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Plumberpro
Plumberpro, Plumber
Category: Plumbing
Satisfied Customers: 634
Experience:  Heating and plumbing answers. 20 years experience
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BIASI 28s COMBI BOILER; HOT WATER NOT FIRING UP, central heating

Customer Question

BIASI 28s COMBI BOILER; HOT WATER NOT FIRING UP, central heating works, water pressure, gas supply and electric supply ok. Running hot water taps, gives small amount of hot water when CH is on. Why is this happening?
Submitted: 1 year ago.
Category: Plumbing
Expert:  Plumberpro replied 1 year ago.
Hi , take the car off and run hot water tap. Check that the pin on the diverter valve is making the microswitch
Customer: replied 1 year ago.
Pin is making contact in the microswitch
Customer: replied 1 year ago.
I have checked the diaphragm and it is sound, but there was a lot of rust pieces in there so cleaned out and reassembled. About to refill system with water
Expert:  Plumberpro replied 1 year ago.
Hi, maybe fault is the microswitch. Try pushing the microswitch in with a a few driver and see if the burner lights. If it does then that leaves the hot water thermistor
Customer: replied 1 year ago.
Just getting back, there was a bigger problem. The boiler was giving off a burning smell, so quickly switched of electrics to boiler.The burning was coming from the PCB, but tested the pin before shut down and it made no difference.Scared to plug boiler back into the electrics. Do you think it needs a new PCB?
Expert:  Plumberpro replied 1 year ago.
Hi , yes if the pcb was giving off that smell, but for the cost of a pcb it might be worth considering a new boiler as there could be something shorting the board.
Customer: replied 1 year ago.
I had a look at the board and the burnt area seem to be near the lock out light.I have switched electric to boiler back on, but boiler still locking out, pump starts but then stops.Cannot smell any more burning.
Expert:  Plumberpro replied 1 year ago.
Hi , if there are burn marks on the board I think it will definitely need replacing. There are places that do reconditioned ones.
Customer: replied 1 year ago.
Thanks for your advice. I had a heating engineer to have a look at the boiler. He agrees with you that the pcb needs changing. Part has been ordered.
Expert:  Plumberpro replied 1 year ago.
Ok , all the best . If happy with my answer would you mind rating g it please, thanks
Customer: replied 1 year ago.
PCB replaced. Boiler fires up and central heating now working again, but hot water not working. With knobs set to central heating and hot water, when hot water tap is opened boiler flames shut down and water runs cold.Replaced microswitch on diverter, but problem continues. Could the problem be with another heat sensor?
Expert:  Plumberpro replied 1 year ago.
Hi , sorry to hear that , yes it could be the hot water temperature sensor/thermistor. They are relatively cheap and easy to change.
Plumberpro, Plumber
Category: Plumbing
Satisfied Customers: 634
Experience: Heating and plumbing answers. 20 years experience
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Customer: replied 1 year ago.
I can replace the hot water thermistor. Thanks.
Customer: replied 1 year ago.
Thanks to your advice, I replaced the hot water thermistor and boiler is now giving hot water in demand. Central heating system also working. Happy customer
Expert:  Plumberpro replied 1 year ago.
Thats great. Well done .Please dont forget to rate me , thanks

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