Vaillant boiler not connecting to Salus Thermostat

[stem]

The green light shows that the boiler should be on. But if it isn't going on/off, there is something not right with the thermostat / receiver. However, in this state I would expect the boiler to be continually on when the green light was showing.

First of all try turning the power off to the receiver so that all lights are extinguished. Wait a few minutes and restore power. The older versions of the RT500RF had a switch on the front, but if yours doesn't have a switch it will probably mean turning off the power at the boilers fused spur.

After that, if nothing has changed and the boiler still doesn't work you can still do the test as I described and if the boiler comes on then you know the boiler is OK.

 

[Charly Pitman]

@stem well I have hot water and the rads do come on when I put it into service mode so do you still think it could be an issue with the boiler? I have switched the receive off previously and turned back on but still didn’t work so may have to try the wiring. If it is the receiver/ thermostat would this be any good to buy? Thanks so much for your help

 

[stem]

The fault code S 30 indicates that the boiler is not receiving a signal from the thermostat, couple that with the boiler working in service mode does suggest that it is unlikely to be the boiler at fault. However, a bad connection of the wire connected at the boiler terminals that comes from the thermostat, or an internal wiring fault with it inside the boiler could cause the symptoms you describe.

Having said that, as we have determined there is still something wrong with the thermostat, because the receiver isn't switching on/off when told to by the thermostat, nor is it starting the boiler despite the green light being on, so it will probably need replacing anyway.

The test would just confirm that, and if it worked, would allow you to have the heating on, until you could fix the thermostat.

 

[Charly Pitman]

Thank you so much @stem will let you know how I get on