Oil fired boiler won't light - SOLVED!

[Sam Gangee]

We had an oil-fired boiler installed two years ago. It worked fine for 2 winters. Last week we tried to fire it up for the first time since February and failed. We got the local plumber (Greek) and his apprentice round. The apprentice did a "service", which I didn't watch but he started by cleaning out the soot. I don't know if he cleaned out the oil filter. Eventually they (with my help) traced the fault to the Siemens thermostat, one of whose "finger" contacts was not making connection and showed signs of arcing. I swapped over a pair of (unused) good terminals and all was well. The boiler fired up and the plumbers left.

5 minutes later, as I was bleeding the radiators, the boiler stopped working and I can't restart it.

I've set the thermostat to permanently "on" and the contacts are definitely closed because the red circular lamp on the boiler (see photo) is brightly lit.

I hold the start button in for 5 seconds then release.
The blower runs loudly for 5 seconds, then I hear a click and a humming sound like an AC-powered solenoid for just over a second, then everything goes quiet. I can repeat this ad infinitum.

I'm a 60 year old electronics engineer with electrical and mechanical knowledge so I can do pretty much anything, although I may not understand specific plumbing terminology.

I have access to a reasonably comprehensive tool kit, multimeter, current probe, soldering iron and other stuff.

There's over 700 litres of diesel oil in the tank outside the boiler shed.
The two knobs are set the the correct temperatures that they've always been set to.

Can anybody tell me what I should be testing/ looking for, please?

I can provide additional information as required. Many thanks in advance.

(I'm in Greece right now, by the way.)

 

[xr4x4]

May have air in the line, have you tried bleeding the pump?

Take off the front red cover, find the pump and there should be a hex nut, undo it until liquid comes out.

 

[Sam Gangee]

Thanks. I'm not familiar with the terminology. By "the line" I assume you mean the flexible pipe connecting the filter to something inside the red box.

It's dark and blooming cold here right now but I'll go see if I can remove the red cover. Not sure how it's secured but I'll take my torch and reading glasses!

 

[Sam Gangee]

I can see a hex nut with a slotted screw in the middle. Also a hex head bolt. I'll upload a photo in a couple of minutes.

 

[Sam Gangee]

Here's what I see.

 

[xr4x4]

It's the bottom hex nut, don't adjust the one with the slot.

Make sure the system is off, undo the lower hex bolt until fluid runs out, tighten back up and try again.

Also check any valves on the oil line are fully open.

 

[Sam Gangee]

OK, the bottom nut that looks like a hex bolt head?

By "system off" do you mean switch off the main power switch to the boiler?

I don't know what a valve looks like but the tap outside on the tank outlet has the handle inline with the pipe which I *think* is fully open.

(Thanks for your patience! Sorry, I'm an engineer but I need everything spelled out on this. I don't want to screw this up.)

 

[Sam Gangee]

I switched the power off, slackened the bottom bolt a little until oil trickled out then retightened it.

I switched the power back on and held the red button a few seconds then released it. The system did exactly as described above. No difference.

 

[xr4x4]

How many times did you try and reset, maybe worth two or three.

Don't try to many times, you could damage the pump.

 

[Sam Gangee]

I found the manual: http://oilburnerspares.com/products/images/pages/file/reillo manual/RIELLO-40-G5-3744451-444T50.pdf

I tried only twice.

The manual suggests a different screw.

 

[xr4x4]

I found the manual: http://oilburnerspares.com/products/images/pages/file/reillo manual/RIELLO-40-G5-3744451-444T50.pdf

I tried only twice.

The manual suggests a different screw.

The gauge connection, the one I said!

I could go on, but we are going into unchartered territory by removing the burner unit and checking for fuel and spark at the nozzle.

 

[Sam Gangee]

Thanks, I'll get the plumber back!

(The correct screw appears to be the one at the side with a recessed 3mm hex socket. I used an Allen key to slacken it and oil came out.)

 

[MANDATE]

Is it a combi boiler.
Just thinking if it is and the radiators have been bled, the water pressure will have dropped and that might be the problem

 

[Sam Gangee]

Sorry, I have no idea what a "combi boiler" is but you can see the photo of the boiler in my first post.

 

[Sam Gangee]

A combi boiler is the name given to a boiler that provides heat for central heating and heats water instantaneously on the opening of a hot tap. With a combi there are no tanks in the loft and no storage cylinder. The water is fed from the mains so the water pressure is generally greater.

No, definitely not. It's a central heating boiler which, as a sideline, can also feed hot water (by convection, when the up-feed tap is open) to the solar-heated tank on the roof. It doesn't produce hot tap water on demand. The hot tap water comes from the solar tank on the roof by gravity feed.

When the friggin boiler is working or the sun shines.