284806-YIM-A-0107
20
Unitary Products Group
•
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 fac-
tory-installed BAS options due to space limita-
tions in the control box.
A solid-state, lock-out relay (LR) and 100-
μ
F, 50 VDC
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.
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 ....................... 10" 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
have to be mounted within a NEMA-4 enclosure for
outside installation or elsewhere within the building on
a perpendicular wall which is not subjected to exces-
sive temperature, vibration, humidity, dust, corrosive
gas, explosive gas, etc.
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.
A terminal block located in the control box is provided
for field connection of the VFD speed reference signal
(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 normally-open, SPST relay located in the unit
control box must be wired to the building's VAV boxes
to ensure fully open dampers during heating operation.
OPTIONAL HOT GAS BYPASS (HGBP)
To allow for low cooling load operation, a direct-acting,
pressure-modulating bypass control valve installed on
the system #1 discharge line is used to divert high tem-
perature, high pressure refrigerant around the TXV in
order to maintain a desired minimum evaporator pres-
sure.
The opening pressure of the bypass valve is fully
adjustable between 0 and 80 psig with a factory-setting
of 60 psig. HGBP is standard on all units with VAV and
optional with CV units.
Do not connect AC power to the T1, T2, T3
drive terminals to prevent damage to the VFD.
