On 01/10/2020 20:22, alan_m wrote:
On 01/10/2020 20:08, rick wrote:
On 01/10/2020 19:40, alan_m wrote:
On 01/10/2020 18:23, Andy Burns wrote:

Â*From my back of envelope previous investigations, an air sourced
pump can give 3kW thermal energy for every 1kW of electricity but as
the outside temperature falls to 0C this efficiency also drops to
more like 2KW thermal per 1KW.


This is backed up by very good article by Prof at Cardiff University
...... air to air heatpumps great in a bar or club where loads of
people giving off heat

Is this for cooling the building rather than heating during the winter?


For heating

On 01/10/2020 20:22, alan_m wrote:

This is backed up by very good article by Prof at Cardiff University
...... air to air heatpumps great in a bar or club where loads of
people giving off heat

Is this for cooling the building rather than heating during the winter?


for heating, though they can be run in reverse.

On 02/10/2020 10:39, Dave Liquorice wrote:
On Fri, 2 Oct 2020 10:13:17 +0100, The Natural Philosopher wrote:

in merely cool weather a heat pump can achieve a 4:1 uplift which puts
it at about 5p/KWh.

That's comparable in my case with oil at 50p/liter.

Not bought oil or looked at prices recently? Around 30p/litre these
days. (32.37 + VAT on 18th March...) Pre Covid 'twas around 50p/l.

And remember in the depths of winter even a 5KW heat pump at 2:1 uplift
may not be enough...

10 kW certainly wouldn't be enough here. Retrofitting a heatpump
system to and old property and greatly upping radiator sizes to get
enough output from them at 40 to 50 C strikes me as fraught with
problems. It certainly won't respond quickly to a cold snap.
Underfloor at least stands a chnace with a big thermal mass and
surface area to store and release heat at hopefully a decent rate.



I have Underfloor heating and I did consider a Heat Pump ..... but
Timber Frame manufacturer advised of well known Heat Pump based system
was in one of his house ..... the occupants were freezing, heat pump
could not get house warm.
Solution was a Propane powered space heater .... blasting in hot air,
once house was warm then heat pump could keep it that way.

I decided not to use a Heat Pump based system

I'll wait maybe Combined Heat & Power units are the way forward.

rick wrote:

Timber Frame manufacturer advised of well known Heat Pump based system was in one of his house
heat pump could not get house warm.

implying the pump and/or ground array were undersized* ... what did the
well known manufacturer have to say about that?
[*] I suppose the level of insulation as-built might not have met the
levels specified when the gshp was sized?

In message , Andy Burns
writes
rick wrote:

Timber Frame manufacturer advised of well known Heat Pump based
system was in one of his house
heat pump could not get house warm.

implying the pump and/or ground array were undersized* ... what did the
well known manufacturer have to say about that?

I believe the *slinky* pipe system can suffer from dry soils leading to
poor thermal transfer.
If my house was closer, I'd be tempted to quietly put a thermal
collector in the river:-) Nice and warm output from Luton sewage
treatment and much warmer than subsurface water.

[*] I suppose the level of insulation as-built might not have met the
levels specified when the gshp was sized?

--
Tim Lamb