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Note:
As a general rule, these velocities require an intake louver sized approximately 1.25
to 1.5 times the dimensions of the duct connection on the unit, and a discharge louver sized
approximately 1.5 to 2 times the duct connection dimensions
To ensure the unit does not short circuit, only use louver sections that provide different deflection
angles for air discharge and air intake. Protect the unit from weather such as rain or snow entering
through the condenser air intake.
Pitch all outdoor air ducts away from the unit and toward the outside wall. Connect all ducts to the
unit with canvas section duct connectors or choose another suitable noise and vibration absorbing
device.
Note:
The manufacturer will not accept any liability resulting from incorrect installation of this
equipment. Follow installation instructions carefully.
Variable frequency drive (VFD)
Indoor fan VFD
A standard VFD controller for the evaporator (indoor) fan applies on 8–25 ton models. Mounted in
the evaporator module section, the VFD allows the operator to set the duct static pressure or to
control discrete indoor fan speed steps. To meet the desired supply duct static setpoint or a specific
discrete speed step, the VFD controls the evaporator fan motor's frequency (or speed). For reliable
operation, the unit must have a factory installed HGBP circuit on refrigeration circuit # 1 for units
with a duct pressure control option. Unless requested by the customer as a selectable feature, the
unit setup for discrete speed steps does not require HGBP for reliable operation.
In 8 and 12 ton units, the standard discrete speed step configuration is that the VFD has been setup
for three automatically adjusted discrete speeds. 15, 20, and 25 ton units feature 4 discrete speed
steps. In both cases, the discrete fan speeds are matched and adjusted automatically based on the
active cooling stage.
Note:
The unit does not carry a failsafe circuit to bypass the factory installed VFD and run the
evaporator or condenser fan in the event of a VFD malfunction.
The VFD is factory mounted and wired. The installer must provide and field install two sensor
tubing lines complete with static pressure probes (except to the configuration for discrete speed
application). The installer must field wire the fan power wiring between the evaporator VFD and
the unit electrical box (located in the condenser section) because the unit ships factory-split. For
units with a static pressure control option, low voltage wiring from the pressure transducer must be
connected to the unit controller (see the unit schematic for more details).
The power (and optional low voltage wiring for transducer) wiring can be found inside the VFD
enclosure. No extra power wiring is required; sufficient length is provided. The VFD option does not
include an evaporator fan bypass circuit in case of microdrive failure. Microdrive must be replaced
to re-activate the unit. In case of a VFD failure, the evaporator fan stops running. However, unit
compressors continue to run until a low pressure safety trip activates.
For detailed installation and operation instructions, refer to
Variable Frequency Drive Installation and
Operation Instructions
(
Form 145.13-NO2
).
Note:
Do not run evaporator fan motor below 30Hz otherwise coil freeze-up and nuisance
lock-outs may occur.
CAUTION
Building excessive ductwork pressure can cause damage to unit or personnel.
D-Series Vertical (DSV060C-300C) Air-Cooled Self-Contained Units, C Generation with Smart Equipment Controller
18
Johnson Controls