Daikin Altherma 3M heat pump no longer starts the compressor

[AL Ken]

We have 2 Altherma systems, the first (11kW) has been running for 3 years driving UFH perfectly well with over 20,000 hrs of operation. Recently I added another circuit and had to repeat the air purge and flow commissioning tests which passed successfully.  The problem is shown in the 2 photos attached where the system just sits there (12 hours) without starting the compressor. The settings are the same as they were before I added the extra circuit (setpoint fixed). In order to test the system I turned off the new circuit I added. The initial flow is 22.1 LPM but drops to the 11 LPM as shown in the photo after a while without the compressor ever starting. 

The 2nd Altherma is running perfectly with the same settings. I have compared all the settings by exporting them and comparing the .INI files but cannot see any differences. I am happy to share this setting file (.INI file) if there is a Daikin specialist capable of looking at it and spotting the issue. 

Can anyone advise where I should target my efforts please? 

 

[JohnMo]

Are you sure you don't have an air lock?

 

Do you have a call for heat? Is this from anything external?

[AL Ken]

Hi JohnMo

The system passes the flow rate test with 22 lpm and I have run repeatedly the air purge cycle. So there is enough water flowing but the compressor refuses to start. I attach more photos in case someone sees a screwup. 

Best Regards, AlKen

Edited yesterday at 12:57 by AL Ken

[JohnMo]

Is the menu saying you have external thermostat(s), if so are there calling for heat?

[Dillsue]

In your screen shots it says the flow switch is OFF. I don't know which way round Daikin set things up but if flow is detected I'd expect the flow switch status to be ON???

 

If you're using an external thermostat what are the heating minimum and maximum setpoints doing? I'm assuming those are air temperature limits rather than water flow temp??

Edited yesterday at 13:39 by Dillsue

[AL Ken]

Hi DillSue

No I do not have an external thermostat so I do not understand why this choice is enabled but when you select it the choices are 1 contact or 2 contacts. The 2 contacts is selected (blue) but cannot be changed. In the Installer sensor section I have External Thermostat set to None so I do not understand why the Thermostat is shown (Note on the other nearly identical Altehrma system which is a bit newer the Thermostat choice is greyed out).  

[Dillsue]

No idea if it's the same on your HP but on our Therma V whether you have an external thermostat or not is set with a DIP switch on the controllers PCB. If ours is set to be using an external thermostat it would need a shorting link(or closed contact from the thermostat) fitting on the thermostat terminals to give a call for heat and get the HP to run. Might be worth checking how your thermostat interface is configured to make sure you've not inadvertently selected it to run under thermostat control when there isn't one. Or just drop a link on the thermostat input.

 

Still puzzling why your flow switch is showing OFF