How to Hook Up a Pull-Out Disconnect Switch

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A pull-out disconnect switch gives a technician a safe way to work on high-voltage appliances without the need to access the appliance's circuit breaker. The National Electrical Code requires that all appliances over 300 volt-amps or over 1/8-horsepower use some sort of "means of disconnect," unless the appliance connects to the electrical system in the same room as and within "line of sight" of the circuit breaker panel. This code specifically refers to large appliances like air conditioning equipment. Air conditioning equipment installers must hook up a disconnect box that can disengage the equipment's electric supply.

Things You'll Need

  • Flat-head screwdriver
  • Knife
  • Wire strippers

Turn off the circuit breaker feeding electricity to the pull-out disconnect switch. This circuit breaker should have a label identifying its appliance.

Grip the disconnect switch's pull-out bus bar and take it out.

Remove the screw at the bottom of the disconnect box's panel cover with a flat-head screwdriver, then remove the cover. This exposes the pull-out disconnect switch's wire terminals. Each terminal has a lug with a slotted screw penetrating its surface.

Loosen the lug's screws with the flat-head screwdriver. A pull-out disconnect switch uses four lugs for the hot wires and one or two lugs for ground, sometimes called earth. The ground lugs connect to a terminal strip mounted on the pull-out disconnect switch's housing.

Remove 3/4 inch of the insulation from each wire in the pull-out disconnect switch. If the wires use braided wire strands, remove the insulation with a sharp knife. If the wires use a single solid-wire strand, use either the sharp knife or wire strippers.

Separate the two wire sets entering the pull-out disconnect switch. Each wire set contains three wires: two hot and one ground.

Insert the ends of the two ground wires, one from each wire set, into the pull-out disconnect box's ground terminal block. Tighten the slotted screws on the grounded block with the flat-head screwdriver. The wire set uses the wire without insulation or the wire with green insulation as ground.

Route the hot wires from one wire set to the pull-out disconnect switch's top wire terminal lugs. Slide one of these wires into one lug and the other wire into the other lug, then tighten the lug's slotted screws with the flat-head screwdriver. The wires and lugs are interchangeable as long as they connect to the top set of lugs.

Position the second wire set's hot wires under the second set of lugs located below the pull-out disconnect switch's bus bar. Slip each wire into a lug, then tighten the lug's slotted screw.

Replace the pull-out disconnect switch's cover and bus bar.

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