51
Table 13 - 55, 65 and 75-140 ton Gas
Connections
Option
Input
MBH
Quantity Size
2
After verifying gas inlet pressure and
manifold pressure the service technician
must time the gas flow rate through the gas
meter with a stopwatch to verify the gas
input rate.
Unit nameplate input rate value has been
calculated at the altitude where the unit was
shipped. Above 2,000 ft the input rate is
adjusted 4% for every 1,000 ft.
Figure 30 - RN Series Gas Heat Exchanger
Table 14 - Natural Gas (ft
3
/hr) Maximum Piping Capacities
Specific Gravity = 0.6, Supply Pressure ≤ 0.5 psi, Pressure Drop = 0.5” w.c.
Table 15 - Propane (kBtu/hr) Maximum Piping Capacities
Specific Gravity = 1.52, Supply Pressure = 11” w.c., Pressure Drop, 0.5” w.c.
Do not use gas piping smaller than unit gas
connections. Natural gas pipe runs longer
than 20 feet and propane gas pipe runs
longer than 50 feet may require a larger
supply pipe than the unit connection size.
Some utility companies may also require
pipe sizes larger than the minimum sizes
listed.
Piping Sizing Examples
A 100 ft pipe run is needed for a 1080 MBH
natural gas heater. The natural gas has a
rating of 1000 Btu/ft
3
and a specific gravity
of 0.6 (Obtain these values from the local
gas supplier.)
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