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503,214M Dallas, Texas 1/95 REPLACEMENT DEFROST CONTROL BOARD INSTALLATION INSTRUCTIONS FOR REPLACEMENT DEFROST CONTROL BOARD KIT (11K71) USED WITH HP29, 10HPB, 12HPB SERIES UNITS Package 1 of I contains: 1-Replacement defrost control board The replacement defrost control board for the HP29 and 10HPB series units is part number 68J84. This board replaces the original control board with part number 68J24. Unit wiring to the defrost board is the same. More options are provided in the replacement board such as ambient thermistor and service light connections. The replacement board has the same basic functions as the original board along with the following functions: five minute compressor anti-short delay; pressure switch safety lockout circuit; and field connection for ambient thermistor and service light connections. WARNING CAUTION The provided board is a direct replacement. Remove wires from original board and remove board from control box area. Secure replacement board stand-offs into mounting holes. Wire as shown on unit wiring diagram. The unit's defrost system includes two components; a defrost thermostat (see unit installation instructions) and a defrost control. The following section describes defrost control functions. The defrost control board has the combined functions of a time/temperature defrost control, defrost relay, time delay, diagnostic LEDs and field connection terminal strip. The control provides automatic switching from normal heating operation to defrost mode and back. During compressor cycle (call for defrost), the control accumulates compressor run times at 30, 60 or 90 minute field adjustable intervals. If the defrost thermostat remains closed when the accumulated compressor run time ends, the defrost relay is energized and defrost begins. Defrost Control Timing Pins Each timing pin selection provides a different accumulated compressor run period during one thermostat run cycle. This time period must occur before a defrost cycle is initiated. The defrost interval can be adjusted to 30, 60 or 90 minutes. See figure 1. The defrost period is a maximum of 14 minutes and cannot be adjusted. If no timing is selected, the control defaults to 90 minutes. The factory and recommended setting is 60 minutes. A TEST option is provided for troubleshooting. When the jumper is placed across the TEST pins, the timing of all functions is reduced by a factor of 128. For example, a 90 minute interval during TEST is 42 seconds and the 14 minute defrost is reduced to 6.5 seconds. The TEST mode may be started at anytime. If the jumper is in the TEST position at power-up or for longer than five minutes, the control will ignore the TEST selection and will default to a 90 minute interval. Page 1 REPLACEMENT DEFROST CONTROL BOARD PRESSURE SWITCH SAFETY CIRCUIT CONNECTIONS DIAGNOSTIC LEDs / CONNECTION FOR DEFROST INTERVAL ONE OPTIONAL SWITCH TIMING PINS PS2 PS1 24V TERMINAL STRIP CONNECTIONS FOR TWO OPTIONAL CONNECTIONS SWITCHES SERVICE LIGHT ....... ONNECT,ON [] ps2 Psi ......................... ......................... FIGURE 1 Time-Delay control board. See figure 1. When only one pressure switch is used, wire the switch to the two outside The timed-off delay is five minutes long. The delay terminals of the pressure switch connections. feature is provided to help protect the compressor in case of an interruption in power to the unit or when a NOTE: If not using a pressure switch, the pressure switch resets. factory-installed jumper wire must be connected. Pressure Switch Safety Circuit Diagnostic LEDs The defrost control incorporates a pressure switch The defrost board uses two LEDs for diagnostics. safety circuit that allows the application of up to two The LEDs flash a specific sequence according to the optional pressure switches; high pressure and/or loss condition. of charge. See figure 1. During a demand cycle, the TABLE 1 defrost control will lock out the unit on the third DEFROST CONTROL BOARD DIAGNOSTIC LED instance that the unit goes off on any pressure switch MODE LED 1 LED 2 wired to this circuit. The diagnostic LEDs will display a pattern for a lockout pressure switch on the third Normal Operation/ Flash together Flash together Power to board with LED 2 with LED 1 open pressure switch occurrence. See table 1. The unit will remain locked out until the switch is reset. _me Delay Alternating Alternating To Protect Compressor Flashes Flashes with LED 2 with LED 1 Remove factory-installed jumper before connecting optional pressure switches to control board. When Pressure Switch Open Off On Pressure Switch Lockout On Off two pressure switches are used, wire each switch to one set of terminals PS1 and PS2 on the defrost Board Malfunction On On Page 2 ...