Just wanted to say thank you very much for your videos. Ive managed to set my unvented central heating up as a hot water priority system thanks to information i got from your videos that wasn't even in the boiler manual (SL2 on an ideal boiler ignoring flow temperature setting). Education on this subject is severely lacking in the UK and we desparately need more people like yourself spreading the good word.
Great video with good information helping to dispel myths and lack of knowledge. Doing the basics; heat loss, index circuit and flow calcs is vital for edge systems like this, but as you point out should be standard practise on all system design.
Thanks for the video - I'm 2 weeks into new ownership of a heat pump with 10mm microbore. A buffer tank was installed with the wilo pump set similar to in your video. I was worried given the amount of negativity about buffer tanks that are on YT and the various heat pump communities that it was a mistake, but you've made me feel a lot happier now!
Really interesting. I have 10mm micro bore (copper) to all rads (4 bed detached), uninsulated concrete ground floor slab & insulated cavity walls. I've been holding back on a Heat Pump for a few reasons. Micro bore pipework, outdoor space issues for HP & my current boiler is only 5 years old. At least the Microbore issue can probably be discounted now leaving just the other two issues to be overcome. Was thinking about Air to Air with a separate solution for HW but now leaning towards a Monobloc ATW or perhaps even a split ATW. Lack of BUS for ATA will probably rule it out.
The copper microbore is actually quite a bit less restrictive than the plastic as it doesn’t have the inserts so even less of a worry… as long as the calculations say it’s ok of course.
@@UrbanPlumbers yeah, I didn’t think about that. I suppose you just have to hope it’s not kinked or repipe it. The one I did was fine but it was a pretty small place
This is another really useful video. I especially like the introduction to flow rates, pipe sizes and index circuits. Which I am very families with as I used those parameters a lot when designing commercial and very large domestic systems. I think that the requirement to understand and apply this design process is going to become increasingly important in the domestic market and this will present a steep learning curve for many domestic installers. I would always use a buffer store when installing a heat pump to an existing microbore system. They operate in a similar way to a low loss header. I only ever use Grundfos pumps😊
My home has 10mm plastic microbore drops down, 15'mm copper 1st, with a 7kw Daikin monoblock installed over three years ago on a gov trial. SCOP for heating and DHW is 3.15 consistently annually, but DHW alone is about 2.3 and in cold months heating is 3.5, so not bad. The installer put a 20 litre volumiser in to increase the volume. Flow is about 19 litres per minute, heat loss 4.3 kw. The living room radiator is at The end of The run and does struggle to warm up, so what you are saying runs true. But overall the ground floor microbore hasn't been tragic for our set up
Hi! Great video! I was wondering about piping of a buffer tank - I thought installing buffer tank as hydraulic separator hurts systems efficiency... Is this 3-pipe return buffer piping better than other piping arrangements and do you you always use it when installing buffer as hydraulic separator?
Impossible to explain the diffrence in piping in a YT commnet. Heat Geek mastery course has the best explanation of diffrent piping arrangements I have ever seen. Have a look at the course if you are curious.
@user-lb4od2mq5k as far as my understanding goes & if I'm wrong hopefully I will be corrected by someone, you would use a three pipe return piping arrangement for a buffer when the output on the secondary side of the buffer is lower than the primary, this will ensure the cooler return water has a more direct path back the the heat source instead of going straight back into the buffer and going back into the secondary flow & cooling the heat emitters, he has piped with the tee facing down to avoid a thermal syphon, also the common pipe is a bigger diameter to avoid the secondary return going back through the heat source when the primary pump is off, it should be sized for a velocity of no more than 0.5 meters per second in that bit of pipe. Please if I'm wrong which I probably am hopefully someone will correct me.
What insulation have you used in the airing cupboard ? Looks great. Having experimented with my own system it’s very clear flow is king with a Heat Pump if you can get better than required cop will improve.
8mm copper - 50 years old. Sounds like it could be made to work, but probably better replumbing before we get a heat pump? Is a manifold set up better for heat pumps (all radiators no underfloor heating). I could essentially replace all the existing runs but upsize the pipes from 22/8 to 28/15mm. Plastic pipe so no joints between manifold and rads?
Excellent educational video. How do you go about matching the flow rates on both sides. As in the ciculator in the outdoor unit modulates up and down based on demand and the indooor one you have wont? Have you ever thought of buying the same circulator that the outdoor unit has and using that as the post buffer circulator and then using the same pwm control that the outdoor unit uses to also control the pwm on the post buffer circulator?
The Vailant pump hardly modulates. Matching the pumps would not give matched flow unless the primary and secondary system curves match. They won't match.
Did you consider using a bypass gate valve between the primary flow and primary return to allow some of the 800l/h required by the heat pump to be routed directly to the return, reducing the flow round the microbore to, say, 600 l/h with 200 l/h going straight to the return and then being mixed back with the radiator return. The delta on the rads would then be more like 7K but mix back to 5K with the bypassed flow added. I’m planning to try this approach on an upcoming install. I like the approach because it simpler and requires less kit and space. Do you think it will work ok?
I’d love it if you could give a couple of examples of issues with this approach. By way of context the house has a design heat loss of 4.2kW across 17 rads in a 5 year old house. Largest rad output is 600W and with 12mm plastic pipes I’m getting a peak output of 1kW at delta5 at a flow velocity of 0.9m/s. As such it should be fine without a bypass gate valve, but to be on the safe side I was planning to include one and hence the question.
@@pete_pump bypass achieves nothing in this situation. It will just make the heat pump cycle. Much better to try running it direct or even use a buffer. I don’t use bypass valves at all on heat pump installs.
@@UrbanPlumbersthank you so much for your response. Wrong term. Agreed, a regular bypass valve is not useful at all as it should never open. Apologies. What I’m talking about a simple gate valve that is set if needed to allow some water to miss out passing through the rads and to go directly to the return. This reduces flow volume and velocity through the rads resulting in higher delta through rads (and associated lower cop) but which then blends back to delta 5 on the return when the water from the gate valve joins it.
I've yet to transition to an ASHP and presently running a boiler. All the drops to the ground floor radiators are behind plasterboard in 10mm microbore (15mm in the ceiling before each drop). I've done my own heat loss spreadsheet - it's a complex building (1990 build, but not a simple rectangular box) - which seems to correlate reasonably well with my worst case daily gas use. I've compiled a map of my radiator plumbing detailing the pipe gauges and all the Tees, but I've not estimated the lengths of each segment. How necessary is this step? I believe the index circuit can be identified without.
Thanks for this video. I have microbore but 10mm copper attached to 22mm with heat loss of 8.5kW. Would you typically expect a buffer or additional circulation pump to be required like in this video installation?
Thanks for the video, I have a question on the increased flow rates when switching from gas to heat pump. If the gas boiler is already running at 35'40'C DT5 and keeping the house warm, with 10mm plastic does that mean a heat pump can/will also work without buffers etc?
@@UrbanPlumbers Thanks for the info. I thought that would be the case. I have the most basic boiler without any smart stuff. For the last few years I've been heating water with the immersion using solar and off peak electricity so I started trying to run the boiler as cool as possible. We only need to adjust flow temp up to 40 when it gets below 0 outside. And I went to 45 when it got below -5 for a day or two. Otherwise it sits at 35 but runs for a lot longer. I don't make any adjustments to DT just twiddled the flow temp knob. The house is much nicer this way and it hasn't increased gas usage. But I'm now thinking we should get rid of gas and go to a heat pump.
Probably quite lucky that the existing system was designed on 11k dT. I would have expected the usual 20k dT. Ive got the same issue, with grey plastic microbore all over. Doing my calcs has suggested i need a separate circulator so going with larger pipework to/from the Heat Pump and a low loss header. That gets me a reasonable amount of volume into the system and also hydraulic seperation. Fingers crossed!
When you turned off the gate valve to the buffer did that remove the resistance of the secondary pump? If you had of removed the pump and put a straight through pipe, would that have removed enough resistance to then run it without the buffer?
Yes the pump would put some resistance on the circuit but not enough to be worth playing with. What’s telling is that a 6m post buffer pump also had to run 100% to provide 800l/h without having to go through pre buffer pipework
Thanks for a great video. When you need to achieve hydraulic separation because 2 pumps are needed because of the pressure loss on the index circuit, what is the advantage of a vessel compared to a Plate heat exchanger? Heat geek videos always seem to use a vessel when addressing the subject of separation. Vaillant even has a hydraulic unit for ASHPs which is basically a PHE and a circulator in an insulated box. Is one clearly superior to the other? This question is really bugging me.
Vaillant uses PHEX to separte glycolc from water. We do not need that, as we use anti freeze valves instead. PHEX is much more problematic - it can block and be very hard to clean, it does not provide addtional system volume and also can only be piped one way. Buffer if it has to be used is a much better option with heat pumps.
@@UrbanPlumbers Thank you for your answer. Very helpful. One last thing regarding the table you popped up on your great video, I think the flow values for 0.7 & 0.8 kw are off by a factor of 10. Where can I look up those tables for copper pipe - I can’t find them when I look. Thank you again!
I have no idea on the flow rate! A bad set of fittings, or where they used a couple of unnecessary elbows where a sweeping bend would have worked, would make a huge difference. The turbulence caused by fittings can represent many meters of straight lamina flow through a pipe. It might be worth mapping the circuit with a borescope through small test holes in the ceiling to inspect cross joist junctions. If you find any culprits, you could swap out a few bad sections - as a few access holes, in the plaster board, aren't that hard to patch up especially if you know where the joist are, and you could save the costs and space of the second pump/buffer. I'm a big fan of fitting the largest cylinders possible, because they act as thermal batteries ready for higher RE grids with super low/free off-peak tariffs. There's a lot we could do to increase the packing factor of storage volume in mechanical spaces. The other question is whether the effect of the volumizer/buffer could be replicated with larger volume rads - at the end of the day, that would give you the thermal inertia you need too, as well as more surface area. Edit:yup, mapping the system for future leaks is also a nice bonus!
Could you also have plumbed the secondary pump in series with the internal one in the heat pump (i.e. as a booster)? In my mind the heads of the two pumps would add together and the flow would increase. Is there some problem with this - the heat pump control loop fights against the external pump or something? Or is the buffer just the neater install?
You never want to install any pumps in series. They will fight against t each other when set to auto on external unit or proportional pressure in system pump. You are also running a risks of cavitation. You can however for a bigger pump if external unit doesn’t have one and if you run within allowable limits of velocity.
@@UrbanPlumbers Yes, I can definitely see that setting the unit pump to auto and the system to proportional pressure could lead to oscillations. But with a nice open system flow should just need to be commissioned once so constant speed operation would work fine, and no chance of oscillations there. I _think_ you could even leave the unit pump in auto so it can vary the flow without any issue? I don't think cavitation should be a problem really either as long as there's enough pipe in between to avoid "dirty" turbulent water. The flow rate through both pumps and thir rotation speed should both be normal and below their respective maximums anyway. Definitely safer to go for one pump that's been specified and engineered to work for the system, rather than trying to engineer your own pump out of two and risking more problems. It just seems like there ought to be a way to do it cheaper/more efficietly!
Design is clearly everything, and there few like you who have the required skill set. I live in a 1994 build 4-bed detached house with 8 mm copper microbore and original oil-fired boiler, burning through 1,100 litres/yr (+ wood-burning stove with free wood in a semi-rural location, so smoke pollution isn't an issue). It works very well, and I wouldn't even dream of changing this set-up until the boiler finally dies, because I could so easily end up with a cold house from a mis-designed system.
May I ask something? We have an oil burner split into 3 zones. 1st zone goes to the water boiler for hot water supply. 2nd zone is connected to a series of radiators inside the house (bedrooms and kitchen) and the 3rd zone is again connected to radiators in the hall/sitting area. Can a heat pump be retrofitted and utilize the existing water radiators and can they run on single phase electricity?
Short answer is yes. Longer answer is, you want all a single zone for heating. The radiators can be reused if they are sized appropriately for the design flow temperature, otherwise you have to run hotter and less efficient. Also on the single phase electricity depends on the heat loss of the property, and therefore heat pump size. Most properties aren't mansions so don't need three phase. I would get a Heat Geek trained engineer to do a heat loss survey and can then truly tell you what you can/should do.
@@socas_nic Erm, in theory yes. In practice, not really. The problem is condensation when the flow temperature is below the dew point of the water in the air. If you're too low then it will condense then drip on the floor. Not great. However there other possibilities to have almost like air-con but using the chilled water from the heatpump to drive it, which would have to be on its own zone (to avoid the radiators). Not common (yet?!) though.
@@SeanW-zi6kj funnily enough i completely forgot about dewpoint for some reason I thought that because heat pumps work much slower than a typical ac unit, it wouldn't build up condensation, however almost any type of cooling will result in condensation, especially with the absence of a fan on the radiators, (evaporators)
I really love what you do but in this particular case, condens boiler with new rads would be better option. Looking that hot press packed is worst nightmare for any technician and any repairs in future.
Not really. A decent weather comped boiler (viessmann, vaillant) with pdhw and new cylinder would cost the same as this set up plus vat - so not much sense to go gas route.
I would have left buffer in, as we don’t have x-ray eyes with an old system very difficult to get all the dirt out and people need to consider reliability. It will reflect badly on your system if it’s constantly erroring. This will be the bread and butter job in the next 10 years.
Yes - it's much the same as 10mm plastic, so it might work if heat load not to high and runs not too long, but replacing it is best for efficiency so do that if you can.
@@UrbanPlumbers Thanks . Are all of your heat pump instalations work on prioritý hot wate ? and does the space heating turn off when the cylinder is being charged at a higher temperature.
@@UrbanPlumbers Priority hot water should be the norm . I upgraded a system to priority hot water on a Worcester .with addon diverter . . The problem I had was the original unvented cylinder was very noisy when charging. I didn't trust it .
@ 10:20 - it will not get weaker with time … it will only fail … it is an electronic pump with monitoring… The old pumps have running capacitors for the motors - if the capacitor value degrades the motor will run at lower speed …. But in electronic pumps if there is something wrong it will show an error or it will totally fail …😊
Certainly possible for flow to reduce over time. It's not just pump rotation speed. There's also impeller erosion, fouling and corrosion to consider. Unlikely to make a massive difference as these pumps work for ages but a tiny bit of material accumulated will make a bigger difference to flow. System pressure loss won't be constant either - fouling of pipes and orifices with dirt or corrosion products (just think even about the tiny strainer in the heat pump, not much junk needed to increase its pressure drop).
@@mihaiachim5299the fact that flushing is necesary proves that there is debris in the system. Flushing is definitely a good idea but won't remove 100%. even brand new radiators have dirt inside that gets slowly released over time
@@UrbanPlumberspersonally I think it would have been more of a success story if you left the buffer out. This would have been more a mass market install. Why didn’t you design to 45 or even 50? Would still have been a very efficient system mate.
@deanchapple1 can’t leave it without a buffer. Pump in external unit was 860l / hour on 100% power. With a buffer it runs at 50% power with post buffer pump also on 50-60% Small blockage to a strainer or pump getting weaker with age and the system would be pretty bad
@ 9:40 In this case I never replace the whole pump ; only the motor and I keep the pump body on the pipe if they are the same brand of pumps from the same family…😊
@@UrbanPlumbers I promise that are 100% identical (the pumps cast iron bodies) 😊 … the difference is only in the external diameter of the impeller or in the maximum turning speed 🙂
@mihaiachim5299 not quite. I had grundfos pumps dying when I used to swap the head only. Then I realised they had a difference of around 1mm in depth between the same manufacturer models. It will work initially.
@@UrbanPlumbers if they are newer electronic pumps they are having some problems with them… if i Will have the time I will measure all the Grundfos pumps from 2015 upwards to see if they have made changes to them … for now I didn’t have problems switching only the motor body But Grundfos pumps used to keep working for 30-40 years(with the running capacitors replaced when is needed) … now is not the same … maybe greedy management
We have a (small) buffer and the outdoor unit needs only 45% pump power to reach its nominal 860l of flow. The secondary pumpe can easily match that for the rest of the house (floor heating). It would probably have been enough to run everything with one pump, but Vaillant in Germany essentially forbids installing anything without a (parallel) buffer.
@@UrbanPlumbers Probably. My Installer is a Vaillant Premium partner and always asks Vaillant for "permission"...and says they are against it. I could probably have forced the issue, but we have the VP45RW buffer with 45l which is supposed to be quite good and as far as I can measure, the flow temp differential between outdoor unit and the sensor behind the secondary pump is less than 1K, so no big deal.
Just looking for 1) How much a heat pump would cost over 10 years including the gas/electric/servicing cost in the UK. 2) How much a gas boiler would cost over 10 years including the gas/electric/servicing cost in the UK. I can work it out for the gas boiler but just get if's and but's from heat pump sales people.
Too many variables to be able to answer this question as a generic answer. Heat pump is the only heat source that can be run for or close to £0 a year when combined with solar PV and battery storage. Can’t do it with gas.
At the moment there's not a strong TCO argument for going with either type of install, generically. Some properties will work better with a heat pump, others with a boiler. The big factor though is labour (not just for install, for service as well). At the moment most plumbers prefer to work on gas boilers and will charge lower prices for an equivalent job, but this may change in the future. In principle heat pumps are much simpler than boilers and there are fewer barriers to entry (no CORGI &c.) so ought to be cheaper to install and service.
The opposite is actually true. MCS and skill barrier is much much greater than Gas Safe and installing boiler. Complexity of installing g heat pumps x 5 as compared to boilers. Difficulty of MCS is x 10 compared to running Gas Safe registration. Generally heat pumps are much more expensive on memberships in professional organisations, way more admin and red tape and much higher skill set of installer required. It’s like driving a car vs flying a plane at the moment.
@@UrbanPlumbers Agree, MCS is difficult and does make things more expensive compared to Gas Safe (not just through certifications and paperwork, but restrictions on equipment and system design). In my imagined future they wouldn't be necessary; and it's a shame you need MCS to get the grant. The whole reason Gas Safe exists is because gas is dangerous otherwise, there's no safety argument for regulating (monobloc) heat pump installs/servicing. That said, I got a non-MCS install and ended up with a bad experience. But no gas, no flue with all their complexities, lots more packaged into one box. With a proper system design the plumbing should just be flow and return, a cylinder, zone valves and that's it. With weather comp, not even any need for a thermostat. It's simpler than a system boiler properly installed by someone like Andrew Millward. Not as integrated as a combi but you have to compare like with like and the combi heat pump has yet to take off.
Hmmm what I would do ? I would use Tado, and switch of the rooms that I don't use, rather than running all the house at full tilt all the time .... still cheaper than a heatpump installation cost + electricity used.
you're still indirectly heating unused rooms, unless you've got external-level insulation on the internal walls. This means you need to heat the heated rooms more, pushing down efficiency. Only in certain layouts and scenarios would it be cheaper to close off and not heat certain rooms. Also, for insurance purposes, you need to keep the unheated rooms above a certain temperature anyway.
@@BenIsInSweden yeah, that's why the unheated rooms drop to about 10C within 4 hours during winter ... I'll extend to olive branch and let you know that unused rooms are living room, kitchen, dining room, utility room etc - al of which are at the ground floor, and heat travels up not down. during the day all 6 bedrooms are dropping to about 14C during the day due to warm sun exposure - tested this over the two weeks I was out during the winter. So my point still stands, rather than using heat pump and nearly breaking even on cost of instalation + cost of electricity VS heating the whole house with gas - it's better to heat only what you need with gas. And no, radiator driven by a heat pump doesn't have enough of "umph" to heat up a room in less than 30 minutes.
@@tommybronze3451 well you're likely invalidating your insurance then, as many UK policies need it kept above 12C. Most people won't want to run their system where it's 10-14C during the day. You also lose a lot of boiler efficiency with fast heating, as you don't get the benefit of condensing. And you're applying more thermal shock to the system by doing so. Even with gas, in a normally-occupied house, it's more efficient to run it on weather compensation, than to keep turning it on and off.
@@BenIsInSweden wait, what are you talking about ?! condensing boilers are MORE efficient the colder the water you feed to them, so actually I'm extracting MORE heat out of exhaust fumes. Also, your grand blanket statements are blatantly wrong: - my insurance doesn't give a toss about the heat as long as it's above the freezing point - your statement about "it's more efficient", where do you get your data sir ? pulled out of the thin air ? with family of 6 my house is pretty well occupied and gas consumption dropped by 36% year to year and I still use gas stove, so heating savings are definitely more significant than that. You sound like a heat-pump activist that is going to stick fingers up his ears every time when somebody points out the facts.
@@tommybronze3451 no you aren't, that's not how condensing boilers work. You need a lower temperature on the return for it to work. Which conversely means a lower flow temperature, if you only need to heat for 30 minutes to get the rooms up to temperature, then you are running the boiler flow temperature hotter than it needs to be, and also not making much use of the condensate. And not sure why you think I'm a heat-pump activist when I'm talking about how to make a gas boiler run more efficiently too. Weather compensation on a gas boiler adapts the flow temperature to the outside temperature, and it doesn't take a maths genius to wrk out how it is more efficient. There's plenty of resources online as well that demonstrate how weather compensation on a gas boiler is more efficient.
I think it is a huge mistake to still use the location of the old central heating spot as a starting point....you should use the heat pump as the central starting point
Whilst I struggle to follow the detail as a householder, as someone really keen to switch to an ASHP in a house with 8mm (copper) pipework this is really reassuring to watch. Not a question of “it can’t be done” - rather here are the things that need to be taken into account. Thanks for all your great work and for sharing your learnings along the way.
@@richardwaller7721 Micro-bore can work. It just needs to be calculated and designed carefully. Heat loss first, then working out possible pipe runs followed by index circuit calculations. 8mm is a bit small, but if it is a new build it can work without repipe. Case by case with microbore.
@@UrbanPlumbers Have done the heat loss calcs with Heat Engineer software but was great to learn about the index circuit, influence of pipe resistance, pressure drops etc. Every day’s a school day as they say…
Just wanted to say thank you very much for your videos. Ive managed to set my unvented central heating up as a hot water priority system thanks to information i got from your videos that wasn't even in the boiler manual (SL2 on an ideal boiler ignoring flow temperature setting).
Education on this subject is severely lacking in the UK and we desparately need more people like yourself spreading the good word.
Great video with good information helping to dispel myths and lack of knowledge. Doing the basics; heat loss, index circuit and flow calcs is vital for edge systems like this, but as you point out should be standard practise on all system design.
Excellent job, just shows it's critical that those calculations are done correctly. Thanks for sharing/
Thanks for the video - I'm 2 weeks into new ownership of a heat pump with 10mm microbore. A buffer tank was installed with the wilo pump set similar to in your video. I was worried given the amount of negativity about buffer tanks that are on YT and the various heat pump communities that it was a mistake, but you've made me feel a lot happier now!
Really interesting. I have 10mm micro bore (copper) to all rads (4 bed detached), uninsulated concrete ground floor slab & insulated cavity walls. I've been holding back on a Heat Pump for a few reasons. Micro bore pipework, outdoor space issues for HP & my current boiler is only 5 years old. At least the Microbore issue can probably be discounted now leaving just the other two issues to be overcome. Was thinking about Air to Air with a separate solution for HW but now leaning towards a Monobloc ATW or perhaps even a split ATW. Lack of BUS for ATA will probably rule it out.
The copper microbore is actually quite a bit less restrictive than the plastic as it doesn’t have the inserts so even less of a worry… as long as the calculations say it’s ok of course.
@Biglenton trouble is most copper microbore seems to be kinked making it at times much worse than plastic
@@UrbanPlumbers yeah, I didn’t think about that. I suppose you just have to hope it’s not kinked or repipe it. The one I did was fine but it was a pretty small place
This is another really useful video. I especially like the introduction to flow rates, pipe sizes and index circuits. Which I am very families with as I used those parameters a lot when designing commercial and very large domestic systems. I think that the requirement to understand and apply this design process is going to become increasingly important in the domestic market and this will present a steep learning curve for many domestic installers. I would always use a buffer store when installing a heat pump to an existing microbore system. They operate in a similar way to a low loss header. I only ever use Grundfos pumps😊
My home has 10mm plastic microbore drops down, 15'mm copper 1st, with a 7kw Daikin monoblock installed over three years ago on a gov trial. SCOP for heating and DHW is 3.15 consistently annually, but DHW alone is about 2.3 and in cold months heating is 3.5, so not bad. The installer put a 20 litre volumiser in to increase the volume. Flow is about 19 litres per minute, heat loss 4.3 kw. The living room radiator is at The end of The run and does struggle to warm up, so what you are saying runs true. But overall the ground floor microbore hasn't been tragic for our set up
If they installed a 4kw Daikin instead of 7 your scop would have been miles better
I wish i had your knowledge on these kind of things. Great video
Hi! Great video! I was wondering about piping of a buffer tank - I thought installing buffer tank as hydraulic separator hurts systems efficiency... Is this 3-pipe return buffer piping better than other piping arrangements and do you you always use it when installing buffer as hydraulic separator?
Impossible to explain the diffrence in piping in a YT commnet. Heat Geek mastery course has the best explanation of diffrent piping arrangements I have ever seen. Have a look at the course if you are curious.
@user-lb4od2mq5k as far as my understanding goes & if I'm wrong hopefully I will be corrected by someone, you would use a three pipe return piping arrangement for a buffer when the output on the secondary side of the buffer is lower than the primary, this will ensure the cooler return water has a more direct path back the the heat source instead of going straight back into the buffer and going back into the secondary flow & cooling the heat emitters, he has piped with the tee facing down to avoid a thermal syphon, also the common pipe is a bigger diameter to avoid the secondary return going back through the heat source when the primary pump is off, it should be sized for a velocity of no more than 0.5 meters per second in that bit of pipe. Please if I'm wrong which I probably am hopefully someone will correct me.
Excellent Syzmon, you are knocking these out of the park now.👍 Did you OE monitor this install?
No, no OEM on this one. Just V Gateway so i can see scop remotely
Outstanding, I really need to speak to you about doing a survey on my house for a heat pump
What insulation have you used in the airing cupboard ? Looks great. Having experimented with my own system it’s very clear flow is king with a Heat Pump if you can get better than required cop will improve.
k-flex - it’s a armaflex knock off
Great video! Could you just sketch out the 3-pipe buffer setup?
8mm copper - 50 years old. Sounds like it could be made to work, but probably better replumbing before we get a heat pump? Is a manifold set up better for heat pumps (all radiators no underfloor heating). I could essentially replace all the existing runs but upsize the pipes from 22/8 to 28/15mm. Plastic pipe so no joints between manifold and rads?
Manifold systems are easier to balance
If you are matching flow rates why use a buffer when you only want hydraulic seperation? If you pipe up 3 pipe do you get hydraulic separation?
Excellent educational video. How do you go about matching the flow rates on both sides. As in the ciculator in the outdoor unit modulates up and down based on demand and the indooor one you have wont? Have you ever thought of buying the same circulator that the outdoor unit has and using that as the post buffer circulator and then using the same pwm control that the outdoor unit uses to also control the pwm on the post buffer circulator?
The Vailant pump hardly modulates. Matching the pumps would not give matched flow unless the primary and secondary system curves match. They won't match.
Did you consider using a bypass gate valve between the primary flow and primary return to allow some of the 800l/h required by the heat pump to be routed directly to the return, reducing the flow round the microbore to, say, 600 l/h with 200 l/h going straight to the return and then being mixed back with the radiator return. The delta on the rads would then be more like 7K but mix back to 5K with the bypassed flow added. I’m planning to try this approach on an upcoming install. I like the approach because it simpler and requires less kit and space. Do you think it will work ok?
Without going into too much details: it’s a bad idea - don’t do it.
I’d love it if you could give a couple of examples of issues with this approach. By way of context the house has a design heat loss of 4.2kW across 17 rads in a 5 year old house. Largest rad output is 600W and with 12mm plastic pipes I’m getting a peak output of 1kW at delta5 at a flow velocity of 0.9m/s. As such it should be fine without a bypass gate valve, but to be on the safe side I was planning to include one and hence the question.
@@pete_pump bypass achieves nothing in this situation. It will just make the heat pump cycle. Much better to try running it direct or even use a buffer. I don’t use bypass valves at all on heat pump installs.
@@UrbanPlumbersthank you so much for your response. Wrong term. Agreed, a regular bypass valve is not useful at all as it should never open. Apologies. What I’m talking about a simple gate valve that is set if needed to allow some water to miss out passing through the rads and to go directly to the return. This reduces flow volume and velocity through the rads resulting in higher delta through rads (and associated lower cop) but which then blends back to delta 5 on the return when the water from the gate valve joins it.
@@pete_pump yes, it’s not a good idea as the return will get too hot to quickly and heat pump will just start cycling.
I've yet to transition to an ASHP and presently running a boiler. All the drops to the ground floor radiators are behind plasterboard in 10mm microbore (15mm in the ceiling before each drop). I've done my own heat loss spreadsheet - it's a complex building (1990 build, but not a simple rectangular box) - which seems to correlate reasonably well with my worst case daily gas use. I've compiled a map of my radiator plumbing detailing the pipe gauges and all the Tees, but I've not estimated the lengths of each segment. How necessary is this step? I believe the index circuit can be identified without.
Thanks for this video. I have microbore but 10mm copper attached to 22mm with heat loss of 8.5kW. Would you typically expect a buffer or additional circulation pump to be required like in this video installation?
That depends on the heat loss and index circuit pressure drop.
Room heat loss on index circuit is 1.15kW
How many rads in that room ?
Just the one
Yeah that probably will not work without a buffer or partial re pipe. I would try it first and test - it might just work.
Thanks for the video, I have a question on the increased flow rates when switching from gas to heat pump. If the gas boiler is already running at 35'40'C DT5 and keeping the house warm, with 10mm plastic does that mean a heat pump can/will also work without buffers etc?
Would have to be running dt5 at -2c outside
@@UrbanPlumbers Thanks for the info. I thought that would be the case. I have the most basic boiler without any smart stuff. For the last few years I've been heating water with the immersion using solar and off peak electricity so I started trying to run the boiler as cool as possible. We only need to adjust flow temp up to 40 when it gets below 0 outside. And I went to 45 when it got below -5 for a day or two. Otherwise it sits at 35 but runs for a lot longer. I don't make any adjustments to DT just twiddled the flow temp knob. The house is much nicer this way and it hasn't increased gas usage. But I'm now thinking we should get rid of gas and go to a heat pump.
Probably quite lucky that the existing system was designed on 11k dT. I would have expected the usual 20k dT.
Ive got the same issue, with grey plastic microbore all over. Doing my calcs has suggested i need a separate circulator so going with larger pipework to/from the Heat Pump and a low loss header. That gets me a reasonable amount of volume into the system and also hydraulic seperation. Fingers crossed!
When you turned off the gate valve to the buffer did that remove the resistance of the secondary pump? If you had of removed the pump and put a straight through pipe, would that have removed enough resistance to then run it without the buffer?
Yes the pump would put some resistance on the circuit but not enough to be worth playing with.
What’s telling is that a 6m post buffer pump also had to run 100% to provide 800l/h without having to go through pre buffer pipework
Thanks for a great video. When you need to achieve hydraulic separation because 2 pumps are needed because of the pressure loss on the index circuit, what is the advantage of a vessel compared to a Plate heat exchanger? Heat geek videos always seem to use a vessel when addressing the subject of separation. Vaillant even has a hydraulic unit for ASHPs which is basically a PHE and a circulator in an insulated box. Is one clearly superior to the other? This question is really bugging me.
Vaillant uses PHEX to separte glycolc from water. We do not need that, as we use anti freeze valves instead.
PHEX is much more problematic - it can block and be very hard to clean, it does not provide addtional system volume and also can only be piped one way. Buffer if it has to be used is a much better option with heat pumps.
@@UrbanPlumbers Thank you for your answer. Very helpful.
One last thing regarding the table you popped up on your great video, I think the flow values for 0.7 & 0.8 kw are off by a factor of 10. Where can I look up those tables for copper pipe - I can’t find them when I look. Thank you again!
I have no idea on the flow rate!
A bad set of fittings, or where they used a couple of unnecessary elbows where a sweeping bend would have worked, would make a huge difference. The turbulence caused by fittings can represent many meters of straight lamina flow through a pipe.
It might be worth mapping the circuit with a borescope through small test holes in the ceiling to inspect cross joist junctions. If you find any culprits, you could swap out a few bad sections - as a few access holes, in the plaster board, aren't that hard to patch up especially if you know where the joist are, and you could save the costs and space of the second pump/buffer.
I'm a big fan of fitting the largest cylinders possible, because they act as thermal batteries ready for higher RE grids with super low/free off-peak tariffs. There's a lot we could do to increase the packing factor of storage volume in mechanical spaces.
The other question is whether the effect of the volumizer/buffer could be replicated with larger volume rads - at the end of the day, that would give you the thermal inertia you need too, as well as more surface area.
Edit:yup, mapping the system for future leaks is also a nice bonus!
Are all units that you install mono block? I didn't see any split units, or at least refrigerant fill ups
Could you also have plumbed the secondary pump in series with the internal one in the heat pump (i.e. as a booster)? In my mind the heads of the two pumps would add together and the flow would increase. Is there some problem with this - the heat pump control loop fights against the external pump or something? Or is the buffer just the neater install?
You never want to install any pumps in series. They will fight against t each other when set to auto on external unit or proportional pressure in system pump. You are also running a risks of cavitation.
You can however for a bigger pump if external unit doesn’t have one and if you run within allowable limits of velocity.
@@UrbanPlumbers Yes, I can definitely see that setting the unit pump to auto and the system to proportional pressure could lead to oscillations. But with a nice open system flow should just need to be commissioned once so constant speed operation would work fine, and no chance of oscillations there. I _think_ you could even leave the unit pump in auto so it can vary the flow without any issue? I don't think cavitation should be a problem really either as long as there's enough pipe in between to avoid "dirty" turbulent water. The flow rate through both pumps and thir rotation speed should both be normal and below their respective maximums anyway.
Definitely safer to go for one pump that's been specified and engineered to work for the system, rather than trying to engineer your own pump out of two and risking more problems. It just seems like there ought to be a way to do it cheaper/more efficietly!
What make is the phone please and which brand was the insulation thanks
If I fit much larger radiators can I run on a gas boiler at at very low kw out oug puts .
Yes gas boilers also become more efficient with lower flow temperatures
No. The heatload will not change. Your boiler will run more efficiently though
@andrewmillwardwatford9410 What happened to system design on fb ?
Design is clearly everything, and there few like you who have the required skill set. I live in a 1994 build 4-bed detached house with 8 mm copper microbore and original oil-fired boiler, burning through 1,100 litres/yr (+ wood-burning stove with free wood in a semi-rural location, so smoke pollution isn't an issue). It works very well, and I wouldn't even dream of changing this set-up until the boiler finally dies, because I could so easily end up with a cold house from a mis-designed system.
8mm won’t work. Best to re pipe the whole house……
@deanchapple1 why? 8mm copper will be similar pressure loss to 10mm plastic. It can work.
@@UrbanPlumbers as you say, there’s probably kinked pipes.
I always draw the line at 8mm pipe work.
@deanchapple1 yes safer to repipe, but if rads are not bigger than 500-600 watts it might just be doable
Szymon, is the neutral point at the buffer now or is that an issue with heat pumps higher flow rate?
It should be at the buffer if possible
May I ask something? We have an oil burner split into 3 zones. 1st zone goes to the water boiler for hot water supply. 2nd zone is connected to a series of radiators inside the house (bedrooms and kitchen) and the 3rd zone is again connected to radiators in the hall/sitting area. Can a heat pump be retrofitted and utilize the existing water radiators and can they run on single phase electricity?
Short answer is yes. Longer answer is, you want all a single zone for heating. The radiators can be reused if they are sized appropriately for the design flow temperature, otherwise you have to run hotter and less efficient. Also on the single phase electricity depends on the heat loss of the property, and therefore heat pump size. Most properties aren't mansions so don't need three phase. I would get a Heat Geek trained engineer to do a heat loss survey and can then truly tell you what you can/should do.
@@SeanW-zi6kj according properly sized radiators, the system can provide cooling, right?
@@socas_nic Erm, in theory yes. In practice, not really. The problem is condensation when the flow temperature is below the dew point of the water in the air. If you're too low then it will condense then drip on the floor. Not great. However there other possibilities to have almost like air-con but using the chilled water from the heatpump to drive it, which would have to be on its own zone (to avoid the radiators). Not common (yet?!) though.
@@SeanW-zi6kj funnily enough i completely forgot about dewpoint for some reason I thought that because heat pumps work much slower than a typical ac unit, it wouldn't build up condensation, however almost any type of cooling will result in condensation, especially with the absence of a fan on the radiators, (evaporators)
I really love what you do but in this particular case, condens boiler with new rads would be better option. Looking that hot press packed is worst nightmare for any technician and any repairs in future.
Not really. A decent weather comped boiler (viessmann, vaillant) with pdhw and new cylinder would cost the same as this set up plus vat - so not much sense to go gas route.
I would have left buffer in, as we don’t have x-ray eyes with an old system very difficult to get all the dirt out and people need to consider reliability. It will reflect badly on your system if it’s constantly erroring. This will be the bread and butter job in the next 10 years.
We do have x ray - it’s called thermal imaging
Thanks
Thank you!
Any thoughts on 8mm copper pipework?
Yes - it's much the same as 10mm plastic, so it might work if heat load not to high and runs not too long, but replacing it is best for efficiency so do that if you can.
Without the buffer in this system the HP would begin to ice up quite a bit and reduce eff% of the actual HP .
Yes/no ?
Not really. System has enough volume without one and is not zoned so not an issue.
Will the system be noisy with a larger pump and small pipework ?
Not if you keep the velocity within limits
@@UrbanPlumbers Thanks . Are all of your heat pump instalations work on prioritý hot wate ? and does the space heating turn off when the cylinder is being charged at a higher temperature.
Yes
@@UrbanPlumbers Priority hot water should be the norm . I upgraded a system to priority hot water on a Worcester .with addon diverter . . The problem I had was the original unvented cylinder
was very noisy when charging. I didn't trust it .
@ 10:20 - it will not get weaker with time … it will only fail … it is an electronic pump with monitoring…
The old pumps have running capacitors for the motors - if the capacitor value degrades the motor will run at lower speed …. But in electronic pumps if there is something wrong it will show an error or it will totally fail …😊
Certainly possible for flow to reduce over time. It's not just pump rotation speed. There's also impeller erosion, fouling and corrosion to consider. Unlikely to make a massive difference as these pumps work for ages but a tiny bit of material accumulated will make a bigger difference to flow. System pressure loss won't be constant either - fouling of pipes and orifices with dirt or corrosion products (just think even about the tiny strainer in the heat pump, not much junk needed to increase its pressure drop).
@@bearbin he is a good plumber - I think he washes the sistem after install…
@@mihaiachim5299the fact that flushing is necesary proves that there is debris in the system. Flushing is definitely a good idea but won't remove 100%. even brand new radiators have dirt inside that gets slowly released over time
What if you increased flow temp a little to compensate for a smaller rad?
a better solution would be to increase the radiators size to compenstate for a wider DT between flow and return!
What DT are you looking for?
What was designed flow temperature?
40c
@@UrbanPlumberspersonally I think it would have been more of a success story if you left the buffer out.
This would have been more a mass market install.
Why didn’t you design to 45 or even 50? Would still have been a very efficient system mate.
@deanchapple1 can’t leave it without a buffer. Pump in external unit was 860l / hour on 100% power.
With a buffer it runs at 50% power with post buffer pump also on 50-60%
Small blockage to a strainer or pump getting weaker with age and the system would be pretty bad
I love these guesses - 600
Oh man, was I right - maybe I'll never know. You're pushing heat pump installs forward massively, well done!
@ 9:40 In this case I never replace the whole pump ; only the motor and I keep the pump body on the pipe if they are the same brand of pumps from the same family…😊
Quicker to undo 2 compression fittings than 4 hex bolts and you can never be 100% sure if different sizes are identical
@@UrbanPlumbers I promise that are 100% identical (the pumps cast iron bodies) 😊 … the difference is only in the external diameter of the impeller or in the maximum turning speed 🙂
@mihaiachim5299 not quite. I had grundfos pumps dying when I used to swap the head only. Then I realised they had a difference of around 1mm in depth between the same manufacturer models. It will work initially.
@@UrbanPlumbers if they are newer electronic pumps they are having some problems with them… if i Will have the time I will measure all the Grundfos pumps from 2015 upwards to see if they have made changes to them … for now I didn’t have problems switching only the motor body
But Grundfos pumps used to keep working for 30-40 years(with the running capacitors replaced when is needed) … now is not the same … maybe greedy management
@@mihaiachim5299i hear that grundfos are now problematic. Those Wilos are very noisy - it sure I will keep installing them
860 L/hr is bang on 5KW. The heat pump would never exceed that on central heating?
Yes but would run 100% pump power
We have a (small) buffer and the outdoor unit needs only 45% pump power to reach its nominal 860l of flow. The secondary pumpe can easily match that for the rest of the house (floor heating). It would probably have been enough to run everything with one pump, but Vaillant in Germany essentially forbids installing anything without a (parallel) buffer.
That’s probably not true re Vaillant. It’s only a recommendation but installers like to treat it as a rule.
@@UrbanPlumbers
Probably. My Installer is a Vaillant Premium partner and always asks Vaillant for "permission"...and says they are against it.
I could probably have forced the issue, but we have the VP45RW buffer with 45l which is supposed to be quite good and as far as I can measure, the flow temp differential between outdoor unit and the sensor behind the secondary pump is less than 1K, so no big deal.
I'd put 22mm copper with short 15mm bits to the radiators
Just looking for
1) How much a heat pump would cost over 10 years including the gas/electric/servicing cost in the UK.
2) How much a gas boiler would cost over 10 years including the gas/electric/servicing cost in the UK.
I can work it out for the gas boiler but just get if's and but's from heat pump sales people.
Too many variables to be able to answer this question as a generic answer.
Heat pump is the only heat source that can be run for or close to £0 a year when combined with solar PV and battery storage. Can’t do it with gas.
At the moment there's not a strong TCO argument for going with either type of install, generically. Some properties will work better with a heat pump, others with a boiler.
The big factor though is labour (not just for install, for service as well). At the moment most plumbers prefer to work on gas boilers and will charge lower prices for an equivalent job, but this may change in the future. In principle heat pumps are much simpler than boilers and there are fewer barriers to entry (no CORGI &c.) so ought to be cheaper to install and service.
The opposite is actually true. MCS and skill barrier is much much greater than Gas Safe and installing boiler. Complexity of installing g heat pumps x 5 as compared to boilers. Difficulty of MCS is x 10 compared to running Gas Safe registration.
Generally heat pumps are much more expensive on memberships in professional organisations, way more admin and red tape and much higher skill set of installer required.
It’s like driving a car vs flying a plane at the moment.
@@UrbanPlumbers Agree, MCS is difficult and does make things more expensive compared to Gas Safe (not just through certifications and paperwork, but restrictions on equipment and system design). In my imagined future they wouldn't be necessary; and it's a shame you need MCS to get the grant. The whole reason Gas Safe exists is because gas is dangerous otherwise, there's no safety argument for regulating (monobloc) heat pump installs/servicing. That said, I got a non-MCS install and ended up with a bad experience.
But no gas, no flue with all their complexities, lots more packaged into one box. With a proper system design the plumbing should just be flow and return, a cylinder, zone valves and that's it. With weather comp, not even any need for a thermostat. It's simpler than a system boiler properly installed by someone like Andrew Millward. Not as integrated as a combi but you have to compare like with like and the combi heat pump has yet to take off.
Nice work 🙂
Hmmm what I would do ? I would use Tado, and switch of the rooms that I don't use, rather than running all the house at full tilt all the time .... still cheaper than a heatpump installation cost + electricity used.
you're still indirectly heating unused rooms, unless you've got external-level insulation on the internal walls. This means you need to heat the heated rooms more, pushing down efficiency. Only in certain layouts and scenarios would it be cheaper to close off and not heat certain rooms.
Also, for insurance purposes, you need to keep the unheated rooms above a certain temperature anyway.
@@BenIsInSweden yeah, that's why the unheated rooms drop to about 10C within 4 hours during winter ...
I'll extend to olive branch and let you know that unused rooms are living room, kitchen, dining room, utility room etc - al of which are at the ground floor, and heat travels up not down. during the day all 6 bedrooms are dropping to about 14C during the day due to warm sun exposure - tested this over the two weeks I was out during the winter. So my point still stands, rather than using heat pump and nearly breaking even on cost of instalation + cost of electricity VS heating the whole house with gas - it's better to heat only what you need with gas. And no, radiator driven by a heat pump doesn't have enough of "umph" to heat up a room in less than 30 minutes.
@@tommybronze3451 well you're likely invalidating your insurance then, as many UK policies need it kept above 12C. Most people won't want to run their system where it's 10-14C during the day. You also lose a lot of boiler efficiency with fast heating, as you don't get the benefit of condensing. And you're applying more thermal shock to the system by doing so.
Even with gas, in a normally-occupied house, it's more efficient to run it on weather compensation, than to keep turning it on and off.
@@BenIsInSweden wait, what are you talking about ?! condensing boilers are MORE efficient the colder the water you feed to them, so actually I'm extracting MORE heat out of exhaust fumes.
Also, your grand blanket statements are blatantly wrong:
- my insurance doesn't give a toss about the heat as long as it's above the freezing point
- your statement about "it's more efficient", where do you get your data sir ? pulled out of the thin air ? with family of 6 my house is pretty well occupied and gas consumption dropped by 36% year to year and I still use gas stove, so heating savings are definitely more significant than that.
You sound like a heat-pump activist that is going to stick fingers up his ears every time when somebody points out the facts.
@@tommybronze3451 no you aren't, that's not how condensing boilers work. You need a lower temperature on the return for it to work. Which conversely means a lower flow temperature, if you only need to heat for 30 minutes to get the rooms up to temperature, then you are running the boiler flow temperature hotter than it needs to be, and also not making much use of the condensate.
And not sure why you think I'm a heat-pump activist when I'm talking about how to make a gas boiler run more efficiently too.
Weather compensation on a gas boiler adapts the flow temperature to the outside temperature, and it doesn't take a maths genius to wrk out how it is more efficient. There's plenty of resources online as well that demonstrate how weather compensation on a gas boiler is more efficient.
Prediction from 7m34s: It'll work! Maximum flow 700 litres/hour.
Ha - it actually did more than that which was surprising! One rad did not quite work direct without a buffer though.
@@UrbanPlumbers And as you commented, over time, this will only get worse. Good decision to keep the bufffer and secondary pump.
I think it is a huge mistake to still use the location of the old central heating spot as a starting point....you should use the heat pump as the central starting point
Thanks
You must be made of gold mate! Thank you.
@@UrbanPlumbershaha better than that, I install heat pumps 🤑🤑😂😂
I appreciate your videos mate. They are a great resource for learning.
Whilst I struggle to follow the detail as a householder, as someone really keen to switch to an ASHP in a house with 8mm (copper) pipework this is really reassuring to watch. Not a question of “it can’t be done” - rather here are the things that need to be taken into account. Thanks for all your great work and for sharing your learnings along the way.
@@richardwaller7721 Micro-bore can work. It just needs to be calculated and designed carefully. Heat loss first, then working out possible pipe runs followed by index circuit calculations. 8mm is a bit small, but if it is a new build it can work without repipe. Case by case with microbore.
@@UrbanPlumbers Have done the heat loss calcs with Heat Engineer software but was great to learn about the index circuit, influence of pipe resistance, pressure drops etc. Every day’s a school day as they say…
11:03
780l/h my guess
👍
The chances of an Irish installer knowing this sort of thing is about 1/40.
Ohhh, that not too bad, over here it is more like 1/80