Bard W12A2-A Important Installer Note, Service Hints, High & Low Pressure Switch, Start Up

START UP

IMPORTANT INSTALLER NOTE

For improved start up performance, wash the indoor coil with a dishwasher detergent.

SERVICE HINTS

1.Caution owner to maintain clean air filters at all times. Also not to needlessly close off supply and return air registers. This reduces airflow through the system which shortens equipment service life as well as increasing operation costs.

2.The unit is equipped with a high pressure cut out switch.

3.Check all power fuses or circuit breakers to be sure they are the correct rating.

4.Periodic cleaning of the outdoor coil to permit full and unrestricted airflow circulation is essential.

HIGH & LOW PRESSURE SWITCH

The W12Aà models are supplied with a remote reset high and low pressure switch. If tripped, this pressure switch may be reset by turning the thermostat off then back on again.

SEQUENCE OF OPERATION

HEATING – 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 a call for heating, circuit R-W1 make at the thermostat pulling in heat contact for the strip heat and blower operation.

COMPRESSOR CONTROL MODULE

The compressor control module is optional 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 on break time starts and prevents restart until the delay on break and delay on make periods have expired.

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.

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 that 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.

Manual	2100-509E
Page	14 of 17