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UHA STANDARD UNIT HEATER INSTALLATION OPERATION AND SERVICE MANUAL
6 of 51
SECTION 3: CRITICAL CONSIDERATIONS
3.1 Basic Information
UHA[X][S] heaters have automatic ignition burners
for ON/OFF operation only.
3.2 Manufactured Units
Gas-fired, power-vented unit heater 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.
The use of stainless steel heat exchanger unit is
recommended w
hen air inlet temperatures are
below 40° F (4.4°C) or temperature rise is less
than 40° F (22.2° C) as condensation may form
on the heat exchanger resulting in corriosion that
may shorten its life.
3.3 Location and Suspension
All models:
•Must be installed indoors.
•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 10,
Figure 5) or from wall brackets of sufficient
strength to support the heater as listed in the
Technical Data Table on Page 49, Section 16.2.
Drop rods must be a minimum of 3/8" diameter
mild steel. Four suspension points (3/8" nuts)
are located on top of the heater.
•Must be installed in a manner which allows
access to all serviceable components.
See Page 7, Figure 4 for details.
3.4 Minimum Required Installation Clearances
Clearances around the heater and vent must be as
indicated on Page 7, Figure 4 and Page 13, Figure 6
to ensure access for servicing and correct operation.
3.5 Ventilation
It is important to ensure that there is adequate air
space around the heater to supply air for
combustion, ventilation and distrib
ution in
accordance with local and national codes on Page
11, Section 7.
3.6 Gas Supply
It is important that the gas supply pipe is sized
correctly to provide the inlet pressure as stated on
the heater data plate. The gas supply pipe and
electrical connections must not support any of the
heater's weight on Page 19, Section 9.
3.7 Electrical Supply
A permanent 120 V / 60 Hz / 1 Ø electrical supply is
required for the main electrical power. The heater
also requires suitable controls in accordance with
See Page 21, Section 10.
3.8 Vent
Choose heater orientation to allow for the proper
location of the vent. Each heater must be fitted with
a correctly sized sealed vent system.
If vented horizontally, no other appliance may be
connected to the vent. See Page 11, Section 7.