Cycling off A/C or Heat Pumps by Utility Companies


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.

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 .

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.  In the attachment, the common wire has been disconnected from the contactor and connected to the entering side of the monitoring device. A new wire would then be connected from the leaving side of the monitoring device to the common side of the contactor. This would insure that the outdoor unit can be properly cycled off.

By breaking the common wire, to the contactor, we disable 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.

Attached below is a simple wiring diagram showing this.

Cycling off AC by Energy Companies W_D

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About yorkcentraltechtalk

I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired. One of my goals has always been to "educate" dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it. The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way. I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about. Thanks for taking the time to read my postings! Mike Bishop
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