349218-JIM-F-0512
Johnson Controls Unitary Products
31
•
OH -
a 0-10 VDC analog input provided by a field-installed
outdoor air relative humidity sensor for single enthalpy
economizer configuration.
•
RH -
a 0-10 VDC analog input provided by a field-installed
return air relative humidity sensor for dual enthalpy
economizer configuration (used with OH).
•
IAQ -
a 0-10 VDC analog input provided by a field-installed
carbon dioxide sensor which monitors indoor air quality
(CO2 concentration) and enables call for Demand
Ventilation mode for units installed with economizer option.
•
OAQ -
a 0-10 VDC analog input provided by a field-
installed carbon dioxide sensor which monitors outdoor air
quality (CO2 concentration) and, along with IAQ, enables
call for Differential Demand Ventilation mode for units
installed with economizer option.
•
APS -
a 24 VAC binary input provided by a field-installed
air proving switch which monitors the pressure difference
across the indoor blower.
•
PUR -
a 24 VAC binary input for building purge calls from
an external source.
•
OCC -
a 24 VAC binary input used to set the building
occupancy status for the control.
•
LIMIT 2 -
a 24 VAC binary input which either confirms
2nd-stage gas heat operation or receives an error signal
from the variable frequency drive.
Outputs:
•
FAN -
a 2-10 VDC analog output signal sent to the VFD to
modulate the speed of the indoor blower motor.
•
ECON -
a 2-10 VDC analog output signal sent to the
economizer actuator to modulate position of the return air
and outdoor air dampers (optional).
•
EXH ~ -
a 24 VAC binary output signal used to turn on/off
the power exhaust relay (optional).
•
VAV BOX (gas/electric heat only) -
a normally open
relay contact connected to a terminal block, used to drive
the building's VAV boxes to full-open during heating
operation.
Programmable set points:
The
duct static set point
is the pressure that the drive will
maintain when operating the unit in VAV mode. The set-point is
adjustable between 0" WC and 5" WC with the default setting of
1.5" WC.
The
duct static high-limit set point
is the maximum allowable
duct pressure to prevent damage from over-pressurization of
the ductwork in the event of either a drive or damper failure.
The high-limit set-point is adjustable between 0" WC and 5" WC
with the factory default setting of 4.5" WC. If the duct static
pressure reaches the high-limit set point, then the supply fan
motor will be shutdown.
NOTE:
Either of the set points described above can be
changed through the unit control board (UCB) with the
use of a USB-to-RS485 converter, personal computer
or PDA and a down-loaded copy of the Simplicity®
software available at the UPGnet Commercial Product
Catalog website.
Factory-installed VFD
The factory-installed VFD is mounted in the Blower Access
Compartment above the blower assembly. 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.
The customer must be aware of the duct pressure
design limit, and what the duct pressure sensor is
reading when the peak pressure is reached (i.e. the
pressure transducer sensing tube may not be located at
the place of highest pressure in the system).
