@cathoderay yes there is an indication of quite a bit of recovery energy being used. Do you have any way of quantifying numerically the energy being used?
@robs - I was also looking at @robs graph….. please forgive my limited knowledge of these graphs, but the recovery graph shows several additional portions of energy if I’m reading it correctly.there also looks like an increased heat output for a period after the defrost which isn’t noticeably visible in the energy line… presumably it does mean more energy being used to make up for the loss of heating during the defrost? Just wondering if there’s any way of getting a value for all these aggregated energy extras? Possibly @robs might have some way of pulling them together. Also
This might obviously be a naive question, so apologies if it is… my only experience is the limitations of MELCloud.
That’s an interesting stat. I’m thinking that the 0.1 KWh might be the energy used during the flow reversal process….? I’m also thinking that the real energy which provides the heat for the defrost isn’t recorded during the defrost because it is the hot water which is already created and stored in the radiator circuit. Is it possible that the 0.1kw you refer to plus the 1 kWh water heat to provide the defrost was created at a cop of circa 3.8 and would result in the total energy for the defrost?
Yes the bulk of the energy comes from the already heated water, you can see that as the yellow area above the blue dashed line in the image below:
But as already mentioned, the energy in (electricity) to achieve this is approximately the same as the energy saved during the defrost (as the compressor isn't using as much electricity during the defrost).
So one thing puzzles me, given such good insulation and draft proofing, why do you need flow temperatures of 38-40C? Are you radiators (IIRC you have fancoils?) very small and low power output? Because with larger radiators or UFH you could be running flow temperatures 5-10C lower.
Yes you’re quite right I’ve worked out we should have at least 3 more radiators to give us enough output to operate at a lower flow temperature. This is a legacy issue from the original design. The extra volume would also allow us to operate at higher ambient temperatures without cycling….
Thank you for your comments they are very helpful regarding the effects of thermal insulation and heat retention. Regarding drafts we are about half way… Our house is old and we are still working on a few leaky doors and an old thin walled fireplace but it is all being addressed one step at a time.
Ah, puzzle solved! I'm sure you'll enjoy lower flow temperatures and greater efficiency once these changes have been made.
@cathoderay yes there is an indication of quite a bit of recovery energy being used. Do you have any way of quantifying numerically the energy being used?
@robs - I was also looking at @robs graph….. please forgive my limited knowledge of these graphs, but the recovery graph shows several additional portions of energy if I’m reading it correctly.there also looks like an increased heat output for a period after the defrost which isn’t noticeably visible in the energy line… presumably it does mean more energy being used to make up for the loss of heating during the defrost? Just wondering if there’s any way of getting a value for all these aggregated energy extras? Possibly @robs might have some way of pulling them together. Also
This might obviously be a naive question, so apologies if it is… my only experience is the limitations of MELCloud.
I hope the annotated image and description below helps describe what is happening.
A) Output falling due to evaporator starting to frost/ice up.
B) Compressor and water pump running to defrost evaporator, note the negative heat is shown as the yellow area below (from B to C).
C) Compressor starts heating again, heat output not immediately seen due to lag caused by distance from heat pump outside and plant room inside that has the flow/temperature monitors.
D) Duration of extra heat pump input (and hence output) post defrost.
E) Input back to pre-defrost but boost in flow temp during D results in additional "free" heat output (due to thermal lag of the system).
Do you have any way of quantifying numerically the energy being used?
Yes, by calculating it manually from the minute data, which doesn't happen automatically as it does for hourly data. It's in the manually calculated minute data energy in values that you see the negative flow, ie the energy in is flowing the wrong way (from house to heat pump). I'll do a sample, probably later today, for a period covered in the chart.
But as already mentioned, the energy in (electricity) to achieve this is approximately the same as the energy saved during the defrost (as the compressor isn't using as much electricity during the defrost).
I agree, that is what I was also getting at when I waffled my way through this:
"I dare say the extra amps in during the bulges approximate to the amps in saved during the defrost trough, meaning the defrost has little overall effect on the energy in over time"
Midea 14kW (for now...) ASHP heating both building and DHW
