Mid_Tier Inverter Outdoor Wiring
Wiring the Outdoor Unit
Line Voltage Wiring
The line voltage wiring to the (-)A5AZ, (-)A16AZ, and (-)P16AZ Mid-Tier Inverter models is different than a standard unit with a contactor. Simply wire the appropriate size wire from the service disconnect to the L1 and L2 terminals on the line voltage connection block and connect the ground wire to the ground lug. Do not use aluminum wire.
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.
Regarding a similar subject, breaker size should be sized from the minimum breaker size to the maximum breaker size, or anywhere in between. There is no code that says you may only use the maximum breaker size. Local codes may be more stringent than the NEC, but they can’t be more liberal. That is to say, they can’t demand the breaker be sized for the maximum, when the NEC states a smaller breaker can be used. Minimum and Maximum breaker sizes are printed on the unit rating plate.
Communicating Low Voltage
The mid-tier inverter units require 4 wires and must communicate with the indoor unit if variable operation is expected regardless if you use an EcoNet Smart Thermostat or a traditional legacy, 24V thermostat off the shelf. The outdoor unit will receive commands from the indoor unit and in turn will control the indoor blower speed to match the compressor speed to provide best comfort. While the unit's control board has legacy terminals, a few installers have decided to go down this road and it will operate as a single stage unit. That is to say when a call comes to Y1, it will ramp up and jump to line. If a two stage thermostat is used, there is a good chance the outdoor unit will be running on high and the indoor on low causing ice or low pressure faults. If you are going to wire it this way, use a single stage thermostat and make sure the indoor unit goes to high speed. This is ill advised but some of these units, cooling only, are rated as a coil only system. See blow "Legacy Low Voltage wiring"
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.
Utility connections
U and U2 are provided as a convenience when a system is wired with EcoNet and a utility load shedding device is installed by the power company. The utility simply provides a dry set of contacts. Should this be used, the technician or utility service provider will need to configure the utility connections in the EcoNet thermostat. Please see the EcoNet thermostat instructions on how to access this. There is a downloadable letter that describes these instructions for the utility company since they are generally the only ones authorized to make these connections.
Legacy Low Voltage Wiring
The Mid-Tier Inverter products will not run properly when the low voltage wiring from indoor to outdoor are not communicating. That is they should be wired E1, E2, R & C. If it is wired legacy using the standard Y, B, W etc. It will essentially run as a single stage unit. This means if you are using a 2 stage thermostat and the indoor unit gets a call for single stage, it will in fact run on low blower speed but the outdoor will be running on high which may lead to iced indoor coil, low pressure switch trips etc. You will have to jump Y1-Y2 in the furnace or air handler or at the thermostat.
