I bought a Heat Pump

matelodave

shinytop said:

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.  

You are correct, the RHI is based on the EPC and SPF. In the early days of the RHI heatpumps were assumed to have a COP of 2.5, so that's what my RHI is based on (I've had my ASHP for ten years and eleven winters). The alternative was to have a heat meter fitted and report the actual COP.  However in the intervening period they've refined the COP to SCOP to take into account seasonal performance and if your RHI is based on 3.2 then you'll get more than if it was based on 2.5. Perhaps you could give us an idea of what you get.
To get maximum efficiency you need to run it at the lowest possible flow temperature. Ours feeds underfloor heating at between 30-42degrees depending on the outside temperature and the 200l hot water tank is set to 45 degrees.
You may be able to improve your COP by reducing the flow temp a bit, it will take longer to heat the place but the pump wont have to work so hard - knocking it down by 5 degrees could reduce your energy consumption by more than 10%. Heatpumps are usually specified at 7/35 (seven degrees outside to 35 degrees flow) and the rule of thumb is that every degree outside that will increase consumption by around 2-2.5%

There's lots more info on heatpumps on the energy thread https://forums.moneysavingexpert.com/discussion/1464827/updated-air-source-heat-pumps-air-con-full-info-guide-is-it-cheaper-to-run-than-mains-gas#latest and this is a long thread on tweaking https://forums.moneysavingexpert.com/discussion/6219931/most-efficient-way-to-run-underfloor-heating#latest (ignore that title as its about heatpumps)

Reed_Richards

shinytop said:

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.

It's up to your installer to choose an appropriate water temperature for your radiators; that's the only way they can influence the SPF.  Everything else is based on the heat pump manufacturer's specifications.    

shinytop

Reed_Richards said:

shinytop said:

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.

It's up to your installer to choose an appropriate water temperature for your radiators; that's the only way they can influence the SPF.  Everything else is based on the heat pump manufacturer's specifications.    

45 degrees for the rads.  What was yours?

matelodave

Lots of info here - https://heatpumps.co.uk/

Reed_Richards

shinytop said:
45 degrees for the rads.  What was yours?

50 C in and 45 C out so an average of 47.5 C.

matelodave

Reed_Richards said:

shinytop said:
45 degrees for the rads.  What was yours?

50 C in and 45 C out so an average of 47.5 C.

See what effect it has on your room temps and consumption if you knock it down to 45 input. Especially as its now beginning to warm up a bit outside. - mines set to weather compensation and it's about 11 outside at the moment with a flow temp of 32 and the lounge is toasty warm at 20.6 (as weve got u/f heating you can get a away with a degree or so less than with rads because the heat come up from the floor and is even all over.

michaels

I was also surprised to hear that weather comp wasn't mentioned, we have this with our 10 year old gas boiler which along with a wide modulation range means it can run almost 24/7 in most circumstances, at the optimum temp for condensing and the rads are never uncomfortably hot - however it also means I know that once we get to minus outside we start to need a flow temp in the 50s which I understand is very expensive to achieve with a heat pump (via of low cop).  When I was investigating options, bore hle GSHP seemed least likely to suffer from COP falls over the season (assuming you avoid freezing the subsoil which immediately reduces heat transfer).

shinytop

I made some enquiries about the quote I got and was told the rad temperature varied between 45-55 depending on outside temperature, based on an inside temp of 21.  I assume this is the weather compensation mentioned?  He also said all this is adjustable but that's what's used to size the system along with the EPC. 

Reed_Richards

matelodave said:
See what effect it has on your room temps and consumption if you knock it down to 45 input. Especially as its now beginning to warm up a bit outside. - mines set to weather compensation and it's about 11 outside at the moment with a flow temp of 32 and the lounge is toasty warm at 20.6 (as weve got u/f heating you can get a away with a degree or so less than with rads because the heat come up from the floor and is even all over.

At the moment I am experimenting with knocking the flow temperature from 50 C down to 40 C at about 9 am - because that is about the time that the house has recovered from its night time temperature set-back.  That seems to be working fine as far as keeping the house warm thereafter. 
Surely an ASHP has to pump harder when the outside air temperature is colder?  So I don't understand what "weather compensation" means in this context.   

Reed_Richards

michaels said:

I was also surprised to hear that weather comp wasn't mentioned, we have this with our 10 year old gas boiler which along with a wide modulation range means it can run almost 24/7 in most circumstances, 

My gas boiler from 1998 monitored the outside temperature and the room temperature and knowing the required room temperature decided how much to modulate its output.  I was very disappointed that the Heat Pump did not seem to be as smart and seemingly cannot modulate down to a very low power.  The consequence is that it cycles, relying on a buffer tank to keep the interior water temperature more constant. 

michaels said:

When I was investigating options, bore hle GSHP seemed least likely to suffer from COP falls over the season (assuming you avoid freezing the subsoil which immediately reduces heat transfer).

Swings and roundabout here.  If the air temperature is lower than the underground temperature then the GSHP beats the ASHP.  But if the air temperature is higher than the underground temperature then the ASHP beats the GSHP.  You really need both and a system that chooses which to use depending on the outside air temperature.  Now that really would be weather compensation!