10
GUNE-SVX001A-EN
Installation
Locating Units
Important:
Location of unit heaters is related directly to
the selection of sizes. Basic rules are as
follows,
Clearances
Maintain adequate clearances around air openings into
the combustion chamber:
Accessibility Clearance
The duct furnace must have 18 inches (457 mm) clearance
on the control cabinet end. Provision should also be made
to assure accessibility for recurrent maintenance
purposes.
Atmospheric Considerations
Atmospheres containing commercial solvents or
chlorinated hydrocarbons will produce corrosive acids
when coming in contact with the flames. This will greatly
reduce the life of the gas duct furnace and may void the
warranty. Avoid such areas.
Important:
If the gas duct furnace is to be used in a
building classified as having a hazardous
atmosphere, the installation must comply
with the standards set by the National
Board of Fire Underwriters. Consult the
authorities having jurisdiction before
starting the job.
The duct furnace must be installed on the positive
pressure side of the air circulation blower.
Aircraft Hangars
In aircraft hangars, duct furnaces must be at least 10 feet
(3.05 m) above the upper surface of wings or engine
enclosures of the highest aircraft to be stored in the hangar
and 8 feet (2.4 m) above the floor in shops, offices, and
other sections of the hangar where aircraft are not stored
and housed. Refer to current ANSI/NFPA No. 409, Aircraft
Hangars. In Canada, installation is suitable in aircraft
hangars when acceptable to the enforcing authorities.
Public Garages
In repair garages, duct furnaces must be installed in a
detached building or room separated from repair areas as
specified in the latest edition of NFPA 88B, Repair Garages.
In parking structures, duct furnaces must be installed so
that the burner flames are located a minimum of 18 inches
(457 mm) above the floor or protected by a partition not
less than 18 inches (457 mm) high. Refer to the latest
edition of NFPA 88A, Parking Structures.
In Canada, installation must be in accordance with the
latest edition of CSA B149 “Installation Codes for Gas
Burning Appliances and Equipment.”
Important:
•
The duct furnace must be installed such that the gas
ignition control system is not directly exposed to water
spray, rain, or dripping water.
•
Duct furnaces should not be installed to maintain low
temperatures and/or freeze protection of buildings. A
minimum of 50°F (10°C) thermostat setting must be
maintained.
If duct furnaces are operated to maintain lower than 50°F
(10°C), hot flue gases are cooled inside the heat exchanger
to the point where water vapor (a flue gas by-product)
condenses onto the heat exchanger walls. The result is a
mildly corrosive acid that prematurely corrodes the
aluminized steel heat exchanger and can actually drip
water down from the duct furnace onto the floor surface
below. Additional duct furnaces should be installed if a
minimum 50°F (10°C) thermostat setting cannot be
maintained.
NOTICE:
Equipment Damage!
Do not install unit heaters in corrosive of flammable
atmospheres! Premature failure of, or severe damage to
the unit will result!
NOTICE:
Equipment Damage!
Avoid locations where extreme drafts can affect burner
operation. Duct furnaces must not be installed in
locations where air for combustion would contain
chlorinated, halogenated or acidic vapors. If located in
such an environment, premature failure of the unit will
occur!
WARNING
Combustible Materials!
Failure to maintain proper clearance between the unit
heat exchanger, vent surfaces and combustible
materials could cause a fire which could result in death
or serious injury or property damage. Refer to
for proper clearances.
Table 3.
Minimum safety clearances
(a)
(a) When clearances required for accessibility are greater than the mini-
mum safety clearances, the accessibility clearances take precedence.
Sides
6 inches (152 millimeters)
Top
6 inches (152 millimeters)
Bottom
6 inches (152 millimeters)
Flue
6 inches (152 millimeters)
