sorry if this has been covered before. looking at various heatpumps on heatpumpmonitor.org it would seem standard that heat meters only work in one direction - i.e measure heat going into the house - however when defrosting the heatpump - heat is taken out of the heating circuit as shown by the flo…

Might have answered my own question - looking at the detail view on the heatpump app it looks like it does measure negative values - since the range can go negative - but it is not displayed on the graph - so maybe the calculation underlying is correct??

A good question. Most heat meters are configured for heating only and while they output heat power as a positive or negative (cooling) value their energy register usually only accumulates the heating component. It is possible to calculate a heating and cooling cumulative energy value by using the ‘…

Thanks Trystan, that’s very clear. I don’t have a heat meter - I am using a carefully calibrated delta T multiplied by a magic number that represents both flow rate and heat capacity of the glycol/water mix - in my system I believe the flow rate is reasonably constant as I have a low loss header a…

here is my accumulated heat graph - as you can see the heat output does not go negative during defrost - I will change that. [image]

I have an Ecodan with a MMSP compliant and calibrated heat meter provided by the manufacturer. Looking at the minute-by-minute energy report downloaded from MELCloud I can confirm that it does indeed only count up and never reports negative energy. However, for RHI payments, OFGEM take the defrosts…

Not sure what the accuracy of these heat meters is - but 3% sounds like it would be likely within the measuring tolerance anyway.

Heat meters are first and foremost a fiscal device. Contracts are concluded based on gross heating / gross cooling; so the cumulative registers for heat / cool can ONLY go up. Likewise elecrticity meters. The cumulative registers for import / export can ONLY go up. Heat meters with dual registers…

Interesting discussion. I implemented a live daily meter for the ecodan (esp32) and output negative when defrosting. Also tried to estimate these, and it cost around 0,4kWh per defrost on my system. On bad days you can easily get 30 defrost and that adds up. When I compare my calculated totals with …

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COP calculation during defrost cycle

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