UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

matelodave

Cardew wrote: »

must be a soap????

Ah, that explains it then, if he can't get his head around a soap then he's got no chance with a heatpump;)

thenudeone

matelodave wrote: »

I think that's a bit optimistic I don't think it's the EPC estimate that they use.
It's either based what you actually produce if you've got a heat meter or the projected amount detailed on your MCS certificate. So try the calculation on the MCS figure to see if it's as good. I hope you aren't going to be too disappointed:(

Because I have retained the old oil boiler for when it's very cold and the ASHP can't cope, the system has to be fully metered.

The EPC provided to the installers stated the energy requirement as 67Mwh pa. I haven't received the MCS certificate yet but I can't see why it would be different.

I don't expect to receive exactly the amount shown, because we will use less than the "nominated" amount of heating and the meters will reflect actual usage and actual efficiency.

With a large old house and an old oil boiler, we have grown used to going without heating when others would have it on (or using electric heaters in individual rooms as required), and although we will be using central heating much more, we won't be setting the thermostats at what others might do (21C).

But in any case, I expect the RHI to pay for a very substantial part of the ASHP installation cost.

[Deleted User]

offitmassive wrote: »

ahh i see what ufh means, no i dont have that, im a motor vehicle technician with F gas license so am aware it works in reverse to air conditioning to an extent. and that it draws in the ambient air temperature to change the gas to a liquid (or vice versa?) and this in turn heats the water which is then pumped around the home. I get that bit. i also dont understand why say the temps are preset at 50c but recommended temps for water are 55c? i dont understand either way error code u1 keeps appearing, twice yesterday infact. I dont understand why peter barlow is keeping things going with carla when tina is sniffing around either!

Sounds like you could be getting confused. Domestic Hot Water temp may well be set to 55c but central heating water temp, being rads, may well be set to 50c. The Ecodan will happily heat water to 55c and, if set, will use the electric immersion to boost the water temp to either 60c or 65c at every cycle/15 cycles/150 cycles/not at all depending on DIP switch settings.


Note: EcoDan packaged systems do not use an immersion for heating duties, no need as works into minus double figures no probs which we have had here in Scotland.


I don't use the boost function as I have a solar immersion instead which heats to 65c no probs. Saves money too.


From memory U1 may mean insufficient flow rate as I mentioned earlier. Do you have a buffer tank (if it is a packaged system I doubt it will)? Which leads me to... what size are the pipes to the rads. The install manual makes it clear they have to be a certain bore or will not work as intended - Ecodan cannot dump it's heat fast enough and will shut down.


None of us here can see your house, system etc. If you are confident you can jot down all your existing settings. Then program the system with the recommended settings for a rad based system in the install manual. Then tweak from there... But if unsure get a pro in...


Food for thought...


Cheers


PS Do you have a note of what your heat curve settings are?

[Deleted User]

thenudeone wrote: »

It's per annum.

My EPC states an energy usage of 67,000kwh pa :eek::eek:

Assuming a legacy COP of 2.5, 60% of this will be renewable (1.5/2.5)
= 40,200 kwh pa
x 7.3p/kwh
= £2,934 pa

I hope.:o

Hi,


Using your formula I'll get £12625 over seven years. Certainly more than I had calculated previously. That's using the figure on the MCS cert.


Time will tell...


Cheers

zeupater

thenudeone wrote: »

Because I have retained the old oil boiler for when it's very cold and the ASHP can't cope, the system has to be fully metered.

The EPC provided to the installers stated the energy requirement as 67Mwh pa. I haven't received the MCS certificate yet but I can't see why it would be different.

I don't expect to receive exactly the amount shown, because we will use less than the "nominated" amount of heating and the meters will reflect actual usage and actual efficiency.

With a large old house and an old oil boiler, we have grown used to going without heating when others would have it on (or using electric heaters in individual rooms as required), and although we will be using central heating much more, we won't be setting the thermostats at what others might do (21C).

But in any case, I expect the RHI to pay for a very substantial part of the ASHP installation cost.

Hi

I'm pretty sure that one of the qualifying conditions for legacy RHI is that major recommended energy efficiency measures such as loft or cavity wall insulation which are mentioned on the EPC are addressed before registration can go ahead ... if so, & if they've not already been addressed, you'll have a limited time to get this sorted or the RHI qualification period will lapse ...

If your heating requirement is >60MWh.t/year then it would need to be a mighty big system - 2x15kW ? ... I only base this on a 15kW system running 24x7 at max performance for the 6 heat provision months would only provide (15x24x180/1000) ~65MWh.t, which would provide enough heat on an average basis, but leave little leeway to provide sufficient heat in the colder months ...

What is the setup you have & are the major insulation energy efficiency measures already in place ?

HTH
Z

AsaMac

I know the new government intensive has changed the game a wee bit and, since I'm re-mortgaging, I was thinking of taking an extra bit to pay for the ASHP. I don't know anyone with a system and everyone seems to have massively conflicting views on the validity of the potential system.

I live in Devon and have a big old house (1850) with 4ft thick flint walls, new double glazing, underfloor heating downstairs and radiators upstairs. My loft is fully insulated and I already have solar PV.

I currently have an LPG system which costs me about £1200 a year, I use the hot water and heating as sparingly as possible but the house is about 190m2 (6.5ft ceilings though) so it takes a lot to heat it up.

I've had a quote from Ecovision of £9k for a Mitsubishi Ecodan 14kW and a Mitsubishi 250L Cylinder and the marketing says:
Expected annual saving compared to LPG: £600 x 20 = £12,000
Expected annual RHI payment: £853.95 x 7 = £5,977.65
Replacement cost of LPG boiler within lifespan of heat pump: £3,000
Total 20 year (lifespan of heat pump) benefit: £20,977.65
So that's a 6.5 year period to break even. Seems not bad.

Has anyone got any advice, opinions and insights?

thenudeone

zeupater wrote: »

What is the setup you have & are the major insulation energy efficiency measures already in place

The original EPC showed 77000 kWh pa!
Loft insulation to 270mm and cavity wall insulation were installed just before the ASHP, and a new EPC was prepared.

It's a 16kW Daikin Altherma HT with a (200l?) buffer vessel.

The supplier advised that the ASHP alone wouldn't be adequate in the coldest weather, which is why the existing oil boiler was left as part of the system. (Other suppliers had quoted twin 16kW units). The bivalent point is set on an outdoor thermostat (although I've installed a manual override switch). In practice, because we don't expect to be able to walk around in shorts and a t-shirt in December like some people do, it should provide most of the heat we need (or all of it in a mild winter like the one we've just had)

matelodave

AsaMac wrote: »

I know the new government intensive has changed the game a wee bit and, since I'm re-mortgaging, I was thinking of taking an extra bit to pay for the ASHP. I don't know anyone with a system and everyone seems to have massively conflicting views on the validity of the potential system.

I live in Devon and have a big old house (1850) with 4ft thick flint walls, new double glazing, underfloor heating downstairs and radiators upstairs. My loft is fully insulated and I already have solar PV.

I currently have an LPG system which costs me about £1200 a year, I use the hot water and heating as sparingly as possible but the house is about 190m2 (6.5ft ceilings though) so it takes a lot to heat it up.

I've had a quote from Ecovision of £9k for a Mitsubishi Ecodan 14kW and a Mitsubishi 250L Cylinder and the marketing says:
Expected annual saving compared to LPG: £600 x 20 = £12,000
Expected annual RHI payment: £853.95 x 7 = £5,977.65
Replacement cost of LPG boiler within lifespan of heat pump: £3,000
Total 20 year (lifespan of heat pump) benefit: £20,977.65
So that's a 6.5 year period to break even. Seems not bad.

Has anyone got any advice, opinions and insights?

Do some of your own heat calculations and it will help you understand how much heat you'll require - there are several calculators on the web to try and assess how much heat you'll need for each room and do a whole house one as well. That will help you understand if a 14kw h/p will do the job.

Secondly you need to asses the heat emitters (radiators & underfloor heating) to see what they'll output at varying system flow temperatures - if a room needs 2kw and the rad is spec'd to deliver 2kw at 70 degrees then it won't be big enough to deliver 2kw at 35 degrees so it will need to be at least twice as big.

Just shoving a heatpump on the system no matter how big it is won't do the job if the existing system can't deliver the heat at low flow temperatures. Increasing the flow temperature will significantly increase the running costs as the heat pump will have to work harder. Most are specified at 35 degrees and it takes about 2.5% more energy for every degree above that - so to run it at 50 degrees will cost you nearly 40% more than running it at an optimum 35 degrees.
Understanding what you need will help you ask the right questions and hopefully allow you to make a considered decision.

offitmassive

jeepjunkie wrote: »

Sounds like you could be getting confused. Domestic Hot Water temp may well be set to 55c but central heating water temp, being rads, may well be set to 50c. The Ecodan will happily heat water to 55c and, if set, will use the electric immersion to boost the water temp to either 60c or 65c at every cycle/15 cycles/150 cycles/not at all depending on DIP switch settings.


Note: EcoDan packaged systems do not use an immersion for heating duties, no need as works into minus double figures no probs which we have had here in Scotland.


I don't use the boost function as I have a solar immersion instead which heats to 65c no probs. Saves money too.


From memory U1 may mean insufficient flow rate as I mentioned earlier. Do you have a buffer tank (if it is a packaged system I doubt it will)? Which leads me to... what size are the pipes to the rads. The install manual makes it clear they have to be a certain bore or will not work as intended - Ecodan cannot dump it's heat fast enough and will shut down.


None of us here can see your house, system etc. If you are confident you can jot down all your existing settings. Then program the system with the recommended settings for a rad based system in the install manual. Then tweak from there... But if unsure get a pro in...


Food for thought...


Cheers


PS Do you have a note of what your heat curve settings are?

Sorry but I don't , it could be anything as to what it was set at by the housing association. I mean the book says factory defaults hot water is 50c , recommended temp is 55c hot water. Had a housing association dude out today apparently, and said a fuse had gone and has replaced it. I notice the wila pumps are now off when it's not set to heat up . I can work my way round the manual but I think I'm better off leaving it as he has said to my other half to leave it at 3-5am and 3-5pm ( I changed it again for an extra hour because IT DOESNT GET HOT!) . I'll be calling them again I think by tomorrow eve to put a call through for another repair and il just say "I told you so" I had a look at dip switch 2-2 this morning, it's set at speed priority rather than cop. I use the immersion due to the ecodan not heating the water enough

Cardew

zeupater wrote: »

Hi


If your heating requirement is >60MWh.t/year then it would need to be a mighty big system - 2x15kW ? ... I only base this on a 15kW system running 24x7 at max performance for the 6 heat provision months would only provide (15x24x180/1000) ~65MWh.t, which would provide enough heat on an average basis, but leave little leeway to provide sufficient heat in the colder months ...



HTH
Z

However no ASHP will output 15kW under all conditions!