Ruud 90+ Model UGRA 10EZAJS is started up in the the morning by setting the tstat to 66 F (actual room temp 59-60 F). Furnace starts and runs fine for a long time (30-40 minutes) as the home temperature climbs to about 63 F - 64F. Then the furnace goes through what appears to be a reset where the flame drops out, the air circulates for a few minutes then the flame tries to come back on. The gas valve cycles open/closed several times but only a partial flame comes up. After several tries the furnace goes into safety lockout and will stay down for 30 minutes. Then the furnace restarts and runs fine the rest of the day. The problem only appears in the morning at first startup. I thought it might be an overtemperature issue. I checked airflow and it is at around 1500 SCFM. Gas (propane) pressure is good. Flame sensor was replaced, gas valve is new. Orefices and gas distribution tubes are clean. Pressure diaphragm switches are new. Furnace filter is clean.
Check for condensation buildup in the Induction Blower housing. The condensate tubes or canister may be blocked and causing the diaphragm switch to trip the unit out causing the burners to shut down.
I would change the thermostat it maybe the issue if that doesn't help check the control board on the furnace
Thermostat is working fine. On startup the IFC board shows 2 green lights (OK & PWR). After about 15 minutes of continuous heating the yellow (flame light) comes on. I have seen the flame come up on a partial burn on occasion. When that happens the gas valve shuts down and the cycle repeats. On the 2nd try there is a full burn and the furnace blower kicks on. Gas pressure is 10-11"WC (propane).
×
1,252 views
Usually answered in minutes!
Removed and sanded flame sensor. Yellow light came on several seconds after ignition. I will observe the furnace further over the next few days to see if that solved the trip out problem.
There were multiple issues at play.
First the condensate drain was clogged and the condensate trap as well. Had to disconnect condensate hoses and blow out any blockage. Then I flushed with hot water. Then I added a small shot of bleach to keep bacteria from growing in the lines.
Second the Condensate buildup flooded the pressure switches used to sense if the purge blower was operating. I had to clean these out and reinstall the switches
Third the wing tips between each burner flam were dirty so the flame would not propagate to the flamerod. I had to remove the burner assemply and remove any soot from the wingt placing a razor thru each wing tip slot.
Now the furnace works perfectly. No control board issues either.
×