Logic Control Board; Phase Monitor; Condenser Fan Operation; Sequence Of Operation - Bard Q-TEC Q A4D Series Installation Instructions Manual

The freeze stat switch is located on the return bend
tube located on the evaporator coil. When there is a
fault related to the freeze stat switch, a red LED light
will give notice by illumination, indicating a fault
condition is present.

Logic Control Board

Three of the four switches have normally closed
contacts and one contact (CO = unused) has a
normally open contact. If any of the four switches
fault, their corresponding light will blink and initialize
a soft lockout of the compressor circuit. If recurrence
happens on the same cooling call cycle, a hard lockout
of the compressor circuit will occur requiring a manual
system reset.
The compressor logic control board has five LED lights
providing status updates of the system operation (see
Figure 24). When the green status light is blinking, this
is an indication that there is 24V power to the board.
Upon an alarm detection from one of the four safety
switches, there will be a blinking light indicating a
fault. The faults are as follows:
HP = Green fault illumination
LP = Orange fault illumination
FS = Red fault illumination
CO = Yellow fault illumination

Phase Monitor

All units with three phase scroll compressors are
equipped with a three phase line monitor to prevent
compressor damage due to phase reversal.
The phase monitor in this unit is equipped with two
LEDs. If the Y signal (call for cooling) is present at the
phase monitor and phases are correct, the green LED
will light.
NOTE: The phase monitor will not show phase reversal
until the compressor is energized during a call
for cooling operation.
If phases are reversed, the red fault LED will be lit and
compressor operation is inhibited. The phase monitor
will also inhibit operation for an imbalance exceeding
12% at 208 VAC and 8% at 460 VAC.
If a fault condition occurs, reverse two of the supply
leads to the unit. Do not reverse any of the unit factory
wires as damage may occur.

Condenser Fan Operation

NOTE: Certain models may be equipped with a low
ambient control (LAC), and if so, the condenser
fan motor will have a delayed start until system
refrigerant operating pressure builds up. After
starting, the fan motor may or may not cycle
depending upon ambient conditions. This is
normal operation.
FIGURE 24
CCM LED Fault Illumination
Green Status Light

Sequence of Operation

With Y1-Y2 jumpers installed, circuit R-Y1 makes at
thermostat pulling in compressor contactor, starting
the compressor, indoor blower (rated air) and outdoor
motor. (See NOTE under Condenser Fan Operation
concerning models equipped with low ambient control.)
The G (indoor motor) circuit is automatically completed
by the thermostat on any call for cooling operation or
can be energized by manual fan switch on subbase for
constant air circulation.
On a call for heating, circuit R-B/W1 makes at the
thermostat pulling in the heat contactor for the strip
heat and blower operation. On a call for emergency
heat, R-W2 makes, bringing on second heat contactor,
if so equipped.
HP = Green Fault
Illumination
LP = Orange Fault
Illumination
FS (Evap) =
Red Fault
Illumination
CO = Yellow Fault
Illumination
Manual 2100-752C
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