Biasi 24s boiler problem

[graham.]

My problem is with the hot water side of the boiler,it only works intermittently.But when the central heating is on it works ok.When the dhw is turned on by itself there it doesn't always spark. Grateful for any help.

 

[Gasguru]

Probably just the DHW diaphragm perished - cheap part plus a callout charge.

 

[graham.]

Don't think its the diaphram, as the DHW micro-switch is being operated every time, even when the DHW flows cold.Wondered if it could be a faulty K1 relay? On the wiring diagram in CH mode this relay is bypassed.

 

[Gasguru]

Check the contact resistance of the DHW microswitch, also check the pump flow microswitch is being operated in hot water mode and the hot water thermistor is OK. Only if these are OK then suspect the board (I've yet to change a Biasi board)

 

[Agile]

Also look at the DHW switch unit to see if water has leaked from the gland.

Tony