SECTION 3: C
RITICAL
C
ONSIDERATIONS
3
SECTION 3: CRITICAL CONSIDERATIONS
3.1 Basic Information
UHD[X][S][R] heaters have automatic ignition
burners for ON/OFF operation only.
3.2 Manufactured Units
Gas-fired, power-vented duct furnace with tubular
heat exchanger. Units shall have a minimum of 82%
thermal efficiency. The standard unit shall consist of
a non-separated combustion design with an
aluminized heat exchanger. Design and heat
exchanger alternatives shall be offered as follows:
• Separated Combustion: A separated
combustion unit shall feature an enclosed,
sealed burner box. A piece of flexible air duct
connects this burner box to a flange on the
cabinet. Combustion air should be ducted from
outside the heated space, with the ductwork
connecting to the unit with the use of the flange.
• Stainless Steel Heat Exchanger: A stainless
steel heat exchanger unit shall consist of heat
exchanger tubes, heat exchanger tube supports,
heat exchanger tube plates and vent box
produced of 409 stainless steel.
3.3 Location and Suspension
All models:
• Must be installed indoors.
• Must be installed on the positive pressure side of
the air circulation blower.
• Must be installed in a level position with
horizontal discharge.
• May be mounted on a shelf of non-combustible
material.
• May be suspended from above (
See Page 8,
Figure 3
) or from wall brackets of sufficient
strength to support the heater as listed in the
Dimension Data Table
on Page 37, Section 15.1
.
• Must be installed in a manner which allows
access to all serviceable components.
See Page 3, Figure 1
for details.
3.4 Minimum Required Installation Clearances
Clearances around the heater and vent must be as
indicated
on Page 3, Figure 1
and
Page 11, Figure 4
through Page 14, Figure 9
to ensure access for
servicing, and correct operation.
3.5 Clearances to Combustibles
Clearances must be as indicated
on Page 3, Figure
1
. If clearances to combustibles are not indicated,
then installation clearances apply.
Figure 1: Clearances to Combustibles
WARNING
Fire Hazard
Some objects can catch fire or explode
when placed close to heater.
Keep all flammable objects, li
q
uids and
vapors the re
q
uired clearances to
combustibles away from heater.
Failure to follow these instructions can
result in death, injury or property dama
g
e.
6"
(15 cm)
6"
(15 cm)
31"*
(79 cm)
6"
(15 cm)
Clearance to Vent: 2" (5 cm)
*31" (79 cm) minimum is necessary
for servicing.
