Optional Variable Air Volume (Vav) - York ZF150 Installation Manual

518674-YIM-C-0610
the assembly. Field installed Motorized Outdoor Damper
accessories include complete instructions for installation.
Economizer
The Economizer can be a factory installed option or a field
installed accessory. If factory installed, refer to the instructions
included with the outdoor air hood to complete the assembly.
Field installed Economizer accessories include complete
instructions for installation.
There are two Economizer options:
1. Down Flow application with barometric relief hood standard.
2. Horizontal Flow application that requires the purchase of a
barometric relief hood.
Power Exhaust
The Power Exhaust can be a factory installed option or a field
installed accessory. If factory installed, refer to the instructions
included with the outdoor air hood to complete the assembly.
Field installed Power Exhaust accessories include complete
instructions for installation.
The Power Exhaust factory installed option is for Down Flow
application only.
There are two field installed Power Exhaust accessories:
1. Down Flow application.
2. Horizontal Flow application that requires the purchase of a
barometric relief hood.
Rain Hood
All of the hood components, including the filters, the gasketing
and the hardware for assembling, are packaged and located
between the condenser coil section and the main unit cabinet, if
the unit has factory installed options. If field installed
accessories are being installed all parts necessary for the
installation comes in the accessory.

Optional Variable Air Volume (VAV)

A variable air volume (VAV) option using a variable frequency
drive (VFD) is available for applications requiring a constant
supply-duct static pressure. A differential pressure transducer is
used to monitor supply duct static pressure and return a speed
reference signal to the VFD to control the output of the indoor
blower motor.
Duct Static Pressure Transducer
A 0-5" WC pressure transducer, located in the control box
compartment, is used to sense static (gauge) pressure in the
supply air duct and convert this pressure measurement to a
proportional 0-5 VDC electrical output. Pressure-transmitting
plastic tubing (1/4" diameter) must be field supplied and
installed from the transducer to both the ductwork and to the
atmosphere. Connect the tubing from the 'HIGH' pressure tap of
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,
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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.
VAV Control Board
A VAV control board, located in the control box, is used to
convert the pressure transducer input signal into a speed
reference signal that the drive uses to control the speed of the
blower motor. This modulating speed reference signal is
generated using an algorithm which continuously calculates an
output value.
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 monitors outdoor air
quality (CO concentration) and, along with IAQ, enables
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Johnson Controls Unitary Products