Bard CH4S1 Phase Monitor, Service Hints, Sequence Of Operation, Manual, 2100-455M, Page, 18 of

PHASE MONITOR

All units with three phase compressors are equipped with a 3 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 is present at the phase monitor and phases are correct, the green LED will light. If phases are reversed, the red fault LED will be lit and compressor operation is inhibited.

If a fault condition occurs, shut off main power and reverse two of the supply leads to the unit. Do not reverse any of the unit factory wires as damage may occur.

SERVICE HINTS

1.Caution owner/operator 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 operating costs.

2.Switching to heating cycle at 75°F or higher outside temperature may cause a nuisance trip of the remote reset high pressure switch. Turn thermostat off then on to reset the high pressure switch.

3.The heat pump wall thermostats perform multiple functions. Be sure that all function switches are correctly set for the desired operating mode before trying to diagnose any reported service problems.

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

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

SEQUENCE OF OPERATION

COOLING STAGE 1 – 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.

COOLING STAGE 2 – Circuit R-Y1 makes at the thermostat energizing the 2nd stage solenoid in the compressor. Default position is not energized. Compressor will run at low capacity until this solenoid is energized.

HEATING STAGE 1 – A 24V solenoid coil on reversing valve controls heating cycle operation. Two thermostat options, one allowing “Auto” changeover from cycle to cycle and the other constantly energizing solenoid coil during heating season and thus eliminating pressure equalization noise except during defrost, are to be used. On “Auto” option a circuit is completed from R-B and R-Y on each heating “on” cycle, energizing reversing valve solenoid and pulling in compressor contactor

starting compressor and outdoor motor. R-G also make starting indoor blower motor. Heat pump heating cycle now in operation. The second option has no “Auto” changeover position, but instead energizes the reversing valve solenoid constantly whenever the system switch on subbase is placed in “Heat” position, the “B” terminal being constantly energized from R. A thermostat demand for Stage 1 heat completes R-Y circuit, pulling in compressor contactor starting compressor and outdoor motor. R-G also make starting indoor blower motor.

HEATING STAGE 2 – Circuit R-Y2 makes at the thermostat energizing the 2nd stage solenoid in the compressor.

cOmpressor current & pressure control module

The compressor control module monitors compressor current and pressure and prevents internal overload trips due to low voltage or extremely high ambient temperatures by de-energizing the full capacity compressor solenoid. The control monitors current to the compressor and discharge pressure. If current is sensed that is in excess of 93% of the compressor maximum continuous current rating or pressure is sensed greater than 540 PSI (located on liquid line and is marked with Bard Part #8406-111), the compressor control module de-energizes the second stage solenoid in the compressor for a time as determined by the time potentiometer on the compressor control module. This will drop the current draw and pressure and allow the compressor to run at 75 percent of capacity rather than not at all. Once the time period has elapsed the full capacity compressor solenoid will re-energize and try again to run at full capacity. If the pressure or current is exceeded again, the coil will again de-energize. This sequence will repeat until the ambient temperature drops or the line voltage increases enough that the trip values are not exceeded.

The relay on the compressor control module is a single pole double throw relay. The full capacity compressor solenoid connects to the common terminal of the relay. Once current is sensed by the compressor control module, the relay closes and the second stage cooling call (if present) is sent to the full capacity compressor solenoid. This sequence prevents damage to the full capacity compressor solenoid by ensuring that the solenoid is not energized when the compressor is

not running. A brief time delay in this sequence also prevents locked rotor amperage during start-up from tripping the device and engaging the time delay period.

Manual	2100-455M
Page	18 of 28