It should be within reach of the compressor or if the fan/ condenser is remote, within reach of it. The point of it is to allow the mechanical equipment to be shut down without any confusion as to whether the "right" switch was thrown or not, and to allow rapid shut down if there's an accident or problem.
so how does it happen that some of these switches has no breaker or fuse , i mean if there is a fault and the line is not off really, can it be dangerous to open the switch? an arc perhAPS???
A disconnect and fault protection are different. One is just to remove power for service or accident prevention. The other is for automatic disconnection during fault conditons.
A disconnect CAN also be fault protection if it is a circuit breaker or has fuses associated with it.
A disconnect must be able to cut the power OFF to the machinery, so no, there should be no arc flash issues associated with a closed enclosure disconnect switch. If the disconnect includes fuses they should be disconnected by operating the disconnect. This would allow one to replace the fuses. Of course if there is any question about power still being present after operation of a disconnect you should use a voltmeter to test for it.
A fault condition will be disconnected immediately by the fuses or breaker. A high resistance fault may persist for some seconds. The fault does not wait for the serviceman to arrive and disconnect the power.
The mechanism used in an approved disconnect switch is rated to interrupt fault current in the rare event that the switch may be opened during a fault.
The code mandates that a disconnect must be installed within sight and within a certain number of feet of the equipment protected. There are exceptions.
Bill
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"Why not the best?"
Jimmy Carter
