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Brian, Plumber
Category: UK Plumbing
Satisfied Customers: 848
Experience:  16 yrs. experience as plumber, including full bathroom and kitchen installations.
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I have a rdb 1 burner which I think has an intermediate

Customer Question

I have a rdb 1 burner which I think has an intermediate fault.
The boiler starts up perfectly when cold however when hot it may do the following
starts up on purge cycle but after about 10 seconds instead of lighting up I hear a clicking sound the boiler does not light up this purge cycle will continue for up to3 -4 times before before boiler lights up and runs perfectly.
i have checked and set electrodes and they are clean and bright
the pump pressure is at 8 bar checked with gauge,however during purge cycle it is under1 bar
the flame seem fine exactly as it has been for ages
I am wondering if there is an intetmittent fault in either coil or photocell or even control box
All filters etc are clean .The red lock out light light never comes on.
any help /advice would be greatly appreciated
Submitted: 2 years ago.
Category: UK Plumbing
Expert:  Brian replied 2 years ago.

Hi this is usually a fuel supply problem but as you say it only happens when its hot its very unusual.

The photocell either produces a lock out Or the motor will just keep purging without trying to fire.

The transformer which is combined with the control box also produces a lock out.

yes its quite normal for the pump pressure to be low until the coil activates.

The Coil will normally produce a lock out but i suppose if its activating and the valve is sticking it will produce this fault, because no fuel will be getting through to the nozzle.

If your absolutely sure fuel has a positive gravity pressure to the pump at all times then i would try the solenoid valve first.

Customer: replied 2 years ago.
Thanks the tank is higher than burner so gives gravity flow to burner
I have checked coil for continuity and is ok
Customer: replied 2 years ago.
I have now checked coil voltage it is 36 volts when boiler running
Ialso removed photocell when boiler running and blacked out photocell but boiler continued to run does that photocell is on the way out
Expert:  Brian replied 2 years ago.

coil voltage should be 29 volts on start up and 3 volts when running but I didn't think it was a problem when its running. I am thinking you may have a sticky solenoid valve

The photocell didn't produce a lock out or shut the flame off? Then yes I would certainly try another one in there