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3.0
Installation
•
Gas Supply Installation Instructions
Refer to Chart 3.2 for natural gas and Chart 3.3 for propane to determine the cubic feet per hour (CFH)
required for the type of gas and size of unit to be installed. To determine the proper pipe diameter, use
the CFH value and the length of pipe necessary from Chart 3.4. In the case where several units are
serviced by the same main gas line, the total capacity (CFH) and length of main must be adequate to
service all appliances downstream of this main.
Chart 3.2 •
Natural Gas Consumption
Manifold
Pressure
Model
(Inches W.C.)
UH-30N
3.5
UH-45N
3.5
UH-60N
3.5
UH-75N
3.5
*Assumes an average heating value of 1050 BTU/SCF and a Specific Gravity of 0.60.
Chart 3.3 •
Propane Gas Consumption
Manifold
Pressure
Model
(Inches W.C.)
UH-30P
10.0
UH-45P
10.0
UH-60P
10.0
UH-75P
10.0
*Assumes an average heating value of 2500 BTU/SCF and a Specific Gravity of 1.53.
Chart 3.4 allows for a 0.3 inch W.C. pressure drop in the supply pressure from the building main to the
inlet of the unit. Refer to the chart for the appropriate range of inlet pressures for each gas type. When
sizing the inlet gas pipe diameter, make sure that the unit supply pressure can be met after the 0.3 inch
W.C. pressure drop has been subtracted from the main pressure. If the 0.3 inch W.C. pressure drop is
too high, refer to NFPA 54 or the Gas Engineer's Handbook for other gas pipe capacities.
Min. Inlet
Max. Inlet
Pressure
Pressure
(Inches W.C.)
(Inches W.C.)
5.0
5.0
5.0
5.0
Min. Inlet
Max. Inlet
Pressure
Pressure
(Inches W.C.)
(Inches W.C.)
11.0
14.0
11.0
14.0
11.0
14.0
11.0
14.0
Gas
Consumption
(CFH)*
14.0
28.6
14.0
42.9
14.0
57.1
14.0
71.4
Gas
Consumption
Gallons
per hour
(CFH)*
12.0
18.0
24.0
30.0
18
UH
Orifice
Number
Size
of Orifices
49 DMS
49 DMS
49 DMS
49 DMS
Orifice
Number of
Size
Orifices
*
0.33
57 DMS
0.49
57 DMS
0.66
57 DMS
0.82
57 DMS
Series
2
3
4
5
2
3
4
5
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