Y Plan fault - damaging programmer

[PClem]

Hi Chris,
Just to update you on my original problem. I fitted pump suppresor cable and Honeywell ST9400C programmer as advised and system is now operating as it should.
Although I did not mention it in my original post, I also had issues with micro switches on 3 port valve. Tried equivalent Corgi head but these soon went so reverted back to Honeywell, which appear to be better quality.
Sounds to me that you have a similar issue with excessive current. Although I have no experience of your lowara ecocirc 25-4/130 pump, would suspect this before boiler. Perhaps you could try measuring current to both pump and boiler to try and isolate fault. Otherwise change of pump would be best bet. Hopefully somebody on here could advise best reliable alternative pump for you.
Good luck

 

[Johnny B]

Hi,

I have a Y Plan system that has worked fine for years but recently developed a strange fault where the hot water on/off is only controlled by the Cylinder thermostat. The HW relay on the programmer is permanently on and although the relay clicks, its output does not change status with the indicator when selected.

System consists of:
Baxi Bermuda 45/4 Electronic Back Boiler
Drayton LP722 Programmer
Honeywell V4073A 3 way valve
Honeywell L641A Cylinder thermostat
Satchwell TLX 2259 Room thermostat

The wiring, following the Honeywell Sundial Y Plan diagram, has been double checked by another electrician and confirmed correct. I have replaced the Programmer, 3 way valve and cylinder thermostat. After replacing the programmer it worked correctly at first but the following day the HW fault had returned and it appears that something in the circuit is damaging the programmer HW relay.

By process of elimination I now suspect the boiler PCB – 237730 but would appreciate any suggestions or advice from those with experience of a similar fault.

Thanks in advance

Pete

This might help

Regards

 

[static zap]

Cheers @Johnny B , way more involved than was expecting .
(AC motor + DC braking=Mid.position )

 

[Johnny B]

Hi,

I have a Y Plan system that has worked fine for years but recently developed a strange fault where the hot water on/off is only controlled by the Cylinder thermostat. The HW relay on the programmer is permanently on and although the relay clicks, its output does not change status with the indicator when selected.

System consists of:
Baxi Bermuda 45/4 Electronic Back Boiler
Drayton LP722 Programmer
Honeywell V4073A 3 way valve
Honeywell L641A Cylinder thermostat
Satchwell TLX 2259 Room thermostat

The wiring, following the Honeywell Sundial Y Plan diagram, has been double checked by another electrician and confirmed correct. I have replaced the Programmer, 3 way valve and cylinder thermostat. After replacing the programmer it worked correctly at first but the following day the HW fault had returned and it appears that something in the circuit is damaging the programmer HW relay.

=================

This is of some interest of how it all works

Y Plan animation video of the system

By process of elimination I now suspect the boiler PCB – 237730 but would appreciate any suggestions or advice from those with experience of a similar fault.

Thanks in advance

Pete