Heat detectors in the elevator machine room are used to shunt power to elevator equipment as well.
The shunt trip or rather automatic disconnecting means comes from sprinkler requirements for elevator hoistways and machine rooms - ANSI/ASME A17.1 and is referred to in NFPA 72
NFPA 72 just tells us if you are going to do this here is how it will be done. Elevator inspectors in the Denver area have differing opinions as well and I have never seen a fire inspector over ride the elevator inspectors decision.
In one case I had to install two heat detectors in the shaft and machine room that tripped at two different heat levels. The lower temp detector fired a warning horn in the cab to warn the fire fighters of a fire in the shaft or machine room and the second one tripped the power to the equipment.
Edit to add that this system was to give the fire fighters time to get out of the car.
[This message has been edited by kentvw (edited 10-14-2004).]