Page 9 of 20
507389-02
Issue 1733
Junction Box
Use screws to secure
Junction Box
No Gap
Remove Knock-out over opening, pull unit wiring leads through
Figure 7.
Figure 8.
Air Filter
All indoor return air must be filtered. A permanent-type
filter is furnished with the unit, located directly behind the
access panel. Removing the panel permits access to the
filter. See Figure 5.
If an installation is made in which it is more desirable to
mount the filter exterior to the unit, in the return duct work
or elsewhere, the permanent filter can be used or replaced
with a disposable filter. If a disposable filter is used, refer
to the information provided in Table 1 when sizing the
disposable filter.
Model Number
Filter Area
(sq. in.)
HWC9-12
300
HWC9-18
480
HWC9-24
480
HWC9-30
480
Table 1. Minimum Required Surface Area for
Disposable Filters
Supply and Return Duct(s)
Provide duct(s) sized sufficiently to handle the larger of the
air volumes for heating or cooling provided by this model.
Connect the supply duct to the top of the unit using canvas
connections or other flexible connections to prevent noise
transmission into the duct system.
To connect the return duct to the system, use a straight
piece of duct 22” wide by 6” deep. Insert the duct into the
return opening in the bottom of the unit and flange the
duct over the existing flanges around the opening inside
the unit. Make sure that all sides of the duct are flanged
over to permit removal of the cooling chassis if required.
Use a flexible connection to attach the remainder of the
return duct. The return duct should be sealed to the unit
casing and must terminate outside the space containing
the furnace.
Adjustments – Heating Section
Temperature Rise
At time of installation, the temperature rise must be
adjusted to be within the range specified on the unit rating
plate. See Table 2. Select a lower blower speed to increase
rise. Select a higher blower speed to reduce rise.
Pressure Regulator
The gas input must not exceed the figures shown on the
rating plate. The unit is equipped for rated inputs with
manifold pressures of: 3.5” W.C. for natural gas and 10.0”
W.C. for propane.
The manifold pressure can be measured by removing the
pipe plug in the automatic gas valve. Connect a water
manometer and measure the pressure. See Figure 9.
Only small variations in gas input may be made by adjusting
the regulator. In no case should the final manifold pressure
vary more than 0.3” W.C. for natural gas or 0.7” W.C. for
propane.
To adjust the regulator, turn the adjusting screw on the
regulator clockwise to increase pressure and input or
counterclockwise to decrease pressure and input.
