NOTE: Three factors determine the operating limits of a unit:
(1)entering air temperature, (2) water temperature and (3) ambient temperature. Whenever any of these factors are at a minimum or maximum level, the other two factors must be at a normal level to ensure proper unit operation. See Table 15.
Table 15 — Operating Limits — 50RTG Units
AIR LIMITS | COOLING | HEATING |
Rated Ambient Air | 80° F | 70° F |
Min. Entering Air | 50° F | 40° F |
Rated Entering Air db/wb | 80/67° F | 70° F |
Max. Entering Air db/wb | 110/83° F | 80° F |
WATER LIMITS | | |
Min. Entering Water | 25° F | 25° F |
Normal Entering Water | 85° F | 70° F |
Max. Entering Water | 115° F | 115° F |
LEGEND | | |
db — Dry Bulb wb — Wet Bulb
NOTE: Value in heating column is dry bulb only. Any wet bulb read- ing is acceptable.
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 an elevated level of 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. Check the elevation and cleanliness of the condensate lines; any dripping could be a sign of a blocked line. Be sure the condensate trap in- cludes a water seal.
4.Check the temperature of both supply and discharge water. If temperature is within range, proceed. If tempera- ture is outside the range, check the cooling refrigerant pressures.
5.Air temperature drop across the coil should be checked when compressor is operating. Air temperature drop should be between 15 and 25 F.
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. If temperature is within range, proceed. If tempera- ture is outside the range, check the heating refrigerant pressures.
5.Once the unit has begun to run, check for warm air deliv- ery at the unit grille.
6.Air temperature rise across the coil should be checked when compressor is operating. Air temperature rise should be between 20 and 30 F 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 16. Adjust the water control valve until the flow of 1.5 to 2 gpm is achieved. Since the pressure con- stantly 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 de- signed 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.
Flushing — Once the piping is complete, final purging and loop charging is needed. A flush cart pump of at least 1.5 hp is needed to achieve adequate flow velocity in the loop to purge air and dirt particles from the loop. Flush the loop in both direc- tions with a high volume of water at a high velocity. Follow the steps below to properly flush the loop:
1.Verify power is off.
2.Fill loop with water from hose through flush cart before using flush cart pump to ensure an even fill. Do not allow the water level in the flush cart tank to drop below the pump inlet line to prevent air from filling the line.
3.Maintain a fluid level in the tank above the return tee to avoid air entering back into the fluid.
4.Shutting off the return valve that connects into the flush cart reservoir will allow 50 psi surges to help purge air pockets. This maintains the pump at 50 psi.
5.To purge, keep the pump at 50 psi until maximum pump- ing pressure is reached.
