intermittent lockout on 40 series f5 riello burner

elite_hvac

Hey, guys. Hopefully i can get some insight here. My sister's mother in law has a Carrier low boy furnace with a Riello f5 burner. The system was installed about 6 years ago, and I recently started servicing it for her. She says that ever since installed, there has been intermittent issues where the burner goes off on reset. after taking over the service on this about 6 weeks ago, i have noticed that this is the case. This this will run like a top (although not always that way) for weeks on end and then lockout. At this time, I have done a full tune up and combustion test and have everything up to spec per manufacturer. Initially, everything was out of wack. Draft, CO, electrodes, etc. Those issues have all been resolved. A draft inducer fan was installed and the primary control and cad cell have also been replaced. It has been running beautifully for the last three weeks and the other night i received a call that it had gone off on reset again. Any ideas as to what the problem might be??

HVACNUT

What's the O2 reading? Too much air on a cold start? Could be oil related. Suction leak, high vacuum.
Why the draft inducer?
Being intermittent, I doubt it's a burner component.
Spec charts on an OEM Riello often have the air setting too high.
Close down the air to a trace smoke, then slowly open for 0.

SuperTech

The burner will lock out because the cad cell relay was tripping. It's either not seeing the flame when it should or it is seeing flame or light (hot spot in the chamber?) when it shouldn't.
Combustion analysis during operation will likely explain the issue.

Big Ed_4

Fuel supply , does it only happen on cold days ... Fuel line freezing . Any vacuum or high resistance… Check the porcelain look underneath for cracks . … Does your state allow corn oil to be mixed with the fuel oil ? Move to the "W" nozzle .Check the prongs on the primary holder ... Not too many hit or miss items with an Riello .

STEVEusaPA

No compression fittings.
I would power purge the fuel system, and check for a vacuum leak. I would also ohm out the coil.
Describe the tank, location related to burner, how the oil line is ran (1 pipe, etc.), length, line coming out of the bottom/top of tank, etc. height of burner vs bottom of tank.
You can also slip a standard cad cell eye and wire into the air tube and read ohms, but I think it's more fuel related.
I also wonder about the draft inducer-what were your numbers? Usually with Riello's you have too much draft.

DZoro

Was the tank and line installed new at the same time as the furnace? Have you ran any oil treatment in the tank?
D