180A / 187A
Compressor Operation on 180A Models
The basic scroll design has been modified with the addition of an internal unloading mechanism that opens a
A single speed, high efficiency motor continues to run while the scroll modulates between the two capacity steps. Modulation is achieved by venting a portion of the gas in the first suction pocket back to the low side of the compressor, thereby reducing the effective displacement of the compressor.
Full capacity is achieved by blocking these vents, thus increasing the displacement to 100%. A DC solenoid in the compressor controlled by a rectified 24 volt AC signal in the external solenoid plug moves the slider ring that covers and uncovers these vents.
The vent covers are arranged in such a manner that the compressor operates at approximately 67% capacity when the solenoid is not energized and 100% capacity when the solenoid is energized. The loading and unloading of the two step scroll is done ”on the fly” without shutting off the motor between steps.
NOTE: 67% compressor capacity translates to approximately 75% cooling capacity at the indoor coil.
The compressor will always start unloaded and stay unloaded for five seconds even when the thermostat is calling for
Crankcase Heater Operation
The crankcase heater is energized during unit off cycle regardless of OAT temperature on 187A models.
The crankcase heater is energized during off cycle below 65_F/18.33_C on 180A models.
Outdoor Fan Motor Operation
The outdoor unit control energizes the outdoor fan any time the compressor is operating except for
On 187A models, the outdoor fan remains energized during the
On 187A models, the outdoor fan motor is a PSC type. A fan relay on the control board turns the fan off and on by opening and closing a high voltage circuit to the motor. It does not change speeds between low- and
On 180A models, the outdoor fan is an ECM type. The motor control is continuously powered with high voltage. The motor speed is determined by electrical pulses provided by the PWM outputs on the control board. The ECM motor RPM adjusts to outdoor conditions as described in Table 3. The PWM output can be measured between the PWM1 and PWM2 terminals on the circuit board with a volt meter set to DC volts.
Table 3 – Outdoor Fan Motor PWM
Outdoor Temp (DC volts, Tolerance +/- 2%)
| ||||
MODEL | STAGE | |||
(OAT≤104_F/40_C) | (OAT≤104_F/40_C) | |||
| (OAT>104_F/40_C) | |||
|
|
|
180A024 | 9.57 | 10.88 | 11.90 |
180A036 | 9.06 | 10.23 | 11.90 |
180A048 | 9.91 | 11.04 | 11.90 |
180A060 | 10.83 | 11.70 | 11.90 |
NOTE: |
|
|
|
For 180A models in
and
In low ambient cooling (below 55_F/12.78_C) on 187A and 180A models, the control board cycles the fan off and on.
Time Delays
The unit time delays include:
S Five minute time delay to start cooling or heating operation when there is a call from the thermostat or user interface. To bypass this feature, momentarily short and release Forced Defrost pins.
S Five minute compressor
S Two minute time delay to return to standby operation from last valid communication (with Evolution only).
SOne minute time delay of outdoor fan at termination of cooling mode when outdoor ambient is greater than or equal to 100_F/37.78_C.
SOn 187A models there is a 1 minute time delay between staging from low to high and from high to low capacity. On 180A models there is no delay; the compressor will change from low to high and from high to low capacity on the fly to meet the demand.
Low Ambient Cooling
If this unit will be required to operate below 55_F/12.78_C outdoor temperature, provisions must be made for low ambient operation.
Evolution Controlled low ambient cooling:
This unit is capable of | low ambient cooling | down to |
ONLY when using Evolution control. | ||
A low ambient kit is not required, and the outdoor fan motor does not need to be replaced for Evolution controlled low ambient operation. The Evolution Control provides an automatic evaporator coil freeze protection algorithm that eliminates the need for an evaporator freeze thermostat. Low ambient cooling must be enabled in the User Interface set up. Fan may not begin to cycle until about 40_F/4.4_C OAT. Fan will cycle based on coil and outdoor air temperature.
Evolution controlled low ambient mode operates as follows:
SFan is OFF when outdoor coil temp is < (outdoor air temperature + 3 _F/1.67_C) or outdoor fan has been ON for 30 minutes. (Fan is
turned off to allow refrigerant system to stabilize.)
SFan is ON when outdoor coil temp > (outdoor air temperature + 25_F/13.89_C) or outdoor coil temp > 80_F/26.67_C or if outdoor
fan has been OFF for 30 minutes. (Fan is turned on to allow refrigerant system to stabilize.)
S Low pressure switch is ignored for first 3 minutes during low ambient start up. After 3 minutes, if LPS trips, then outdoor fan motor is turned off for 10 minutes, with the compressor running. If LPS closes within 10 minutes then cooling continues with the outdoor fan cycling per the coil temperature routine listed above for the remainder of the cooling cycle. If the LPS does not close within 10 minutes, then the normal LPS trip response (shut down cooling operation and generate LPS trip error) will occur.
For 180A models, the PWM output for both high- and
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