Servicing the Air Conditioner or Heat Pump
The installation of the DCU DOES NOT complicate the servicing of an air conditioner or heat pump. HVAC units
function normally when the DCU relay is in its closed position. A red or amber light will appear in the window of the switch
when a control event is occurring. If no LED is illuminated, the DCU is in its closed position. If the red or amber LED is
lighted, then the relay is open and the condenser will not run normally. When this is the case, open the control panel of the
condenser and find the wires attached to the compressor contactor. Place a jumper wire between the two blue (or orange)
wires. This will bypass the relay to the DCU. This procedure will allow you to service the unit as if the switch was absent.
After service is complete, remove the jumper. This will restore the DCU to normal service.
THE DCU IS PROPERTY OF DOMINION.
TAMPERING WITH OR DISABLING THE DCU IS PROHIBITED BY DOMINION AND THE TERMS OF THE AGREEMENT.
LEDs and what do they mean?
There are three LEDs in the door of the DCU that indicate the following:
1. The Green LED, when lit or blinking, indicates that both the DCU is receiving power and that the DCUs
circuitry has received the system’s test signal within the past few minutes.
2. The Red and /or Amber LEDs, when lit, indicate that the DCU has been activated and a cycling event is occurring.
3. No LED lights simply means that the DCU is not currently receiving a communication signal.
Replacing the AC unit
If the AC unit must be replaced, disconnect the red, black, and the two blue wires at the compressor contactor. The flexible
conduit can then be removed from the old AC unit. Leave the conduit hanging from the bottom of the DCU. When the
AC unit change-out is complete, please call GoodCents at 886-366-8200.
Does the DCU affect the wear on the contactor?
The compressor contactor connects the 240 volt supply to the compressor and causes it to start. The thermostat controls
the compressor contactor by putting 24 volts on the coil of the contactor. When the thermostat detects the need for
cooling, it connects 24 volts to the relay coil of the compressor contactor, causing the relay to close its contacts. Compressor
contactors are simply relays that have been adapted for this purpose. Most compressor contactors are rated for at least
100,000 operations over the twenty-year life of the compressor. The DCU does not significantly increase the number of
compressor contactor closures/openings and should not have an impact on the life of the contactor.
What happens if the electronics in the DCU fail?
The DCU has a normally closed relay that is wired in series with the thermostat. If the electronics in the DCU fail, the relay
will return to its closed position and the air conditioning unit will operate normally.
Overview
Each air conditioner naturally cycles on and off, as it is needed to maintain a set temperature in the home. The DCU is
simply a radio-controlled device designed to switch air conditioners on and off in response to commands from a central
controller. The DCU is much like a second “smart” thermostat that is remotely programmable, has a memory, and has the
ability to over-ride the existing thermostat’s control of the air conditioner’s compressor. When a control message is sent to
the DCU, the switch executes logic that reduces the air conditioner’s normal cycle time. This means that the air conditioner
will still operate during these high usage periods.
THERE IS NO EVIDENCE THAT A DCU WILL HARM AN AIR CONDITIONING UNIT.
Smart cooling
rewards
Contractor Guide
Dominion’s SMART COOLING REWARDS program helps
manage electrical consumption during periods of peak load
capacity in the summer season and reduces the need to run peak generators
or import electricity into the electrical system. By easing the demand on the power grid,
participating customers can help control costs while keeping power reliable.
What does the DCU do? How does it work?
The DCU acts on commands issued by the utility via a RF paging network much like a cellular network. When the utility
sees a peak system load approaching, or an emergency occurs, it can issue a command over this network that tells the
DCU to begin cycling. The DCU intelligently cycles the unit based on the utility’s need so that the fan continues to run
circulating indoor air throughout the home while still reducing critical demand. When the cycling event ends, the utility
will issue a command that tells the units to gradually come back online one at a time in a random order, helping the
utility to maintain safe and reliable service throughout a critical period. This gradual ramp-up function, called “cold load
pickup”, is pre-programmed into the unit and may activate whenever power is interrupted for more than 20 seconds. This
will delay the unit’s ramp-up by approximately 7.5 minutes.
Installation of the DCU
Dominion will install a device, known as a DCU (AC cycling switch), on or near a customer’s
air conditioner or heat pump system. During periods of high demand, usually the hottest days
of the summer, Dominion may call an “event” which means they will cycle your air conditioner
or heat pump compressor on and off for defined intervals*. The fan will remain on circulating
already cooled air. The Smart Cooling Rewards program is completely voluntary.
participants will receive a $40 check
following each season they participate.
*The Comverge DCU contains a customized adaptive algorithm that realizes the run time of a compressor for the one hour period prior to a cycling event. When an event is called by the utility, the DCU
will allow the compressor to run for a predetermined percentage of time for each hour the event is in progress. For example, Dominion is currently using a 50% cycling strategy for the SCR program.
This means that if the compressor operates for 50 minutes the hour prior to the event, the DCU will run the compressor for 25 minutes during each hour the event is in progress.
1. Circuit Identification- Turn the appliance off at the disconnect. Confirm that the circuit is properly marked and that
the power to the appliance is off.
2. Mounting the DCU- While most units will be mounted on the house, some may be mounted directly on the air
conditioner or heat pump condenser. A junction box at the bottom of the DCU allows for connection to any external
wiring required. Stainless steel screws should be used in each of the three mounting tabs to ensure a clean and sturdy
installation.
Wiring Instructions- All 240 volt cables shall be in flexible conduit with appropriate fittings on each end of the conduit.
Power to run the DCU is supplied through the 14 gauge (black and red) wires to the line-side of the contactor. The low
voltage (Y1) signal from the fan control board to the compressor is wired in series with one of the two 3 amp, normally
closed, control relays in the DCU. Splice the DCU into the low voltage thermostat circuit by cutting the thermostat
wires and utilizing the two blue and/or two orange leads in the DCU to connect it in series with the thermostat. One
relay is required for each compressor controlled, so the second relay in each DCU can be used to control a 2-stage
compressor unit, or to control two AC units that are located near each other.
COMVERGE DIGITAL CYCLING UNIT ( DCU ) DEVICES
Who is Comverge?
Smart Switch
Comverge provides technology hardware and software solutions to electric utilities
across the United States and Canada for the management of “peak load capacity”.
What is “Peak Load Capacity”?
Peak Load Capacity is that point when the level of electrical demand is at its highest.
Peak load usually occurs on hot summer days when many people are running their air
conditioners on high. The cost to produce the energy to meet this peak demand can be
up to 80 times the cost of producing energy on a normal day. *Comverge Technical Manual, 2012
What is a DCU?
The Comverge DCU cycling device is essentially a timer, used to manage the operation
of air conditioning compressors on conventional residential and small commercial
split systems, package units and heat pumps. The intent is to manage/reduce electricity
demand on a power company’s grid during peak load periods. The DCU receives a
RF paging signal from the utility and cycles the appliance on and off as directed. The
device incorporates a circuit board, RF paging receiver, and transformer enclosed in a
water-tight, high-impact poly-carbonate box usually installed near the air conditioning
compressor. This device functions with central air conditioning systems and is not
designed for window-style or small space units.
240 V {
Control
Relay
Condensed Fan Motor
Black
Red
Blue
Blue
Existing
240 VAC
Contactor
240 VAC Supply
24 VAC Thermostat
Control Wiring
X
Control Board
Break Thermostat Circuit
Compressor