Baxi 105e Combi Saga Continues

[Jennywrens]

I have posted replies to my first thread also but I think my thread of today is more up to date, as the CH would not work at all originally.

 

[Jennywrens]

What happens when CH is turned off and DHW is used ?

I am not sure about that one - I will need to check

 

[picbits]

If you turn the boiler on with the CH off and it seems ok and doesnt over heat then .....

Turn on water (with CH off)
Turn off water (with CH off)

This should test to see if DHW is working correctly. If the boiler turns back off and behaves then the chances are its your diverter valve in the boiler.

If the boiler starts to boil then its not being told that the water isnt needed any more.

Does your boiler have an indicator on the front to show if the water is on or if the heating is on ? If it sticks constantly on the hot water indicator then I'd err towards the demand switch sticking on.

 

[baxpoti]

After the dhw is finished what do the lights do?

 

[Jennywrens]

If you turn the boiler on with the CH off and it seems ok and doesnt over heat then .....

Turn on water (with CH off)
Turn off water (with CH off)

This should test to see if DHW is working correctly. If the boiler turns back off and behaves then the chances are its your diverter valve in the boiler.

If the boiler starts to boil then its not being told that the water isnt needed any more.

Does your boiler have an indicator on the front to show if the water is on or if the heating is on ? If it sticks constantly on the hot water indicator then I'd err towards the demand switch sticking on.

Yes our boiler has indicators on the front to show heating or water - I will do this test later tonight and come back to you, thankyou.

 

[Jennywrens]

After the dhw is finished what do the lights do?

I will test later tonight and report back, thankyou.

 

[Jennywrens]

Right, we ran a couple of diagnostics last night and here is what we found:

We have two dials that opertate the boiler - one dial turns on the boiler to either CH/HW, or just HW

The other dial is for the HW Preheat

When in CH/HW mode:

CH radiator light on
Turn taps on, rad light goes out
Turn taps off, rad light comes on
Boiler working fine (not boiling itself)

When in just HW mode (no preheat)

Turn taps on
Water light comes on
Turn taps off
Water light goes out
Boiler working fine (not boiling itself)

When in CH/HW mode, and we turn the other dial to preheat:

CH radiator light on
Turn taps on, rad light goes out
Turn taps off, rad light does not come back on
Boiler keeps telling itself to keep preheating - temp stays up, water light stays on, doesn't switch back to heating

Also, during the night the heating decided to turn itself off during CH/HW mode:

No taps were used
Rad light off
Water light on and temp up
Boiler making a bubbling noise

???? !!!!

 

[picbits]

Bit beyond the scope of my boiler knowledge now I'm afraid.

I suspect that if there is a seperate thermostat or sensor for the preheat side of the boiler it could have gone faulty but thats just a guess.

 

[Jennywrens]

Bit beyond the scope of my boiler knowledge now I'm afraid.

I suspect that if there is a seperate thermostat or sensor for the preheat side of the boiler it could have gone faulty but thats just a guess.

thank you very much for your advice anyway - I think we may go down the route of the motorised 3 way valve being replaced, not sure. I am hoping Baxipoti will be able to help a bit more.

Thankyou, Jenny

 

[baxpoti]

Sounds like the primary (c/h) thermistor needs testing/replacing.

The dhw and c/h thermistors are the same, so they can be swapped for testing.
The dhw pocket is wet the c/h pocket is dry.

If they are black and chrome they are the originals and its just as well to replace them, new ones are white and gold part number 5108265 and you'll also need a washer 248069.

 

[Jennywrens]

Sounds like the primary (c/h) thermistor needs testing/replacing.

The dhw and c/h thermistors are the same, so they can be swapped for testing.
The dhw pocket is wet the c/h pocket is dry.

If they are black and chrome they are the originals and its just as well to replace them, new ones are white and gold part number 5108265 and you'll also need a washer 248069.

Thank you very much Baxpoti - we will give this a go and report back

Jenny

 

[Vic Spanner]

When in CH/HW mode, and we turn the other dial to preheat:

CH radiator light on
Turn taps on, rad light goes out
Turn taps off, rad light does not come back on
Boiler keeps telling itself to keep preheating - temp stays up, water light stays on, doesn't switch back to heating

When the water light stays on is it flashing or solid.

 

[Agile]

But if it was either sensor then surely it would overheat on DHW or CH whereas the OP says it works fine on both and does not overheat?

I am still left suspecting the motor valve actuator but thats so easy to test in front of the boiler as are the sensors when warm.

Tony

 

[baxpoti]

Boiler keeps telling itself to keep preheating - temp stays up, water light stays on, doesn't switch back to heating

When the water light stays on is it flashing or solid.

Well?

 

[Jennywrens]

When in CH/HW mode, and we turn the other dial to preheat:

CH radiator light on
Turn taps on, rad light goes out
Turn taps off, rad light does not come back on
Boiler keeps telling itself to keep preheating - temp stays up, water light stays on, doesn't switch back to heating

When the water light stays on is it flashing or solid.

Solid