Worcester Oil Boiler Trouble

[FrenziedCarrot]

Hi All,
I have a Worcester Danesmoor 20/25 oil boiler which is causing me lots of heartache and grief. About 3 months ago it locked out and wouldn't fire up when reset so I called out the local (but recently retired) engineer to see what he thought. He thought it was the pump so he serviced the boiler and replaced the pump. It fired up and ran for about a week. Then it started making a nasty noise so I called him back in and he said that the fan motor had now failed (bearings had gone) and fair enough it was clear to see that that was the problem. He replaced it and it fired up again and ran for a couple of days before it locked out again. I got the guy back again and he swapped out the controller for another that he had and it fired up again. He suggested that I get a new controller so I did and I fitted it. He also suggested that as it was about the only thing left to replace that I should get a new photo cell, I did, I fitted it and all was well...

The boiler ran fine-ish (a couple of mornings it had locked out but I reset it and it fired up again) for a few weeks until this morning when it went into lock out again. Knowing that our oil level was low I went out and checked the level in the tank only to find that it was looking pretty dire. I assumed that I'd run out of oil which isn't the end of the world because I have a delivery coming tomorrow. However, I pressed the lock out reset button just to be sure and just as I expected it didn't fire. What I found curious though was that I could smell oil from the flue so I opened the bleed valve and out came oil.

My questions are: Is it possible that the boiler wouldn't fire because the oil level was very low (but clearly not completely empty)? If the oil isn't the problem what else could it be? I'm obviously not a heating engineer but I am an electrical engineer with so I understand how systems work and how to fault find etc. so if there's any practical advice that I could follow to try and trace the issue I'd be hugely grateful. Obviously, if the only advice is "get a heating engineer in to sort it out" then so be it but I'd like to try and understand what's going on and if possible sort it out myself.

Thanks in advance for any help.

 

[SimonG]

It's a combustion appliance definitely not diy.
It sounds like once you have oil it will need bleeding and the combustion setting properly.

 

[Timmy D]

If the oil was low, Rubbish from the bottom of the tank can/will effect the boiler/cause lock outs.

If it’s that low, depending on tank age, if you’ve never had the tank cleaned, maybe now is the time.

At the minimum, the tank should be checked for water (it sits on the bottom, under the oil), water could have been pulled through.

Filters/lines/nozzles etc need cleaning replaced.

Does the burner have no diagnostics to tell you why it locked out?

 

[FrenziedCarrot]

If the oil was low, Rubbish from the bottom of the tank can/will effect the boiler/cause lock outs.

If it’s that low, depending on tank age, if you’ve never had the tank cleaned, maybe now is the time.

At the minimum, the tank should be checked for water (it sits on the bottom, under the oil), water could have been pulled through.

Filters/lines/nozzles etc need cleaning replaced.

Does the burner have no diagnostics to tell you why it locked out?

Thanks for that Timmy D. The tank is about 6-8 years old and as far as I know has never been cleaned out. The in-line filter and nozzle were replaced at the last boiler service but I'll check the filter in the morning. Am I right in thinking there's a product that detects water in the tank, like a sort of litmus paper that changes colour if water is present?

I can't see anywhere on the boiler where it may give any sort of diagnostics. It's about 20 years old and I was all for replacing it but the engineer talked me out of it saying it was a solid machine and it was better to maintain/repair it rather than spring for a new one - I'm not sure.

 

[FrenziedCarrot]

It's a combustion appliance definitely not diy.
It sounds like once you have oil it will need bleeding and the combustion setting properly.

I'm not opposed to getting a professional in, I was just looking to see if there's anything I check first.

 

[FrenziedCarrot]

Update: I couldn't get hold of a heating engineer at short notice but I did have a conversation with a very helpful one who I carefully explained the problem to and he immediately said it sounded like the ignition transformer might have failed. I picked up a new one, fitted it and the boiler fired straight back into life again which, given the temperature last weekend, was a great relief.

The engineer is coming over next week to give the boiler a thorough check over and to adjust the mixture etc as it's running a little sooty.