What Does This Switch Do?

[Jim Robinson]

Just out of curiosity, what does this switch turn on or off? I see it on my Trane rental furnaces, and at other forced air units. Are the P1 and P2 settings relevant to anything in residential use?

[Jim Luttrall]

Manual off switch.

[Jim Robinson]

P1 and P2 are referring to the wire terminals, now that I look closer. So if I switch that to OFF, the gas should stop flowing regardless of the thermostat setting? Not planning on doing that on someone else's furnace, and not really sure why I'd need to on my own.

[Bob Harper]

When setting up a furnace for the first time, you need to go through a process of firing the unit and adjusting the gas manifold pressures on hi and lo. Part of this process involves shutting off the gas while it is still running then switching the gas back on. It allows the board to 'learn' that particular unit with respect to the manifold pressure referenced to the vent pressure sensor tubing. Each unit is different thus the process.
HTH

[Benjamin Thompson]

It's in the furnace, It says "ON" and "OFF". What do you think it does?:)

[Garry Blankenship]

It's in the furnace, It says "ON" and "OFF". What do you think it does?:)

The real challenging ones say NO and FFO.

[Bob Harper]

The real challenging ones say NO and FFO.

You mean like blondes at the auto supply house asking for a '710' cap?

[Benjamin Thompson]

You mean like blondes at the auto supply house asking for a '710' cap?

Took me a minute. I must be part blonde