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These settings are approximate as they do not take into account variations in load. 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 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. Fan Cycling Thermostat Settings Model Design T.D. (°F) Thermostat Settings T1 T2 2-fan units 30 55 - 25 60 - 20 65 - 3-fan units 30 60 45 25 65 50 20 75 55 15 75 65 of the fans are constant speed and are cycled separately using ambient sensing thermostats. Flooded Head Pressure Control Valve (FHP) The FHP system of head pressure control is a completely automatic control that maintains a preset condenser pressure without need of seasonal adjustment. The control maintains head pressure by backing liquid into the leaving side of the condenser, decreasing the effective condenser surface and therefore maintaining a constant head pressure upon a drop in ambient temperature. Several styles of flooding valves or combinations of valves are available. Contact the valve manufacturer for specific recommendations. Operation: During normal ambient operation, the valve allows liquid refrigerant to flow through C port (see Figure 9) and R port to the liquid receiver. As the pressure drops with a drop in ambient temperature, the valve opens to allow high pressure discharge gas to enter B port, pass through the valve and pressurize the receiver to provide adequate liquid flow to the expansion valve. (see Figure 10) This action raises the pressure on the discharge side of the condenser, reducing flow and flooding the leaving side of the condenser until the pressure rises to a proper level to close B port. The liquid receiver size is important in this type of control and must be large enough to hold the total system charge. If the receiver is not large enough, the liquid will be stored in the condenser causing high head pressure at normal ambient temperatures. The refrigerant charge required will often be about two times the normal charge for cold weather operation. The amount of refrigerant that must be added to a system for winter or cold weather operation is determined by Tables 6, 7 and 8. (see page 10) Piping: As on all systems, refrigerant migration must be prevented when using FHP. If the receiver is in a warm location, a check valve should be placed in the line between the FHP valve and the receiver. Good piping practice suggests a trap in the compressor discharge line and an inverted trap at the condenser outlet. Multiple valve applications must have valves piped in parallel. Maintenance Air-cooled condensers require minimum maintenance. The unit coil will require a periodic cleaning and this can be accomplished by a brush, vacuum cleaner, pressurized irstream or a commercially available coil cleaning foam. All of the condenser fan motors have sealed ball bearings. The only acceptable service to these bearings is replacement. Cleaning Instructions Heatcraft recommends that the finned surface of this unit be cleaned approximately every six months; more frequent cleaning may be required if extreme conditions cause clogging or fouling of air passages through the finned surface. Calgon Corporation’s CalClean 41352 (o...

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