Oil boiler lockout

[wolfspark]

For a few weeks now I've been having problems with an oil-fired Heatslave 15/19 locking-out intermittently. The problem lies with the burner not igniting and going into lockout. Having it serviced/nozzle changed and thoroughly checked has failed to cure it but when it was proving particularly stubborn to reset at the weekend I watched the control box go through its operating sequence. I noticed that the contact bar at the top of the control box moved slowly along, engaging the contacts to bring in the motor and solenoid then pausing for a second before moving one last bit to engage the final contact and ignite the burner. When this happens the burner lights, stays lit and the boiler operates perfectly. But sometimes the contact bar reaches the pause position then fails to move further to complete ignition, and the burner enters it's lockout state.

Naturally I assumed the control box was at fault and yesterday fitted a replacement, but the exact same thing is happening, although not so often and it now resets first time.

Now I'm left scratching my head. Any ideas anyone???

 

[martineire]

It could be any of a few possible causes, try photocell first if not try solenoid coil.

 

[casius66]

Call back the fella that serviced it?

 

[wolfspark]

Would a dodgy photocell and/or solenoid affect the operation of the control box prior to ignition though? When the contacts on the control box engage as they should do, the boiler does ignite and operate perfectly which made me think they were both ok

I know the chap who serviced it, and he has been back but the fault won't show itself when I want it to and everything is checking out ok.

 

[casius66]

Can you hear the burner sparking when the control box pauses?
What type of burner is it?

 

[Boilerman2]

Change the Photocell 1st (sounds like it is picking up "false light")

 

[martineire]

Would a dodgy photocell and/or solenoid affect the operation of the control box prior to ignition though? When the contacts on the control box engage as they should do, the boiler does ignite and operate perfectly which made me think they were both ok

Yep of course it would affect it prior to ignition both of them and yes the burner could fire and work and then just lockout because photocell or solenoid could just be faulty and work one min and the next min it will fail. ive seen it happen

 

[Kev F]

if he knows what he is doing you can very easily trick the photocell to check if it works or not

 

[wolfspark]

Can you hear the burner sparking when the control box pauses?
What type of burner is it?

It's a Bentone B9 burner, and it makes no attempt to ignite until the control box progresses past its pause. When the final contacts do close, ignition is instant.

 

[wolfspark]

Would a dodgy photocell and/or solenoid affect the operation of the control box prior to ignition though? When the contacts on the control box engage as they should do, the boiler does ignite and operate perfectly which made me think they were both ok

Yep of course it would affect it prior to ignition both of them and yes the burner could fire and work and then just lockout because photocell or solenoid could just be faulty and work one min and the next min it will fail. ive seen it happen

The burner isn't firing then locking out. It's definitely locking out due to the control box contacts not closing to start ignition.

 

[Boilerman2]

If the burner purges, check for 240v at the solenoid coil plug using a meter if no 240v, as I have already sugested REPALCE THE PE CELL!!!

99% certain a new Photocell will fix this burner

 

[wolfspark]

If the burner purges, check for 240v at the solenoid coil plug using a meter if no 240v, as I have already sugested REPALCE THE PE CELL!!!

99% certain a new Photocell will fix this burner

Thanks for the advice. I've been in the garage twenty times tonight to see if there has been a lock out but it seems to be fine. Replacing the photocell will definitely be the next step though.

 

[martineire]

As i said before photocell or solenoid coil, more than likely PHOTOCELL!

 

[wolfspark]

This is my first oil boiler and I'm still familiarising myself with the way the burner control circuit works so apologies if I'm being a bit thick! Regarding the solenoid, would a faulty one prevent the control box from energising the ignition tranny?
I have followed the schematic for the control box and can see how a faulty photocell could open the flame relay contacts and prevent power from going to the ignition tranny but it seems the solenoid is connected to an outgoing terminal only and has no influence over the operation of the actual control box.

 

[martineire]

This should help you to understand how a oil burner work, this is the boiler start up sequence. Main switch (5 amp fuse) - time clock - room stat - high limit stat boiler stat - capacitor (kick starts motor) - motor spins fan and oil pump - photocell (looks for darkness) - (ok) control box - solenoid coil energizes thus letting oil through while electrodes spark - flame established - photocell reacts to light - run position. By understanding the start up sequence and how the burner works you can find the fault with your burner