When it comes time to service or replace your air conditioner, you’ll need to disconnect the wires connecting it to your home’s electrical system. Selecting the right wire for disconnecting your AC unit is important for safety and performance reasons. In this comprehensive guide, we’ll walk through the key factors in choosing the correct disconnect wire for your air conditioner. We’ll also provide step-by-step instructions for safely disconnecting the wires.
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Choosing the Right Disconnect Wire
The wire you use to disconnect your outdoor AC unit will depend on two main factors:
AC Unit Power Rating
Air conditioners are available in a wide range of cooling capacities and electrical power ratings. Central AC units typically range from 1.5 tons (18,000 BTU) up to 5 tons (60,000 BTU) or more. The larger the cooling capacity, the higher the electrical power required.
Most residential AC units will have a nameplate listing the voltage, phase, and amperage or wattage rating. This tells you how much electric current the AC wiring needs to handle. For example, a 3-ton outdoor AC unit may be rated for 240 volts, single phase, and 36 amps.
Match the wire size to the nameplate amperage/wattage rating. undersized wire can overheat, while oversized wire is safe but wasteful. Refer to electrical code books for appropriate wire sizes.
Distance from Electrical Panel
The longer the wire run from your home’s main electrical panel to the outdoor AC unit, the thicker the wire needs to be. Long wire runs cause voltage drop due to resistance in the copper wire. Thicker wires have lower resistance to counteract this effect.
Refer to electrical wiring codes to determine the appropriate wire gauge based on the circuit amperage and length of the wire run. For example, a typical residential AC unit with a 30 amp circuit may require #10 gauge wire for a run up to 100 feet from the electrical panel.
Commonly Used AC Disconnect Wire Types
Two main types of electrical wire are commonly used for air conditioner disconnects:
THHN Wire
THHN is an inexpensive single copper conductor wire with thermoplastic high heat-resistant insulation. The THHN stands for Thermoplastic High Heat-resistant Nylon coated wire. It can be used for both indoor and outdoor AC wiring.
Key features:
– Copper conductor (typically stranded for flexibility)
– PVC insulation rated for high temperatures
– Nylon outer coating for protection and abrasion resistance
– Rated for wet locations
– Available in a wide range of sizes
THHN is typically used for wiring air conditioner disconnects and circuit breakers. It allows quick wiring changes during AC service or replacement.
Armored Cable (AC)
Armored cable, also known as AC cable or armored clad cable, contains insulated copper wires wrapped in a flexible metal armor. The armor protects against physical damage.
Key features:
– Aluminum or galvanized steel armor over wires
– Available with 2-4 insulated conductors
– PVC outer jacket
– Rated for indoor and outdoor wet locations
Armored cable is more durable than THHN but less flexible. It’s commonly used as a permanent wiring method for air conditioners. The metal armor also provides additional grounding.
How to Disconnect AC Wires
When you’re ready to disconnect the wires from your outdoor AC unit, follow these safe procedures:
Step 1: Turn Off Power at Breaker
Locate the circuit breaker powering the AC unit in your home’s main electric panel. Turn off the breaker and double check power is off at the AC unit with a non-contact voltage tester.
You should always turn off power to the AC unit at the breaker before disconnecting wires. This avoids dangerous shock hazards.
Step 2: Remove Service Panel
The AC wires typically enter through a removable service access panel on the side of the unit. Unscrew the cover and set it aside to expose the wire connections.
You may see wire connectors or terminals blocks inside. There may also be knockouts where conduit or armored cable enters the unit’s outer casing.
Step 3: Disconnect Wires
Carefully loosen any cable clamps and remove any wire terminal connections. Many times you can simply loosen a screw terminal and pull the wire out.
For hardwired connections, you may need to cut the wires. Make sure to leave at least 6 inches of wire to allow reconnecting. Cap any unused wires with wire nuts to prevent short circuits.
Double check all connections are removed and no bare wires are exposed before proceeding.
Step 4: Remove Conduit (if present)
If metal or PVC conduit is running to the AC unit, this will also need to be disconnected before you can fully remove the unit. Loosen any conduit clamps at the entry point.
For flexible metal conduit, unscrew any compression fittings at joints to detach it from the AC casing. For rigid metal or PVC conduit, you may need to cut it with a hacksaw to disconnect it.
Step 5: Pull Wires Back
With all the wire and conduit connections removed, gently pull the disconnected wires out from the AC unit. For easier pulling, you can cut the wires back closer to the conduit entry point.
Pull the wires entirely out from the AC casing so they are fully disconnected. Take care not to damage the wire insulation while pulling.
Step 6: Cap and Tape Ends
Put a wire cap on the end of any cut wires to prevent exposed copper from shorting. For additional protection, wrap the wire ends with electrical tape.
The capped ends will allow you to safely pull the wires out of the way while you remove or service the AC equipment.
Step 7: Replace Access Panel
Once all wiring is disconnected, replace the service access panel and screws. This will protect the interior connections until you are ready to reconnect a new or serviced AC unit.
Reconnecting AC Wires
When it’s time to reconnect the air conditioner, follow these tips for proper and safe rewiring:
– Inspect wires for any damage before reconnecting. Replace wires if insulation is cracked or conductors are exposed.
– Use wire crimp connectors or terminal blocks to securely reconnect wires. Follow manufacturer specifications.
– Match wire colors/labeling between the AC unit and your home’s wiring.
– Use strain relief clamps where wires enter the AC casing to prevent pulling on connections.
– Ensure bare copper or ground wires are securely attached to the metal AC chassis for proper grounding.
– Replace the service access panel and all covers when done.
– Restore power at the circuit breaker and test operation carefully before regular use.
Conclusion
Disconnecting your air conditioner involves shutting off power, removing any conduit connections, detaching the wires, capping the ends, and replacing covers. THHN building wire and armored cable are common disconnect wire types due to their durability, heat resistance, and availability. Following proper electrical safety procedures is crucial when disconnecting AC power. With the right preparation and care, you can safely detach your air conditioner for replacement or maintenance.