Carrier Unit Start-UpCooling Mode, Operating Limits - 50PCH,PCV Units, Through Heat Exchanger

Table 13 — Operating Limits — 50PCH,PCV Units

OPERATING LIMITS	COOLING (F)	HEATING (F)
AIR LIMITS
Min. Ambient Air – db	45	39
Rated Ambient Air – db	80.6	68
Max. Ambient Air – db	110	85
Min. Entering Air – db/wb	50	40
Rated Entering Air – db/wb	80.6/66.2	68
Max. Entering Air – db/wb	110/83	80
WATER LIMITS
Min. Entering Water	30	20
Normal Entering Water	50-110	30-70
Max. Entering Water	120	90
Normal Water Flow	2.5-3.0 gpm per ton
LEGEND

db — Dry Bulb wb — Wet Bulb

Scroll Compressor Rotation — It is important to be certain compressor is rotating in the proper direction. To determine whether or not compressor is rotating in the prop- er direction:

1.Connect service gages to suction and discharge pressure fittings.

2.Energize the compressor.

3.The suction pressure should drop and the discharge pressure should rise, as is normal on any start-up.

If the suction pressure does not drop and the discharge pressure does not rise to normal levels:

1.Turn off power to the unit. Install disconnect tag.

2.Reverse any two of the unit power leads.

3.Reapply power to the unit and verify pressures are correct.

The suction and discharge pressure levels should now move to their normal start-up levels.

When the compressor is rotating in the wrong direction, the unit makes more noise and does not provide cooling.

After a few minutes of reverse operation, the scroll com- pressor internal overload protection will open, thus activating the unit lockout. This requires a manual reset. To reset, turn the thermostat on and then off.

NOTE: There is a 5-minute time delay before the compressor will start.

Unit Start-Up Cooling Mode

1.Adjust the unit thermostat to the warmest position. Slowly reduce the thermostat position until the compres- sor activates.

2.Check for cool air delivery at unit grille a few minutes after the unit has begun to operate.

3.Verify that the compressor is on and that the water flow rate is correct by measuring pressure drop through the heat exchanger using P/T plugs. See Table 14. Check the elevation and cleanliness of the condensate lines; any dripping could be a sign of a blocked line. Be sure the condensate trap includes a water seal.

4.Check the temperature of both supply and discharge wa- ter. Compare to Tables 15-25. If temperature is within range, proceed. If temperature is outside the range, check the cooling refrigerant pressures in Tables 15-25.

5.Check air temperature drop across the coil when com- pressor is operating. Air temperature drop should be between 15 and 25 F.

Table 14 — Water Temperature Change

Through Heat Exchanger

	COOLING		HEATING
WATER FLOW RATE (GPM)	RISE (F)		DROP (F)
	Min	Max	Min	Max
For Closed Loop: Ground Source or	9	12	4	8
Cooling/Boiler Systems at 3 gpm/ton
For Open Loop: Ground Water Systems at	20	26	10	17
1.5 gpm/ton

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