Note that activation of the emergency switch will turn the exhaust fan on and the intake fan off, regardless of the manual switch position. The colors of the microswitch connector may not match those of the unit installed by your fire-suppression-system installers.
I came up with this circuit so I could use 3-conductor MC instead of 1/2" flex with pulled conductors. There is EMT between two handy-boxes; one nippled to the control box, and the other higher up, where the MC ends.
This circuit can be used to control contactors, as well as motors. Note also that some systems use separate intake and exhaust switches, and may require four conductors and both microswitches (in units that have two).
[This message has been edited by Larry Fine (edited 02-04-2006).]