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10
Economizer — Economizer control is used to control the
outside and return air dampers of the unit, to satisfy space cool-
ing demand using all outside air (when permitted), and to satis-
fy cooling in conjunction with compressor operation (when
conditions permit). During Occupied periods without cooling
demand, the outside-air dampers will be at the user-configured
Minimum Damper Position (at P5 on accessory board). During
Unoccupied periods, the outside-air dampers will be closed.
The economizer is a standard feature on 48FM and
50FM,FS units and is available as a factory-installed option on
48FK,JK and 50FK,FY,JK,JY units.
The user can install an accessory differential enthalpy sen-
sor to enhance economizer control. Refer to the installation
section for field wiring of the sensor.
ENTHALPY CONTROL
48FK,JK and 50FK,FY,JK,JY Units — Outside air enthalpy
control is standard with the factory-installed economizer op-
tion. Enthalpy is sensed by a controller located behind the end
outside air hood. The control can be accessed by removing the
upper hood filter. See Fig. 17.
48FM and 50FM,FS Units — The control is located on the
metal upright between the two economizer hoods, on the right
hand side of the unit, and can be accessed by removing the fil-
ter on either economizer hood.
DIFFERENTIAL ENTHALPY — Added efficiencies in econ-
omizer control can be gained by installing a differential en-
thalpy sensor in the return air duct. When differential enthalpy
control is installed, the economizer control will use the air
stream with lower enthalpy (outside air or return air) to provide
for lower compressor operating costs during integrated econo-
mizer cycle operation. The differential enthalpy sensor is
installed in the return-air duct.
Fig. 11 — Thermistor T2 Location, Size 034-048 Units
Fig. 12 — Thermistor T2 Location, Size 034-048 Units
STANDARD
FILTERS
BAG
FILTERS
STANDARD FILTERS AND
PLEATED FILTERS
BAG FILTERS
(054-074 Only)
Fig. 13 — Thermistor T3 and T4 Locations,
Size 034-048 Units