Did your installer fill out the 'Field settings table' located at the end of the heat pump manual and provide you with a copy?
When your system is operating in weather compensation mode, it should be possible to apply an offset that allows the whole curve to be moved up or down by up to 5C. Try increasing your thermostat (Honeywell) by 1C from 20C to 21C, and then use the weather compensation offset on your controller to lower the indoor temperature back down to 20C. In that way you will know the required water flow temperature at the present outdoor air temperature.
If the air temperature in your utility room is fairly representative of the temperature in your main living area, then you could consider setting your controller to operate in leaving water temperature modulation.
Domestic heating system (particularly heat pumps) respond very slowly when changes are made, so allow sufficient time for the system to settle before making further adjustments.
Field settings table - no it hasn't been filled in but I do have a commissioning sheet but no details of the settings used, just test results during the commissioning.
I can apply an offset to the curve, just using the up/down arrows on the main window, which then alters the required flow temperature. I did what you've described early and point noted about making further adjustments too soon.
The Utility rooms isn't very representative of the house unfortunately for this, it's on a shaded corner on the north side of the house.
The system still doesn't run continuously. When I've checked the sensor info I see inlet (to the heat pump) and leaving water temperature showing very similar figures with the refrigerant temperature dropped right down to around 16.5C. I've pasted a screenshot below but only shows as a thumbprint size on my screen.
I suspect that when the screenshot was taken that your heat pump was not actually running, since there should normally be a temperature difference (Delta T) of between 4C and 8C between the Inlet Water Temperature and the Leaving Water Temperature.
I think on your system, like many of the other modern ASHP's, it is actually possible to set the required Delta T, to help prevent frequent cycling of the compressor. It may be useful to check that this setting is not too small.
If you could go through the various settings within your system and make a record, it should be possible to identify any may need improvement.
Correct the heat pump wasn't running when the screenshot was taken but it should have been. Thermostat has been set at 22C since this afternoon now, the room temperature hasn't risen above 20.5C. The heat pump has switched on and off at least a few times. It did reach the desired leaving water temperature at one point but didn't maintain it for long. I looked in the settings and the deltaT is set at 8C.
when it was maintaining 40-41C:
not long after:
I think next step might be to run the system without using the external thermostat. I did notice this had switched off a couple of times on the honeywell hub when I checked the controller. The honeywell hub has a small light on it indicated heat needed/not needed, even though the remote thermostat was still displaying a demand for heat, so something isn't right here.
When operating on weather compensation, the thermostat should be set above the desired temperature, so that it does not switch off your heat pump prematurely.
Your Daikin controller should be setting the required leaving water temperature that is required to match the heat loss, at the desired indoor air temperature, with reference to the present outdoor air temperature. If the outdoor air temperature falls by 1C, then the leaving water temperature will be increased by approximately 1C, to meet the extra heat demand.
ASHP's have an operating range, just as a car engine will not go much below 1000rpm without stalling, so a heat pump has a minimum operating speed. If the heat pump is producing more heat energy than is actually required, even when it is operating at minimum speed, then the water return temperature will start to increase, which will in turn push up the leaving water temperature, till it reaches the point the leaving water temperature hits the higher limit and stops the heat pump. The water pump within the heat pump may continue to run for a period of time afterwards, and should then run periodically to check the leaving water temperature. When the leaving water temperature falls to the lower limit, the heat pump will restart.
If the room temperature hasn't risen above 20.5C, then weather compensation is actually working. If you require the room a little warmer, then you either need to raise one end of the weather compensation curve slightly, or set the offset slightly higher. When weather compensation has been fully optimised, varying outdoor air temperatures should have little or no effect on the indoor air temperature, and your heat pump should be running more efficiently.
The other thing that I forgot to mention is that periodically your heat pump will go through a defrost cycle, after which it may stop for a short period.
I think we are on to something here. The heat pump has been running for longer periods and able to maintain a lower temperature with the house maintaining a steady temperature too. Right now the system is maintaining a leaving water temperature of 38C, the flow rate is just 11l/min and I've not noticed it stall this morning. I'll keep an eye on it over the next 24 hours.
Regarding defrost cycle, I'm aware of that, the controller displays a small symbol when this is running.
So latest on my system. All morning yesterday, and this morning the heat pump appeared to run quite well, I didn't notice it switching on and off, and the few times I've checked the flow and return temperatures have had a good deltaT of about 7-8C. Yesterday, later in the afternoon and through the evening, once the house was warmer I guess, but not confirmed by other temperature measurements (other half, Alexa speaker & the thermostat all said it was either cooler or the same), the pump kept stopping regularly. It was definitely cooler outside though. The run time details show the compressor is starting ~7 times per hour.
Yesterday evening: thermostat was still calling for heat but there was no flow through the system and leaving/return temperatures similar. It then picks up again. About 2 mins after it’s started running the thermostat box next to the controller switches off, despite the remote unit still displaying the symbol demanding heat and house temperature being nowhere near the 22C set point. I witnessed this pattern several times but wasn't watching all evening so not sure the thermostat is the primary cause, I had other things to do believe it not.
@HydroS, I think @derek-m has identified this already. Is this what happens when you run with thermostats and weather compensation?
I think it is with my ASHP and it's how the installers set it up. There are effectively two different control systems telling the ASHP what to do. I'm not sure that's the best idea.
So latest on my system. All morning yesterday, and this morning the heat pump appeared to run quite well, I didn't notice it switching on and off, and the few times I've checked the flow and return temperatures have had a good deltaT of about 7-8C. Yesterday, later in the afternoon and through the evening, once the house was warmer I guess, but not confirmed by other temperature measurements (other half, Alexa speaker & the thermostat all said it was either cooler or the same), the pump kept stopping regularly. It was definitely cooler outside though. The run time details show the compressor is starting ~7 times per hour.
Yesterday evening: thermostat was still calling for heat but there was no flow through the system and leaving/return temperatures similar. It then picks up again. About 2 mins after it’s started running the thermostat box next to the controller switches off, despite the remote unit still displaying the symbol demanding heat and house temperature being nowhere near the 22C set point. I witnessed this pattern several times but wasn't watching all evening so not sure the thermostat is the primary cause, I had other things to do believe it not.
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Hi HydroS,
Am I correct in assuming that your Honeywell thermostat is wireless, since you mention 'the thermostat box next to the controller'? It could be that you are getting drop out due to poor wireless reception. As a check, you could move the thermostat closer to the controller, and see if the heat pump keeps running under the control of the controller, rather than being switched on and off by the thermostat.
If the above does not cure the problem then monitor the water flow indication and the switching on and off of the flow switch as shown on the controller display.
@kev-m I'm not sure I see the last line of your table unless outside temperature is below 10C, this is like a fall back situation to prevent pipes freezing and it runs at 25C. It could be competing settings, the pump was originally setup with a wired Daikin thermostat/controller, so perhaps using the water modulation setup but this was removed by the new installers (the original one was on an outside wall and close to a radiator) and replaced with the Honeywell thermostat. The settings now to appear to be correctly setup for the remote thermostat but maybe some legacy timing settings remain but aren't visible, clutching at straws probably.
@derek-m correct the thermostat is remote. I moved the remote unit close to the pump just after reading your post. I've not see it turn off but the pump happened to stop whilst I was there, not triggered by the thermostat.
Here's the layout of my system, just thought it might help to visualise it. Only thing I missed off was the anti-freeze values on the outside flow/return from the monobloc.
@HydroS, the last line is just meant to indicate when the flow temp is below its target but the thermostat isn't calling for heat. With my ASHP, if the thermostat isn't calling for heat, the ASHP doesn't run no matter what the flow temp is (cold weather protection apart)
