I have a Rheem furnace and a Ecobee3 smart thermostat. I'm having a problem where the Ecobee3 randomly loses power and reboots. I've traced this back to the control board (IFC) inside the HVAC unit. I don't know exactly what is causing the power to cut out, but my guess is that it is some type of kill switch built into the unit. Regardless of the reason the power is cutting out, I want to see if I can first fix my Ecobee3 issue.
To fix the Ecobee3 issue, can I remove the R and C wires from the IFC and wire them directly into the transformer inside the HVAC unit?
EDIT: Here is the wiring diagram image.
Also, the IFC model number is 1012-925A and the HVAC unit is a Rheem Classic 90 Plus. I don't know the if the number on the wiring diagram is the model number, but that number is 90-24007-03.
EDIT 2: I pulled two different switches. One of the limits for the burners (first image) and one for the pressure switches (second image). When the burner switch was open, the thermostat lost power. When the second was open, the thermostat didn't lose power.
It looks like the HVAC system or the IFC is opening one of the limits, which is cutting power to the board. This must be how it prevents the house for exploding. :)
I don't think it is normal that the HVAC/IFC is killing power multiple times per day, but it sounds like it might be time to have someone take apart the whole system and see why that is happening.