36 AGZ 030A through 065A IOM 686
Note: The superheat is factory set and adjustment is not needed unless unless operation is
outside the 8° to 12°F range.
CAUTION
Before adjusting superheat, check unit charge is correct and liquid line sightglass is full with
no bubbles.
The suction superheat for the suction leaving the evaporator is set at the factory for 8° to 12°F at full
load. To have full rated unit performance the superheat must be about 8°F at 95°F outdoor ambient.
Crankcase Heaters
The scroll compressors are equipped with externally mounted band heaters located at the oil sump
level. The function of the heater is to keep the temperature in the crankcase high enough to prevent
refrigerant from migrating to the crankcase and condensing in the oil during off-cycle.
Power must be supplied to the heaters 24 hours before starting the compressors.
Water Cooler
The water cooler is of the direct expansion type with removable internally finned tubes. The copper
tubes are individually rolled into heavy duty steel tube sheets and sealed by a steel refrigerant head.
The water connection nozzles which enter and leave the shell are on the same side of the unit. No
special attention is required for the cooler except that clean, filtered water should be supplied.
Sensors and Transducers
Sensors and transducers are mounted and connected to the Global UNT controller with sensor cable.
The evaporator pressure transducers depress the schrader fittings and can be replaced without pumping
the unit down. The pressure transducers are connected to the Global UNT controller analog inputs
with IDC connectors (Insulation Displacement Connectors). The low pressure transducers have a blue
dot. The leaving water sensor is in a thermal well for easy replacement without draining the water
system. As standard, an outside air sensor is provided on the back of the control box. When other
reset options are selected, the outside air sensor is not provided as only one (1) type of reset is
available.
Control Wiring
Low voltage control wiring is installed, labeled and tested by the factory before shipment.
External Voltage Inputs
The signal for remote reset option (2 to 10 VDC) or demand limit (0 to 10VDC) is provided by the
installing contractor. Connect to TB -7 terminals #134 (+) and #135 (-) as indicated by the unit wiring
diagram. A 4 to 20mA signal conditioned by a 500 ohm resistor can provide the 2 to 10 VDC input
for the remote reset option. Polarity of the external DC signal must match the controller polarity.
Interlock Wiring
All interlock wiring to field devices (such as a flow switch or time clock) is provided by the installing
contractor. All interlocking wiring must be connected to the Global UNT 24Vac power supply.
External power supplies connected to the Global UNT controller can damage the controller. See unit
wiring diagram.
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