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Over and Under Voltage Protection
When an under or over voltage condition exists, the
controller locks out the unit. When condition clears,
the controller automatically releases the unit to normal
operation and the compressor restarts after the random
start and anti-short cycle timings are met. The under
and over voltage protection starts at plus or minus
20% from nominal voltage and returns to operation at
plus or minus 10% from nominal voltage. All four LED
fault lights will flash when an over or under voltage
conditions occurs. The over voltage protection can
be disabled by removing the O/V jumper on the logic
control board (see Figure 23).
FIGURE 23
Compressor Logic Control Board
O/V
Jumper
Intelligent Reset
The compressor logic control board has an intelligent
reset feature after a safety control is activated. The
controller locks out the unit for 5 minutes; at the end
of this period, the controller checks to verify that all
faults have been cleared. If faults have been cleared,
the controller restarts the unit. If a second fault occurs,
the controller will lockout the unit until the control is
reset by breaking Y signal from thermostat. The last
fault will be kept in memory after a full lockout; this is
only cleared by cycling the unit power.
Alarm Output
The L terminal has 24 volts applied when a hard
lockout occurs. This can be used to drive a fault light
or a low voltage relay.
During routine operation of the unit with no power
interruptions, the compressor will operate on demand
with no delay.
High Pressure Switch and Lockout Sequence
If the high pressure switch opens, the compressor
contactor will de-energize immediately. The lockout
timer will go into a soft lockout and stay in soft lockout
until the high pressure switch closes and the delay on
Manual 2100-752C
Page
28 of 41
TEST
Status
Jumper
Light
break time has expired. If the high pressure switch
opens again in the same operating cycle, the unit will
go into manual lockout condition and the alarm relay
circuit will energize. Recycling the wall thermostat
resets the manual lockout.
NOTE: Both high and low pressure switch controls are
inherently automatic reset devices. The high
pressure switch and low pressure switch cut
out and cut in settings are fixed by specific
unit model. The lockout feature, both soft and
manual, are a function of the compressor logic
control board.
Troubleshooting Compressor Logic CCM
The Bard Q**A4D Series is equipped with a high
pressure switch, low pressure switch and freeze stat
switch. The switches are all located in the condenser
section of the unit. Each switch has its own illuminated
diagnostic light, which provides the user an easy
solution for basic troubleshooting.
High Pressure Switch
(Terminals HP1 and HP2) Circuit will be proved
as "closed" prior to energizing A or CC terminals.
If pressure switch opens, compressor will go into
soft lockout mode and compressor operation will be
terminated; green fault light will be illuminated. Logic
control will then go through 5-minute delay on break
plus random start sequence. If no fault is found on
next run cycle, compressor will continue operation. If
fault reoccurs, a hard lockout will be initiated and fault
signal is sent to L terminal.
Low Pressure Switch
(Terminals LP1 and LP2) Circuit will be proved as
"closed" prior to energizing A or CC terminals. The
condition of the LP terminals will then be ignored for
the first 90 seconds after a demand for compressor
operation. Following this 90-second period, if pressure
switch opens, compressor will go into soft lockout
mode and compressor operation will be terminated;
orange fault light will be illuminated. The compressor
control board will then go through a 5-minute delay on
break plus random start sequence. If no fault is found
on next run cycle, compressor will continue operation.
If fault reoccurs, hard lockout will be initiated and the
fault signal is sent to the L terminal.
Freeze Stat Switch
(Terminals FS1 and FS2) Circuit will be proved as
"closed" prior to energizing CC terminal. If freeze stat
switch opens, compressor will go into soft lockout
mode and compressor operation will be terminated; red
fault light will be illuminated. Compressor logic control
will then go through 5-minute delay on break plus
random start sequence. If no fault is found on next
run cycle, compressor will continue operation. If fault
reoccurs, hard lockout will be initiated and fault signal
is sent to L terminal.
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