Boiler switch of problems

[Argentum66]

I have a Valliant boiler controlled by a Danfoss (wired in not remote) programmer. The problem is that the boiler is not switching off when the controller reaches the 'off' time. The programmer seems to be operating the valves correctly, switching off the supply to the radiators/hot water tank but the boiler continues to run. The only way I can switch it off is to cut the power to the boiler.
Any ideas what may be the problem?

Additionally, can anyone tell me what controls the boiler switch off? Is it the control unit that tells the boiler to shut down at the same time as switching the valve, or does the boiler sense the valve closing and automaticly shut down due to lack of demand? This would help me pinpoint where the problem lies.

 

[D_Hailsham]

The boiler is controlled by microswitches inside the motorized valves. When a valve opens the switch closes and the boiler runs.

Is the boiler within the house, or outside, e.g in the garage?

Do you have a room thermostat and cylinder thermostat?

 

[Argentum66]

Thanks for replying D_Hailsham
The boiler is in the Garage. There is definitely no room thermostat and as far as I know no cylinder thermostat either.
What you explained with the micro switches suggests that it is the valves at fault?

 

[D_Hailsham]

The boiler is in the Garage.

It could be the frost protection kicking in.

Are there two thermostats in the garage; one on the wall, the other on one of the boiler pipes?

If not, it could be the boiler's internal frost protection.

Which model Vaillant boiler do you have?

There is definitely no room thermostat and as far as I know no cylinder thermostat either.

So how do you prevent the house and HW cylinder overheating?

 

[Argentum66]

Don't think it's the frost protection kicking in from the wall stat as it still happens in summer and I have tried overriding the thermostat. Not sure about a stat on the boiler itself, its not obvious if it is there. As for the cylinder, on checking there is a thermostat actually mounted on it, although this appears to be non adjustable. The boiler is not labelled or marked other than to say its a Valliant.

 

[D_Hailsham]

Can you post some pics?

 

[Argentum66]

Will do, but it will probably be tomorrow if you don't mind watching out for them. Thanks.

 

[JacktheFitter]

Pump overrun?

 

[Argentum66]

Sorry Jack, what does that mean and how do I fix it?

 

[PK Gas]

What brand of motorised valves do you have?

 

[JacktheFitter]

Not sure about your boiler but sometimes after you turn off the boiler the pump continues for a little while to get rid of all the heat, so when you turn boiler off,it`s sounds like it is still running for a while.

 

[Argentum66]

Hi Jack. Yes I thought the same at first but I have left it running and the burners continues to cycle in and out indefinitely, continuing to heat the water.

 

[Argentum66]

Hi pkent. The valve to the water cylinder is a Honeywell but the central heating valve has no identification on it apart from a code starting BG which may be a Bell and Gossett?

 

[D_Hailsham]

the central heating valve has no identification on it apart from a code starting BG which may be a Bell and Gossett?

More likely to be British Gas.