Indoor Wiring
Wiring the Air Handler
Line Voltage Wiring
Air Handlers require line voltage with a ground from a service disconnect. Voltage connects at the electric heater kit if one is installed. If no heater kit is installed, the terminal block to the right of the blower (in an up-flow application) will be used. The heater kit, if installed will also feed this terminal block.
The National Electric Code specifies that wire size between the breaker and the unit be sized to handle the Minimum Circuit Ampacity of the equipment. Too many electricians, technicians, and even local inspectors try to size the wire for the breaker. Wire size is not as simple as 15 amps for 14 Gauge, 20 Amps for 12 gauge, and 30 amps for 10 gauge and so on. Type of wire, length, ambient temperature wiring is exposed to, and how many wires in the conduit, all play into sizing wire. If you do not own a copy of the NEC, it would be a good idea to purchase one.
Breakers in heater kits are not sized as overload protection, they are essentially switches. Your breakers in the breaker box are the circuit protection.
Communicating Low Voltage
It is highly recommended to wire the system communicating using EcoNet. Low voltage wiring is made simply by connecting R, C, E1, and E2 to the wire leads sticking out of the air handler. R is red, C is brown, E1 is brown with a white stripe and E2 is purple. Be sure to remain consistent in wire colors between equipment. It’s best not to have a bunch of wire nuts beyond that required to hook up the air handler.
Communication circuits use E1 and E2. Common is closely tied to these so installing a second transformer in the outdoor unit because there aren’t 4 wires in the bundle is prohibited. You will need to run 4 wires from the indoor unit to the outdoor unit. The last thing you want is sketchy operation which almost always results in parts changing until someone points out the problem as being improperly wired.
Legacy Low Voltage Wiring
If for some reason you have elected to wire the system with legacy connections, and accept that diagnostics, staging and overall performance will be negatively impacted, you will connect all connections on the low voltage wires. For Heat pumps this means R, C, G, Y, Y2, B and W. For straight cooling you will still need R, C, G, Y, and Y2. Legacy wiring should be limited to emergency use.
Wiring the Auxiliary Inputs
Follow the link below to learn about the use and wiring of the auxiliary inputs found on the air handlers.
