Armstrong World Industries 243, 302, 242, 122 Minimum Required Surface Area for Disposable, Filters

SRM-HW/HWC 8/99

Service Reference Manual INSTALLATION

6-13

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 connec- tion to attach the remainder of the return duct. The return duct should be sealed to the unit casing and terminate outside the space containing the furnace.

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.

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 Table 6-4 when sizing the disposable filter.

TABLE 6-4	Minimum Required Surface Area for Disposable
	Filters
Model Number		Filter Area (minimum)	Supplied Filter Size
HWC122, 123		300 square inches	16.5" x 25.5" x .50"
HWC182, 183		480 square inches	16.5" x 25.5" x .50"
HWC242, 243		480 square inches	16.5" x 25.5" x .50"
HWC302, 303		480 square inches	16.5" x 25.5" x .50"
26 HW		300 square inches	16.5" x 25.5" x .50"
38 HW		300 square inches	16.5" x 25.5" x .50"
51 HW		480 square inches	16.5" x 25.5" x .50"
64 HW		480 square inches	16.5" x 25.5" x .50"

Adjustments - Heating Section

Temperature Rise

At the time of installation, the temperature rise must be adjusted to be within the range specified on the unit rating plate.

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.

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.