ferroli domicompact f24

[okebourne6]

when central heating is on water runs steady hot temp.
on hot water only it runs hot for a minute or 2 then goes cold then hot again! no fault codes appear, gas burner lights and goes out then relights again after water temp has cooled, changed hot water temp sensor but no joy...
can any one advise please,

 

[Blooflame]

have burner pressures checked, press button 3 x times for test mode (I think!!). Anyway ensure you have correct high and low pressures. Beyond that we can consider other factors, like does the flame modulate down if the tap flow is reduced?

 

[Andygasman2010]

It could be a faulty primary/ch sensor too... Other than that, as above!

 

[handsomejackuk]

Also have this fault with hot water getting hot then boiler cutting out, and hot water going cold boiler relights, gets hot, then cold cycling every 2-3 mins... Hot water sensor appears to be working, as the temperature on the LCD display is going up and down.. if i remove the sensor from the pipe, the temp reads really low. I dont suspect it is the senosr... is there any other checks on the electrical side i can do ?

how does the modualting valve work..?