People are looking for ways to save money on their utility costs, especially, air conditioning. To control the power usage in peak times, some Utility Companies regulate consumer usage by cycling off a consumer’s A/C outdoor unit at selected times during high energy demand summer days. In return for allowing them to do this, many Utility Companies give the consumer a “break” on their electric rates. The control they use breaks one of the low voltage wires to the outdoor unit, turning the outdoor unit off for approximately 10 minutes every half hour.
There are a lot of ways to do this. The most common way is, with single stage cooling systems, the Utility Company can break the “Y” wire or Common wire to the unit without an issue. However, with heat pumps and two-stage equipment or any unit with a control board, the wire chosen is more critical. If the Y1 wire is chosen on a two-stage cooling or two-stage heat pump unit, the Utility Company is disabling the first stage cooling, but not the second stage. In this case the unit is not actually being cycled off by the Utility Company. If the unit is equipped with safety controls and a control board, nuisance “lock-outs” and needless service calls can occur .
So to simplify how to do this, in every case the Common wire to the contactor should be chosen as the control wire to be broken through the energy company monitoring device. If you just remember this, it will always work and you won’t have to be concerned about not doing it correctly or having nuisance lock-outs. This would insure that the outdoor unit can be properly cycled off.
By breaking the common wire, to the contactor, you are disabling the compressor and condenser fan motor, effectively shutting off the air conditioner or heat pump regardless of whether it is single stage or 2 stage.
Do not break the wires coming into the outdoor unit from the thermostat but, rather,break the common wire to the contactor. On some units, this may be an output off a unit control board. By doing this, you will eliminate the need for additional relays to shut off a 2-stage unit and accomplish what the Utility Company is trying to do and your customer can take advantage of any rate reduction the Utility Company may be offering.