Daikin Series B hot water troubles

[Simon Ruddy]

I have a Series B Daikin Altherma EKHBH016BA6V3 and EKHWSU300B3V3 with the optional solar thermal kit and was installed in 2012. Been working well up until this week apart from replacing the flow switch and cleaning the strainer a couple of years ago.

This week we've had limited hot water which has been supplied by the solar thermal panels.

There are no fault codes

Hot water is scheduled via the timer to come on between 00h30 and 04h30 (cheap octopus go tariff) but it's not been coming on. I've double checked the times.

If I manually initiate hot water by pressing the shower head button, nothing happens. When it was working this would power up the ESBE valve and start the heat pump. If I hold the shower head button pressed for 5 seconds to initiate the immersion, it comes on for a few seconds then turn off again (I can hear the relay kicking in and out.)

I've checked the thermal cutouts on the hot water tank and also the thermostats. The ESBE valve has also been changed.

What have I missed?

[frank]

With a solar kit attached, the altherma is disabled from heating whenever the solar kit has heat to input.
There is a small pcb fitted just above terminal strip where the cables from the solar are connected. My guess is that the solar input relay is welded.
First thing to do is disconnect the solar input and see if dhw heating comes back on line.
Power down then disconnect the fly lead connection from the small pcb where it plugs into the main pcb. (can't remember the terminal number without looking it up). Power up and test.
If that works, you will need a replacement solar interface pcb.

[Simon Ruddy]

With a solar kit attached, the altherma is disabled from heating whenever the solar kit has heat to input.
There is a small pcb fitted just above terminal strip where the cables from the solar are connected. My guess is that the solar input relay is welded.
First thing to do is disconnect the solar input and see if dhw heating comes back on line.
Power down then disconnect the fly lead connection from the small pcb where it plugs into the main pcb. (can't remember the terminal number without looking it up). Power up and test.
If that works, you will need a replacement solar interface pcb.

Hi Frank,

Thanks for your reply.

Turn out that it was a faulty DHW sensor.

Cheers.

[frank]

Thanks for the update Simon