things that go bump in the night

[Dave Workman]

I have a Baxi solo 3 with cylinder in loft complete with three port valve
every evening on several occasions a load banging noise comes from the loft. Plumber has replaced 3 port valve clipped all the pipework added a bypass before the three port and a new board in the boiler. Any idea as to what we can do to resolve the issue as this has been going on for weeks and keeps waking us up in the night and can't be doing the system any good.

 

[stevetheplumber]

dont know why he fitted a bypass three way valve is always open has the boiler been serviced gasrate etc?

 

[Sparkgap]

Is there a pump overrun? Could it be localised boiling when pump shuts off?

 

[TVP&H Ltd]

The noise is the valve being forced back to HW only from mid position. Turn the pump speed down and then put HW and CH ON. Making sure that both thermostats are calling. Then turn room stat off and see what occurs. Your plumber was part way to solving it, but an auto bypass only works under pressure, and in this instance would be after the valve has moved.

 

[gassafe]

Might be a cheap 3 port valve... Pump could be failing, boiler overheating... It's difficult to diagnose on a forum without more info?

 

[Unregistered]

It only happens during the night when everything is switched off