Vaillant ThermoCompact 615 - no central heating

[RichSt]

please can anyone suggest what I can try next to fix my CH?

Hot water is working fine. Boiler diagnostic display says S.30, which is the code for no external heating demand. I replaced the Honeywell 6400C programmer with a new ST9400C, as I had read they can develop faults. The programmer seems to be working fine, and uses the same pin-out and connections. I also replaced the wall thermostat just in case. Still no CH.

Pressing the plus and minus buttons on the boiler seems to fire it into life in the diagnostic mode, but weirdly only sometimes will the radiators heat up.

Both temperature dials on the boiler are set over half way.

Water pressure gauge reads just under 1.5 bar.


What can I try next please? This all started a few weeks ago with the CH intermittently not working. I wonder if the boilers electronics have developed a fault..?


Many thanks
Rich

 

[simond]

Almost certainly heating zone valve not moving all the way across.

 

[RichSt]

Is that something I could test/fix myself? Thanks

 

[simond]

Yep, find the heating valve, probably a 2 port (google 2 port heating valve).

Assuming the above, The cables coming out of it are;
Brown
Blue
Grey
Orange
and possibly an earth, Green.

If the programmer and room stat are working, the brown will be at 230v. Turn off the HW.

If the heating valve has motored all the way open, the grey and orange cables should have 230v on them both. If they haven't, but the brown is 230v, the valve hasn't motored to the end stop microswitch, which joins orange and grey, this fires up the boiler.

Valve is therefore faulty.

 

[RichSt]

Thanks, is it this box? It has one pipe coming in from bottom and two going out each side.

I just moved it from "auto" to "max open" after turning HW off at the programmer. Now my rads are heating up !

 

[RichSt]

Whats the downside to leaving it in Manual open? is that safe to do for now?


I guess I need to order one of these: http://www.amazon.co.uk/Honeywell-V...6312&sr=8-1&keywords=Honeywell+diverter+valve


Many thanks for your help -hugely appreciated.

 

[muggles]

You'll need to do some electrical tests as Simon had suggested before ordering anything or you'll end up randomly changing parts that are working