Which Heat Pump recommendation would you pick

swanny65

Hi,

Having had solar panels with a Tesla battery fitted earlier this year I am looking to replace our old gas boiler with a heat pump. We also have a 26 yr pressurized cylinder that is likely to need to be replaced in the future. He also switched from a gas to and electric cooker a couple or month ago. There is only my wife and I living in the property.

Our house has UFH in a floating floor downstairs and hung in the roof joists upstairs. The house was extended 12 years ago and UFH was put in a screed in one room and in a floating floor in the other room - there was a mistake made with this UFH installation which means we dont get enough heat in the room with a floating floor. This is because I believe we have a 22mm supply to the original two manifolds in the property. However when the UFH for the extension was plumbed into the existing UFH the plumber tee'd off the 22mm pipe with a 15mm pipe. As part of the heat pump quotation process I now understand that as a result not enough hot water gets to the UFH in the room with the floating floor and its cold in winter (never above 17c) but it is okay in the screeded floor (gets to 23c okay).

I have had 3 local installers visit and quote.

I also had Octopus visit but I agreed with their representative there was no point quoting as they wont fix the UFH installation mistake and they wanted to rip up our recently refitted kitchen floor, and possibly mess around with a couple of kitchen units, as they insist on a 28mm supply from the heat pump to the hot water cylinder which we dont have, but they other 3 installers are happy with the length of 28 mm supply we do have.

The quotes all after deduction of the £7500 Gov grant:

1. Grant HP R290 12. This installer inpressed me with his tech knowledge. He insists we need an additional radiator for the "cold" extension room. Even after I queried this with him following installer 3 visit.
   Cost £7800 no other costs. 250 Litre HW cylinder
2. Navien PEM750 10kW, Media R290 Thermal Arctic HTSeries v14 or Viessman Vitocal 150-A 13kW. This installer was also great on the plumbing side and had several heat pump options. He initial quoted to fit an additional radiator in the "cold" extension room but agreed after I queried installer 3 opinion this could be left out and done later if needed. His recommendations include a Navien heat pump which is the cheapest option. Whilst he was content to remove the additional radiator from the quotes it is included in the Media install price as I had ruled this heat pump out and asked for other options.
   Cost £4700 (Navian) £7000 (Viessman inc's premium to increase to 7 yr warranty) £5400 Media not other costs. 225 litre HW cylinder.
3. Nibe S2060 R290 10kW. This installer was recommended to me. He took time to explain why the extension room was cold and how it could be fixed, not only by fitting the correct size supply pipe but by also, forgive my poor explanation, fitting an additional pump to "push" the return water back to the heat pump - less return water mixes with the hot flow.
   Cost £7400 plus I have to pay for the EPC. 200 Litre HW cylinder
   
   Installers 1 and 2 sent quotes using Spruce ? and their calcs are almost identical. Installer 3 provided far less information.The warrany on all is 7 yrs except Media at 10 years.

Appreciate this is a long read but wanted to try and set out all the facts. I could make a case for each installer. Does anything stand out as good, wrong etc. Are the quotes reasonable. Most importantly which way would you jump.

Please dont refer me to Heat Geeks as I have contacted them. They are notnear enough to my location.

I have also set aside money to add a second Tesla battery in prep to move to an Octopus tariff

Thanks very much

NedS

Hi, and welcome to the Heat Pump forum.

I believe the government BUS grant is now £9,000.

Firstly, a heat pump is just a source of heat, so if you are using existing emitters (UFH or radiators), changing from a boiler to a heat pump is not going to change (or fix) any underlying issues with the UFH.

You will need a new cylinder that is specifically designed for use with a heat pump.

Although I'm not an expert, I think it's good installer 3 has tried to understand the issue and offer a solution other than the room is cold so we'll throw in an additional radiator.

Regarding the choice of heat pumps - theoretically the boxes are all the same. There is no new cutting edge technology in them, just a compressor, evaporator etc, all of which have been around for many many years. That said, I'd be happy with the Grant (installer 1) and the Nibe (installer 3), but less so the brands offered by installer 2. Both option 1 & 3 are similarly priced.

Given the size of the heat pumps being recommended, the primary pipework fitted between the heat pump and the hot water cylinder will need to be 28mm. 22mm pipework may be OK for smaller heat pumps up to 6kW, but you will definitely need 28mm for the 10-13kW models you are being quoted.

See here for more information on pipe sizing:

https://www.heatgeek.com/articles/does-my-pipework-need-upgrading-for-a-heat-pump-with-cheat-sheet

From everything you've said in your opening post, I'm leaning towards installer 3. Installers using Nibe tend to be knowledgable (not a cheap volume option) and they have offered a technical reason for the issue in the cold room together with a solution to that issue. Presumably you don't want a radiator fitted in that room, you want the room to be warm from the UFH? If the increased flow from the extra pump does not work, you may end up having to put an additional radiator in there but it's worth a try. Ultimately you have to choose an installer you feel comfortable with and whom you trust.

FlorayG

Pick the one that will give you the best after sales service.

I had problems originally with my Octopus heat pump, they sent out several people to investigate before finding out that their own surveyor had recommended the wrong size pump; they fitted the correct one with no charge to me. The cost of this would have been a massive strain on any small business.

Which representative knew his/her stuff and answered all your questions? How long do you expect each company to remain in business?

Also be aware that you may need to increase the size of all your radiators

QrizB

I believe the government BUS grant is now £9,000.

Only for oil or LPG customers; if you've got mains gas, it's still £7500.

Media R290 Thermal Arctic HTSeries v14

I'm assuming you mean "Midea" and that Media is an autocarrot?

OP you've been quoted for a range of heat pumps with notional capacities ranging from 10kW to 15kW. What did your heat loss calculation work out to be? Fitting too large a heat pump can be just as expensive a problem as fitting too small a one.

I also like the sound of the Nibe. The datasheet shows it has a minimum output of only 2kW, which should mean you get reasonable performance all year round. The same datasheet says the minimum supply pipe size is 22mm so, depending on exactly how it's installed, you shouldn't need to rip up your kitchen.

NedS

@QrizB wrote:

I also like the sound of the Nibe. The datasheet shows it has a minimum output of only 2kW, which should mean you get reasonable performance all year round. The same datasheet says the minimum supply pipe size is 22mm so, depending on exactly how it's installed, you shouldn't need to rip up your kitchen.

That's interesting. The heat Geek pipe sizing sheet says 22mm for 6kW and 28mm for 10kW, but there is certainly some wiggle room in those figures. The Nibe 10kW unit only outputs 8-9kW at common design temperatures. If the heat loss of the property is actually in the 7-8kW range (making the Nibe unit suitable), then I agree 22mm pipework should be fine (I'd still specify 28mm on a new install, but as you say not worth ripping up a kitchen floor over).

An accurate heat loss is key here. If it is actually in the 10-13kW range of the faceplate ranges of the heat pumps quoted, then I'm less convinced 22mm is sufficient as you'd be looking to move twice the recommended amount of heat down those 22mm pipes.

@swanny65 do you have smart meter data for your gas usage on the coldest day in January of this year, as this should give us an excellent indication of your actual heat loss? Just look at your highest daily gas usage figure in kWh (adjusted for any cooking usage) and divide it by 24 to get your heat loss figure.

swanny65

Thank you @NedS and @QrizB for the additional information provided.

Sorry, Midea not Media.

I am not going to die over whether a radiator is fitted or not as the room design is such that a tall slim radiator could be fitted and sort of be hidden - noting installer 1's quote include this as he insists, based on his heat loss calculation, the radiator is required. And like you say it may need to be retro fitted anyways.

The heat loss has been calculated at 10.68kW by installer 1 and 10.87kW by installer 2. Installer 3 hasn't given me a figure but safe to assume its going to be a high 10kW…..

I do have a gas smart meter. I had a few 130 - 135 kWh readings this past winter. Unadjusted for cooking that is 5.625 kW. Must confess I dont get why this figure is significantly less than the calculations of installers 1 and 2.

I know there is a 28mm pipe leaving the gas boiler to the HW cylinder as all installers told me this, but somewhere in the 2-3 metres it runs under the floor to get the the HW cylinder cupboard its downsized to 22mm - does such a short distance make a significant impact.

I have also looked at the pipe feeding the downstairs UFH and it comes up from the floor at 28mm and is then downsized before the manifold to 22mm. Upstairs its 22mm pipe. The extension as mentioned is 15mm tee'd off the upstairs feed.

Like you both I was leaning towards installer 3. He has been doing heat pump installations for many years, he said he has a Nibe heat pump, and he worked on a property who's owner I know (not a heat pump install) and they rated him. Its the lack of a Spruce report / detailed calculations thats putting me off them. However like you point out he understand and explained the cold room issue and is confident it can be fixed.

Thanks again

QrizB

I do have a gas smart meter. I had a few 130 - 135 kWh readings this past winter. Unadjusted for cooking that is 5.625 kW. Must confess I dont get why this figure is significantly less than the calculations of installers 1 and 2.

It's possibly because the heat pump heat loss calculations are based on an outdoor temperature of minus-something degrees C, and it didn't get that cold for a prolonged period during the winter of 2025/26.

Even so, it suggests to me that the Nibe is going to big enough for your property.

FreeBear

I know there is a 28mm pipe leaving the gas boiler to the HW cylinder as all installers told me this, but somewhere in the 2-3 metres it runs under the floor to get the the HW cylinder cupboard its downsized to 22mm - does such a short distance make a significant impact.

The problem with using 22mm instead of 28mm is at the same flow rate, the smaller pipe incurs greater pumping losses and more noise. The length of the pipe is also a factor in the calculations (including bends). Over a short distance, 22mm can be used when 28mm is specified. If you are prepared to accept more noise and higher pumping losses, then 22mm could be used throughout. The other alternative is to have a greater difference between flow & return temperatures…

Rough back of fag packet calculations - Assume a flow of 1.2m³/h through 22mm pipe. For a 5°C difference in flow/return temperature, you'd transfer ~7kW of heat to your radiators & UFH. Increase the temperature differential to 7°C and you get 9.7kW.

Increase the flow to 1.4m³ with a 7°C drop, and you get a little over 11kW of heat. 1.2m³ is the upper limit of what many heating engineers would specify, but some will ignore the table recommendations and tell you that the system might be a little noisier and the pump uses a bit more power. 5-7°C is the typical range of temperature differentials, so nothing wrong there..

With all that in mind, most houses only need 5-7kW of heat to warm the place up. Once up to temperature the demand could drop to 3-4kW. With smart controls, adaptive pump that can change flow rates on demand, and an inverter driven heat pump (most are), running a 10kW heat pump on 22mm pipework is possible. It is likely that a heat pump in your property would only be running at 50-75% of capacity in heating, and 25% (or less) to maintain the temperature.

swanny65

https://forums.moneysavingexpert.com/discussion/comment/82102529#Comment_82102529

Thank you.

I had a Q&A with ChatGPT last evening and it told me the difference in heat loss figures was not unusual as 10.6 kW was max demand at -3c, whereas my calculated heat loss of 5.6 kW was what was likely to be needed. Chat GPT said the Nibe heat pump would be sufficient.

Chat CPT went on to confirm everything installer 3 told me he would do was what is needed with my UFH set up e.g. remove room stats, and actuators and pumps from all manifolds as the Nibe heat pump will work most efficiently with this set up.

Chat GPT also said 28mm / 22mm pipe set up I have should work - but with the additional of a buffer tank (which i can check with the installer). Because you already have a 28mm main line traveling from your current boiler position to your primary underfloor heating (UFH) manifold, the core foundation of your system is already correct. You can integrate the 10kW Nibe S2060 smoothly without any major pipe tear-outs by managing the plant room layout correctly. Why Your Existing Pipes are Fine

• The 28mm Main Line (Perfect): This is the most critical piece. By connecting the outdoor Nibe S2060 directly to this existing 28mm run, the heat pump has the wide, unrestrictive path it needs to push its high volume of water out of the plant room.
• The 22mm Extension to the Second Manifold (Fine): Since your home's total peak heat load is only 5.6 kW, that second manifold is only handling a small fraction of the load (likely 2 kW to 3 kW). A 22mm pipe can easily carry that smaller amount of energy without choking the system. [1]
• The 3-Metre 22mm Hot Water Run (Acceptable with a tweak): While a 10kW heat pump prefers 28mm for hot water, a short 3-metre run of 22mm copper is perfectly manageable. [1]

I know not to take everything Chat GPT says as gospel but in this case it is agreeing with everything you folks and the installer are tell me.

Thanks again

swanny65

https://forums.moneysavingexpert.com/discussion/comment/82102691#Comment_82102691

Thanks @FreeBear Apologies i did not ignore you I was writing my earlier reply when you posted

Got to admit some of this is going over my head !

The installer has quoted to fit a pump in a close coupled tee configuration on the furthest UFH manifold to, as i understand it, push the return water back to the heat pump / lessen the amount of return water blended with the incoming hotter water. I assume this will help to keep the flow/return to around 5°C. As my actual smart meter calculated demand is around 5.6kW then your final summary appears an accepatble fit for my situation.

FreeBear

Chat GPT also said 28mm / 22mm pipe set up I have should work - but with the additional of a buffer tank (which i can check with the installer).

Whilst a buffer tank can improve efficiency by reducing short cycling, it can also have a negative affect. because it provides hydraulic separation between the heat pump side and the heating system, the HP has to operate at a higher flow/return temperature compared to the CH side. The difference may only be a couple of degrees, but it is likely be enough to go from a top performing system to a meh installation (or worse). Worth discussing the options with your installer. Also read up on the downsides to buffer tanks before trusting anything ChatGPT has to say.

Another reason often given for installing a buffer tank is to ensure the system has sufficient volume to pump round if/when a heating zone is shut off - Wrong solution to the problem in my opinion. A small volumizer tank is a better solution if zoning is baked in to the system design.

In my opinion, there are better ways to reduce the effects of short cycling - I had been experiencing this issue with my gas boiler over the winter (had been playing with flow temperatures and TRVs to see how low I could go). Ended up with the control system monitoring the flame, and as soon as it detects a flame off event, a timer is started that prevents a flame on for at least 20 minutes. Also rolled back a few tweaks to reduce the propensity to short cycle.