Bard WA721 - Manual (Page 17)

Manual 2100-425
Page 15
Low Pressure Switch, Bypass, and Lockout
Sequence
If the low pressure switch opens for more than 120
seconds, the compressor contactor will de-energize
and go into a soft lockout. Regardless the state of the
low pressure switch, the contactor will reenergize after
the delay on make time delay has expired. If the low
pressure switch remains open, or opens again for
longer than 120 seconds the unit will go into manual
lockout condition and the alarm relay circuit will
energize. Recycling the wall thermostat resets the
manual lockout.
Alarm Relay Output
Alarm terminal is output connection for applications
where alarm relay is employed. This terminal is
powered whenever compressor is locked out due to
HPC or LPC sequences as described.
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 air conditioner or heat pump unit
model. The lockout features, both soft and
manual, are a function of the Compressor
Control Module.
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 break time has expired. If the high pressure
switch opens again in this 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.
SEQUENCE OF OPERATION
COOLING – Circuit R-Y makes at thermostat pulling
in compressor contactor, starting the compressor and
outdoor motor. The G (indoor motor) circuit is
automatically completed on any call for cooling
operation or can be energized by manual fan switch on
subbase for constant air circulation. On all 208/230
volt models, when G circuit is de-energized the indoor
blower motor will continue to run for one minute. On
a call for heating, circuit R-W1 make at the thermostat
pulling in heat contact for the strip heat and blower
operation. On a call for second stage heat, R-W2
makes bringing on second heat contactor, if so
equipped.
COMPRESSOR CONTROL MODULE
The compressor control module is standard on the
models covered by this manual. The compressor
control is an anti-short cycle/lockout timer with high
and low pressure switch monitoring and alarm relay
output.
Adjustable Delay On Make And Break Timer
On initial power up or any time power is interrupted to
the unit the delay on make period begins which will
be 2 minutes plus 10% of the delay on break setting.
When the delay on make is complete and the high
pressure switch (and low pressure switch if employed)
is closed, the compressor contactor is energized.
Upon shutdown the delay or break timer starts and
prevents restart until the delay on break and delay on
make periods have expired.
2. Check all power fuses or circuit breakers to be sure
they are the correct rating.
3. Periodic cleaning of the outdoor coil to permit full
and unrestricted airflow circulation is essential.
SERVICE HINTS
1. Caution homeowner to maintain clean air filters at
all times. Also, not to needlessly close off supply
and return air registers. This reduces air flow
through the system, which shortens equipment
service life as well as increasing operating costs.