Problem getting burner to keep firing

[Robert Tyrrell]

ok - I'm on holiday at the moment and I can't get to the boiler to try anything at the moment but this is bugging me so I'd like your opinions on probable causes/remedies.
Just a few hours before I left for my holiday I got called to a breakdown of a Worcester heatslave because it had started to play up with the burner firing, staying on for 9 seconds, and then going to lockout.
I've done all my diagnostics. Changed the nozzle, pump, photocell, and oil line but I still couldn't get it to work for longer than 9 seconds.
Customer said it started to play up about 2 weeks ago and has steadily got worse.
They aren't too worried about it not working at the moment but I'll be going back as soon as I return from my holiday so any advice would be gratefully received

 

[ShaunCorbs]

Heating pump not pumping?

 

[Robert Tyrrell]

Heating pump not pumping?

Ahhh - now there's a thought. Just goes to show what goes out of the window when you're trying to get packed in time to catch a flight eh?
Thanks.
That'll be my first check when I get back to it

 

[mache]

Solenoid on its last legs. ???

 

[quality]

Ive had that before

 

[Chalked]

What pressure were you getting at the pump?

 

[Robert Tyrrell]

Solenoid on its last legs. ???

Forgot to add that to the list but it was a new danfoss pump, and solenoid. The pressure I set was from the MI

 

[SimonG]

Control box.

 

[Gazzt]

What about the capacitor, it should be 3uf or 4uf, if you have a multi multimeter you can test capacitor.
Also if it was a danfoss L 21 or R21 you have to remove the bypass screw as they now come setup for 2 pipe rather than 1 pipe. Just something to check.

 

[SimonG]

Burner wouldnt fire if it was capacitor. Just buzz.

 

[Best]

Since he ruled out the solenoid and cell, then has to be control box doing a steady second fail.
But you can get new solenoids failing.
I would have swapped the box for a new one to test it instantly.

 

[Robert Tyrrell]

I have swapped out the control box with a new one but it was an older model.
The pump is an 11L3, if memory serves me right. Do they come set up for two pipe now as well?

 

[Best]

I have swapped out the control box with a new one but it was an older model.
The pump is an 11L3, if memory serves me right. Do they come set up for two pipe now as well?

I am not sure, but as it is a wee washer in the 11L3 for one pipe, I would assume it will remain done that way and washer only needs removed for any that are 2 pipe

 

[Gazzt]

I think the danfoss 21r and 21l are set for two pipe, bfp11 come 1 pipe, but check documentation.
After changing all the parts are you still getting lock out.

 

[Gazzt]

I know this might sound daft but is there enough oil in the tank, and if you use a vacuum gauge on the pump it will let you know if you have a blockage, i has seen remote fire valves block with sludge and also they can fail and stick in the closed position.

 

[Robert Tyrrell]

I know this might sound daft but is there enough oil in the tank, and if you use a vacuum gauge on the pump it will let you know if you have a blockage, i has seen remote fire valves block with sludge and also they can fail and stick in the closed position.

Definitely enough oil in the tank and yes, it still went to lockout. There's no blockage at the fire valve either so unless there's any other suggestions I'm going to look at the heating pump, although I don't see how a faulty heating pump would stop the burner working on the hot water side.

 

[Gazzt]

Heating pump failure would affect the high limit on the stat. Are the electrodes correct and aren't cracked, also check the transformer. If the burner locks out after 9 sec the control box is not satisfied a good flame is established. Usally the electrodes should buzz for 12 secs or longer to ensure good ignition and to satisfy the photocell the flame is established. What type of burner is on it.

 

[Best]

Burner going to lockout means fault is at burner only, or oil problem.
Just check if flame is established and is reasonable before burner locks out.
I don't want to go into more detail on open forum about how I test burners

 

[Robert Tyrrell]

Heating pump failure would affect the high limit on the stat. Are the electrodes correct and aren't cracked, also check the transformer. If the burner locks out after 9 sec the control box is not satisfied a good flame is established. Usally the electrodes should buzz for 12 secs or longer to ensure good ignition and to satisfy the photocell the flame is established. What type of burner is on it.

The burner is a sterling 50 as per the MI. I've set it up as per the MI as well

 

[Robert Tyrrell]

Burner going to lockout means fault is at burner only, or oil problem.
Just check if flame is established and is reasonable before burner locks out.
I don't want to go into more detail on open forum about how I test burners

I agree with your assessment that it's at the burner but as it's clearly causing me a problem I'm open to all suggestions as food for thought while I'm lying on my sunbed by the pool
I did check that there was a good flame at the burner so it might be the transformer, or the leads, but surely that would cause an intermittent fault with the initial firing as well. It fires every time, after the reset but still goes to lockout

 

[Best]

I agree with your assessment that it's at the burner but as it's clearly causing me a problem I'm open to all suggestions as food for thought while I'm lying on my sunbed by the pool
I did check that there was a good flame at the burner so it might be the transformer, or the leads, but surely that would cause an intermittent fault with the initial firing as well. It fires every time, after the reset but still goes to lockout

Once the flame is ignited (even just to make my point, if it were to be ignited by a match!) the burner should continue to operate.
Shutting off a few seconds after flame is established suggests control box, but can still be photocell faulty.
Transformer wouldn't have anything to do with lockout once it starts the flame.
Got to check the oil pump to motor drive shaft and drives are not worn and slipping.
Only you said the oil pump is renewed, I would also say check oil pump hasn't a broken drive pin

 

[Gazzt]

I miss read the problem, I thought the burner ran for 9 sec and went to lock out due to ignition failure

 

[Gazzt]

Sterling 50 manual in pdf

 

[SimonG]

Check for loose connection in control box base. Also check if it's over aired.

 

[GH77]

You could run it on an alternative supply of fuel to eliminate any problems with the tank, fuel line, check valve etc, but like best says, not going to divulge exactly how I would do that on an open forum.