Intake Piping
The ML193DF furnace may be installed in either direct vent or non−direct vent applications. In non−direct vent applications, when intake air will be drawn into the furnace from the surrounding space, the indoor air quality must be considered. Guidelines listed in Combustion, Dilution and Ventilation Air section must be followed.
Follow the next two steps when installing the unit in Direct Vent applications, where combustion air is taken from outdoors and flue gases are discharged outdoors. The provided air intake screen must not be used in direct vent applications (outdoors).
1 − Use cement to secure the intake pipe to the inlet air connector.
2 − Route piping to outside of structure. Continue with installation following instructions given in general guide lines for piping terminations and intake and ex- haust piping terminations for direct vent sections. Re- fer to table 7 for pipe sizes.
TYPICAL AIR INTAKE PIPE CONNECTIONS
NON−DIRECT VENT APPLICATIONS
AIR
INTAKE SCREEN (Provided)
NOTE − Air intake screen and elbow may be rotated, so that screen may be positioned to face forward or to either side.
FIGURE 22
Follow the next two steps when installing the unit in Non- Direct Vent applications where combustion air is taken from indoors and flue gases are discharged outdoors.
1 − Use field−provided materials and the factory−provided air intake screen to route the intake piping as shown in figure 22. Maintain a minimum clearance of 3" (76mm) around the air intake opening. The air intake opening (with the protective screen) should always be directed forward, or sideways.
2 − Use cement to secure the intake pipe to the connector, if desired.
General Guidelines for Vent Terminations
In
In Direct Vent applications, combustion air is taken from outdoors and the flue gases are discharged to the out- doors. The ML193DF is then classified as a direct vent, Category IV gas furnace.
In both
Position termination according to location given in figure 23 or 24. In addition, position termination so it is free from any obstructions and 12" above the average snow accumula- tion.
At vent termination, care must be taken to maintain protective coatings over building materials (prolonged exposure to exhaust condensate can destroy protective coatings). It is recommended that the exhaust outlet not be located within 6 feet (1.8m) of a condensing unit because the condensate can damage the painted coating.
NOTE − If winter design temperature is below 32°F (0°C), exhaust piping should be insulated with 1/2" (13mm), Ar- maflex or equivalent when run through unheated space. Do not leave any surface area of exhaust pipe open to out- side air; exterior exhaust pipe should be insulated with 1/2" (13mm) Armaflex or equivalent. In extreme cold cli- mate areas, 3/4" (19mm) Armaflex or equivalent may be necessary. Insulation on outside runs of exhaust pipe must be painted or wrapped to protect insulation from de- terioration. Exhaust pipe insulation may not be necessary in some specific applications.
NOTE − During extremely cold temperatures, below approximately 20°F (6.7°C), units with long runs of vent pipe through unconditioned space, even when insulated, may form ice in the exhaust termination that prevents the unit from operating properly. Longer run times of at least 5 minutes will alleviate most icing problems. Also, a heating cable may be installed on exhaust piping and termination to prevent freeze−ups. Heating cable installation kit is available from Lennox. See Condensate Piping section for part numbers.
IMPORTANT
Do not use screens or perforated metal in exhaust terminations. Doing so will cause freeze−ups and may block the terminations.
IMPORTANT
For Canadian Installations Only:
In accordance to CSA International B149 installation codes, the minimum allowed distance between the combustion air intake inlet and the exhaust outlet of other appliances shall not be less than 12 inches (305mm).
Page 18