Oil burner locks out after running for a few minutes

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Background: HCC Thermotronic T2 oil-fired condensing boiler, that uses a Sterling 40 burner, which is fitted with a Danfoss BFP11 pump.

Fault: When first switched on, the burner fires up and runs normally for about 4 minutes. Then the flame goes out, and the burner locks-out after a few seconds. If I reset it immediately, it will not re-ignite and just locks-out again. If I leave it for about 15 minutes, it will re-light, but just goes out again after another 3 or 4 minutes.

Action so far: I thought it was simply being starved of oil, so I've replaced the oil line filter (Crossland 489) and ensured that oil is flowing freely right up to the burner pump. I've also removed the pump filter to check that is clean too.

Question: what would cause the burner to run normally for a few minutes and then just stop for no apparent reason?

Any suggestions would be most appreciated.

Cheers, DickM
 
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Have to agree with gremlin16. I had a relay on a tumble dryer where the wire in the coil had broken down. When cool it worked fine for about 3mins then stopped when it got warm, but it could be restarted again after a couple of mins, for the process to be repeated.
:rolleyes:
 
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Might be the oil pump solenoid wiring breaking down when it gets warm.

Thanks for the quick responses! The burner is only running for a couple of minutes, so nothing has much chance of getting warm - the external wiring to the solenoid valve is definitely still cold when the burner goes out.

However, your suggestions has made me think there could be something fundamentally faulty with the solenoid, perhaps internal wiring that's failing after being under load for a few minutes, or something mechanical. Does anyone know if the solenoid valve is removable without dismantling the whole pump?

Cheers, DickM
 
don't know about removing the whole valve, You can buy the coil and I assume it is fairly simple to replace. just seen them EOGB site
:rolleyes:
 
The valve is mechanical only. It is operated by current in a coil which is externatl to the pump body.

It could be the coil, photocell, control box or poor adjustment. I have had any of these give those symptoms.

Of more interest though, what is your opinion of the boiler? Do you have the HCC control system for it? Do you find it an efficient boiler?
 
The valve is mechanical only. It is operated by current in a coil which is externatl to the pump body.

It could be the coil, photocell, control box or poor adjustment. I have had any of these give those symptoms.

Thanks for your comments oilman. I guess fitting a new coil on the value is the only way I'm going to know if it's this that's causing the problem or not. :rolleyes:
Any other advice on isolating the problem would be appreciated.

Of more interest though, what is your opinion of the boiler? Do you have the HCC control system for it? Do you find it an efficient boiler?
The boiler itself has given pretty good service since it was installed about 10 years ago. It was bought as part of a complete underfloor heating system for a new barn conversion. I didn't go for the fancy electronic control system if that's what you're referring to.
Since it's the first oil-fired boiler I have experience of, it's a bit difficult for me to judge how efficient it is as I have nothing to compare against. I do know it costs me a small fortune to fill the tank up these days though!

DickM
 
OK, so thanks to the suggestions posted earlier, I connected test leads to the valve solenoid circuit. At startup, current flowed to the solenoid, the valve opened and burned for 4 minutes. Then the flame went out and the valve was switched off ... the two things happened almost at the same time, but I'm convinced that the valve was closed as a result of the flame going out, not vice versa.

Therefore I'm pretty sure the control circuitry and wiring are all fine. And it appears that the solenoid works ok, although obviously I can't tell what's going on inside the valve.

So I think I'll have to replace the whole pump assembly, including valve. Which is a bit of a shame 'cos I'll have to get someone in to adjust the pressure, as I don't think that's something you can do without the right gear.

Thanks to everyone who's chipped in with comments.

Regards, DickM
 
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:LOL:
 
Coil is most likely problem. If you buy a pump, just swap coil first, if it works, you have a spare pump ready for when the pump fails.
 
Oilman! Is there no way the coil can be tested in situ. If the coil was powering up from a switched extension lead instead of the control box and if it failed after 4 mins, the failure I think could be indentified by using a clamp on amp meter. When the amps drop to zero that would prove the coil had basically switched itself off. Would that not work? or am I missing something.
:rolleyes:
 
Good way to test coil is to supply it with mains power external to boiler with the coil in vice or similar. Insert screwdriver, steel with handle down, and switch on and leave. If coil fails then screwdriver will fall out!

Common fault with Danfoss oil pump coils. Boiler runs and then cuts out after short time.
If the coil was powering up from a switched extension lead instead of the control box and if it failed after 4 mins, the failure I think could be indentified by using a clamp on amp meter. When the amps drop to zero that would prove the coil had basically switched itself off. Would that not work? or am I missing something.
Don't try this with boiler running because if oil is gravity fed the boiler might well cut out but if the coil cools before you notice anything you could well end up with a pool of oil in bottom of boiler combustion chamber.
 

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