The optional Dual Unit Control is designed to control two InteleCool or two InteleCool2® units in a
lead/lag fashion. The control contains an electronic timer for switching the operating sequence of two
units at intervals of one, two, four or eight days.
It also contains a two-stage heat/two-stage cool electronic thermostat with individual heat and cool
setpoints. Light emitting diodes (LEDs) indicate Lead Unit 1 or 2 and power to Unit 1 or Unit 2. If
required for service, thelead/lag unit may be selected manually with the P2 jumper on the Dual Unit
Control board.
1.1Connecting the Dual Unit Controller to an Electronic Thermostat
The instructions below refer to Liebert’s original InteleCool and newer InteleCool2.
1.1.1Connecting the Dual Unit Controller to an InteleCool2
1. Install and level the Dual Unit Control. Leveling is not critical because the electronic thermostat
does not contain mercury-filled limit switches.
2. Wire the InteleCool2 Units to the Dual Unit Control using industry standard thermostat cable.
Each IntlelCool2 will need at least 4 conductor, 20 gauge copper, Class 2 wire for distances up to
50 feet (15.2m). Use 18 gauge copper, Class 2 wire for distances between 50 and 75 feet
(15.2 - 22.9m).
3. Wire the Dual Unit Control per the diagram on the inside cover of the Dual Unit Control. The
InteleCool2 to Dual Unit Control low voltage control wiring connections are:
Installation
InteleCool2 TerminalsDual Unit Control Terminals
R - 24 VACR
1 - 24 VAC RTN1/2
W - HeatingW
G - Evaporator FanSee Step 4 below
Y - CoolingY
4. Each InteleCool2 MUST have a jumper wire installed between terminals "G" and "Y". This
ensures that the fan will energize on a call for cooling.
For continuous operation of InteleCool2 unit evaporator fans, the “G” and “R” terminals may be
connected. In this mode the jumper between the “G” and “Y” terminals should be removed, and
the lead/lag function will control only the condenser fans, compressors, and heaters.
5. Tighten and check all connections for correct installation.
6. Refer to the thermostat user manual for setup and operation of the electronic thermostat.
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1.1.2Connecting the Dual Unit Controller to the InteleCool
1. Install and level the Dual Unit Control.Leveling is not critical because the electronic thermostat
does not contain mercury-filled limit switches.
2. Wire the InteleCool units to the Dual Unit Control using industry-standard thermostat cable.
Each InteleCool will need at least 4 conductor, 20 gauge, Class 2 copper wire for distances up to
50 feet (15.2m). Use 18 gauge, Class 2 copper wire for distances between 50 and 75 feet (15.2 -
22.9m).
3. Wire the Dual Unit Control per the diagram on the inside cover of the Dual Unit Control. The
InteleCool to Dual Unit Control low voltage control wiring connections are as follows:
InteleCool TerminalsDual Unit Control Terminals
R & 1 - 24 VACR
2 - 24 VAC RTN1/2
W - HeatingW
G - Evaporator FanSee Step 4 Below
Y - Cooling Y
4. Each InteleCool MUST have a jumper wire installed between terminals "G" and "Y". This assures
that the fan will energize on a call for cooling.
5. For continuous operation of InteleCool unit evaporator fans, the "G" and "R" terminals may be
connected. In this mode the jumper between the "G" and "Y" terminals should be removed, and
the lead/lag function will control only the condenser fans, compressors, and heaters.
6. Tighten and check all connections for correct installation.
7. Refer to the thermostat user manual for setup and operation of the electronic thermostat.
Installation
NOTE
The electronic thermostat does not contain mercury, but it is not for use with older versions of
the DUC printed wiring assembly. The electronic thermostat requires a connection to the
24VAC RTN terminal (Connector P1, Terminal 7) on the newer versions of the DUC printed
wiring assembly. This connection is not available on the older version of the DUC.
Mercury thermostats may be used with the newer version of the DUC, but the P1 Terminal 7
connection noted above is not required for the mercury-style thermostat.
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2.0CONTROL STARTUP
2.1Start the Dual Unit Control
1. Turn the thermostat Off.
2. Turn on power to both InteleCool2 units.
3. Turn on circuit breakers in each InteleCool2. Both green “POWER ON” LED’s and 1 of the green
“LEAD UNIT” LED’s of the Dual Unit Control will be lit if the unit has been properly connected.
4. Turn the thermostat switch to the “Auto” setting.
One or both of the InteleCool2 units should start if the thermostat is in a call for heating or cool-
ing.
2.2Check for Operation
1. Raise the thermostat setpoint to force a call for heating.
2. Then lower the thermostat setpoint to force a call for cooling.
The InteleCool2 unit’s fans should run when there is a call for either heating or cooling.
2.3Lead Unit Schedule & Selection
After verifying the connections and startup, the lead unit may be selected and the lead/lag schedule
may be set.
Control Startup
2.3.1Designating the Lead InteleCool2 Unit
The position of the P4 jumper on the Dual Unit Control board determines which InteleCool2 unit is
the lead unit: the P4 jumper will be on pins 3 and 4, or “NORMAL.”
Designation as the lead unit may be determined externally by checking a unit’s LEAD UNIT LEDs on
the front panel of the DUC. The InteleCool2 unit whose LEAD UNIT LED is lit is the lead unit. If the
designation is satisfactory, no changes are necessary.
To change which InteleCool2 unit is the lead unit, place the P4 jumper on pins 1 and 2 or “REVERSE”
on the Dual Unit Control in the InteleCool2 unit chosen to serve as the lead unit.
2.3.2Schedule
The Dual Unit Control lead/lag schedule may be set with jumpers on the printed circuit board. By
using the P2 and P3 jumpers and Table 1, the jumpers may be placed for the desired number of days
between switchover. The P2 jumper is on the lower right hand corner of the board (see Figure 1). The
P3 jumper is on the lower mid section of the board (see Figure 1).
Table 1Switch/jumper settings
# Days for Lead/ Lag
Switchover CycleP2P3
8Pins 8/4DAYPins 1 & 2 (SLOW)
4Pins 4/2DAYPins 1 & 2 (SLOW)
2Pins 4/2DAYPins 3 & 4 (FAST)
1Pins 2/1 DAYPins 3 & 4 (FAST)
NOTE
If the lead/lag schedule is changed while the unit is running, the schedule change may not
take effect until the original schedule is completed. Also, the unit will retain the lead/lag order
of the units, even if power is removed, for two to five days, depending on the setting of the P2
and P3 jumpers.
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Figure 1Dual Unit Control Board
RYWR YW
1/2
DRAWING IS
NOT TO SCALE
1/2
Unit 1Unit 2
P4
Slow
Fast
12
Reverse
Normal
34
1
2
P3
34
P1
Control Startup
P5
P5
to LED
Panel
1
2
3
4
5
6
7
P1 to
Thermostat
TB1
P2
WARNING
!
InteleCool and InteleCool2 units contain potentially lethal voltage.
Shut off power before performing any service work.
During service, the P2 jumper should be placed on the pins that identify the unit NOT being
serviced. Refer to Table 2 for required jumper pin connections. The P2 setting will override
the lead unit setting until the jumper is returned to the proper number-of-days location.
Table 2Jumper settings for servicing InteleCool2 unit
To service desired unitJumper Settings P2Jumper Setting P4
Unit 1Lead 2Pins 3 & 4 (normal)
Unit 2Lead 1Pins 3 & 4 (normal)
8/4Day
4/2Day
2/1Day
Lead1
Lead2
S
e
r
v
i
c
e
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3.0DISPOSALOF DUAL UNIT CONTROL
Some thermostats used on this control may contain mercury in a sealed tube. Do
not place the control in the trash at the end of its useful life. If this control is
replacing a control that contains mercury in a sealed tube, do not place the old control in the trash.
Contact your local waste management authority for instructions regarding recycling and the proper disposal of this control or of an old control containing mercury
in a sealed tube. If you have questions, call the thermostat manufacturer at
1-800-468-1502.
Disposal of Dual Unit Control
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