It will be good then to see some plots tomorrow morning to compare!
I'm beginning to wonder from your description if it's delaying starting defrost a bit too late. I have no idea why that may be, I don't know how heat pumps decide it's time to defrost. I guess it's a sensor and of course sensors can get dislodged etc.
Ps. According to duck.ai Hitachi heat pumps use oat and refrigerant pressure to determine whether a defrost is necessary. Not sure if this can be trusted but a more general search suggests it quite possibly can.
This post was modified 1 month ago 2 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
2024 build bungalow
Southern england 179 m2 High level of insulation Underfloor heating All 12 circuits are fully open all the time 1 thermostat in family room 7KW heat pump 50 litre buffer tank (4 port)
3.6KW solar panels Energy used by heating 2527 KWh - 7527 KWh (SCOP 3.5 approx)
Thats a bit suspicious. Some (older?) heat pumps apparently defrost on a timed cycle rather than on demand. I wonder if these are in that category (which might explain why you have to tell it what type of climate you have is).
@trebor12345did you manage to get any overnight plots?
2024 build bungalow
Southern england 179 m2 High level of insulation Underfloor heating All 12 circuits are fully open all the time 1 thermostat in family room 7KW heat pump 50 litre buffer tank (4 port)
3.6KW solar panels Energy used by heating 2527 KWh - 7527 KWh (SCOP 3.5 approx)
I am seeing just prior to the defrost, an evaporator of -25C. At this temperature the heat pump is really iced up and I believe the ice is touching the fan. The heat pump in this iced condition does make a rattling noise.
The defrost occurs every 45 minutes and the defrost does clear the evaporator of ice.
Something odd about this diagram; the refrigerant is moving in the wrong direction for defrost - warm refrigerant from the compressor should be heading for the evaporator (at least thats how I understand defrost). Perhaps they dont represent it properly on the diagram when its in defrost mode, in which case spending too much time worrying about it may be a mistake
What did the heating do overnight without night shift, how did that affect defrosts?
@sim0n0 I feel (almost!) left out; one defrost in the last seven days with my Daikin EDL08 monobloc. 😉 Toodles.
My Vaillant was defrosting every 45-60mins overnight (chart shows FT). As you can see it doesnt fully recover from the defrosts because noise reduction mode is set from 11pm-71m, and struggled particularly to recover from the deep defrost following the DHW cycle. As a result IAT fell 1C overnight, but is now recovering again. Some would of course program this behaviour deliberately and call it 'setback'.
This post was modified 1 month ago 2 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
I am seeing just prior to the defrost, an evaporator of -25C. At this temperature the heat pump is really iced up and I believe the ice is touching the fan. The heat pump in this iced condition does make a rattling noise.
The defrost occurs every 45 minutes and the defrost does clear the evaporator of ice.
Something odd about this diagram; the refrigerant is moving in the wrong direction for defrost - warm refrigerant from the compressor should be heading for the evaporator (at least thats how I understand defrost). Perhaps they dont represent it properly on the diagram when its in defrost mode, in which case spending too much time worrying about it may be a mistake
What did the heating do overnight without night shift, how did that affect defrosts?
I’ve noticed their graphics are a bit odd in places. I would ignore
I am seeing just prior to the defrost, an evaporator of -25C. At this temperature the heat pump is really iced up and I believe the ice is touching the fan. The heat pump in this iced condition does make a rattling noise.
The defrost occurs every 45 minutes and the defrost does clear the evaporator of ice.
Something odd about this diagram; the refrigerant is moving in the wrong direction for defrost - warm refrigerant from the compressor should be heading for the evaporator (at least thats how I understand defrost). Perhaps they dont represent it properly on the diagram when its in defrost mode, in which case spending too much time worrying about it may be a mistake
What did the heating do overnight without night shift, how did that affect defrosts?
I didn't run the heating over night. Only just now switched on.
All I can add on the defrost is that the refrigerant temperature does drop as it goes through the defrost cycle. The image was taken the moment the HP started the defrost cycle.
2024 build bungalow
Southern england 179 m2 High level of insulation Underfloor heating All 12 circuits are fully open all the time 1 thermostat in family room 7KW heat pump 50 litre buffer tank (4 port)
3.6KW solar panels Energy used by heating 2527 KWh - 7527 KWh (SCOP 3.5 approx)
My Vaillant was defrosting every 45-60mins overnight (chart shows FT). As you can see it doesnt fully recover from the defrosts because noise reduction mode is set from 11pm-71m, and struggled particularly to recover from the deep defrost following the DHW cycle. As a result IAT fell 1C overnight, but is now recovering again. Some would of course program this behaviour deliberately and call it 'setback'.
You can also see how the temperature rose during the evening as the OAT was falling. Also a deep defrost at midnight, prior to the DHW cycle, following the DHW cycle and then again at about 7am.
This post was modified 1 month ago 2 times by JamesPa
2024 build bungalow
Southern england 179 m2 High level of insulation Underfloor heating All 12 circuits are fully open all the time 1 thermostat in family room 7KW heat pump 50 litre buffer tank (4 port)
3.6KW solar panels Energy used by heating 2527 KWh - 7527 KWh (SCOP 3.5 approx)
