I am trying to decide on whether to change from oil to an ASHP system for central heating and water. At present I am using a combi oil boiler which is 14 years old. We live in the S.W. in a 5 bedroomed house which is technically mid terraced. The hose is mainly pre 19th century with a few modern bits. We are as well insulated as we can be.
My cocerns are whether the system will heat the house well enough even though we do not have the heating set to high temperatures. Any info I have, and from discussions with the firm giving a quote, the figures are all based on Sweden or northern climates. Will the difference between outside temperature and house temperature be enough to generate the energy for our hating. Also the water temperature figures range from 35-45c therefore requiring an alteranative way to boost the water temperature if needed.
Has anyone fitted such a system to an 'old' radiator system in the S.W.?

I do mean ASHP. We do not have mains gas in the area. Our alternatives to oil are LPG,total electric or some form of wood e.g. pellets.

Thanks for your input. I look forward to your future comments.

I have the 11.5KW from this site
http://www.wharfplumbing.co.uk/air_source_heat_pump.htm

imison: if you already have a heating circuit in place, £12,000 seems very high to me.

The ASHP I mentioned above only cost me £1200 and all it required was for it to be tapped into the existing heating circuit, and a mains supply fed from the fuse board to the unit. Less than a mornings work. Any competent plumber can do it. If you allowed even one day for installation at plumbers rates, the total cost should be well under £2000 including additional pipework etc.

Maybe the £12000 you were quoted was for a complete system?

With regard to noise, these are normally installed outside (although mine is in an outhouse next to my existing oil boiler) and the noise level I find more than acceptable. The compressor is the noisy part and it is similar to the noise from an air conditioning unit seen on many commercial buildings, or large commercial fridge/freezers when they kick in.

imison:

I see that the unit you are referring to has a built in water tank and is more complex than the average ASHP (such as the one I have - http://www.wharfplumbing.co.uk/air_source_heat_pump.htm) and as such is more complex to install.
I could never justify those sort of costs, having spent money on upgrading insulation as a preference.

I have not had it running long enough to check costs.

However I decided it would be cheaper than the current oil boiler which is costing us over £1500 a year at current oil prices.

The ASHP is an 11.5KW and the power used is 2.5KW when heating. That means that if it runs for 10 hours a day for 365 days per year it will use 9125KW per year which at 11p per KW is £1003.

However the running time per day will be less than that (particularly as the house will be well insulated) and it won't be on 365 days per year, so I estimate it will cost probably around half that - which is a lot cheaper than oil (we have no gas).

The supplier has one in his house and over last winter he monitored the cost at around £250 compared to his estimate for oil of over £700 at 50p/ltr - and oil is a lot more than that now.

However the one you mention appears to be a 10.8kw unit with a lower COP at 2.7 which means the power consumption is going to be around 4KW (and correct me if I am wrong, but appears to be 400V supply) so will probably be more expensive to run - but I'm not sure.

Hi, ASHP is not really my area, but I had a look at the 11.5kw unit you mention. The 11.5 Kw is with an air temp of 20deg, at 7deg the power is 8kw, 0deg 6 Kw and at -5 its 5 Kw. There is some difference in the power input but effectively 2.5Kw so you can see the CoP reducing.

Have you monitored performance at these different temperatures? Maybe at night (cooler) but more heat required.

How does it give the reduced power – lower output temp for fixed vol flowrate or same output temp of 55deg but reduce flowrate. It looks like the later as the spec mentions start stop water temp.

Did you consider running this at night / early morning on E7? Roughly you need about 2-3 Kw hr in the night time / early morning to cover the increased cost of daytime elec. So running this at 2.5 Kw from 5am to 7am would give a cheap boost to the house.

Cheers, Mike up North

<blockquote><cite>Posted By: Mike (Up North)</cite>Hi, ASHP is not really my area, but I had a look at the 11.5kw unit you mention. The 11.5 Kw is with an air temp of 20deg, at 7deg the power is 8kw, 0deg 6 Kw and at -5 its 5 Kw. There is some difference in the power input but effectively 2.5Kw so you can see the CoP reducing.

Have you monitored performance at these different temperatures? Maybe at night (cooler) but more heat required.

How does it give the reduced power – lower output temp for fixed vol flowrate or same output temp of 55deg but reduce flowrate. It looks like the later as the spec mentions start stop water temp.

Did you consider running this at night / early morning on E7? Roughly you need about 2-3 Kw hr in the night time / early morning to cover the increased cost of daytime elec. So running this at 2.5 Kw from 5am to 7am would give a cheap boost to the house.

Cheers, Mike up North</blockquote>

At present I have not run the unit fully as I am still working on modifications to the heating system - so I have not been to do very much by way of testing.
I can't answer the question about the reduced power - not something I had considered, but will investigate further.

As far as E7 is concerned, I calculated that on current electricity usage (approx 10000 units pa excluding the ASHP), to break even on the extra cost of daytime units I would need to be able to use over 40% of our current electric to break even - which is not really practical.
Adding in the anticipated usage of the ASHP, I estimate it would still be cheaper to change electric supplier to British Gas (Energy 5 tariff - no E7 time restriction for usage) who currently would be around £200 -£300 per year cheaper than our current supplier (EDF) on E7 with 50% of all the electric being used off peak.

Does anyone have an update on their installation - problems, costs etc. Particularly interested in PEWE's experience with his unit from Wharf Plumbing. Does anyone else have a unit from them ?

Dear Langst and everyone else following this one.

We have one fitted to an existing radiator system ,15 rads 20 KW system baxi combi disconnected.

We offer the wharf pump on our system and mike up north is correct. It is running at 12kw at 20 degrees and 8 at 7. The pump we also have which is platinum has been tested at 7 degrees not 20 and is a true 11.9 Kw example. It directly replaces oil.lpg and gas.

210 stainless steel Cylinder (25 year manufacturers warranty) and controls (2 years warranty parts ) starts £3500 + VAT.

We also have 250 and 300 cylinders.

You can source the pump or we provide totally up to customer.

The platinum ASHP which are true 12KW at 7 degrees with built in buffer tank start £2500 + VAT
The platinum ASHP at 13.5KW with built in buffer tank is £4500 + VAT

We also have a electronics panel that allows us to build a back up into the system, ie electric boiler, immersion or even using your existing after a survey.

This means that you can have a back up if the temperatures fall as low as 5 withthe wharf ashp or -2 for the platinum one.

Any questions please fire them back probably said to much anyway. E-mail if you want info on my name above. If you type in Enair-G-Flow in google you will have a link to some small adds but brochures have not been produced. It is not readily available from merchants yet as packages still being put together for various different companies.

ps the system can be fitted to rads or ufh. temperature to rad have gone up to 52 degrees but it all depends on the outdoor temps. This system is hot water and heating.

Are you also aware that VAT is only charged at 5% for fitting. Materials are 15%

My personnal use of the wharf pump on the system is ok but it is a cheap machine and you get what you pay for. The compressor is stainless steel and the fluid is the 410 which has benefits. The casing is ok but what we have found is that the total draw on electric when the compressor fires up is a maximum of 16 amps so the 13 amp plug is ok but would recommend connecting to consumer unit. But that is where we were testing we had a live feed runnning back from it which had to be rectified. They only have 1 year parts warranty from wharf but from us you get 2 and you have to get the sensor in the correct place to prevent the compressor overheating E03 as this can happen if it is on a lot and sensor in wrong place. The lifetime of the ashp is about 10 years but if maintained yearly would last a lot longer. The platinum pump we offer has a 5 years parts and labour guarantee and has a 48 hour direct replacements anywhere in the UK 72 hours to other places (channel islands etc)

Mark