MORTEXPRODUCTSINC.501TERMINALRDFORTWORTH,TEXAS76106 Page8
such as full size auxiliary drain pan on all units installed in
a non-conditioned space to prevent damage from
condensation runoff.
9. All return air must be filtered to prevent a buildup of dirt on
the coil surface.
Appliance Clearances
This appliance is approved for zero (0) inches clearance to
combustible material on any part of the air handler exterior
casing and the inlet or outlet ducts providing NO electric heater
is being used. There is a one (1) inch clearance on the supply
plenum and supply air duct when an electric heater is installed
in the appliance. Refer to Table 12 for the clearance to
combustibles.
Figure 4: Clearance – Access for Service
Table 12: Clearance to Combustibles
Un-cased Horizontal Air Handler Return Air
The uncased Air Handler unit can have a non metallic ducted
return that can have a return air opening that is located between
the joists and the sheet rock that can carry the return air from a
return air filter grille in a ceiling to the horizontal Air Handler
unit.
Provisions shall be made in this type of return air system is
large enough to permit the air in the rooms and the living
spaces to return to the Air Handler unit. Failure to comply
may cause a reduction in the amount of return air available to
the blower, causing reduced air flow resulting in improper
heating and cooling of the living space. The reduced air flow
may cause the furnace to cycle on the limit causing premature
heating element failure and/or condensate water blow off.
The return air grille or duct can never be located in a closet.
Cased Horizontal Air Handler Return Air
The cased horizontal Air Handler unit can use the louvered
ceiling access panel on the horizontal Air Handler unit as a
means of returning the conditioned air from the living space to
the Air Handler unit.
The cased horizontal Air Handler unit can also have a non-
louvered ceiling access panel with the return air ducted using a
return plenum and duct system. The ducted return air can be
located straight down to the ceiling where it is terminated using
a return air filter grille. The ducted return can also travel
through the space between the joists and sheet rock and be
terminated with a return air filter grille located away from the
horizontal Air Handler unit.
Provisions shall be made in the duct system to ensure it is
large enough permit the proper amount of air to be returned
from the living spaces to the horizontal Air Handler unit.
Failure to comply may cause a reduction in the amount of
return air available to the blower, causing reduced air flow
resulting in improper heating of the living space. The reduced
air flow may cause the furnace to cycle on the limit causing
premature heating element failure.
Air Filter Location
Horizontal Air Handler Units are not factory equipped with an
air filter. The air filter can be installed on the louvered ceiling
access panel or the air filters can be located remotely in the
return air filter grille.
If a non metallic return system or a ducted return system is
installed and a return air filter grille is used at the opposite end
of the duct a non-louvered ceiling access panel will be required.
The louvered ceiling panel air filter sizes for the SEHX, CEHX,
SCWE and the CCWE models are 20” x 20” x 1”
The recommended minimum filter size for a return air filter
grille is:
Standard Throw away Air Filter @ 300 ft/min or less
600 CFM = 16 x 20 x 1
700 CFM = 20 x 20 x 1
800 CFM = 20 x 20 x 1
900 CFM = 20 x 24 x 1
1000 CFM = 20 x 24 x 1
Pleated filters are not recommended for use with PSC Motors
NON METALIC DUCTED RETURN SYSTEMS MAY
NOT BE ALLOWED IN SOME STATES, COUNTIES,
OR CITIES.
CHECK ALL STATE, LOCAL AND FIRE CODES TO
DETERMINE IF THIS TYPE OF RETURN SYSTEM IS
ALLOWED WHERE THE HORIZONTAL AIR
HANDLER UNIT IS BEING INSTALLED.
FIRE HAZARD:
NON METALIC DUCTED RETURN SYSTEMS WILL
COLLECT DUST AND DEBRIS WHICH CAN RESULT
IN A FIRE HAZARD. BE SURE TO THOROUGHLY
CLEAN THIS SYSTEM TO REMOVE ALL DUST AND
DEBRIS ANNUALLY.
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