Thermostat doesn't turn boiler off

Hello all, hope you can help

I have a Valliant Ecotec pro 24, for heating & instant HW. This was installed earlier this year as a replacement for my 20-year old boiler.

3-bed terrace with 8 radiators, 7 of which have TRVs. There is also a wireless roomstat in the hallway, and a timer on the boiler. So far, so good.

The problem is, the thermostat doesn’t seem to be working as I expect. I’ve never seen/heard the boiler turn off when the central heating is switched on (either constant on or timed on). Even when I turn the thermostat down to frost setting, the boiler continues to whirr and consume gas (as seen at the meter). The little gas flame icon and central heating icon are lit up.

The house certainly gets cooler, so the thermostat is obviously doing something, but nowhere near cold (I can still walk around in T shirt).

Before I contact the installer, am I right in thinking the boiler should be off, and consuming no gas (except for the pilot light) when the thermostat doesn’t require heat? Could it be wired up wrong?

Thanks in advance.

Is it a Thermostat or a Compensator control?? perhaps some pics would clarify?

Hi, thanks for the reply.

Here are the pics

Boiler

Close up

Wireless sender/ receiver

Wireless thermostat

Can you hear a click from the wireless receiver when the thermostat is turned up and down?

Do any lights on the receiver go on and off when you turn the thermostat up and down.

Any lights permanently on or off on the receiver?

I turned the heating on about half an hour ago with the thermostat set to max (30 deg) as a test.

D_Hailsham said:

Can you hear a click from the wireless receiver when the thermostat is turned up and down? Yes

Do any lights on the receiver go on and off when you turn the thermostat up and down. Yes. Green light comes on when thermostat requires heat, off when it doesn't.

Any lights permanently on or off on the receiver? No

Click to expand...

The wireless receiver has a green LED lit.

I've just turned the thermostat down. There is a click from the wireless receiver and the green light goes out. The red light on the thermostat doesn't flash until I keep turning, a few degrees more, then it flashes 8 times.

The boiler continues to run, showing a flame icon and a flashing central heating icon.

-

When I turn the thermostat back up again, I get a long single flash of the red light on the thermostat. This time at exactly the same point as the click. And the green light comes on on the wireless receiver. Again, no change to the boiler.

So the thermostat appears to be communicating correctly with the receiver.

That leaves either a faulty receiver or a wiring fault.

Remove the receiver from the wall (turn elec off while you do this) and check if the boiler still lights when the timer is 'on'.

If it does: there's a wiring fault - most likely is that the link between the room stat terminals in the boiler has not been removed.

If it doesn't: the receiver is faulty - probably the relay terminals stuck together.

Thanks for your help, D_Hailsham. Yep, I came to the same conclusion that the wireless link from the thermostat is OK.

D_Hailsham said:

If it does: there's a wiring fault - most likely is that the link between the room stat terminals in the boiler has not been removed.

Click to expand...

We have a winner.

I didn't want to start taking things apart but I gave the installer a ring. He had an electrician round here within the hour! As you suspect it was a wiring error in the boiler. All fixed now, and behaving as expected.

Thanks for your help in diagnosis.

I know what's wrong with this one!! (been caught myself) you MUST remove the 24v control link on the boiler PCB (otherwise it will operate 24hrs as this one is doing!)