K-Series Packaged Gas / Electric 7.5 to 12.5 Ton / Page 6
FEATURES AND BENEFITS
BLOWER
A wide selection of supply air
blower options are available to meet
a variety of airflow requirements.
Motor
Overload protected, equipped with
ball bearings. Belt drive motors
are offered on all models and are
available in several different sizes
to maximize air performance.
Supply Air Blower
Forward curved blades, double
inlet, blower wheel is statically and
dynamically balanced. Equipped
with ball bearings and adjustable
pulley (allows speed change),.
Blower assembly slides out of unit
for servicing.
Required Selections
Select Constant Air Volume
(CAV) or Single Zone VAV
Supply Fan Supply Air Blower
Option
Order blower motor horsepower
and drive kit number required
when base unit is ordered, see
Drive Kit Specifications Table.
CAV Operation
On units ordered with the Constant
Air volume (CAV) option, the
supply air blower will provide a
constant volume of air.
Single Zone VAV Supply Fan
Operation
Units ordered with the Single Zone
VAV Supply Fan
option utilize a
Variable Frequency Drive (VFD) to
stage the supply air blower airflow.
The VFD alters the frequency and
voltage of the power supply to the
blower to control blower speed.
The supply air blower has two
speeds:
1. Low speed for part-load
cooling operation. Note - Low
speed is 66% of high speed.
2. High speed for full load
cooling and all heat modes.
Full speed blower operation is
set by adjusting the motor pulley
to deliver the desired air volume.
The ventilation speed is selectable
between high and low speed.
H
NOTE - Part load airflow in cooling
mode on
Single Zone VAV Supply
Fan
units should not be set below
220 cfm/nominal full load ton to
reduce the risk of evaporator coil
freeze-up.
The VFD has an operational
range of -40 to 125° F outdoor air
ambient temperature.
Lower operating costs are obtained
when the blower is operated on
lower speeds.
Single Zone VAV Supply Fan
Sequence of Operation
Ventilation speed is determined by
the VENT SPEED switch setting
on VFD control board (LO or HI).
Blower operates in low speed for
mechanical cooling (Y1).
Blower operates in high speed
for any other mode (free cooling,
mechanical cooling Y1+Y2, and
heating).
Economizer damper minimum
position is fully closed in
unoccupied mode.
In occupied mode, the economizer
damper minimum position is
determined by the setting of the
two potentiometers on VFD control
board.
• LO SPD MIN POS
potentiometer sets the
minimum position when blower
is operating at low speed.
• HI SPD MIN POS
potentiometer sets the
minimum position when blower
is operating at high speed.
Options/Accessories
Field Installed
VFD Manual Bypass Kit
VFD Manual Bypass Control is
available as a kit for units equipped
with the
Single Zone VAV Supply
Fan
option.
The VFD Manual Bypass Control
is a manual bypass and is enabled
by re-configuring the wiring on the
unit.
ELECTRICAL
Marked & Color-Coded Wiring
All electrical wiring is color-coded
and marked to identify which
components it is connecting.
Electrical Plugs
Positive connection electrical plugs
are used to connect common
accessories or maintenance parts
for easy removal or installation.
Phase Monitor
(Factory Installed on Units
Equipped with the Single Zone
VAV Supply Fan)
Phase monitor located in the
control compartment detects the
phasing of incoming power. If the
incoming power is out of phase or
if any of the three phases are lost,
an indicator LED on the phase
monitor will turn red and the unit
will not start. In normal operation
with correct incoming power
phasing, the LED will be green.
Required Selections
Voltage Choice
Specify when ordering base unit.
Options/Accessories
Factory or Field Installed
Disconnect Switch
Accessible from outside of unit,
spring loaded weatherproof cover
furnished. Main power to the unit is
field connected to the disconnect
which allows all power to be
shut off for service. See Options/
Accessories tables for ordering
information, page 10.
GFI Service Outlets (2)
115V ground fault circuit interrupter
(GFCI) type, non-powered, field-
wired.
Field Installed
GFI Weatherproof Cover
Single-gang cover.
Heavy-duty UV-resistant
polycarbonate case construction.
Hinged base cover with gasket.
I
