I was thinking yesterday of what happens when my mums central heating
boiler
packs up. Must be getting on for 30 years old. Recently serviced but
the gas fire on the front of the boiler is likely to pack up before
that. Anyway.

I was thinking of a heat pump. Not a ground source one but air source.
I notice that there are a number for sale on ebay.
Basically an air conditioner in reverse but heats a heat exchanger and
pumps
around the normal radiators and hot water tank. So swapping over would
be straightforward.

Anyone out there had any experience of one of these.

The listing on ebay quotes 1.7kw energy for the pump that is the
equivalent of 7.3kw
for the "boiler".

Guy says that although this is lower than a normal boiler the idea is
to leave it on all the time. Heats his house with it.

Anyone any experience of one of these? Or how to correctly size a unit
for a house.
Would running costs be cheaper than gas?

In article ,
" writes:

I was thinking yesterday of what happens when my mums central heating
boiler
packs up. Must be getting on for 30 years old. Recently serviced but
the gas fire on the front of the boiler is likely to pack up before
that. Anyway.

I was thinking of a heat pump. Not a ground source one but air source.
I notice that there are a number for sale on ebay.
Basically an air conditioner in reverse but heats a heat exchanger and
pumps
around the normal radiators and hot water tank. So swapping over would
be straightforward.

Anyone out there had any experience of one of these.

I have an air conditioner which also operates in reverse as
a heater, and I use that when I only want that one room heated.
The range of outdoor temperatures over which it works is quite
limited. In my case, it's unlikely I need any heating unless it's
below 14C outdoors as the house is quite well insulated. If it's
below 5C outdoors, the unit becomes progressively less effective
as condensation freezes on the outdoor unit and it keeps having
to switch over to defrost cycles (where basically, it's just using
energy to defrost the outside unit). I haven't tried it when it's
below freezing outside (as I'd have the central heating on at that
point), but it might be that condensation freezing up is less of
an issue when the air temperature is below freezing to start with.
The efficiency of the unit will be less with the wider temperature
differential indoors/outdoors though. So you need to find out if
the device will work well enough when it's really cold outside,
i.e. when you need it most.

The listing on ebay quotes 1.7kw energy for the pump that is the
equivalent of 7.3kw
for the "boiler".

I suspect that's also allowing for boiler inefficiency.
For this sort of sized unit, a 4:1 ratio (heat output verses power
used) is probably the best you should expect at something like 16C
outdoor temperature for an air based unit. I don't know what effect
using water exchanger on the inside part might have -- the water
return temperature is going to be much higher than air temperature,
so it might well be significantly less efficient. Having a radiator
system designed to operate at cooler condensing boiler temperature
would help I imagine.

Guy says that although this is lower than a normal boiler the idea is
to leave it on all the time. Heats his house with it.

Anyone any experience of one of these? Or how to correctly size a unit
for a house.
Would running costs be cheaper than gas?

BTW, the VAT on heat pump heating system is only 5%, if you find
a seller who is participating in the scheme. OTOH, I found that
when B&Q had a special offer on a couple of years ago, even though
they still charge 17.5% VAT as they aren't part of the scheme,
they were still cheaper than anywhere I could find that operated
the 5% VAT scheme.

You will also generally find anything related to aircon and heat
pump technology gets much cheaper if you buy in some other parts
of Europe. Even just going across the channel can help, but the
further south you go, the cheaper it gets. It's still treated as
a luxury premium price item in the UK, whereas it's a commodity
item in the warmer parts of Europe. If you are buying an expensive
system, it may well be worth a trip to pick it up cheaper.

There are units designed for DIY install (self-sealing plug-in
connectors), and units which require professional install with
vacuum pump and soldering/brazing skills.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]