York ZJ150 Installation Manual page 35

the transducer to a static pressure tap (field supplied) in the
supply duct located at a point where constant pressure is
expected. To prevent an unstable signal due to air turbulence,
there should be no obstructions, turns or VAV terminal boxes
up- or down-stream of the sensing tube location for at least a
distance of 6-10 times the duct diameter. Tubing must also be
run between the 'LOW' pressure tap of the transducer and
atmospheric pressure (outside of the unit).
Do not run plastic tubing in the supply or return air ducts
as air movement could cause erroneous pressure
measurements. If the tubing penetrates through the
bottom of the unit be sure openings are sealed to
prevent air and water leakage.
Factory-installed VFD
The factory-installed VFD is mounted in the blower access
compartment. The drive comes wired from the factory to include
both 3-phase power and control connections (run permit signal,
speed reference signal & fault signal). All required drive
parameters are pre-programmed at the factory, except in the
case of 208-volt applications, in which the parameter that
defines motor nameplate voltage must be changed to a value of
208.00 and the parameter that defines motor-rated current must
be changed to the appropriate value appearing on the motor's
nameplate. Refer to the enclosed drive material or access the
UPGnet Commercial Product Catalog website for instructions
on changing parameter settings.
For units also equipped with gas/electric heat, a terminal block
located in the unit's control box and connected to the VAV
board's "VAV BOX" terminal, must be field wired to the
building's VAV boxes to ensure fully open dampers during
heating operation.
Manual Bypass
An optional, factory-installed manual bypass switch available
with factory-installed VFD can be found in the Blower Motor
Access compartment and has the following three positions:
• DRIVE - routes power through the VFD for modulating
control of the indoor blower motor.
• LINE (or BYPASS) - routes power directly to the motor
which 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/or diagnostics.
If a drive failure occurs, the unit does not automatically switch to
bypass mode. The LINE/DRIVE/TEST switch must be manually
switched to the LINE (BYPASS) position. If there is a call for the
fan, the indoor blower motor will run at full-speed while in the
bypass mode.
Johnson Controls Unitary Products
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 beginning any service, disconnect all power to
the drive. Be aware that high voltages are present in the
drive even after power has been disconnected.
Capacitors within the drive must be allowed to discharge
before beginning service.
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 will depend
upon the need for either AC-output or DC-output. See price
pages for further details.
Once the appropriate relay and capacitor are obtained, install
the capacitor across LR terminals '3' & '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
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