Originally Posted By: dbush This post was automatically imported from our archived forum.
Sorry to the guys in New England, Florida and Arizona.
Okay, not really, I just feel like being cruel today  
Originally Posted By: Blaine Wiley This post was automatically imported from our archived forum.
Well Dave you can say the answer is A if you want, but it is B.
York units come with the Honeywell fan control high limit combination switch with the fan off set at 90, the fan on set at 115 and the high limit preset at 200. The Bryant furnace I just did this morning had a limit switch rated at 200 -25, meaning the limit trips at 200 and resets at 175.
I just looked in one of my inspection books, and it shows a diagram of the Robertshaw switch and it has presets at the same as the York system, and states the high limit setting on most furnaces is 200 degrees.
Oh well, at least I only see two or three gas furnaces per year. 
Originally Posted By: Blaine Wiley This post was automatically imported from our archived forum.
I just note if they aren’t there or aren’t hooked up. I have found them not connected. The Robertshaw and Honeywell ones make it easy to see if the furnace is cycling on high limit, you can just watch the dial!
Originally Posted By: syared This post was automatically imported from our archived forum.
So if I understand this correctly, the high limit is typically 150 degrees, but can be higher based on manufacturers specs. If that’s the case how can we check or report on this if the answer relies on knowing the specs of each furnace, that’s getting too technical and out of our scope, right?
Originally Posted By: jsavino This post was automatically imported from our archived forum.
Joe, You would have to disconnect the load side of the switch. I have installed mostly the Honeywell fan/ limit control. All came pre-set at 100 degrees blower off, 150 degrees blower on and 180 degrees limit.
The newer furnaces come through with a circuit board fan control center that operates by time. Some mounted in the blower compartment. You still have a limit control, but just a mechanical switch, wired to a relay that could be set up to 90 seconds from when the furnace comes on. Regardless if the burners fire up or not. So in the case of a burner malfunction the blower will still start and run for a while.
Manufactures installed these controls to extend the life of the heat exchanger. Only one problem for the service man (Me) that if the blower doesn’t operate, you replace the circuit board. Instead of the F/L switch.
