Friends, I would like to know what happens to heat meter readings during a de-icing cycle.
In my understanding, during this cycle, water circulates around the house either (a) in the opposite direction or (b) with the flow temperature being lower than the return temperature.
In these circumstances a heat flux meter should read negatively - heat is being drawn from the house - and the total kWh of heating delivered should count down instead of up. But this is not what I observe.
So please if my expectation is wrong, could somebody please explain what I should be expecting? Thank you: M
The water always circulates round the house in the same direction, but during a true defrost cycle the refrigerant direction in the Outdoor Unit reverses, so during one you will see LWT becoming less than RWT for a few minutes, and some heat is removed from the house. Any heat meter installed in your water circuit should thus see negative heat flow during this period.
I emphasis “true” because there may also be a frost prevention cycle which doesn’t affect the Outdoor Unit - it just circulates your water for a few minutes if the latter hasn’t been running for a while.
During de-frost cycles I only see either zero or positive readings - i.e. the Sontex meter only seems to increment and never decrement. Curious: Thank you.
On the logging system I have (Passiv Systems MMSP) every 2 minutes they record a single meter reading. So the data is just a succession of meter readings which appears to be just cumulative kWh of heat delivered. This number only ever increases. To calculate heating power I have to divide the delivered heat by the appropriate time interval.
Do you think this could be a hidden setting on the heat meter? Or do you think Passive systems might just ignore cumulative values which show a decrement?
I have a Sontex heat meter feeding pulses into the heat pump for MMSP reporting, and it only reports positive heat output, so none of the defrosts. Seems to be a limitation of how the heat meter is being read.
I think the only way to get the negative heat is to connect to the heat meter directly (via modbus?), and get the data that way.
My Sontex 789 manual states that it will measure heating or cooling duties, but I haven’t actually watched the meter display during a defrost (these are very rare on my Samsung HTP - maybe a handful each winter). But my meter isn’t connected to anything, so could your observation be related to the logging system rather than the meter itself?
I log the reading of an internal counter which records cumulative heat production. The file looks like teh first two columns of data below. I then work out heat flow using by dividing the incremental heat delivered by the time between readings - the third column below.
I was actually replying to @Timbones (see the top right corner of my post), who only counts pulses.
Indeed it does, but are you saying that from 00:21 to 00:25 it might have been or was de-icing? If so, clearly your heat meter ignores reverse flow, and there’s little you can do about it given only that information. Electricity meters will often have two registers - one for each direction. Is it possible that your heat meter is the same?
I think either of these
could be right – in which case, how do you get the numbers; or neither could be right, and you simply cannot get the information you need.
The “cumulative heat” register on a heat meter will ONLY count heating. A pulse output meter that is a “heat meter” will ONLY give pulses for cumulative (heating) energy. Defrost “cooling” will not be decremented in either case.
Some meters have independent cumulative energy integrations for heating and cooling. You get two registers here of “gross” heat and “gross” cool.
Open energy monitor, for a heat meter with an mbus output, ignores the internal “integrations” and does “cloud level” integrations instead based on the instantaneous temperatures/flow rate.
Therefore all meters (that report the instantaneous temperatures/flow rate) effectively become heating/cooling type meters.
