41
UH
Series
High Altitude Operation
The UH Series heater is factory configured for altitudes from 0 – 2,000 ft above sea level. If the
unit heater is being installed at an elevation above 2,000 ft, the input rate will have to be de-rated
to ensure proper operation. The deration is achieved by a gas orifice change.
The installation of the high altitude orifices must be done prior to putting the heater in operation
and prior to connecting the gas supply line. The manifold pressure may need to be re-adjusted
after orifices are installed. Refer to Charts 3.5 through 3.7 for proper high altitude conversion kit.
For altitudes above 9,500 feet, consult factory.
High Altitude Conversion Kit Installation:
1
Remove service access door by unscrewing the 5/16” (#10) sheet metal screws securing the
door.
2
Disconnect all wires connecting to the gas control valve.
3
Remove the manifold pipe from the burner assembly by removing the four mounting screws.
4
Slide the manifold pipe assembly out of the control compartment.
5
Remove gas orifices from the manifold using a 7/16” wrench.
6
Thread in the new orifices of the correct kit, starting threads by hand. Take care not to cross
thread the orifices (See Charts 3.5 through 3.7 for proper kit number and orifice size).
7
Tighten gas orifices to a torque of 150 inch pounds. No thread sealant is necessary, as the
brass is designed to seal to the steel manifold pipe at the proper torque.
8
Inspect all the newly installed orifices to ensure they are straight and aligned 90° to the
manifold pipe. Correct or replace any misaligned orifices.
9
Reinstall the manifold pipe assembly to the unit, ensuring that each orifice is properly aligned
with the burners. Secure with four 5/16” (#10) screws.
10
Reconnect all wires to the gas control valve.
11
Proceed with the installation of the gas supply line as described within this manual.
Chart 3.5
•
High Altitude Conversion Kits for Elevations of 2,000 to 4,500 Feet
WARNING
!
Explosion hazard.
This heater must be converted by a trained gas installation and
service personnel only. Failure to comply could result in personal injury, asphyxiation,
death, and fire or property damage.
Model
Number of
Orifices
Kit Number
Orifice Size
Natural Gas
Propane
Natural Gas
Propane
UH-30
2
HKN-50_2
HKP-59_2
50 DMS
59 DMS
UH-45
3
HKN-50_3
HKP-59_3
50 DMS
59 DMS
UH-60
4
HKN-50_4
HKP-59_4
50 DMS
59 DMS
UH-75
5
HKN-50_5
HKP-59_5
50 DMS
59 DMS
3.0
Installation
•
High Altitude Operation
