ASHP efficiency report 600%

[saveasteading]

Our Highland project has had the phase  2 underfloor heating (UFH) running for about 6 weeks  now. Only the UFH, set for indoor temperature of 16C  because work continues, and no hot water yet.

So that is probably optimum.

The plumber says it is averaging 600% efficiency.

This is obviously very pleasing,  but it seems to exceed the Vaillant  published expectations.

 

Is this level possible? Especially given that the first week included driving off water from the screed.

Over the time, the average outside temperature has been about 5C we would estimate.

[JohnMo]

I would be sceptical especially if it exceeds what the manufacture states.

 

But saying that if you are only flowing a temp of say 30 or less, most of the time with a target of 16 for the house, the heat pump will not have much work to do.  The days have been sunny also (now and then) so if you are getting some solar gain also, the circulation pump is possibly on and the ASHP compressor doing no additional work. But the heat pump recording something going on. Its a good indication that things are working as they should.

[saveasteading]

9 minutes ago, JohnMo said:

the ASHP compressor doing no additional work

Yes, this makes me realise that I know next to nothing about how the efficiency is measured.

I assumed that the energy going along the hot feed pipe is measured...somehow, and divided into  with the power used for the heat pump to create it  =6.

 

Negligible solar gain btw. The big outer  windows face  north and east, and the courtyard windows facing south won't see the sun for a few weeks yet.

 

The plasterboard jointers have been very happy though.

[S2D2]

Arotherm plus? They're known for outperforming the datasheets when installed well. You're a bit above the crowd at https://heatpumpmonitor.org/ but it depends if your plumber was just rounding up and you will be running at a lower flow temp etc.

[SteamyTea]

13 hours ago, saveasteading said:

Yes, this makes me realise that I know next to nothing about how the efficiency is measured.

This can be a bit confusing.

 

Method 1.

 

Energy Out / Energy In times 100

 

5kWh [out] / 1 kWh [in] x 100 = 500%

 

Energy Out plus Energy In / Energy In

 

(5 kWh + 1 kWh / 1 kWh) x 100 = 600%

 

It comes down to where the energy in is actually put in i.e. inside the building or outside the building.

Taking that a step further, if there are thermal losses (and there is) from the outside unit, but the thermal metering is is done within the the unit, but the electrical metering is done at the consumer unit, then the CoP can look better than the delivered performance.

I have no idea if there is an agreed standard/method for measuring CoP, I am sure there is as BSI seem to cover just about everything.

[saveasteading]

Energy used for the heat pump is electricity, through some inbuilt submeter? 

Power out is heat (energy) within the liquid exiting the ashp as compared to the heat (energy) when it entered it?

Any idea how that is calculated? Perhaps just iterated from the temperature difference and flow rate within a known mechanism?

 

Of course we're very happy with the result, and it's a great demonstration of the efficiency of ' low and slow'.

 

 

[billt]

9 minutes ago, saveasteading said:

Power out is heat (energy) within the liquid exiting the ashp as compared to the heat (energy) when it entered it?

Any idea how that is calculated? Perhaps just iterated from the temperature difference and flow rate within a known mechanism?

 

 

Exactly. Measure the leaving water temperature, the return water temperature and the flow rate and you can work out the heat that the heat pump is producing. To raise 1m3 of water by 5C (typical rates for a small heat pump) needs 5.8kWh.

 

I'm not sure that the CoP provided by the internal Vaillant meters is accurate, they seem to sometimes generate very optimistic readings, but 600% with a low flow temperature isn't impossible. My Samsung can get over 5.5 at times, and that isn't as good as the Arotherm plus.

[S2D2]

15 minutes ago, saveasteading said:

Energy used for the heat pump is electricity, through some inbuilt submeter? 

Power out is heat (energy) within the liquid exiting the ashp as compared to the heat (energy) when it entered it?

Any idea how that is calculated? Perhaps just iterated from the temperature difference and flow rate within a known mechanism?

 

Of course we're very happy with the result, and it's a great demonstration of the efficiency of ' low and slow'.

 

 

Yes, Vaillant I think use a MID approved electricity meter but the MID approved heat meters are very expensive so they use cheaper sensors to calculate flow rate and flow/return temp. Generally regarded as accurate enough, some other manufacturers have been shown to be way off.

[joe90]

27 minutes ago, saveasteading said:

Of course we're very happy with the result, and it's a great demonstration of the efficiency of ' low and slow'.

Despite “figures” this Is a good outcome and just shows what can be done, well done 👍

[markocosic]

Absolutely possible given that you're heading to a very low temperature.

 

Enjoy an installation that will perform well.

 

Bloody heat pumps never work blah blah etc. 🙂