I have a Thermo-Pride forced-air oil furnace.
On Oct. 22, the primary controller was replaced because it was obviously broken. Everything seemed fine after that.
The yearly service was done on Dec 10.
Now we have an intermittent problem:
We set the thermostat to 50 degrees when we are not home and at night, and usually 62 otherwise. Three times recently, separated by 5 or 6 days, the controller has tripped the first thing in the morning when the thermostat is turned up. After it is reset, the furnace runs fine again.
This morning, I checked the controller reset button before I turned the thermostat up and it was not tripped. After I turned up the thermostat, I returned to the basement. I was standing next to the furnace when the controller tripped. This was several minutes after the furnace started and long after the 45sec lockout time. There was no indication to me that the furnace was not running normally when it tripped. If the flame had actually gone out, I’m pretty sure that I would have noticed, because I know what it sounds like when the pump is running but the flame is out. A minute or so later when I was able to reset the controller, the furnace again resumed running normally and seems fine now.
It is almost like the furnace has become reluctant to wake up in the morning. I put a min-max thermometer next to it and the temperature falls to 48-50 at night and when we are away during the day, but this was never a problem before the controller was replaced, nor is it a problem most of the time now.
Obviously, I have to get to the bottom of this or we can never leave home for an extended time.
Is the Honeywell R8184g Primary Controller sometimes defective when new? Is it possible that the cad cell is failing intermittently? What is the usual reason that an oil furnace controller will trip suddenly even if the there is a flame burning?