@derek-m this is from my estimated house heat loss based on room by room assessment @ 10 degrees. However these figures just don't represent real world for 24 hours. These are more per hour - and that makes more sense.

you say 4kwh of total heating - that's 166w per hour. Do you mean 4kw/h?

@batalto 

Yes, that would be 4kW per hour, based on your heat loss calculation of 8.774kW per hour at an ambient air temperature of -3C. The calculation I made is on a linear basis, though I suspect the heat loss may not be completely linear.

@derek-m based on 13 degrees ambient I should have needed (delivered heat) 92kw (3.85kw/hr) yesterday to maintain temperature. I used 54kw at an average ambient of 12. So my house is performing much better than I would have expected/budgeted for.

Posted by: @batalto

@derek-m based on 13 degrees ambient I should have needed (delivered heat) 92kw (3.85kw/hr) yesterday to maintain temperature. I used 54kw at an average ambient of 12. So my house is performing much better than I would have expected/budgeted for.

This is one of the problems with heat loss calculations, since to make an accurate assessment it is necessary to have the actual details of the materials used in the construction. Also products are manufactured within tolerances, so even then you cannot be 100% accurate.

The other thing is that the heat loss calculation takes no account of solar gain, human activity, wind chill and rain effect.

I also suspect, but have not found any data yet, that the variation in heat loss will not be linear with changes in ambient temperature, just as the output from radiators reduces more rapidly with a lower delta T between water temperature and indoor air temperature, I suspect that as the delta T between indoor temperature and outdoor temperature reduces with increasing ambient air temperature, that the reduction in heat loss is more rapid.

I'm afraid I have to go and obey, 'she who must be obeyed', AGAIN. Though I should be back shortly, if my 'rain dance' proves successful.

@derek-m by tracking your own power use vs ambient you'll be able to create your own heating curve. You could just use correlation - I'll see if I can knock up a graph

Posted by: @batalto

@derek-m trying to understand what 11kw means. If the house is 70m2 it seems a lot. I used 17kw yesterday to achieve the same results, but my house is 260m2 - so I am using 65w per m2 to heat my house to 21 when the ambient is 13 degrees.

It would be interesting to see others w/m2 of power use and it would provide a levelling which allows us to compare relative performance between houses.

Ours is about 160m2.  Detached bungalow.  

@kev-m looks like it's 68w/m2 (11,000w/160m2) then, basically the same as our detached house (which was a bungalow originally). So we have very comparable figures in relative terms

Posted by: @heacol

@kev-m Try to drop the temperature in the house to 19-20. It will significantly reduce the energy used and will have little impact on comfort, (hide the thermometer), It does appear, looking at the graphs, you may have a low flow problem which may be rectified if you replace the valves.

You don't know Mrs M.  She doesn't need a thermometer! I'll maybe try and see what happens...

Posted by: @heacol

@kev-m Try to drop the temperature in the house to 19-20. It will significantly reduce the energy used and will have little impact on comfort, (hide the thermometer), It does appear, looking at the graphs, you may have a low flow problem which may be rectified if you replace the valves.

Brendan,

this is part of last night. What I think is happening is that there isn't quite enough load to enable the ASHP to run constantly.  I assume it has a minimum.  After it gets up to temp, it modulates down and keeps going at that for an hour or so.  The flow temp is very steady. Then the flow temp starts to edge up, it can't turn down any more so it turns off and the flow temp drops. And then it will do the same again.  The curve is almost always like this except the steady bit has been a lot shorter previously. It was a bit colder last night though, around 8-9.  If I'm right, then when it really gets colder the cycling will stop.

Maybe ...

FYI where the energy trace says 20, it's consuming 1.2kW. 

@kev-m That may be Ok, Do you have the return temperature?

Posted by: @batalto

@derek-m by tracking your own power use vs ambient you'll be able to create your own heating curve. You could just use correlation - I'll see if I can knock up a graph

Hi Batalto,

It is highly useful that members such as yourself and Kev, Mark and Justin, can spend a little time and effort collecting and posting data on the forum.

It would definitely be useful, to try to quantify your heat loss at different ambient air temperatures and differing weather conditions, so that we can see what actually affects the indoor temperatures. Of particular use would be comparing one property against another, so that weaknesses in design or installation can be highlighted and resolved if possible.

As improvements in operation and efficiency are made on one system, it will be interesting to see if the same can be achieved on another system.