York SUNLINE MagnaDRY WR300 Installation Manual page 18

284813-YIM-C-1008
A brief description of the VAV board's I/O terminals that
are used follows:
Inputs:
• DUCT PRES - a 0-5 VDC analog input provided by
a factory-installed duct static pressure transducer
located in the unit's control box.
• SAT - analog input provided by a factory-installed
10k-ohm, type 3 thermistor located in the unit's
supply air compartment.
• RAT - analog input provided by a factory-installed
10k-ohm, type 3 thermistor located in the unit's
return air compartment.
• OAT - analog input provided by a factory-installed
10k-ohm, type 3 thermistor located in the outdoor
air compartment or mounted within the evaporator
base rail for units without the installed economizer
option.
• ST - analog input provided by field-installed space
temperature sensor.
• 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 moni-
tors 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 build-
ing occupancy status for the control.
• LIMIT 2 - a 24 VAC binary input which either con-
firms 2nd-stage gas heat operation or receives an
error signal from the variable frequency drive.
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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,
sonal computer or PDA
of the Simplicity® software available at
www.yorkupg.com.
The customer must be aware of the duct pres-
sure 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).
Johnson Controls Unitary Products
per-
and a down-loaded copy