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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.
If the unit is operated with the manual bypass
switch in the LINE (BYPASS) position and
there are VAV boxes present in the duct sys-
tem, then boxes must be driven to the full-open
position using a customer-supplied power
source to prevent over-pressurizing and possi-
ble 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 con-
trol box (in place of the VAV control board) for field wir-
ing 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.
Factory-installed VFD is not available with fac-
NOTE:
tory-installed BAS options due to space limita-
tions in the control box.
A solid-state, lock-out relay (LR) and 100-
capacitor must be field-supplied and installed to pro-
vide 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-out-
put or DC-output. See price pages for further details.
20
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 vary greatly among manufacturers, horse-
power 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 utilize the unit's mounting bracket, the maximum rec-
ommended drive dimensions are as follows:
For 5-hp motor applications........................13" H x 6" W x 7" D
For 7.5 thru 15-hp motor applications ........13" H x 8" W x 8" D
If the drive will not fit in the allotted space, then it will
need to be mounted elsewhere; either within the build-
ing on a perpendicular wall which is not subjected to
excessive temperature, vibration, humidity, dust, corro-
sive gas, explosive gas, etc., or 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) along with the respective ground
wires are supplied with the unit and need to be con-
nected after the drive is installed.
Do not connect AC power to the T1, T2, T3
drive terminals to prevent damage to the VFD.
A terminal block located in the control box is provided
for field connection of the VFD speed reference signal
μ
F, 50 VDC
(2-10 VDC) and to the normally-open, run-permit auxil-
iary contact. The use of shielded cable is recom-
mended for the above control wiring connections.
For VFD-ready 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" termi-
284816-BIM-B-0707
Unitary Products Group
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Troubleshooting
