Faulty boiler thermostat

[Paul17088071]

Hi all

Please could anyone offer me advice regarding a faulty thermostat for the boiler?

I have a BAXI 400 gravity fed boiler, and I have set the heating to come on via a timer.

As the house is hot as it is, I’ve set the thermostat to 10 degrees so it shouldn’t be triggered (even though it’s by the front door, it’s definitely not 10 degrees). However, the heating is on full blast all throughout the timer.

I’ve taken the thermostat apart to see if it’s controllled by batteries which it isn’t. Would anyone have any advise please, could this be a faulty thermostat?

Pictures of the thermostat attached.

Many thanks, Paul.

 

[cross thread]

When you have the stat removed of its back plate ( probably 240 v) is it still firing the boiler ,if no probably the stat if yes probably a zone valve issue assuming it’s only just started happening

 

[gas112]

Faulty motorised valve the more likely

 

[Paul17088071]

Faulty motorised valve the more likely

Would this be the case even though heat is being pumped out of the radiators? My limited understanding of the motorised valve so far is that if it’s faulty, no hot water will pass through?

 

[gas112]

Would this be the case even though heat is being pumped out of the radiators? My limited understanding of the motorised valve so far is that if it’s faulty, no hot water will pass through?

nope they can jam open keeping the microswitch activated keeping the boiler on with full flow through the valve .
Or with just a faulty stuck microswitch and a worn valve it will still pass heat to rads

 

[Paul17088071]

nope they can jam open keeping the microswitch activated keeping the boiler on with full flow through the valve .
Or with just a faulty stuck microswitch and a worn valve it will still pass heat to rads

Thank you for clarifying, appreciated

I’ve just carried out a test on the thermostat and valve. I turned the boiler on with the thermostat operating at 10 degrees. Turned it up to 30 degrees as a test and I heard the click on the thermostat so I’m fairly confident that’s working.

I recorded the valve upstairs on video, on picture one the lever moved across to this position on the right, which I assume is opening up to let the water through. Turning the thermostat back down to 10, this lever has stayed open to the right , which would align with the fault hopefully? 15 minutes later, and the level is still in the same position.

Is this as easy as just getting a replacement part?

Many thanks

 

[Stuckinarut]

Likely just needs an actuator. Yep, doesn't seem to be disengaging when demand has finished. Although, they do stay in the last known position afaik

 

[Paul17088071]

Likely just needs an actuator. Yep, doesn't seem to be disengaging when demand has finished. Although, they do stay in the last known position afaik

Great many thanks, I’ve found a replacement motor on Screwfix so I’ll give this a go. Thanks so much

 

[cross thread]

Also check the brass base valve turns easily

 

[Paul17088071]

Also check the brass base valve turns easily

Thanks. Can this be done manually, or watched when turning the boiler on to see if there is movement?

 

[gas112]

Great many thanks, I’ve found a replacement motor on Screwfix so I’ll give this a go. Thanks so much

dont just change the motor change the whole head . buy complete valve and just use head its cheaper

 

[Paul17088071]

I’ve just realised, the whole motorised unit wasn’t even connected to the valve on the pipe, it was just on the floor where you see in the picture - only recently bought this house!

Should this be connected to a valve anywhere on here?

Thanks

 

[cross thread]

On the end of the 3 way brass section , probably removed as it’s faulty

 

[Paul17088071]

On the end of the 3 way brass section , probably removed as it’s faulty

Fab thanks. Have just tried connecting it and it seems the head won’t fit on to the connection points. Can anyone recommend a head that will fit the valve please?

 

[kidgreen61]

Looks the correct head to me, you will need to line up the flats on the spindle (brass bit) with the flats in the actuator. Sometimes moving the actuator manually (plastic lever on the end) helps.