwing the cleats in.
Savers did one and they used one meter earth spike.seperate switch outside then ran to the cu.
I wouldn’t treat it any different than any other supply, if no extraneous conductive parts near to touch pme is fine. And if so then TT or connect the extraneous parts to the earthing system via a suitably sized conductor.
It follows the same principle as an electric lawnmower and is protected by the RCD... no earth required... The datasheet for the tub will define requirements anyway otherwise
@@user-sg1ku5hu5d That's an interesting point about the lawn mower. An RCD will detect an imbalance if a fault from live to earth occurs within the appliance, but if it's a PME fault, then we know that RCDs will not respond because current flows from faulty earth to true earth. Live conductors are not involved during that event. Are all garden mowers Class II because of this?
@@westinthewest That and to minimise L and E faults in the appliance or flex I imagine
The majority of the run was going over those old school slabs would have been way better to have buried that SWA underneath but of course down to the client, not much more could have been done up the driveway.
I would make you right in saying you don’t need to put a tt in as it’s all plastic. From what I understand if there is extraneous metallic parts outside of the equipotential Zone then a tt would be needed but no metal parts in the hot tub then no tt. Like to hear what others are thinking 🤔
There is no equipotential zones now mate
Hope they have a good sound system. To block out the sound of the traffic. and planes. Clips 12 inches as a rule. Speak to a hot tub suppliers.and see the requirements.
I buy nothing but snickers as well. Only thing i haven't been able to pull the trigger on the solid gear boots. Are they comfortable?
So just found the pre install paper work for my Hot Tub (aka sex pond) as below. Just wish it wasn't done in SY but oh well. I am guessing electric shock risk is heating element same as a copper tank?
Instead of large earth pit I used 110mm drain access screw cap in black and extended with a coupler.
:Most of our spas are permanently connected to a designated electric supply (hard wired) to the power source using a single phase 230 volt power supply fitted with the correct sized armored cable for the current length of run lo the hot tub. There will need to be a lockable isolator (minimum 2 metres away from the water) suitable for the environment that il is used in. Your electrician will need to connect a length of SY Armoured cable to the isolator, that is suitable in length to reach the front side of the spa, plus 3 metres. A separate Earth Electrode TT Earthing arrangement is required for all outdoor hot tub installations. This is usually connecting the SY tail earth within the isolation switch to an earth electrode and NOT inking ii to the house PME earthing arrangement. Please ask your electrician to call us if he queries this. You will need to get your electrician to return following commission to certify our connection to the spa. A Certificate of Approval to Part P of the Building Regulations will need to be produced. Failure to produce or to meet our terms will result in your hot tub not being connected to the electrics and we will be unable to commission the hot tub.The registration number on the certificate MUST be given to the installers of your hot tub. The connection must be made at the consumer unit, as the installers will only connect at the hot tub end. Hot tub choosen requires 32amp supply.
Check it out, 6.05 in. A bat on the floor. A sign that Bundy is Batman?
Why dont you install a pen monitoring system such as matt:e
Great thumbnail
Definitely stick to using the pme supply , the way I see it you have a very good means of earth supplies by the electricity board then why not use it , I had this debate with someone a few years ago , the fact that you are outside is irrelevant in my opinion, you could be inside a building on a ground floor , have contact with a concrete floor and u wouldn’t think twice about connecting it to pme, cutting off the decent earth and replacing it with a stake with an awful earth seems lunacy to me
Would anyone TT a 13amp plug and play hot tub if day the supply earth was a PME with a split load board?
Testing and certification wise, would just be recorded like a TT car charger.
Take your Zs using the TT earth, and your R1+R2 confirms the supply cable is earthed. And I’m the comments box just be clear about what you’ve done regarding adding a TT earth.
But in your case, I’d read manufacturers instructions and if it doesn’t state must have a TT earth, I wouldn’t bother
TT on a plastic double installed hot tub?
Nick, you said there was no Reg to cover hot tubs. Check out page 251. All covered within section 702.
Leave it on the PME, the chances of someone being in the hot tub , when there’s a N fault on the supply cable to the house and then creating a fault on your circuit while not tripping the RCD is not even worth thinking about, I understand a car charger as they car is metal on rubber tyres but a plastic hot tube no stick with the PME mate 👍🏻👍🏻
John Howard I lost you at neutral current 😂 you defo seem more knowledgeable than me on the subject, I see what you mean about the neutral current A being not switched so it will not trip if you lose the neutral on the installation, my only point is there’s a lot of variables in this example for the fault to occur it’s not a very common fault, in my opinion but like I said I’m not the most knowledgeable I’m just giving my opinion and what the NIC have said to me in the past 👍🏻👌🏻
@@johnhoward2104 thank you ill look into that, love a good read !
@@johnhoward2104 done the course already, great now they gonna change it again haha !! and i need to have a read of AMD 1 too.
found this some where on the web electrical.theiet.org › media › domestic-electrical-supplies-to-hot-tubsDomestic electrical supplies to hot tubs - IET Electrical
Its only right that you must go back to test out the hot tub in use and ensure its electrically sound, some booze and budgie smugglers and all :-D
Did an identical job last summer, I chose to use the PME. When annual inspection came around he wanted to visit that job and had no problem with it, for what that's worth.
Thanks for the shoutout Nick. GSH Electrical has 6 more videos staring the wonderful Nick Bundy coming out over the next few months. Keep up the great work Nick and I look forward to the follow up video 👍. Gaz and Tresham College Learners 🕺
Nicks coming out? I always knew.....
FD1 yes, but six times!
When installing a supply for a hot tub there are a few things to consider. It's all about risk assessing.
If it was going on made up ground such as a raised decked area then pme in my opinion would be fine.
If the hot tub is sat on natural ground and you are able to step into the hot tub while still having one foot on the ground, then I would suggest installing an earth rod.
The hot tub your installing may even be double insulated and if you maintain the double insulation at the hot tub, then pme would be fine also.
If you do install an earth rod then I would make safe to the earth at the isolator and stick the circuit on an rcbo. The maximum zs permitted would be 1667 for it to trip, not suggesting you dont go through the effort on achieving the best earth electrode resistance but it is safe with getting the best you can.
Assuming you are using easycert, you would just put in circuit details as rcbo and your max zs permitted would be 1667, and input your earth rod reading in zs.
If you want to record it as a 2nd result you can also add another line on easycert and label it as the same circuit number to input your pme circuit details. But then r1+r2 clarifies that, so I dont see no need.
Dont forget the certificate has a description of work box for you to write in what you have done and this can be used to explain that you have installed an earth rod etc.
I hope this helps.
And... when drilling inside to outside I have found using a normal hammer drill not sds doesn't blow the brick.
Tidy job 👍🏼
A & R Electrics I know that
regs say anything over 200 ohms may be unstable for disconnection times for 30ma and 100ma rcd's. nic say over 100 ohms may be unstable covering 30ma to 500ma rcd's. personally wouldnt rely on anything over 200 ohms would put extra rods in and do it when the ground is dry so you dont end up with skewed readings.
I’m only an apprentice, but could you just armoured around the building, connecting into the electrical box with some Henley blocks then on the other end, Ip consumer Unit, with RCD or rcbo and then SY out to the hot tub?
@Man Up I think you should have a look and tell me why it doesn't comply with the regs? the whole point of this video is that there isn't any regs for hot tubs and from what I've seen you shouldn't use SY for fixed installation but I don't believe that a hot tub is a fixed installation, and the whole point of my comment was taking about an alternate way of powering the hot tub.
Remember that your practical skills and knowledge will improve as you gain experience working. Your design skills will develop every time you look up a regulation number or read through other published guidance like the Approved Documents of the Building Reguations (Part P etc.). You'll start to recognise your peers who haven't bothered doing any reading because of the way they try to explain things and resist changing their opinions. Compare that with what you see in this video. Nick Bundy is experienced and qualified enough to recognise a situation which might catch him out, and like David Savery with his SPD debacle, he has been open about it and asked for advice on how to interpret the relevant regulations which he has already checked through and told us about. This is the time to get the book out and see if you can spot something useful.
More to the point sy flex degrades in the uv sunlight also the braiding will rust with water penetration from the degraded outer ,not the cable to use for this purpose
@Man Up had this argument with a specifier just this week & we as the customer want to use it for control wiring. He said it can be used full stop regs say so, then quoted the section about BS....I countered with my quotes from regs that say it can be used.
We now have SY going in.
@@darenvitaelectrical5310 when doing a search, I see that SY can be used outside, also SWA would still degrade in the same way
Wonder if it's a typo in the regs for saying it's got to be below 20 ohms. Wonder if its supposed to say bellow 200 ohms.
saying that 20 ohms is possible if the substation is near by or the ground is wet enough wouldnt want to bet on that though most tub are double insulated these days as pme is the go to for 95% of install these days
This is going to sound terrible.... But an old firm I worked for used to flood the ground before we took the reading to write on the report. Not ideal but it worked EVERYTIME.
I think 20 ohms is correct, it is for when you’re using the PME earth and is connected to the supplementary bonding hence it will be in parallel with the PME.
@@cumberland1234 It wouldn't be the first dumb typo in there. There was no excuse for that shoddy 2018 release.
@@westinthewest I think it has been 20 ohms since the 17th edition regs came out in 2008. But I agree, there were some classic errors in the 2018 blue book, some of them corrected in the corrigendum but others were made worse, notably bathroom zones - why they didn't put plan views in there is above me.
Personally I prefer the idea of TT. My reason being that a PME earth will likely have a few volts above mother earth present. The hot tub will have heating elements, pumps etc which are going to almost certainly be class 1 and in direct contact with the water. A person who is wet and in contact with the hot tub water and mother earth may get a tingle. As for the 20 ohm rod/mat, I think that is where you are using the PME earth and is connected in parallel with it. If you were to TT it then I believe the normal 200 ohms max (for reliability) is fine. Best double check with NAPIT though.
That would make sense otherwise any house on a tt supply would be banned from having pools.
I don't see the appeal of sitting in a giant Petri dish in the back garden...
its the same as a pool there is chemical treatment and a carbon/sand filter. but if you dont maintain like most its a petri dish
Then don't let those people in your hot tub and clean it regularly.
I'd have lifted those flags an run as much of the cable underground as possible.
Wow that thumb nail 🤣🤣
My napit inspector would definitely say not to use the pme for the hot tub,
Check the minimum distance from the hot tub to the isolator.👍
External bending of wire armoured cable seams to be to tight, could lead to cable blowing up in high temp conditions on bends.
Exceeds MIBR of swa. I noticed that.
Some comments missing the point about pme: possible danger from (extreme unlikely) lost neutral to supply results in live extraneous conductive parts! Outside location then provides increased shock risk through contact with the ground, further increased by likelihood of persons in tub with wet skin and no foot ware.
TT supply mitigates risk from open circuit neutral. But you should ensure RCD protection of supply to tub regardless of supply arrangement (although possibly this is already at the consumer unit). Hopefully tub will have no extraneous electrical and pme issue then irrelevant?
Sounds like that rug is for a swimming pool, which requires a lot more bonding to ground. As the rebar bar in the concrete around the pool would have to be tied in To decrease the likelihood of a dissimilar ground plane. At least in the US we would require all of that to be bonded together. So you would be essentially a bird on The Wire, As everything would be tied together. We also have our incoming Supply sort of like a pme but it also ties into a local ground rod at each house. Hopefully that's somewhat helpful.
at least in the case of the US electrical code NEC there is a another guy on TH-cam who did a pretty good explanation of how grounding is required around pools I would definitely recommend checking that out I'll try and put the link in
th-cam.com/video/pAs_FmdxXhQ/w-d-xo.html
Not going to comment on whether to TT or not, but in terms of certification / software, surely if you spike it you just record the R2 spike to socket, and the Zs at the socket. The fact you have armor or a redundant core in the SWA that is earthed at the CU protecting the cable is irrelevant from a certificate perspective (a bit like you don't measure the resistance end to end of a metal conduit run unless the conduit is providing the CPC)?
I only ever run a supply for 1 hot tub, it had a moulded plug top and 13A fuse fitted lol.. Plugged into outside IP double socket outlet, via RCBO in CU. No exposed metal parts, all plastic.
Love the thumbnail :-D
2:41 - Am I going overkill on my rods? On my last one I got 16 Ohms. What are you getting typically?
If it's going onto concrete would it be prudent to connect the reinforcing for the concrete to the earth as well? Not withstanding that I think the extra earth stakes needs to go back to the main board not connected local to the tub!
Instead of adding cleats for the swa, why not use 20mm plastic conduit, and push the swa through, no sagging, just leave it short at the corners.
I would export the PME and add a PME fault detection device near the board. As they already have an extraneous metal shed. You will have killed two birds one stone. From the looks of it it's a residential estate so not sure your TT would be a true TT as you'd be very close to other services (they could be plastic i know).
It's never an easy part of the job. Where your designer installer and problem solving guru all in one. Deffo worth phoning NIC to see what they advise aswell but best advice i've seen is JW's videos th-cam.com/video/S5OtLg6voZY/w-d-xo.html
End of the day it's the sparky who is doing the job that supplies the certificate and walks away happy that it's safe ( be that PME or TT ) NICEIC happy with either method.
What was the outcome of this in the end? Currently doing my first hot tub supply and got exactly the same scenario
Hi Nick
I would go off the manufacturers instructions as they’re to be followed more than the WIRING REGULATIONS. I installed a hot tub a few years back using the house PME supply I installed the 6mm three core armoured cable to the rotary isolator switch I connected the cpc to the supply board and straight through to the hot tub using three core rubber cable into the IP65 adaptable box fitted under the hot tub I still had the armoured sheath connected to the consumer unit at source, but was terminated in the rotary switch, the cable was still protected by an rcbo at the source as you have mentioned the hot tub was double insulated.
Wiring regulations take precedence over manufacturer's instructions. You sign a certificate to say that you are responsible for the design and that it complies with BS7671. If you want to follow the design decisions of Happy Hot Tubs Ltd., then they need to sign the certificate.
The problem is that many of these units are directly imported from China and they don't have a clue what PME is
@westinthewest, wiring regulations states you should follow the manufacturers instructions in the 17th edition the manufacturers instructions were above the wiring regulations
@@leebutterworth7465 I must have a different copy of the 17th Edition:
PART 5 SELECTION AND ERECTION OF EQUIPMENT
CHAPTER 51 COMMON RULES
510.3 Every item of equipment shall shall be selected and erected so as to allow compliance with the regulations.... and shall take account of manufacturers' instructions.
It says 'Take account' and not 'Follow'.
The problem for me is that I have to sign a certificate stating that my work complies with BS7671. What do I sign if I follow a manufacturer's instruction that forces me to deviate from this standard?
That thumbnail 🤣🤣🤣
Hi Nick, what is the demand on the hot tub ? 10mm nice size but was it necessary ? please do not think I am being critical. Tony
Volt drop over a long distance for 6mm cable?
Mentioned in another comment by A&R Electrics.
Huge voltage drop with the amount of tight bends he has had to battle with. So 10mm necessary.
I would have thought 6mm would have been adequate.
Do the regs say anything about drilling into mortar to secure the cable?
The correct way is use PME but add an electrode, its caled bonding.
In that house I would have piped up to attic then back down if possible.
What’s this talk about pulling your length off 9:52 😒
He's done a nice job give the guy a break👍👍
I definitely would of went up and over with that swa it would be better job I reckon. And less chance of taking any impact.
Ha! Just realised what the thumbnail was... Amazing!
Nick the element in most hot tubs is in an earthed metal tube just like an immersion heater and is in contact with the water. The water in the tub is likely to be much more conductive than the water that comes out of the tap due to the TDS like the chlorine and other chemicals added to keep the tub clean so if the casing of the element became live suddenly you have an insulated tub full of live water sitting on true earth. Fine till it’s time to get out
Instances of PME failure are thankfully quite rare, but it’s something to consider.
See you and dan are having a swimming time 👀
Hi I'm just wondering if I can ask you a question, I'm a cable jointer for the a dno so I know bits but not a lot. I have a hot tub and my supply is a pme system. I have a armoured feed from my board to a rotary isolated. Now the fun bit yesterday when exiting my hot tub I got a shock when coming into contact with ground. I'm extremely paranoid now as my son had been in the tub with me. What could be causing the voltage in the water and how could I correct it? Any help would be much appreciated.
@@samh10 Its possible that tour pme supply earth in relation to true earth has a very slight voltage leakage ( quite common and normal) . If this is the case I would separate the pme earth from the load side of the rotary switch and install earth electodes . One at the rotary switch and if possible take a bond from the metal work of the element to another earth rod for good measure. This will clear the nuisance leakage .
I think all PME systems should be utterly condmened in the uk as its one of the most dangerous systems devised and bring back continous old school eath wire again.
You said ‘Pull a length off’...lol.
Could you use a MATT:E device on this
John Ward explains it perfectly.
What am I missing? How come is he using L1,L2,L3 SWA cable instead of Twin and Earth cable ?
What did NAPIT Technical have to say? Tried ringing them the other day for a question but could never get through, just got an answerphone!
Did you run the swa into the fuse box? Can you use 10mm t+e to go from the rcd to the isolator then swa from the isolator to the tub? Having one installed myself and keeping the isolator on outside wall nearest the fuse box...
What is the benefit of using the wiska box? 🤔
Oversheath, armour, bedding and then the insulated conductors. I agree, there really should be some proper regulation about hot-tubs and spas installed in a garden.
What with the thumbnail I know I’m late but I’ve been watching a bunch of videos
Here in Australia if a slab has a shower on it the slab has to be earthed which is so stupid
Phone call to the manufacturer might be in order.
You know mandarin?
M H distributor?
All this for a lazy spa 😂
Was there a follow up video to this? or was an earth rod fitted after Napit specified?
just plug a bayonet outlet into one of the garden lights and wire it into that, you may have to bump the lighting circuit fuse up a few amps at the board, should be good it's colder outside, are you liking this idea
ya. for you to get into. even my pet dog wouldnt dare to sniff near. rubbish minded. ☠🔥
What did Napit say? Cheers.
Mega Thumbnail haha 👍😂
I think I would of run the armoured up into the loft and drop down behind the down pipe,, as for the earthing I think using the PME is fine as surely the hot tub is double insulated anyway
Sod that.
Surely this would use twice as much cable🤔
Yeah use more cable maybe,, but looks gash cleated around those bay windows and under that door
10mm T+E protected going up to the loft in 25mm PVC conduit, the same dropping down to the isolator at the other side, longer length of cable but same cost as SWA but far neater job
Paul Craft,, exactly how I did the last one black 25mm up the wall to the loft and white 25mm behind the white gutter
I would put a PEN fault detection device in.
What was napit technical response I can't seem to find it.
I'm glad i'm not the only one that uses the word clobber
No exposed metal parts but chance of water to become live?
10mm 3 core seems chunky for a Hot Tub with a 32amp rotary isolators?
Massive volt drops on the bends
Pme protective MULTIPLE earthing it's very unlikely that you would lose your earth due to the multiple earth spikes along the length of the neutral conductor so PME should be fine if you want to be sure about any extraneous conductive parts run and earth to the main earthing terminal that's my my take on it
I’ve always wondered what the likelihood is of losing the neutral on one of these supply’s considering how common they are and the danger associated.
@@Hammy135 I found this on pme failure rates myenergi.com/wp-content/uploads/2019/09/Protection-against-damaged-PEN-Conductor-r1_0.pdf
@@no_short_circuit Nice find!
If the Hot tub is Double insulated with no extraneous conductive parts then just use the TN system
If there are extraneous parts then only use 2 cores of your armoured for L+N and just earth the armouring at the supply side, but not load side. load side gets its own rod and the extraneous parts are bonded to that. Treat it like a sub main supply for your certificates
Great video as always mate keep it up! from a fellow spark
cleating: i recently saw an installation where the cleats were the other way round... DIYer ..omg why.
No, why are you suggesting it matters?
@@JimWhitaker Being more likely to lever out ain't enough?
Stupid question- when an incoming neutral is lost why doesn't the inside installation become live only the outside?
It does become live inside but you are probably not connected to earth if you touch it (making a return path) like you would be standing on the ground outside
Makes sense thanks
.concrete flooring indoors?
Your work is Spot on 5 Star
10 mm is a bit big for 32a. 6mm would of done
Volt drop mate 3%
No such thing as "too big", only "too expensive" and "too small".
what did Napit say
Napit specified earth rod
Christ, all those well used tabs in the regs book! Loooooooooool!!!!
Im just learning and find this really interesting, May I ask a question? If you split the earth system at your rotary switch, would you then have to put a rcd at that point that runs off the TT system? I'm guessing that the rcd in the CU would just protect the cable unto that point or have I got it wrong???
Greats vids, please keep them coming. Dave
The RCD should still work at the cu as there would still be a imbalance of the conductors but instead of the earth leaking to the pme system it would leak to the tt system. I may be wrong but that's how it makes sense in my head lol
@@dominicgadney5572 Thanks very much Dominic, that'll teach me, i was thinking of the RCBO's with the earth fly lead, I was just reading that it would still protect if neutral was ever lost. Of course the normal RCD's don't have/or need that connection to work. It all makes sense now. thanks again Dave
Hi Adam if you are going to TT the hot tub, I was told to just use the line and neutral from the armour from the house, don't connect the SWA outer sheath at house end and mark it at consumers side stating why. TT the armour cable and the hot tub supply .
I agree with this here.
Yep spot on
Agree
I would have split the tails in the meter box put in a small cu just for the tub, save going indoors at all.
Why is the steel armour better connected to the TT earth and not the network earth?
If someone penetrates the SWA cable with a garden fork, we need enough fault current to trip the 32A or 40A breaker protecting the cable upstream. I know the breaker upstream might be an RCD but aren't we supposed to consider that as 'additional protection' only? We still need to adhere to Zs values in Table 41.3.
@@johnhoward2104 Indeed, but the downstream TT RCD won't protect the distribution cable. If a fault occurs on the SWA, there won't be enough current to operate the MCB on the TN-C-S supply side of the cable. The fault current would be limited by the high impedance of the earth rod. The armour needs to be attached to the network earth instead. Why would you prefer the armour to be connected to the TT earth rod?
Just been reading the comments and some are asking what NAPIT Technical said. I contacted them with regards to hot tub installation which was supplied by 6mm swa on a pme system and they instructed that it be on an earth rod with 6mm cable
This brings up multiple problems:
My method is to run SWA to IP lockable isolator (to be able to protect the Service Engineer) from the house with the sheath earthed at the house end. Overload protection at the house end usually needs a C type breaker, ideally time delayed RCD at the house end and 30mA RCD in IP enclosure local to the tub.
The type of RCD depends on the type of pumps in use. The latest tubs with DC motors need a type B RCD or, with vary speed AC motors, a type A or F. Never use an RCBO unless it switches the neutral (few manufacturers switch the neutral).
I Always prefer a TT connection for the spa with local earth stake - not forgetting that in the summer the resistance will be much higher but on some installations the tub may be heated by LPHW with metal connections that bring the house PME out to the equipment. The 20 ohm earth stake is the only way.
The biggest problem with using PME is when the local network is at maximum load on one phase and there can be a 10V or more difference between the PME earth and true local ground.
On many locations I have put in a temporary stake and measured the voltage between the water and true ground and seen voltage varying from 0 to 14 volts. People with bare feet can feel this.
Other things to consider:
If you switch a tub off in winter and it freezes, high value damage can occur.
Some tubs have two 2-3HP pumps, these have very high starting currents.
Some built on site systems have 12KW electric heaters and two 2HP pumps and air blowers - a significant load.
Never use the main house RCD to protect pools or tubs, always a separate one because if a service engineer trips it, they may not be able to get in the house to restore the supply.
Air blowers on spas are a brush motor driving a vacuum cleaner type compressor which is open to the air and humidity from the system, these can be a cause of low insulation readings as when the blower is switched off water re-enters the air pipe work and can send damp air back through the blower.
Health and safety regulations require the system to purge every day to prevent the water in the pipes and air lines going stale.
Because of these high starting currents sometimes house circuits RCBOs or RCDs trip, this is usually because the neutral to earth voltage has spiked just enough to trip the RCD. This is after a low test on an heating element.
Hope this helps
Roger Caplin - www.electair.co.uk
Your direct experience in this type of installation is very useful, thanks. Investigating effects such as differences in voltage between network and true earth can develop one's perception of what's going on, and it consolidates our understanding of the theoretical scenarios we might read in the text books.
One thing I'm not sure about is the upstream RCD at the house end. What is its purpose when the distribution cable is SWA? Wouldn't an MCB be more appropriate?
@@westinthewest Hi of course there has to be an MCB at the supply end and this should be a C type The object of the Time delayed RCD ay the house end is because these installations can be very difficult with the cable route it protects against external damage it gives that extra level of protection i have seen cables just pushed under hedges fixed to fencing
of course these cables may of been installed correctly originally but a landscape contractor may move things " that sort of thing " If ever a situation went to court and the question was asked " is there anything else the could of reduced the risk"
they may find for the plaintiff very good to have thes posts
some good points ,which type B RCB would you recommend as i can only find £200 versions? would your earth rod be installed adjacent to the tub ,bonded to the earth in the tub and run to the isolator switch or leave it in the tub?
I would expect the Hot tub to be double installed. I would not install an earth rod with it be so close to the house.
I installed a 3 core armoured cable via a rotary isolator on a tncs earthing system and rccb protection . And on the hot tub I came across there was a connection for the earth as they have a pump motor connected to it and an electric heater on the water for the hot tub .
John Waby
Definitely the way to do it 👍🏼
And just be careful of the final connection inside the hot tub some of the control boxes dont take the swa into them
I had to finish the final connection in black rubber flex