I'm new to the forum and I've been in the field for about 4 yrs now but I ran into something that I never seen before. On this lennox unit there was this fan limit switch with a heater. I call lennox tech support and the guy on the phone act like he did not know what it was and what it was used for. Could some one please explain to me what's its function and is it me or is lennox tech support the most complicated people to deal with for information? And also do anyone think that they over control their units?
This was a 80% upflow 100,000 BTU furnace. I can't find the model # but I know the control was a old Honeywell part and the insert size that goes inside the furnace was 8" long.
Heat assist fan switch: Probably the best thing about this type of switch is it's ability to control blower short cycling. When the t'stat is energized it also energizes the heater portion of the fan switch. As it heats a bi-metal strip, the strip warps and closes the fan switch prematurely. As long as the t'stat is calling for heat the blower will stay on. Lets say the return air is pulled from a tile floor area. Since that area would be cold in the morning the air from that area would also be cold and as it passed over the fan switch it would cool it down and it would open, hence short cycling. IF you had a conventional fan switch.