Your home's central air conditioning condenser and compressor are located in the outdoor unit, and their power supply passes from the house to the unit via a pull-out disconnector handle. This handle is located inside a small box located near the outdoor unit and will be mounted to your home's exterior wall. On occasion, these disconnect boxes can be short-circuited if the handle is not pushed into its socket; this loose connection causes damage to the panel and handle if arcing occurs. Fortunately, replacement is easy and inexpensive, and below is how you can perform this work yourself:
Tools and materials needed
- 60 amp pull-out disconnect rated for 240 volts
- Rubber washers and grommets
- Diagonal cutting pliers
1. Shut off the electrical power at the circuit breaker panel - Before you begin to perform the replacement, it is critical to shut off the electrical current that flows through the disconnect box. The 240-volt current is strong enough to kill or seriously injure anyone touching it, and you don't want to risk making accidental contact. Locate the wiring diagram on the circuit breaker panel door to identify which breaker should be switched to its "off" position, then flip the switch firmly to ensure the current is disconnected.
2. Understand the layout of the disconnect box - Once you have shut the power off to the disconnect, open the small metal cover to the box by swinging it upward and out of the way. Inside you will see the black plastic disconnect handle and several wires connected to the wiring panel. Immediately beneath the disconnect handle, there are four parallel terminals with wires connected to each; beneath the terminals, there is a ground bar with two terminals and two additional attached wires.
The top four terminals are where the current-carrying wires are attached; the outer two terminals connect power from the house supply, while the inner two wires lead to the condenser and compressor unit. On the disconnect panel, the house supply terminals will be labeled as "line" while the condenser/compressor terminals are designated as "load." Finally, the silver-colored bar at the bottom is where ground wires from both the supply and outside unit are connected.
3. Remove the wiring and old disconnect box - After double-checking the breaker switch to ensure power hasn't been accidentally restored, begin by unscrewing the terminal connectors attached to each of the six wires. Carefully pull the wires free from the terminals and straighten them to make removing the disconnect box an easier task.
Next, loosen the retaining nut inside the disconnect box that attaches the wiring conduit to the box and slide the nut out of the way. Locate and remove the mounting bolts that hold the disconnect box to the wall of your home. At this point, the box should be gently pulled over the wires and away from the wall.
4. Prepare the new disconnect box - Installing the new disconnect box is simple, but it will require some advance preparation of the box. Looking at the old box, find the two knockout plugs located on the new box that correspond to where the previous holes were made. Next, using a steel punch and hammer, sharply strike the center of the knockout plugs, and the metal plugs will "pop" out of the openings. If the conduit is attached using a ¾-inch connector, you will also need to use a pair of diagonal wire cutters to snip and remove the inner rings surrounding the holes before attempting installation.
Once the knockout plugs are removed, insert wire grommets into each opening to protect the wires from being cut. You may be able to remove the grommets from the old box and reuse them if they are in satisfactory condition.
5. Install the new disconnect box - After preparing the new disconnect box, slide the wires leading from the condenser and compressor unit into the bottom opening of the box; do the same with the wires from your home through the back of the box. Pull the wires up and through and adjust the box until it is aligned with the conduit connector. Slip the retainer ring for the conduit over the wires and tighten it on the threaded connector; it only needs to be hand-tight, as the weight of the disconnect box is supported by the wall bolts.
Next, push the wall bolts you removed from the old box through tight-fitting rubber washers and use them to attach the disconnect box to the wall. Tighten the bolts to prevent the box from coming loose and to keep out moisture.
6. Reattach wiring to the new disconnect box - The last step is to reattach the wiring to the terminals inside the disconnect box. Taking the two wires leading from the home, attach them to the outer "line" terminals with your screwdriver. Make the connections as tight as possible, since loose connections can cause arcing or electrical fires. Repeat the process with the two wires from the condenser/compressor by attaching them tightly to the 'load' terminals. Note that there are no positive and negative wires since you are working with alternating current (AC). The remaining two bare, non-insulated wires are ground wires; attach them to the grounding bar found beneath the other terminals.
If you feel you cannot do this on your own, contact a professional electrical contractor or AC repair person, such as those at All American Air & Electric, Inc..