Micro Panel Contents

1.13ANTI-RECYCLE TIMER

The programmable Anti-Recycle Timer allows the user to select the compressor anti-recycle time to best suit their needs. Motor heating is a result of inrush current when the motor is started. This heat must be dissipated before another start takes place or motor damage may result. The anti-recycle timer assures that the motor has sufficient time to cool before it is restarted.

An adjustable timer allows for the motor cooling, but gives the user the ability to extend the anti-recycle timer to cut down on cycling. In some applications, faster compressor start response is necessary and shorter anti-recycle times are required. These needs should be kept in mind, but whenever possible the timer should be adjusted for the longest period of time tolerable. 600 seconds is recommended, although 300 seconds provides adequate motor cooling time. Longer periods will allow more heat dissipation, reduce cycling, and possibly increase motor life. See Section 8.2, page 166 for programming of the anti-recycle timer.

1.14ANTI-COINCIDENCE TIMER

The Anti-Coincidence Timer assures that 2 systems do not start simultaneously. This assures that inrush current is kept to a minimum. A 60 second time delay will always separate motor starts. This timer is not programmable.

1.15EVAPORATOR PUMP CONTROL

Dry contacts are provided which transition (close) when the Daily Schedule is calling for chiller opera- tion, the unit switch is on, and power has been applied to the Micro Panel for 30 seconds. If for some reason the evaporator pump contacts have been closed to run the pump and a power loss or Daily Schedule shuts the pump down (contacts open), the contacts will not reclose for any reason until 30 seconds has elapsed after power re-application or 30 seconds have elapsed between a Daily Schedule shutdown and restart.

If the Daily Schedule is not used, (On/Off times equal 00:00) the contacts will be closed at all times.

FORM 201.19-NM1 (204)

1.16COMPRESSOR HEATER CONTROL

Each compressor has its own heater. The heater will be off whenever the compressor is running. As soon as the compressor shuts off, the heater will turn on and stay on for 5 minutes. After 5 minutes has elapsed, the heater will shut off if the discharge temperature rises above 150 °F (66°C) and will turn on when the discharge temperature is equal to or less than 150 °F (66°C).

1.17EVAPORATOR HEATER CONTROL

The evaporator heater is controlled by ambient tem- perature. When the ambient temperature drops below 40°F (4°C), the heater is turned on when the compressors are turned off. When the temperature rises above 45°F (7°C), the heater is turned off. An under voltage condi- tion will keep the heater off until full voltage is restored to the system. The heater will provide freeze protection to -20°F (-28°C).

115VAC power must remain “ON” through CB3 for freeze protection. Otherwise, the evaporator must be drained.

1.18PUMPDOWN (EEV) CONTROL

Each compressor undergoes a pump down on shut- down. This assures that liquid refrigerant does not enter the compressor on start-up, eliminating the need for recycling pump down, saving energy and reducing compressor starts and wear.

On start-up, the controls unload the compressor and im- mediately energize the pilot solenoid on the electronic expansion valve. Normal operation commences without pumpdown.

On shutdown, the microprocessor controls unload the compressor, the pilot solenoid on the electronic expan- sion valve is de-energized, and the Economizer Liquid Supply Solenoid Valve is de-energized. The compressor continues to operate until it either pumps down to the

Remote evaporator applications equipped with thermostatic TXV and Liquid Line solenoid will also pump down on shutdown.

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YORK INTERNATIONAL

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