I bought a Heat Pump

Solarchaser

shinytop said:

michaels said:

Martyn1981 said:

If I'm reading the graphs correctly they look OK to me. They appear to consume around 50kWh (leccy) pm for DHW, providing ~180kWh of water heating a month, so roughly 6kWh per day. It appears the UK average is about 5kWh/day (that's assuming I'm understanding it, and converting 16.8MJ correctly, which I may not be).

UK average, hmm - no wonder the tubes and trains always small so bad.  5 of us use 33kwh gross of hot water heating a day, in the summer when the incoming is 10+ degrees warmer than now.

6kwh is only 170l of water, less in the winter.

That's a lot of hot water.  I reckon 2 of us use 3-4 kWh/day.  Not soap dodgers and use a dishwasher.        

I LOL'd at soap dodger 😂😂

Martyn1981

shinytop said:

michaels said:

Martyn1981 said:

If I'm reading the graphs correctly they look OK to me. They appear to consume around 50kWh (leccy) pm for DHW, providing ~180kWh of water heating a month, so roughly 6kWh per day. It appears the UK average is about 5kWh/day (that's assuming I'm understanding it, and converting 16.8MJ correctly, which I may not be).

UK average, hmm - no wonder the tubes and trains always small so bad.  5 of us use 33kwh gross of hot water heating a day, in the summer when the incoming is 10+ degrees warmer than now.

6kwh is only 170l of water, less in the winter.

That's a lot of hot water.  I reckon 2 of us use 3-4 kWh/day.  Not soap dodgers and use a dishwasher.        

Yep, same here. In fact a while back Michaels showed that their gas consumption for DHW was greater than our household's entire gas consumption (DHW, cooking and GCH).
I think the point is, that for some, heat pumps may not be suitable, but that isn't necessarily the fault of the heat pump.

Cardew

A very comprehensive report here:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606818/DECC_RHPP_161214_Final_Report_v1-13.pdf

You can take what you like from the various tables; but the bottom line is you will be lucky to get a SPF of 3.0 and with Michael's usage you have no chance

shinytop

Cardew said:

A very comprehensive report here:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606818/DECC_RHPP_161214_Final_Report_v1-13.pdf

You can take what you like from the various tables; but the bottom line is you will be lucky to get a SPF of 3.0 and with Michael's usage you have no chance

Very interesting. The median numbers are spookily close to what I worked out/assumed would be the case for my house. I just need to see what the install costs are to see whether it's viable. Got someone coming tomorrow.  

Reed_Richards

ASavvyBuyer said:

You may have seen this before, but someone has done a very detailed analysis of before & after the installation of a heat pump.

Heat pump performance and home energy 2020

They are achieving COP's in the 3-4 range.

It's like a scaled-down version of my system.  5 kW heat pump vs my 12 kW.  9700 kWh per year heat requirement vs my 22000 kW h per year.  My system was designed around a flow temperature of 50 C and return of 45 C which is higher.  Nominally my hot water tank temperature is 50 C but I have seen cylinder temperatures as low as 43 C so I am not sure what the average is, but also higher.  I let my house cool down during the first half of the night and the heat pump then comes on to warm it back up.  It seems to achieve about 0.5 C per hour increase in temperature.  No mention of whether the noise from the heat pump annoys the neighbours.   

ASavvyBuyer

shinytop said:

Cardew said:

A very comprehensive report here:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606818/DECC_RHPP_161214_Final_Report_v1-13.pdf

You can take what you like from the various tables; but the bottom line is you will be lucky to get a SPF of 3.0 and with Michael's usage you have no chance

Very interesting. The median numbers are spookily close to what I worked out/assumed would be the case for my house. I just need to see what the install costs are to see whether it's viable. Got someone coming tomorrow.  

Agree, that is a very interesting report. However, there are a few things I was not able to find in it; like which models of heat pumps were they assessing and what were the claimed COP's from the manufacturers. That detail may be in the references, but I could not find it. The image on the front appears to be quite an old model of heat pump.

Also, could not see any details of whether some of the heat pumps had rotary inverter compressors or more basic compressors (which can make quite a difference to their efficiency). Interesting to note that quite a few also had additional “cassette” heaters, using resistive heating elements.

However, very useful to see the difference between the worst & best performing systems, as shown in Figure 6.2 and Paragraph 6.7 Factors influencing performance.

One main observation gleaned from the report and from comments elsewhere, is that the most important aspect is to ensure the whole system is correctly designed and set up, as it appears that quite a few assessed in the report were not, or were not being used in the most efficient way.

Thanks for posting the link.

Reed_Richards

I don't understand why heat pumps are stated to be 100% efficient.  In my case the pipes are all in the loft so must be losing some heat there.  If you have underfloor heating then some heat goes down instead of up.  Unless you live in a multi-storey building heated by radiators and with all heating pipes run between storeys then some of your heat output will not contribute to heating the building.  Now Night Storage Heaters really are 100% efficient. 

shinytop

Reed_Richards said:

I don't understand why heat pumps are stated to be 100% efficient.  In my case the pipes are all in the loft so must be losing some heat there.  If you have underfloor heating then some heat goes down instead of up.  Unless you live in a multi-storey building heated by radiators and with all heating pipes run between storeys then some of your heat output will not contribute to heating the building.  Now Night Storage Heaters really are 100% efficient. 

I thought the efficiency related to the boiler/heat pump/storage heater itself and not the onward distribution through the house.  Underfloor heating loses heat downwards even if it's powered by gas or oil, and wall radiators, even NSHs, radiate some of their heat outside through external walls.   You have a point about the pipes in the attic but that's a design/layout issue and not really a heat pump issue.  You could choose to route all your pipes inside the heated part of your house and indeed won't most non-bungalow owners end up doing that?  If I were installing oil heating my pipes would be in the attic the same as for an ASPH.  It might lose a bit of heat but it's a heck of a lot easier and cheaper than ripping up floors.   

Reed_Richards

shinytop said:

You have a point about the pipes in the attic but that's a design/layout issue and not really a heat pump issue.  You could choose to route all your pipes inside the heated part of your house and indeed won't most non-bungalow owners end up doing that?  If I were installing oil heating my pipes would be in the attic the same as for an ASPH.  It might lose a bit of heat but it's a heck of a lot easier and cheaper than ripping up floors.   

An air source heat pump is of necessity outside.  I suppose you could put one in the loft and get better efficiency but nobody (except me) has thought of that.  So at least some of the pipes will be outside which means you can never achieve 100% conversion of electricity to useful heat.  As for the rest, you have answered your own question.  Pipes installed when the house is built are best placed between floors but after that it becomes impractical. Heat pumps like to have larger bore pipes than other forms of heating based on circulating hot water so if you install a heat pump in an old building the chances are you will end up with some pipes in your loft, even if there were none before.  

shinytop

Reed_Richards said:

Installation cost is a bit awkward because a normal installation would get you a heat pump, hot water cylinder and new radiators and I wanted new pipework to all the radiators as well.  The cheapest (provisional) quote I got was £15,500 which would have got me a Grant 17 kW heat pump, cylinder and 10 new radiators.  But they could only guess at what the extra pipework would cost and did not include that in the quote.  One of the problems is that sizing the heat pump and the radiators requires a full heat loss calculation and you don't normally get that done until you sign-up.
The quote I went for was just under £17,000 for a LG 12 kW heat pump, 300 l hot water cylinder and 9 new radiators (as it turned out one was adequately sized) plus all the new pipework.  This quote also included splitting the house into two heating zones and the company did the full heat loss calculation before giving me the quote so it was a much firmer quote than the rest.
Obviously this is a huge sum of money compared to the cost of a new oil boiler and a new oil tank, which was the alternative of least resistance.  But I hope to claw-back a fair bit of this cost through the RHI (Renewable Heat Incentive) payments.  And there are some big wind turbines a few miles from my house which, hopefully, are what provides me with the bulk of my electricity.

I just got my first quote from a medium sized local company. Very similar set up to yours, in effect a totally new install as we have no radiators.  So, for a 14 kW Mitsubishi pump, 12 radiators, 250l tank, 2 zone control, all pipework, fitting and comissioning, a shade over £16k.  I thought it would be more.  But as you say, a lot of money and without RHI it would be too much.  OTOH for me the alternative would be a new oil system, which I can't imagine being a lot less and there would be no RHI sweetener.  

The quote came with some running costs and RHI estimates. The running costs are a bit optimistic but that's expected as the SPF used was 3.2.  Even with my more pessimistic numbers I reckon on something around break-even over 7 years, based on the current heating and DHW using NSHs, immersion heater, a coal stove, wood burner and various other small electric heaters.  Even if it ends up costing me a bit that's OK because I don't mind paying for a better heating system and using a few less Co2s.   

One question - I think the RHI payments are based solely on the EPC and the MCS documentation the supplier provides.  So if he rates the system at a 3.2 SPF and the EPC says 20000 kWh, that's what's used.  Is that right?  If the SPF turns out to be less I pay more in running costs but still get the RHI as specified.

I probably need to get a couple more quotes but so far so good.