shower valve or boiler fault

[mutley racers]

Evening chaps. I have a worcester 28 cdi boiler which when a certain shower valve is turned on, it gets hot and then the boiler just cuts out. They said it was happening at other taps occasionally. But I could not get it to happen. I felt the flow and return going into the hex and the flow was red hot and return was Luke warm. So thought it worth a try smacking it on the floor a few times. Amazing how many scales I got out, but no difference. So now I am thinking the shower valve.

Another thing I noticed is that when ever a hot tap is running and you turn a cold tap on some where else the boiler turns off. Not sure if it's related or not. Or that the cold steals on the flow from the boiler for it to cut out.

Cheers

 

[Aquazone]

Could be a perished diaphragm. If shower is thermostatic when water gets hot lowers flow and microswitch drops off? Probably would explain the cold tap knocking the HW off too.

 

[mutley racers]

Spot on

 

[townfanjon]

I have one at the minute , I think it's the shower valve or the bath mixer rather than the boiler, anybody any tips of the best way to suss it.

sorry mutely , not trying to nick post lol

 

[Millsy 82]

Pop your head underneath and you will see the plunger come away from micro switch then remove micro switch and press manually. Or get multimeter out and check the voltage on it.