Heatcraft Refrigeration Products 2500018 warranty Start Up, Operation

Installation and Operations Manual

Start Up

Check for proper fan rotation. Air is drawn through the coil on all units. Be sure the fans turn freely. Rotation of the motors and blades should be in a clockwise direction looking at the unit from the blade side. On three-phase units, it may be necessary to reverse two of the three power leads to the unit.

NOTE: The manifold assembly is not designed to support field piping. Any damages to the condenser due to excessive weight, pressure or vibration will not be covered by standard warranty.

Operation

Winter Operation Head Pressure Control

The capacity of an air-cooled condenser varies with the difference between the entering air dry bulb temperature and the condensing temperature of the refrigerant.

Because air temperature in some regions varies as much as 100 degrees from summer to winter, some means must be employed to keep the condensing temperature sufficiently high to ensure proper operation of the refrigerant expansion valve during low ambient operation, and also allow sufficient capacity so that excessively high condensing temperatures do not result during high ambient conditions. The low limit of the head pressure is dependent upon the required pressure drop across the thermostatic expansion valve.

For normal air conditioning applications, head pressure should be maintained above a condensing temperature corresponding to 90°F. This corresponds to a normal lower limit of about 60°F ambient air. Because air conditioning is not normally required at these lower ambient temperatures, condenser head pressure control may not always be necessary.

However, for those applications below 60°F ambient air temperature, two methods of condenser head pressure control are available to meet specific job requirements and engineer/ owner preference: Fan Cycling, Variable Speed and Flooded

Head Pressure Control (FHP).

Fan Cycling Method

This is an automatic winter control method and will maintain a condensing pressure within reasonable limits by cycling fan motors in response to outside air temperature entering the condensing coil. When voltage other than 230/208 is supplied to the unit, a transformer will be provided for field installation. Electrical protection must be provided for this transformer.

Fan Cycling Operation and Installation

The fan cycling control package consists of a weather-tight enclosure with motor starting contactor(s), as required, and thermostat(s). The contactor coil is 24 volts, 115 volts or 240 volts as ordered. The thermostats and contactors are wired as shown on Diagrams 3 and 5.

Factory-installed packages are mounted on the unit and have all motor connections completed. Field wiring consists of connecting this panel to a power supply and fused disconnect(s) together with the control circuit to the contactor coils.

Fan cycling is suitable for outside temperatures above those shown in Table 4. The thermostat should be field set to shut off the fan when the condensing temperature is reduced to approximately 90°F.

Where operation at ambients below the range shown on Table 4 were required, FHP must be added.

Table 4. Minimum Ambient for Fan Cycling

Model		Design T.D.
	30°F	25°F	20°F	15°F
2-fan units	45	55	65	70
3-fan units	30	40	50	60

Table 5 lists approximate settings for several system T.D.’s. These settings are approximate as they do not take into account variations in load.

Table 5. Fan Cycling Thermostat Settings

Model	Design T.D. (°F)	Thermostat Settings
		T1	T2
	30	55	-
2-fan units	25	60	-
	20	65	-
	30	60	45
3-fan units	25	65	50
	20	75	55
	15	75	65

NOTE: Fans closest to the headers should not be cycled on standard temperature or pressure controls. Dramatic temperature and pressure changes at the headers as a result of fan action can result in possible tube failure. Fan motors are designed for continuous duty operation. Fan cycling controls should be adjusted to maintain a minimum of five (5) minutes on and five (5) minutes off. Short cycling of fans may result in a premature failure of motor and/or fan blade.

Variable Speed

Condenser head pressure control is provided by varying the air flow through the condenser by changing the RPM of the condenser fan. This control package is offered in combination with ambient fan cycling. The fan motor next to the header end of the condenser is the variable speed fan. The remainder

Part # 2500018