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rdkenney · Nov 18, 2009, 03:29 PM

HELP.

I have a Lennox OF23Q3 oil burner. It is tripping out the safety button on the primary control erratically during operation. Sometimes it runs 20 minutes before tripping and sometimes only a few minutes. When it does trip the blower just constantly runs until the power is cut.

I have changed filter, nozzle, cad cell, adjusted the electrodes. With no help. I have also jumped the cad cell terminals as described in the service manual. It did not trip off which is supposed to eliminate the primary control as a problem.

Any idea what I should be looking at to repair it? Perhaps the blower control board?

Joshdta · Nov 18, 2009, 03:58 PM

Could be a weak transformer, or a air leak in the line. Or even a bad pump, did you bleed some oil in a cup and look to see how much air there was, or any water?

KC13 · Nov 18, 2009, 04:04 PM

Was the burner firing (flame present) at the time you observed the primary control lockout? Does the CAD cell have a clear line-of-sight toward the firing assembly? I doubt the blower control is contributing to the problem in any fashion.

rdkenney · Nov 18, 2009, 04:13 PM

Originally Posted by KC13

Was the burner firing (flame present) at the time you observed the primary control lockout? Does the CAD cell have a clear line-of-sight toward the firing assembly? I doubt the blower control is contributing to the problem in any fashion.

The burner was firing and I believe the new cad cell is aimed right at the flame/electrodes

I wonder why it would fire for 20 minutes before tripping the safety button? The safety button trips based on flame failure correct?

rdkenney · Nov 18, 2009, 04:14 PM

The pump was bled and is air free...

KC13 · Nov 18, 2009, 04:16 PM

The CAD cell is very similar to a photocell. Its resistance varies with the level of exposure to light. The primary control is seeking an acceptable resistance value to prove successful ignition & sustained firing.

KC13 · Nov 18, 2009, 04:17 PM

Check for pinched/damaged CAD cell leads.

rdkenney · Nov 18, 2009, 04:24 PM

OK I'll check the leads, perhaps replace them.

The old cad cell was dirty so not to take a chance we just replaced it.

Even though the furnace is 8 yrs old it is used in our 3 season 'camp' and has probably seen only a year's worth of use.

Thanks for your help.

KC13 · Nov 18, 2009, 04:27 PM

With fuel oil units, more problems arise as a result of sitting idle than from running. Think of it as a diesel that is parked for months...

rdkenney · Nov 18, 2009, 04:34 PM

Yes I have found that out ! I have an outside tank full of 50/50 fuel oil.

Usually use the LP gas logs for heat but the women use the camp and have trouble getting it lit.

puzzles1 · Mar 17, 2013, 11:55 AM

The furnace comes on and runs tills blower comes on , runs about 10 min. when blower stops, furance stops and furance will not come on again until you hit the reset bottom. This is when the house is cold.