Furnace fan switch settings?

[Whoaru99]

On the Honeywell-type of furnace fan switch with the dial and the two adjustments for fan off and on, which edge of the trips should be aligned with the temp setting I want?

Does it work like a rising and falling trip where I'd use the lower edge of the fan off and the upper edge of the fan on?

Or, is it like a window where I'd use the upper edge of the fan off and the lower edge of the fan on?

[low277]

If this is the type that I remember with the bi-metal probe the adjustable pointers are fairly large, the pointer may cover a few degrees.

Does the one you have use a metal dial with 3 adjustable pointers for fan on, fan off and limit? It may also have a push/pull switch for auto/manual?

[Whoaru99]

Yes, that's it, but no auto/manual switch on this one.

[low277]

I don,t remember how fine the adjustment is these, I thought the dial was marked in about 10 degree increments and the adjustable point lever was maybe about 3-5 degrees in width.

You may need to play the the settings a little if you are looking for a specific range. It would be helpful if you had a duct thermometer or another way to check the accuracy of the fan limit switch.

Not sure if helps you any...

[Whoaru99]

I have a way to monitor and data log several channels of temp and have thought of doing that just for kicks - return air temp, plenum temp, outlet temp at ends of longest runs, etc. but I'm not quite that bored just yet. Maybe middle of winter.

Will probably just tinker with some different settings. The goal being to see if I can get a little more heat out of the exchanger. My thought was I might be able to extract a little more heat from each burn cycle by turning on the blower a little sooner and off a little later...as long as I don't create a short cycle of the fan or blow around a bunch of cool air causing a drafty feeling.

[low277]

It sounds like you have some nice equipment to work with.

Are you in the hvac business?

[Whoaru99]

Yes, my employer provides some nice gear to work with but it's not directly related to HVAC. Although, I could be involved in instrumenting an HVAC system if the need arose.