The potentiometer locations and functions are as follows:
P1 Ð
P2 Ð ECONOMIZER POSITION Ð Economizer feedback potentiometer is located on the economizer motor. The micro- processor is programmed to indicate an alarm if the travel during initialization is less than 10% of the total potentiom- eter's resistance. An alarm condition will also be signaled if the potentiometer fails during operation, indicating that the damper blades are stuck. If either situation occurs, the pro- cessor will try to drive the economizer dampers closed.
P3 Ð RESET LIMIT Ð This potentiometer is located on the accessory board (provided standard from the factory) in the unit main control box and establishes the maximum amount of reset that can be applied to the
P4 Ð DEMAND LIMIT Ð This potentiometer is located near TRAN4 in the unit control box. The demand limit po- tentiometer is used only if accessory,
P5 Ð ECONOMIZER MINIMUM POSITION Ð This po- tentiometer is on the accessory board (provided standard from the factory) located in the unit main control box. This po- tentiometer speci®es the minimum opening position for the optional economizer. If a fault condition is detected by the processor, an alarm condition will be signaled and the econo- mizer dampers will close.
P6 Ð
P7 Ð SASP (SUPPLY AIR SET POINT) RESET TEM- PERATURE Ð This 10 Kohm potentiometer is used only if the accessory,
PROCESSOR BOARD OUTPUTS Ð The processor board also controls outputs through the relay board. The relay board plugs into the processor board using a ribbon cable.
In addition, the processor board controls the display board. The display board is connected to the processor board by a ribbon cable, and has an LED
CONFIGURATION HEADER AND DIP SWITCH ASSEM- BLY Ð The processor board is programmed to control a va- riety of air conditioning units. To tailor the processor to the particular unit being controlled, 2 devices are used. One is the con®guration header, and the other is the DIP switch assembly.
The con®guration header (part no. 30GB660001) is a series of 8 small wires that are broken or unbroken in a pattern to indicate several unique characteristics of the unit. The con®guration header is factory set and should not be changed. Changing the factory setting may cause the unit to malfunction.
The DIP switches con®gure the unit for several ®eld- installed options, as well as for several other options that may be unique to the unit. The DIP switches are located un- der a plastic enclosure which must be removed for access. The switches can be ®eld adjusted, but must be adjusted only when the unit control circuit breaker is off.
Relay Board Ð The relay board is used to control
Display Board Ð The display board is located in the main unit control box and is connected to the J10 port of the processor board through a ribbon cable. The display board contains the
Thermistors Ð The processor uses up to 5 thermistors to sense the temperatures at various points in the system. See Table 1 and Fig.
219 ohms. Thermistor details and locations are as follows:
T1 Ð
T2 Ð
T3 Ð SATURATED CONDENSING TEMPERATURE, CIR- CUIT 1 Ð This thermistor is located on the condenser coil return bend. See Fig. 13 and 14. It controls the staging of the unit condenser fans based on the condensing temperature of the refrigerant at the designated position on the condenser coil.
T4 Ð SATURATED CONDENSING TEMPERATURE, CIR- CUIT 2 Ð This thermistor is located on the condenser coil return bend. See Fig. 13 and 14. It controls the staging of the unit condenser fans based on the condensing temperature of the refrigerant at the designated position on the condenser coil.
T10 Ð RESET TEMPERATURE Ð This thermistor is used only if the accessory temperature reset package is used. It provides occupied space temperature information to the pro- cessor, which determines whether or not reset is required. The thermistor is remotely mounted outside the unit in the conditioned space.
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