Thermo Pride MHA1-50N Installation And Service Manual page 22

All installations and services must be performed by qualified service personnel.
When venting the MDA1 series through the blower compartment a vent chute
(AOPS4941) must be used. Refer to Figure 4. This option requires the removal
of the two 4-inch diameter plastic plug from the blower pan and the top panel of
the unit. After removing the plastic plugs, run the 3-inch diameter vent through
the vent chute and the top and bottom openings.
The MDA1-75, MDA1-100 and MDA1-125 will require the use of the 3-inch to 4-
inch adapter provided. This adapter is to be installed after the 3-inch vent exits
the furnace.
The 3-inch diameter vent running through the vent chute must be a continuous
section. No connections should be within the vent chute.
If this venting option is not utilized, the 4-inch diameter plastic plug in the blower
pan and the 3 1/2 inch diameter plastic plug in the top panel of the unit should be
left in place for proper furnace operation.
The flue may exit the unit through the top, left side, or right side of the unit, refer
to Figure 5. The inducer can be rotated by removing the four (4) inducer
mounting screws and rotating the inducer housing. Ensure that inducer gasket is
in place before reinstalling inducer.
Figure 5: Inducer Mounting
All vent connectors connecting the furnace to the vent must be rigidly supported
with hangers and straps in order to prevent sagging and movement after
installation. The vent connector must be supported at a maximum of every four
feet depending on the design and weight of the material used, to maintain
clearances, and to prevent physical damage. The vent pipe must slope upward a
minimum of 1/4" for each foot of horizontal run away from the furnace.
Vent connectors used in connecting the furnace to the vent cannot be channeled
through floors, ceilings, and walls without the proper protective construction. This
construction must be in accordance with the requirements of the National Fuel
Gas Code, NFPA 54/ANSI Z223.1-2002 or the latest edition thereof.
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