Whole home heating with air/air heat pumps FAQ

Heat pumps can be quite noisy I've found, but then I don't know how old the installations are. Most seem to be built by Mitsubishi. Brian

Yes well I tend to use a mixture of storage heaters and electric oil filled radiators that can heat up fast and seem quite economic. I also have one movable fan heater to use when I get tradespeople in who are seemingly all born in a field and leave doors open to the garden all the time. I don't like it too hot though, since its sends me to sleep! Brian

There was a report in the Financial Times on Wednesday that the government intends to shift its "green" surcharges from electricity to gas over the next few years. That will make a difference to the economics.

If you want to read the article and you are a FT subscriber, it's here:

If you are not a subscriber, do a Google News search on UK Electricity Surcharges and today it's the first article you find. Click through to read.

(For anybody who didn't already know, the FT paywall is designed to open up when you are brought to an FT article from a search engine.)

Nick

I was more wondering about the physics of the differences. I was considering the fact that the portable unit (I have one which is used maybe 3 days a year for cooling a room) when used as a heater has to vent the cold air and the amount of cold air exhausted is probably in direct proportion to the heating. This exhaust air has to be replaced with air infiltrating from the cold outside. I feel the induced air changes will be higher than what would normally occur.

With the split unit there is no loss of internal air and if the house is well sealed a whole house heat exchanger can mitigate heat losses due to air changes.

I was due to investigate heating a small house 700 metres asl in southern spain for a very close friend who had moved there. Heat pumps and bottled gas looked like the only options. It became moot as she died in August.

Reminds me of a gas "real coal" fire that was installed many years ago, very much against my advice. It threw so little heat into the room, and took so much air up the chimney, that I am convinced its overall heating effect was negative.

Chris

Gosport Handyman - Why didn?t we install an Air Source Heat Pump?

Yup, and that is one of the main design limitations of monoblock units. When trying to cool a room, they are normally having to throw air extracted from the place you are trying to heat or cool outside.

(You can hack some to use multiple ducts so they can draw their source air from outside)

ISTR that there was a time electrical supplies in some parts of spain vere very limited in capacity - which can make extensive use of heat pumps difficult. Not sure if that is still the case?

Apologies, I got the product mixed up. I was referring to this one, which is a monobloc with inlet and outlet ducts:

Still noisy though.

Theo

Yes that solves the massflow problem and cheaply, I suppose it needs two fans, one for the outdoor side and one to circulate heat inside.

Oddly its heating COP is lower than its cooling. That suggests that the thing is only able to vent the waste heat from the motor outside - even when in heating mode.

Pet rant: Why are some many sites unable to distinguish energy and power output? (A BTU is a measure of energy not power - if you want to equate them then you mean BTU/h for watts or BTU to Joules or kWh!)

Difficult to solve without an outside unit...

That sounds fair. If I were in that sort of property I might make the same decision, although you can do a lot of future proofing by fitting larger radiators and regular 22mm piping. I'm not sure of his dislike of unvented cylinders though, as many other people don't seem to have problems.

Theo

then follow the referrer link that google returns as #1 result

Gosforth!

Yup that was a bit odd...

When installed in suitable circumstances[1], the combination of high flow rates of mains pressure hot water at all outlets is hard to beat. Especially as they can be heated from multiple heat sources.

IME servicing them is trivial to DIY.

You are going to need one hell of a lot of insulation before the air source system can supply enough heat to make it comfortable to live in!

That is a little pessimistic. We had a house in Belgium with a ducted hot air system in addition to a wet central heating and it could cope with providing fast immediate heat and a low background heat OK.

It was noisy though if you wanted a lot of hot air in a hurry. Somehow it extracted heat from the back of the fireplace and also the wet CH.

I think the main thing is that air has such a very low thermal mass so you really can't transfer much heat that way. Heavily insulated homes might just stand a chance but conventional build forget it!