Rheem trouble

SPB

working on a Rheem 80% (RGDJ-12EARGR) Out in the country so I installed a universal integrated control board. (Original board would not energise the ignitor.) The pressure switch was also intermitant. Replaced the switch also. Switch work fine after the change out. After installing the new board the furnace would fire and then go right out. Would not stay on long enough to get a good micro amp reading but it was 3.9 for that brief second.  Changed out the flame sensor still the same problem, ran a wire from the flame sensor to the control board sensor terminal, still the same problem. Ran a wire from the burner to the board ground wire still the same problem. Next day came back with the Rheem board for that unit, same problem....any ideas?

Mark Eatherton

Check the blower assembly...

Inducer fans get a build up of corrosion on their blades and it significantly negatively affects their ability to move flue gasses, and cause lock outs.



Also, check the vent piping against the manufacturers specs. Some guys cut corners, or push the allowable length limits and the problems raise their ugly heads as components get older. You've replaced everything that could have been defective. Now its time to start looking at the "system" as a whole. Happy Hunting.



ME

Ironman

Also Check...

The ground connection all the way back to the electric panel. If the ground is lost anywhere along the way, the board won't sense a flame and will drop the gas valve out after 4-7 seconds. If you temporarily jump the neutral and ground together at the furnace, and the problem ceases, then you have a bad ground. Make sure there is proper 120v polarity before doing this.



Also, make sure that the flame is properly impinging on the sensor and that it has the proper gap between itself and the burner. Make sure the burner has a good ground.



If you have a good manometer, you can Tee it into the pressure switch and see if the draft remains in the acceptable rating as the burner fires. As Mark said, check the venting system closely.

lchmb

gas pressures

check incoming and manifold gas pressures also. I'm with Mark in that I've seen this system "pop" the pressure switch on burner ignition. Generally caused by undersized venting or blockage. Does it do it with the door off or just when you close up the unit? Has it had this issue?

Steve Whitbeck

Flame out

I would put a temporary Jumper on the pressure switch after the inducer starts and see if the flame stays on.

sometimes the act of ignition will kick out the pressure switch.