Riello G5X Burner Logic

[Johntheo5]

After exactly 20 years of running a Firebird 90S boiler fitted with a Riello G5X burner & a RBL 530 SE control box I'm beginning to wonder whether I have a control box problem or if the logic itself isn't logical. I have never ever got a combustion failure lockout.

I have solar thermal water heating so don't use the boiler for ~ 5 months of the year but do fire it up for around 5 minutes every fortnight and last fired it about 9 days ago.

Today, I changed the fire valve as it was sticking and not shutting off the fuel supply, after replacement, I bled the oil right at the pump but when I started up the boiler, it just ran and ran (no flame) until I shut it down after ~ 30/40 secs, seemed like it would have run for ever if I didn't shut it down.

I checked the 3 wire, two winding, oil solenoid coil at (correctly) 1.4ohms & 1.4k ohms, I then removed the 1.4ohm (starting winding) black wire at ter.8 on the control box and just remade it, boiler then fired up as per normal, I then removed that wire again and the boiler just ran and ran again with no lockout after the expected 17 secs, I replaced the wire, boiler fired as normal.

Is this normal behaviour?????.

 

[oilhead]

Classic photocell failure for the first fault. When you remade the connection and it fired, what did you do with the wire when you next removed it?

 

[Johntheo5]

I just left it hanging there in mid air.
There surely couldnt have been photocell failure again because when I reconnected it, the boiler then refired but again just ran and ran when i again removed it and refired again on replacing it.

 

[Johntheo5]

Even though I have a neurotic dislike for running any fuel pump dry I shut off the fuel by closing the new Fire Valve and the burner did cut out about 10 secs or so after no flame visible in the viewing port after ~ 90 seconds when the oil ran out but it didn't illuminate the lockout light, also the burner wouldn't reset for ~ 2 minutes, back to normal again.

Edit: Also found that if I remove terminal1, supply to the holding in oil valve solenoid coil winding that the exact same sequence occurs as with removing terminal8, continuous running with no lockout.

 

[oilhead]

The Control Box is detecting incomplete circuitry with the coils disconnected, As you 'cured' the situation, I would not be tempted to analyse the internal workings of one of the most reliable units in the industry.

 

[Johntheo5]

Just to confirm that photocell failure is not a problem I removed the photocell and fired the boiler, the boiler fired up, ran for 2 or 3 seconds and then locked out.
With the boiler firing normally I also removed the wire from terminal1, the supply to the holding winding of the oil valve solenoid coil and the boiler tripped and locked out.
Its also seemingly apparent that if the oil valve does not open for whatever reason on start up that the the burner will run continuously so even though I may think this is also quite strange to say the least, its the way the logic is built and as you say, and my 20 year old boiler proves it, this control box is ultra reliable.

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