S.30 issue with Vaillant ecoTEC Plus 831 boiler

[pixi123]

Have an issue with our ecoTEC 831 boiler. Having returned from a short break, we have no CH, but HW is fine. Boiler is showing an S.30 status (no heating demand from external controls).

The timer unit (timeswitch 140) seems to be functioning OK (the HW is switching on and off when it should) and the wireless thermostat also seems to be OK. To check these, I have removed them and shorted out the bridge connection between terminals 3 and 4 and the display is still showing an S.30 error when turned on. Does this point to the main controller board having gone faulty?

I can get the CH working by pressing the + and - buttons at the same time. The controller displays SF.H and fires up for about 10 mins then switches off. I cannot find any reference to what this does in any literature, but shows that the boiler is actually functioning as it should, just not being told to fire up correctly.

Do I need to replace the main control board?

 

[mickyg]

is the control knob turned up? does the temp change as you turn the ch knob around? might be broken

 

[pixi123]

They are both (CH and HW) turned up to about 55C and the temp changes as you move them, so don't appear to be stuck at all.

 

[gas4you]

SFH is the boiler being over ridden to run on maximum power.

 

[pixi123]

So would this point to the main control board being faulty and not providing the correct signal to tell the boiler to turn on?

 

[mickyg]

sounds like it but very unsusual. cant say i've come across it before. The only thing that might cause that is if the diverter valve is leaking into the motor. This can in turn blow the board, causing unusual faults. but if as you say, you've removed the clock and linked 3&4 and nothing happens...pcb

 

[pixi123]

Just to confuse things a little further, the CH clicked on right on time last night at 6pm (when it's set for) and seemed to be working fine (status S.4).

When the hot water was turned on, CH turned off (as supposed to) and boiler went through HW cycle. On turning the HW off, the boiler went back to the S.30 status and the CH wouldn't come on again.

Guess I'll just change the controller board and see if it cures it.

Is there anything that I need to look out for when changing the controller board, or is it just a case of swapping over the connectors and firing it up?

 

[gas4you]

I may be wrong, but I thought that when the 140 was plugged into the boiler, the 3-4 link had to be left in, as the 140 is an ebus control is it not

 

[mickyg]

nope, all plug ins hold the boiler off not on. so when you remove it the boiler defaults on.
op- I think you should get someone to look at this, pcbs are very expensive and your fault is one i've not come across that i can think of. I would want to check the hot water ntc as well as this can throw strange faults when out of cal.