34
UH
Series
Separated Combustion Systems
All UH Series heaters come with a factory-installed combustion air adapter for attaching air intake
ducts to the heater. Attach the air intake duct material to the adapter with three (3) non-corrosive
sheet metal screws. If necessary, drill pilot holes prior to attaching the air intake ducts. The
diameter of the intake ducts must not be smaller than the factory installed adapter.
When operating this unit as a separated combustion unit heater system, combustion air must be
supplied to the heater by outdoor means through the factory installed vent connector. The
combustion air intake duct may terminate horizontally through a sidewall or vertically through the
roof. Ideally, the intake should terminate within the same pressure zone as the venting terminates,
which should minimize the effects of wind.
All Separated Combustion systems must comply with the following items:
• Air intake ducts must be of galvanized steel or an equivalent corrosion-resistant material.
• Do not exceed a length of 30 feet.
• Do not exceed more than two (2) 90° directional changes (elbows) in the system.
• Seal all joints with metallic tape or silicone sealant. Wrap the tape two full turns around the
vent pipe.
• Slope air intake pipe ¼ inch per foot upward or downward away from the unit, as shown in
Figure 3.12.
• Do not draw air from attic space.
• Do not draw fresh air from the remaining space around a chimney liner, gas vent, special
gas vent, or plastic piping installed within masonry, metal, or factory built chimney.
• Combustion air ducts may be insulated if they pass through an unconditioned space.
• A factory approved sidewall intake cap must be used when terminating the combustion air
ducts horizontally through the sidewall.
• When combustion air ducts terminate vertically through the roof, a minimum of 18 inches
above the roof grade must be maintained (see Figure 3.13)
• Separate the air intake duct from vent pipe a minimum of 4 feet. Also, place vent pipe higher
than adjacent air intake duct.
• Air intake duct must terminate a minimum of 3 feet below any forced air vent discharge that
is located within 10 feet.
• The bottom of the air intake duct termination must be located a minimum of 12 inches above
grade level. Air intake ducts that terminate adjacent to public walkways must be installed a
minimum of 7 feet above grade level.
• The air intake duct must be installed to prevent blockage by snow, debris, or other possible
obstructions.
3.0
Installation
•
Separated Combustion Systems
