Baxi 2 60 PF Overheat

[darren haynes]

Hoping someone can help
We have a Baxi boiler in garage
We live in a bungalow, occasionally we get a horrible banging in the pipe work / loft, water pours out of the expansion tank overflow and boiler shuts down on overheat.
I have replaced potentiometer and temp sensor (clipped to pipe work next to boiler)
Also fitted new pump approx 1 year ago. Seems to only happen when heating requested.
Any advice gratefully received

 

[cross thread]

is the pump wired from the boiler

 

[Terrywookfit]

It should be.

 

[darren haynes]

yes I believe it is

 

[darren haynes]

yes I believe so
It does still run even when boiler on overheat, but direction of wiring would lead me to believe it is, also when I have isolated boiler in the past no power to pump

 

[Terrywookfit]

Check the bypass is adequate.

 

[darren haynes]

Can you tell me where I would find this, there are loads of bits of copper around pump and cylinder
I have 5 22mm drops one of which is pump
1 to 3 port valve which links to pump at valve with 15mm coming off
2 would others with another 15mm - imagine the 2 15mm are the rad circuit
Another 22mm with drain cock at like level

 

[darren haynes]

 

[FlyingFish]

If you can catch the system doing it you need to test (multimeter) for power to the pump during overheat (banging/boiling), and also feel if the pump is actually running. It could be pump failure or pcb failure.
If both test to be sound then you may be looking at a faulty 3-port, I've seen the internals come away before and block the ports so stopping circulation and causing an overheat.

 

[darren haynes]

It usually happens once heating has been on a while, there is a cog on the bottom of the 3 port and I have felt this move when calling heating etc
Pump has lit display so pretty sure it's staying powered up and can hear it running