Vaillant combi boiler problem - heating always on.

[danieljamesscott]

Hi,

I have a a problem with my Vaillant combi boiler with wireless controller.

The problem is that the heating is always on when there is power to the boiler, no matter what the setting on the controller. The only way to stop it is to turn off the power at the mains. It sounds like the pump is always running, and the gas fires up frequently. The thermostat on the controller is set to 15 degrees, there is no hot water demand and the controller says says 'off', but the boiler keeps running.

There is also a switch on the boiler which looks like it switches between hot water only, and both hot water and heating. Even with this on the hot water only setting, the heating stays on.

Any idea what the problem could be?

Thanks,

Dan

 

[dreadnoughtheating]

If you could tell us the model of the Vaillant Boiler, ecomax/turbomax/ecotec etc, and the make/model of the room stat, that would aid us no end.

DH

 

[danieljamesscott]

Hi,

The controller is a Honeywell CM 721. The boiler model I'm not sure but it's very old (~20 years). It doesn't appear to have a model number on it, but there are some basic operating instructions on a sticker with the number 806962GB on it. There's another sticker with safety information with 808930Int on it.

Images:

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• danieljamesscott
• 15 Jan 2014
• 1

Untitled

• danieljamesscott
• 15 Jan 2014
• 1

Untitled

• danieljamesscott
• 15 Jan 2014
• 1

 

[dreadnoughtheating]

AH, that's a combi Compact…. well old.

Some Vaillant Guru's will be along shortly I am sure.

On the receiver unit ( the box somewhere near the boiler, not the portable part) , is it showing a green or red-light?

DH

 

[danieljamesscott]

'compact' - I like it. Thanks for the info.

The receiver has two lights, neither is on. There is a button which I think is the manual override. When I press it, a green light comes on, but makes no difference to the boiler.