vaillant ecotech 831 boiler - no CH but hot water fine

[shil0464]

Hello, wondered if anyone has any experience or tips. Boiler working fine for 18 months until 2 days ago (quite chilly here atm!), it will now happily produce hot water but the heating will just not turn on. The boiler seems to think it's producing heat, but is not firing, it thinks its in central heating mode - the radiator light it on, the pump appears to be making a noise like it's on (internal pump indicator on), but it's not burning gas.
Status wise it thinks S. 0 - no heat required? When I the hot water goes on, the heating will cut in for 10secs or so afterwards until it enters anti-cycling mode and then reverts back to this "thinking I'm on when I'm not" mode. It sometimes seems to go to S. 7 - pump overrun?

I'm going to get someone out (you can tell I have no idea about these things) but seeing as it's -8degrees and saturday, if there's an easy way to turn it on, please let me know before next week!

We have a remote controller for it - that shows the current room temp and that also thinks the boiler is on, shows the flame etc. The green light that indicates the boiler has received this intruction is also on. There seems to be no pressure issue - it's on 1.5bar atm.

Any help appreciated! Thanks.

 

[simond]

This sounds like an unusual set of circumstances.

First thing i'd check is the CH temperature knob, when you turn it up or down does the display temp change?

If it doesn't, the knob spindle has broken in half....... Temporary solution is to turn the power off outside the boiler and twiddle it from inside the wiring cover.

You dont say if it is a Vaillant rf controller or a 3rd party one, if it is a vaillant, you could try removing/disconnecting it. There should be a red wire link between terms 3&4 inside the boiler if it is Vaillant controls.

Bear in mind the outer white lid is part of the safety seal making the room sealed so it is important it goes back properly.

 

[shil0464]

Thanks for your reply. No, the heating temp goes up and down as normal. Everything seems completely as normal, just the damned thing won't come on. At least we've got hot water when it works as normal.

The controller is third party - Salus.

Just tried turning it on again, upped the thermostat on the controller - everything clicked on, it lit, then about 5 secs later, goes into anti-cycling mode, then the radiator symbol goes solid and is back in "heating mode". Status showing as S.7 Pump Overrun and then 30 secs later S.0 No heat required. It's as before now, thinks it's working but it's not! Controller showing 10degrees and is telling the boiler to work, the green remote on the boiler is saying it's working, and I think it thinks it is.