Brittony 80 Combi - Hot Water goes cold then hot then cold!

[joneng]

Brittony 80 Combi

Pressure 2.5 bar (too high?!)

Hot water goes cold when showering, then heats up again, then cold, then hot again!
Not so bad in kitchen.
Valve to adjust pressure has seized up?!

Can anyone offer some guidance and direct me to an online service guide.

Cheers...

 

[joneng]

Central heating works fine. Hot water works fine in kitchen but not in the bathroom. Boiler keeps turning itself on and off when hot tap in bathroom is running.

Please help!

 

[gas_man_gaz]

sys pressure should be around 1 - 1.5bar, you will have to drain some water out or the prv may open wen the ch is on and ya might end up having to replace the valve.
as for the hw id say the thermistor or the plate to plate would have to be the favorites to be at fault

 

[joneng]

gaz - I have relieved the pressure to around 1- 1.5.

Is the thermistor or plate to plate easy to change? How do I tell which it might be or do I need to change both?

 

[gas_man_gaz]

cant say for sure without doing any tests (including taking burner pressures, which you cant do).
you could try changing the thermistor as this part is easy to do and not really expensive, but if the boiler is cycling on and off i think its more likely to be the plate to plate which can be awkward to change.

if ya slow the flow rate dwn out of your bath tap does the boiler work ok? also try running a tap and feel if the central heating pipes start to get hot

 

[joneng]

last night boiler stopped working altogether and dirty water was flooding from the over flow pipe...

 

[g20]

Is water still coming out of the Blow out pipe? If so try isolate the cold water inlet to the boiler, you could have a hole in the DHW heat exchanger.