Elevator Shunt Trip Primer
Elevator Shunt Trip Primer
The shunt trip breaker used in elevator service is to prevent the mixing of water and electricity, generally considered a "bad thing". At the top and possibly bottom of the elevator shaft you may have a sprinkler. The sprinkler will have a temperature rating of, say, 155F or 165F. Not more than 24" from the sprinkler will be a heat detector operating at a temperature below that of the sprinkler, say 135F fixed (no rate of rise, thank you very much). The theory is that if the fire breaks into the elevator shaft, the heat detector will activate just before the sprinkler opens up. When the heat detector activates, the fire alarm control panel (FACP) closes a relay (located within 3' of the elevator control circuit) which causes the elevator controller to power the shunt trip coil, activating the shunt trip, killing power to the elevator stopping it dead where it is and possibly leading to "extra crispy" passengers who are, at this point, most likely to be fire fighters. Depending on the various codes, the FACP may trip the coil directly, in which case it will most likely use 24VDC from the panels AUX power terminals.
I have heard of jurisdictions allowing the car to return directly to some floor before the juice is actually cut, but if the fire is in the shaft you could send the car right through the fire or land it on the fire floor. At this point you probably need to prepare to have a very bad day.
There are undoubtedly a few details I've missed, but I think I've given you the jist of it.
