Riallo OIL Boiler strangeness.

Do you have a pump overrun? Maybe the boiler got itself hot, the thermostat turned it off, the pump stopped, the water in the heat exchanger overheated, and the overtemp stat kicked in?

Or maybe something with the fuel: blocked filter, damp fuel more sludgy when cold?

Theo

that doesn't make sense

the ufh has a secondary circulation pump that will keep water circulating - including through the boiler until its up to temp.

could be. it was near the end of a tank ]

My feeling is thicker fuel. Back in the really bad winters before Trucks had tank heaters, you could see whole rows of them with frozen fuel or at least sticky fuel in the feed lines.

Brian

The Natural Philosopher snipped-for-privacy@invalid.invalid posted

Faulty oil pump coil? Tripped overheating protection thermostat?

Pump is very new.

Overheating sounds likely, Under what conditions does it trip?

Perhaps the power supply to the heater (and pump) was switched off while the heater was still very hot, without allowing a pump overrun to cool it down. An automatic timer might have done that. Or a power cut?

OK, at first sight that seems unlikely. But that's at first sight. The boiler would only get switched off if the thermostat for the UFH registered full temperature. At that point the UFH pump shuts down, and that drops the relay that controls the boiler and its circulation pump. I would have thought that would not happen when the boiler was at full chat. Well food for thought. Fresh fuel is in, and the weather is warmer, and it hasn't locked out yet

Maybe there's a drop or two of water lying in a low point of the fuel line or the fuel filter medium is wet with water and the water turned to ice. Not necessarily as a solid plug but sufficient to create a restriction, starving the oil pump so the fuel didn't atomise properly on start up to light from the ignition arc. I'd check/clean the oil filter and blow out or purge the fuel line between tank and burner.

I suspect the fuel in this case will be kerosine not diesel.

That sounds a bit on the chilly side? Digit missing? Or do you mean ambient outside is 0C or above.

I had something a bit like that once. It turned out to be a very slow leak on the solenoid so that when it fired up first thing in the morning there would be a sooty flame of excess fuel that built up overnight. It doesn't take much and soot is cumulative on the flame sensor.

It would invariably either work fine all day or lockout when it first fired in the morning. Being an intermittent fault it took a while to find it. Regular cleaning of the flame sensor made it more bearable.

The other candidate for misbehaviour after a long burn is some sort of leak in the exhaust gas flue - that is potentially more serious.

Is there a filter in the oil supply line which has an element that needs to be changed or cleaned regularly?

Not sure - there are some little cylindrical things here and there.

Nothing's been touched for 20 years since installation :-)

Like the Biodigester sewage treatment plant, and the lawnmower, no regular maintenance has ever been done.

Just fix em when they break.

Cheaper that way...