349218-JIM-F-0512
Johnson Controls Unitary Products
29
Check all connections for leaks when piping is completed using
a soap solution.
NEVER USE A FLAME.
Vent And Combustion Air
Two vent hoods and a combustion air hood (with screens) are
shipped attached to the blower housing in the blower
compartment. For units with factory installed VFD option, the
hoods and accompanying hardware are shipped inside the
gas heat section. These hoods must be installed to assure
proper unit function. All hoods must be fastened to the
outside of the gas heat access panel with the screws
provided in the bag also attached to the blower housing.
The screen for the combustion air intake hood is secured to
the inside of the access panel opening with four fasteners and
the screws used for mounting the hood to the panel. The top
flange of this hood slips in under the top of the access panel
opening when installing. Refer to Vent and Combustion Air
Hood Figure 15.
Each vent hood is installed by inserting the top flange of the
hood into the slotted opening in the access panel and securing
in place.
The products of combustion are discharged horizontally
through these two screened, hooded vent openings on the
upper gas heat access panel.
Figure 15: Vent and Combustion Air Hood
Options/Accessories
Electric Heat
Electric heaters are available as a factory-installed option.
These heaters mount in the heat compartment with the
heating elements extending into the supply air chamber. All
electric heaters are fused and intended for use with single
point power supply.
Economizer/Motorized Outdoor Damper Rain Hood
The instruction for the optional economizer/motorized damper
rain hood can be found in the rain hood kit. Use these
instructions when field assembling an economizer rain hood
onto a unit. The outdoor and return air dampers, the damper
actuator, the damper linkage, the outdoor and return air divider
baffles, and all the control sensors are factory mounted as part
of the “Factory installed” economizer option.
Power Exhaust/Barometric Relief Damper and Rain Hood
The instructions for the power exhaust/barometric relief damper
and rain hood can be found in the rain hood kit. The exhaust
fan, all supporting brackets, angles, and the wiring are factory
installed as part of the power exhaust option.
Economizer And Power Exhaust Set Point
Adjustments
Remove the top rear access panel from the unit. Locate the
economizer control module, where the following adjustments
will be made.
Minimum Position Adjustment
• Check that the damper blades move smoothly without
binding; carefully turn the Minimum Position Adjust screw
(found on the damper control module) fully clockwise and
then set the thermostat indoor fan switch to the ON
position and then OFF or energize and de-energize
terminals “R” to “G”.
• With the thermostat set to the indoor fan ON position or
terminals “R” to “G” energized, turn the Minimum Position
Adjusting screw (located on the damper control module)
counterclockwise until the desired minimum damper
position has been attained.
Enthalpy Set Point Adjustment
• The enthalpy set point may now be set by selecting the
desired set point shown in the Enthalpy Set Point
Adjustment Figure 16. Adjust as follows:
• For a single enthalpy operation carefully turn the set
point adjusting screw (found on the damper control
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warning exactly could result
in serious injury, death or property damage.
Never test for gas leaks with an open flame. use a
commercially available soap solution made specifically
for the detection of leaks to check all connections. A fire
or explosion may result causing property damage,
personal injury or loss of life.
Vent Air
Outlet Hoods
Slotted Openings in
Access Panel
Combustion Air
Intake Hood
Gas Heat
Access Panels
Extreme care must be exercised in turning all set point,
maximum and minimum damper positioning adjustment
screws to prevent twisting them off.
