Manual 2100-484E
Page 7 of 22
LOW VOLTAGE FIELD WIRING
The DC3000 is powered from the air conditioners that it
is controlling, 24VAC (18-32V) low voltage only.
Circuitry in the DC3000 isolates the power supplies of
all connected air conditioners so that no back feeds or
phasing problems can occur. Additionally, if any air
conditioner loses power, the DC3000 and the other air
conditioner are unaffected and will continue to operate
normally.
Connect the low voltage field wiring from each unit per
the low voltage field wiring diagrams in Section on
“Controller Wiring”.
CONTROLLER GROUNDING
A reliable earth ground must be connected in addition to
any grounding from conduit.
CONTROLLER POWER-UP
Whenever power is first applied to the controller, there
is a twenty (20) second time-delay prior to any function
(other than display) becoming active. This time-delay is
in effect if the controller On/Off button is used when
24VAC from air conditioners is present, and also if
controller is in “ON” position and 24VAC from all
connected air conditioners is removed and then restored.
FIRE SUPPRESSION CIRCUIT
To disable the DC3000 and shut down both air
conditioners, terminals F1 and F2 may be used. The F1
and F2 terminals must be jumpered together for normal
operation. A normally closed (nc) set of dry contacts
may be connected across the terminals and the factory
jumper removed for use with a field-installed fire
suppression system. The contacts must open if a fire is
detected. See appropriate connection diagram - Figures
1, 2 or 3 for this connection. Contacts should be rated
for pilot duty operation at 2 amp 24VAC minimum.
Shielded wire (22-gauge minimum) must be used, and
the shield must be grounded to the controller enclosure.
IMPORTANT NOTE: Some Bard models employ an
electronic blower control that has a 60-second blower
off-delay. In order to have immediate shutdown of the
blower motor, in addition to disabling the run function
of the air conditioners will require a simple wiring
modification at the blower control located in the
electrical control panel of the air conditioners being
controlled by the lead/lag controller. To eliminate the
60-second blower off-delay, disconnect and isolate the
wire that is factory-connected to the “R” terminal on the
electronic blower control, and then connect a jumper
from the “G” terminal on the blower control to the “R”
terminal on the blower control. The electronic blower
control will now function as an on-off relay with no off-
delay, and the blower motor will stop running
immediately when the F1-F2 fire suppression circuit is
activated (opened).
STAGING DELAY PERIODS
The following delays are built in for both cooling and
heating:
Stage 1 –
0 seconds for blower (if not already on as
continuous)
10 seconds for cooling or heating output
Stage 2 –
10 seconds after Stage 1 for blower
10 additional seconds for cooling or heating
output
Stage 3 –
10 seconds after Stage 2
Stage 4 –
10 seconds after Stage 3
Note: For cooling Stages 1 and 2, the stage LED will
blink for 10 seconds while the cooling output is delayed
after that stage is called for. There is also a delay after
the stage is satisfied, and after the LED stops blinking,
the stage will turn off. There is a minimum 10-second
delay between stages 2 & 3, and 3 & 4, but no delayed
output when stage is turned on or off, and LED for those
stages will not blink.
BLOWER OPERATION
The controller can be configured to have main HVAC
blowers cycle on and off on demand; have all blowers
run continuously (for DC3003, the blower is not “On”
continuously for HVAC #3, but runs on demand only
condition); or have the lead unit blower run continuously
with the lag unit blower cycling on demand. Lead unit
blower operating continuously is the default setting.
There is also an option to have all blowers cycle on if one
remote sensor is connected, and a temperature difference
of more than 5F between any two sensors is observed.
This helps to redistribute the heat load within the structure
and should reduce compressor operating time.
When any of the stages are satisfied, the stage LED will
blink for ten (10) seconds before the stage is actually
turned off.

ADVANCE (SWAP) LEAD/LAG UNIT

FEATURE

Pressing the Advance button for one (1) second will cause
the lead and lag units to change positions. This may be
useful during service and maintenance procedures.
Note: DC3003 always operates HVAC #3 in last position:
only HVAC #1 and #2 operate in lead/lag sequence.
ACCELERATE TIMER FEATURE
Pressing the UP arrow button for five (5) seconds will
activate an accelerate (speed-up) mode, causing the
normal changeover time increments of days to be
reduced to seconds. Example: 7 days becomes 7
seconds. When “ACC” displays, release button.
Whichever LED is on, indicating lead unit will blink
over for each second until the controller switches. This
is a check for the timer functionality.