CH systems does not work on radiators only setting.

[Qwackers]

Hi. I've scanned the forums and not quickly found a solution unfortunately.

Hot water only works fine.
Hot water and CH together works fine for a period of time then can lock out and boiler tries 3 times to refire then shuts down.
CH on it's own doesn't work at all. Doesn't even try to fire up. Red light on boiler control panel.

Motorised valves seem to be working fine. If CH only is selected and I move the HW motorised valve over to manual, the system fires up, but shuts down as soon as I allow the HW motorised valve to return.

If CH and HW are selected, system works fine initally, if you then turn HW off, it's shuts down immediately.

Boiler type Potterton Suprema 60.
Valves are Myson power extra.

It had an issue with the boiler locking out (shutting down) also. I've removed the circuit board and re-soldered to fix any dry joints. Refitted and there was no apparent change. The system will still eventually lock out so I don't think I achieved anything there, if there was a problem or not.

A new circuit board is an option, but I feel the problem also lies elsewhere. Maybe it is more than one issue. I don't want to fork out for a new circuit board when it might be another issue.

The circuit board shows signs of very mild scorching around a couple of diodes, but nothing severe, shall we say a "tanned" mark.

Thanks for any suggestions.

 

[D_Hailsham]

CH on it's own doesn't work at all.

Motorised valves seem to be working fine. If CH only is selected and I move the HW motorised valve over to manual, the system fires up, but shuts down as soon as I allow the HW motorised valve to return.

If CH and HW are selected, system works fine initally, if you then turn HW off, it's shuts down immediately.

Sounds like a fault in the CH valve.

Do you have a multimeter (and know how to use it )?

If so test as follows:

Turn CH ONLY on and the CH stat up.

Check voltage as follows:
CH valve brown-blue (240Vac)
CH Valve grey-blue (240Vac)
CH Valve orange-blue (240Vac)

Turn CH stat down and check them again.

The grey-blue should still be 240Vac, but the other two should be 0Vac.

If brown-blue is always 0Vac, the fault is possibly in the CH thermostat or the programmer.

If orange-blue is always 0Vac, the fault is in the CH valve actuator.

 

[Qwackers]

CH on it's own doesn't work at all.

Motorised valves seem to be working fine. If CH only is selected and I move the HW motorised valve over to manual, the system fires up, but shuts down as soon as I allow the HW motorised valve to return.

If CH and HW are selected, system works fine initally, if you then turn HW off, it's shuts down immediately.

Sounds like a fault in the CH valve.

Do you have a multimeter (and know how to use it )?

If so test as follows:

Turn CH ONLY on and the CH stat up.

Check voltage as follows:
CH valve brown-blue (240Vac)
CH Valve grey-blue (240Vac)
CH Valve orange-blue (240Vac)

Turn CH stat down and check them again.

The grey-blue should still be 240Vac, but the other two should be 0Vac.

If brown-blue is always 0Vac, the fault is possibly in the CH thermostat or the programmer.

If orange-blue is always 0Vac, the fault is in the CH valve actuator.

Hi, thanks for you reply. I needed to get a multimeter as couldn't find my old one, last seen years ago!

ok, got a multimeter. The system has no CH stat and works just on radiator thermostatic valves. EVERY radiator has these valves. I turned the rad valves up high, switched CH only on.

Brown/blue = 237v
Grey/blue = 157v! - this fluctuates from 240 but settles around 157, dropping off quickly from the high at start up.
Orange/blue = 237v

The system started, the motorised CH valve lit up and opened, the pump started, ran for a minute or so then shut down. The boiler itself never flamed up though it did try but then the red shut down light comes on and a reset is needed to repeat the process.

When the system is switched off, the CH valves closes and I'm left with the boiler in red light mode needing a reset.

Is the low voltage on the grey/blue the problem?

fyi - I did the same test with the HW valve and all 3 voltages were 237v and the system works fine on HW only or indeed CH+HW.

Thanks for your valuable input.

 

[Qwackers]

Hi, I've drawn a blank. Still none the wiser. Having checked the voltages on the wires and got the results as stated... anyone any clues what to do/check next? Thanks

 

[Terry7556]

what voltages did you get when the c/h was off , as requested above?
i recently had the same problem on this boiler with a myson valve. i had similar voltages as well. i bought a complete valve but only changed the head, so didnt drain down. with the head removed i had 15 degrees or so movement on the valve spindle. this valve change stopped the problem

 

[Qwackers]

what voltages did you get when the c/h was off , as requested above?
i recently had the same problem on this boiler with a myson valve. i had similar voltages as well. i bought a complete valve but only changed the head, so didnt drain down. with the head removed i had 15 degrees or so movement on the valve spindle. this valve change stopped the problem

This CH system does not have room stat so I cannot conduct that part of the test. Unless there is another scenario that will produce the same situation?

 

[Terry7556]

apart from fitting a roomstat, not really. i would still change the c/h valve