Baxi duotec banging

[deanr1979]

When running the hot tap the boiler makes a loud banging noise and the presseure dial goes upto 3 bar. Burner lights up till temperature shows 99 then it goes out and reignites again. Flow pipe gets hot when hot tap is running?
I thought it was the diverer valve diaphragm split thus sending hot water into the central heating causing the pressure rise and hot flow pipe.
Any advice much appreciated.

 

[rojaca]

How's the heating. Sounds like a very blocked plate heat exchanger. Newer design uses plate as bypass hence rpessure increase. I'm guessing the system wasn't thoroughly flushed when it was installed.

Went to one of these recently and questioned installer as he was adamant sysstem had been flushed. Turned out he'd been removing the pump head and was flushing through the boiler.

 

[deanr1979]

central heating seems to be fine.
is the plate exchanger awkward to remove with it being positioned at the back of the boiler?

 

[rojaca]

Not at all. turn off iso's, drain htg and dhw from boiler (not through prv). Undo two screws securing plate. Need something to catch any remianing water. Slide plate to rear and top of boiler. Rotate through 90 degress towards you so thinner side facing towards you. You should now be able to move it to top right above pump and remove it through that gap.

 

[deanr1979]

Not at all. turn off iso's, drain htg and dhw from boiler (not through prv). Undo two screws securing plate. Need something to catch any remianing water. Slide plate to rear and top of boiler. Rotate through 90 degress towards you so thinner side facing towards you. You should now be able to move it to top right above pump and remove it through that gap.

Nice one. I'll give that a go tommorrow.

 

[deanr1979]

Plate exchanger was the problem. Full of sludge and debris. Looks like when the boiler was installed the installer hadn't flushed the system aithough he said he had.
Replaced with plate exchanger with a new one and added sludge remover and cleanser to the system. Going back next week to drain down and add inhibator.