Carrier 50RHE006-060 Unit Start-Up Cooling Mode, Unit Start-Up Heating Mode, Cooling Heating

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 proper 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 8. 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 Table 9. If temperature is within range, proceed. If temperature is outside the range, check the cooling refrigerant pressures in Table 9.

5.Check air temperature drop across the coil when com- pressor is operating. Air temperature drop should be between 8.3 and 13.9.

Table 8 — Water Temperature Change

Through Heat Exchanger

	COOLING		HEATING
WATER FLOW RATE (l/s)	RISE (C)		DROP (C)
	Min	Max	Min	Max
For Closed Loop: Ground
Source or Cooling/Boiler	5	6.7	2.2	4.4
Systems at 0.054 l/s per kW
For Open Loop: Ground	11.1	14.4	5.6	9.4
Water Systems 0.027 l/s per kW

Unit Start-Up Heating Mode

NOTE: Operate the unit in heating cycle after checking the cooling cycle. Allow five minutes between tests for the pres- sure or reversing valve to equalize.

1.Turn thermostat to lowest setting and set thermostat switch to HEAT position.

2.Slowly turn the thermostat to a higher temperature until the compressor activates.

3.Check for warm air delivery at the unit grille within a few minutes after the unit has begun to operate.

4.Check the temperature of both supply and discharge water. Compare to Table 9. If temperature is within range, proceed. If temperature is outside the range, check the heating refrigerant pressures in Table 9.

5.Once the unit has begun to run, check for warm air deliv- ery at the unit grille.

6.Check air temperature rise across the coil when compres- sor is operating. Air temperature rise should be between 11.1 and 16.7 C after 15 minutes at load.

7.Check for vibration, noise and water leaks.

Flow Regulation — Flow regulation can be accom- plished by two methods. Most water control valves have a flow adjustment built into the valve. By measuring the pressure drop through the unit heat exchanger, the flow rate can be deter- mined. See Table 10. Adjust the water control valve until the flow of .027 to .054 L/s per kW cooling is achieved. Since the pressure constantly varies, two pressure gages may be needed in some applications.

An alternative method is to install a flow control device. These devices are typically an orifice of plastic material designed to allow a specified flow rate that are mounted on the outlet of the water control valve. Occasionally these valves produce a velocity noise that can be reduced by applying some back pressure. To accomplish this, slightly close the leaving isolation valve of the well water setup.

To avoid possible injury or death due to electrical shock, open the power supply disconnect switch and secure it in an open position before flushing system.

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