5566019-BIM-B-1118
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Johnson Controls Ducted Systems
•
Drive
- routes power through the VFD for modulating
control of the indoor blower motor.
•
Line (or bypass)
- routes power directly to the motor that
provides full-speed motor operation and complete
electrical isolation of the drive.
•
Test
- routes power to the VFD but not to the motor to
allow for drive programming and diagnostics.
If a drive failure occurs, the unit does not automatically switch to
bypass mode. You must set the manual bypass switch to the
Line position. If there is a call for the fan, the indoor blower
motor runs at full-speed while in the bypass mode.
BAS-ready VFD
Factory-installed VFD is also available with BAS-ready models.
Terminal blocks are provided in the control box (in place of the
VAV control board) for field wiring of a customer-installed BAS
to receive 24 VAC power and to connect to the following control
signals:
• a duct static pressure transducer input signal (0-5 VDC)
• an economizer actuator input signal (2-10 VDC)
• an economizer actuator output signal (2-10 VDC)
• a VFD speed reference output signal (2-10 VDC)
The use of shielded cable is recommended for the above
control wiring connections.
Note:
Factory-installed VFD is not available with factory-
installed BAS options due to space limitations in the
control box.
A solid-state, lock-out relay (LR) and 100 microfarad, 50 VDC
capacitor must be field-supplied and installed to provide a
means to transmit a potential fault signal back to the BAS
controller. The specific relay part number required depends on
the need for either AC-output or DC-output. Refer to the price
pages for further details.
When the appropriate relay and capacitor are obtained, install
the capacitor across LR terminals 3 and 4 and make the
following wiring connections:
• LR '1' to BAS controller
• LR '2' to BAS controller
• LR '3' to UCB 'X'
• LR '4' to UCB 'C'
VFD-ready for customer installation
Units configured as VFD-ready provide provisions for a
customer-installed drive. The physical dimensions of VFDs can
vary greatly among manufacturers, horsepower ratings, and
voltage requirements. Keep in mind that drive manufacturers
also require various minimum clearances to allow for adequate
internal cooling of the drive during operation.
The unit comes with a mounting bracket installed in the blower
access compartment which may accommodate other vendor's
drives depending on their size. In order to use the unit's
mounting bracket, the maximum recommended drive
dimensions are limited to approximately 9 in. H x 5 in. W x
7.5 in. D.
If the drive does not fit in the allotted space, then it must be
mounted elsewhere. It can be mounted in one of the following
locations.
• Within the building on a perpendicular wall that is not
subjected to excessive temperature, vibration, humidity,
dust, corrosive gas, or explosive gas.
• Within an appropriate enclosure rated for outside
installation to safeguard against moisture, dust, and
excessive heat.
The power leads to the drive (L1, L2, L3) and from the motor
(T1, T2, T3) are temporarily spliced together with wire nuts.
After you remove the wire nuts, connect the wires to the field-
installed VFD according to the VFD wiring diagram (See Figure
27). The VFD must also be grounded according to the
manufacturer's specifications.
Figure 27: Simplified VFD wiring
If the unit is operated with the manual bypass switch in
the Line (bypass) position and there are VAV boxes
present in the duct system, then boxes must be driven to
the full-open position using a customer-supplied power
source to prevent over-pressurizing and possible
damage to the ductwork.
Before you begin any service, disconnect all power to
the drive. Be aware that high voltages are present in the
drive even after power is disconnected. Allow the
capacitors within the drive to discharge before you begin
service.
Do not connect AC power to the T1, T2, T3 drive
terminals to prevent damage to the VFD.
ELEMENTARY DIAGRAM
VFD
TB8 (IN CONTROL BOX)
RUN PERMIT
(DIGITAL)
SPEED REF
(ANALOG)
(2-10 VDC)
GND
GRN
GND
GRN
GND
1 DMTR
118 / BK
119 / BR
120 / Y
3
M
(T1)
(T2)
(T3)
( )
(L1)
(L3)
(L2)
722 / BK
725 / BR
728 / Y
720 / PR
723 / BR
726 / O
TB1
FU3
FU5
FU4
1
2
3
4
5
6
L3
L2
L1
T1
T2
T3
