York YCAS0130 Commissioning, Interlocks, System Switches, Start-up, Oil Pressure, Fan Rotation

Commissioning

FIRST TIME START-UP

During the commissioning period there should be sufficient heat load to run the unit under stable full load operation to enable the unit controls, and system operation to be set up cor- rectly and a commissioning log taken. Be sure that the Micro Panel is prop- erly programmed (page 166) and the System Start-up Checklist (page 117) is completed.

Interlocks

Verify that liquid is flowing through the evaporator and that heat load is present. Ensure that any remote run in- terlocks are in the run position and that the run schedule requires the unit to run or is overridden.

System Switches

Place the ‘Sys 1’ switch on the microprocessor board to the ‘ON’ position – (Fig. 46, page 130).

Start-up

Remove the locking device from the unit Auto/OFF switch which prevents unauthorized starting of the unit before commissioning. Press the ‘Status’ key, then turn the unit switch to the “1” position to start the unit (there may be a few seconds delay before the first compressor starts because of the anti-recycle timer). Be ready when each compressor starts, to switch the unit OFF imme- diately if any unusual noises or other adverse conditions develop. Use the appropriate emergency stop device if necessary.

Oil Pressure

When a compressor starts, press the relevant ‘System Pressures’ key and verify that oil differential pressure develops immediately (Discharge Pressure minus Oil Pressure). If oil pressure does not develop, the automatic controls will shut down the compressor. Under no cir- cumstances should a restart attempt be made on a com- pressor which does not develop oil pressure immediately. Switch the unit switch to the ‘0’ position (OFF).

Refrigerant Flow

When a compressor starts, a flow of liquid refrigerant will be seen in the liquid line sight glass. After several minutes operation and providing a full charge of refrig- erant is in the system, the bubbles will disappear and be replaced by a solid column of liquid.

FORM 201.19-NM1 (204)

Fan Rotation

As discharge pressure rises, the condenser fans operate in stages to control the pressure. Verify that the fan op- eration is correct for the type of unit.

Suction Superheat

Check suction superheat at steady full compressor load only. Measure suction temperature on the copper line about 6" (150 mm) before the compressor suction ser- vice valve. Measure suction pressure at the compressor service valve. Superheat should be 10°F to 12°F (5.6°C to 6.7°C).

Expansion Valve

The electronic expansion valves are factory set and should not need adjustment.

Economizer Superheat

(Not all models are equipped with economizers)

Check economizer superheat at steady full compressor load only, under conditions when the economizer sole- noid is energized. (See Section 1.22, page 134) Measure gas temperature on the economizer outlet pipe next to the expansion valve bulb. Measure gas pressure at the back seat port of the economizer service valve. Superheat as measured should be 10°F to 12°F (5.6°C to 6.7°C).

Subcooling

Check liquid subcooling at steady full compressor load only. It is important that all fans are running for the system. Measure liquid line temperature on the copper line beside the main liquid line service valve. Measure liquid pressure at the liquid line service valve. Subcooling should be 12°F to 15°F (6.7°C to 8.3°C). No bubbles should show in the sight glass. If subcooling is out of range add or remove refrigerant as required. Do not overcharge the unit. The liquid flow to the main evaporator TXV is subcooled further by the economizer, increasing subcooling to between 22°F and 28°F (12°C and 15°C) at ambients above 90ºF.

General Operation

After completion of the above checks for System 1, stop the unit, switch OFF the ‘SYS 1’ switch on the main panel microprocessor board and repeat the process for each subsequent system. When all run correctly, stop the unit, switch all applicable switches to the ‘ON’ position and restart the unit.

44 YORK INTERNATIONAL