I understand that this indicates the ASHP is carrying out a 'freeze stat' operation and is perfectly normal, if annoying.
Not quite Right Morgan… the freeze stat function monitors system internal water temperature and activates the circulation pump to ensure the outside water is replaced with internal water temps and furthermore to reheat the water using the compressor when it drops below 20c. This is only reheated to a safe store temperature when the outdoor ambient temp drops below the selected activation temperature. This is to ensure the water doesn’t freeze and there is also sufficient heat to handle a defrost if one was needed.
It’s the defrost process itself which usually shows the flow temp dropping below the return temp for a few minutes because the compressor isn’t producing heat during the defrost. (The flow temperature water is chilled by the defrost process.)
Having said that the above graph doesn’t look like it’s defrosted at all. In fact the report readout states 0% Defrost energy.
So my best guess is that the flow temperature doesn’t really drop below the return temp. And this is a graphic anomaly. In other words, the apparent lower flow temperature line representation in this particular 24 hour report is a little distorted by the granular scale of the graph lines and the nature of cramming a lot of minute data into a 24 hour timeline.
The best way to see in graph form, the visual representation of the defrost is on a one hour scaled graph on MELCloud. Unless Melpump can also do a 1 hour scaled graph……? I haven’t seen all of melpump settings so there may be a way to do a one hour graph.
This post was modified 3 hours ago 2 times by SUNandAIR
Is there any negatives to running such low outflow temps? Also during summer months is it better to leave the temperature compensation curve on or turn the heating off?
Just wondering if it's better for the pump to continue to work through the summer, sometimes things like this don't like being turned off and are better just left to run.
@patch I think @ashp-bobba gave you some great pointers about low temperature operation. While it is more efficient to operate at lower flow temperatures there are other factors at work when flow temperatures are as low as 20c as this is also within the fixed control of the freeze stat function. Having said that it is illogical that you would be entering the freeze stat function zone with an ambient of 12c so there may be other issues which may restrict things when as low as 20c flow.
How did you arrive at a WCCURVE low end of 21c? What size HP and emitters do you have and is it the R290 model OR THE R32 model since the major limiting factor at warmer ambients and low output is minimum output of the HP. They have different minimum outputs.
On the face of it you are having only one cycle every hour at a flow rate of 30c which is very encouraging…. but I dont know much else about your overall installation.
Hope that helps
This post was modified 59 minutes ago by SUNandAIR
This post was modified 55 minutes ago by SUNandAIR
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