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

albyota

richardc1983 wrote: »

Good to hear you are happy with the system... any chance of you taking some pictures for us to see?

What flow temperature are you using, you need to have a lower flow temp to avoid the backup electrical heater coming on.

richardc1983, there is NO electric backup heater with this system, there is an immersion heater element in the cylinder as standard, and this only needs to come on once a week for an hour or so for thermal disinfection.

richardc1983

Andy_WSM wrote: »

Hi Rhubarbe,

Like Richard, I would also be interested in seeing some pics - If you don't have webspace to post them up then you could email them to me (PM me for email address) and i'll post them up for you.

I'd also be interested in hearing more about the system. Operating temperatures, install cost & running costs going forward.

I have a cheap & cheerful heat pump (Trianco) at the moment, which is doing the job, but I am looking to install a somewhat better system going forward (like the Ecodan).

I seem to be having a problem with my lg units at the moment, one of them does not like to operate the timer function. If I set it to come on at say 10am the flap will open into the angle of cooling mode but not heating mode. However if I reset the power and try again the timer function works fine. Very odd seems like there may be a glitch in the system!

rhubarbe

Yes, I will do. I am at work today so it'll have to be later on.

Flow temperature. Don't know yet. Installers still there today tidying up. Will hopefully get a pile of paperwork to enable me to answer that one.

paceinternet

rhubarbe, very interested to know what they have specified it to do.
According to the 8.5kw owner manual:
Heating A7/W35
Capacity 9.0kw
COP 3.85
Power input 2.34kw

Heating A2/W35
Capacity 8.5kw
COP 2.95
Power input 2.88kw

But then it has "varying factors".
So for ambient deg C temperatures with inlet/outlet water temperatures:
degC, 30/35, 40/45, 50/55
it shows:
-15, 1.77,1.41, ?
-10, ?, ?, 1.37
-7, 2.41,1.89,1.46
2, 2.97, 2.27, 1.81
7, 3.96, 3.05, 2.28

So at 2 deg C ambient temperature, for 2.88 kw input, you would get 8.5 kw output if your water flow temperature was 30 in and 35 out.
Your radiators will be giving very low kw out at 35 deg C, probably 30% of their rated output, but check your individual models to confirm this.
If you increase the flow temperature to 50/55 inlet/outlet, you will improve the radiator output to about 50% of their rated kw, but the Ecodan efficiency will change from a COP of 2.97 to 1.81. Meaning if it runs with the same 2.88 kw input, you will get 5.2 kw output.
They do not make this clear in the docs as to exactly how much the output is reduced, but take it down to -10 at 50/55 and use 1.37, you will get less than 4kw.
You need to be running at that 30/35 flow temperature to be in with a chance of heating a house in winter. Unless it is a small incredibly well insulated property.
I hope albyota can add to this, and rhubarbe can tell us what the installer expects to achieve.

Cardew

As Pace above indicates, it is one thing for 'rhubarbe' to have nice warm radiators(50/55C) in late April but in mid winter the system just won't cope.

As mentioned previously, the advantage of a conventional CH system with water flowing through the radiators at 80+ C is that if you are out at work all day, you can time the CH to come on, say, 20 minutes before you return and are welcomed by a warm house.

With ASHP heated water at 35/40C you really need to have the heating on all day.

apoorman

Soon, you will be able to have it running 24/7, heating an empty home, and everyone else will subsidise your electricity bill! So look forward to the RHI!

rhubarbe

With the introduction of the RHI Feed in Tariff next April I am expecting an electricity cost of zero for leaving it on all day. And if it does cost a tad, I don't expect it'll approach the £1 an hour that the old LPG boiler was costing to run.

The ASHP has cost about £800 more than installing a new bunded oil tank and new oil boiler (including the RHI grant of £900). And there ain't no FIT for 28sec heating oil.

I have electric underfloor for bivalency on the very coldest days that we don't get in many of our recent winters, so am expecting no problems keeping warm.

As a final point, the house is not empty all day. My very aged mother lives in it, too.

apoorman

Yes, an amazing opportunity for some, cash in if you can & it sounds ideal for you even if the RHI does not go ahead, it still stacks up versus LPG. Was it installed by a certified installer? this is required for getting any RHI.
My point was, the RHI distorts the playing field. HP's dont stack up against mains gas in a level market... in my opinion... you lose the flexibility.

rhubarbe

Oh yes. The installer is Ecodan Approved and MCI Accredited. Had we mains gas then I should never have started down this route.

150 litres of hot water this morning (and it was very cold last night) took just 20 minutes.

Sure, the RHI distorts the playing field but if HMG lets itself be talked into accepting Euro Quotas for co2 reduction and it has to achieve them somehow. Clever HMG makes the suppliers of conventional fuels pay for the RHI so it costs them nothing but another stealth tax.

I appreciate that it penalises those without the capital but we're not rich, we had to borrow some money to buy our HP, but then again, we'd have had to do so to buy a new oil boiler and bunded tank.

paceinternet

rhubarbe, going forward, how about some daily electricity meter readings to give the readers some idea of real costs?