AAON HB-005 - Manual (Page 21)

21
Gas Piping
Size gas piping to supply the unit with 6” to 10.5” water
column (w.g.) pressure for natural gas, or 11” w.g. for
propane (when a natural gas to propane conversion kit
has been field installed) when all gas consuming
devices in the building connected to the same gas
system are operating. Install piping in accordance with
local codes, the piping must conform with the latest
ANSI-Z223.1 National Fuel Gas Code; in Canada,
Current Standard CAN/CGA-B149, Installation for Gas
Burning Appliances and Equipment.
Gas piping MUST BE supported DIRECTLY AT
CONNECTION TO UNIT, and must not be strained or
bent, and must be supported by metal straps, blocks,
or hooks at intervals not to exceed that shown in Table
21.2.
Pipe joint compounds used on all gas piping
connections must be resistant to the action of
petroleum gases. A 1/8” NPT plugged tap is required
immediately ahead of the unit gas control valve.
All piping connections should be checked for gas leaks
before operating the unit. The furnace must be
isolated by closing the manual shut off valve, or
disconnected from the gas supply during pressure
testing of the piping system with pressures in excess
of 1/2 PSIG.
Gas Pressure Regulator & Over-Pressure
Protection Device (Optional)
On applications where gas service to the unit is
greater than 10.5” w.g., and less than 2 PSI, a gas
pressure regulator must be installed.
In compliance with the ANSI Z21.80 Line Regulator
Standard, installations with gas supply pressures in
excess of 2 PSI, and less than 5 PSI require a tested
and approved over-pressure protection device (OPD)
for use with the regulator as a means to limit the
downstream pressure to 2 PSI maximum in the event
of regulator failure.
For proper heating operation, pressure to the regulator
MUST NOT BE greater than 5 PSI.
DO NOT USE OPEN FLAME OR OTHER
SOURCE OF IGNITION FOR LEAK TESTING.
When pressure testing the gas supply piping, the
furnace must be isolated, or disconnected by
closing the individual manual shut-off valve from
the gas supply. Gas valves can be damaged if
subjected to more than 0.5 PSIG pressure.
WARNING
Some soaps commonly used for leak detection are
corrosive to certain metals. If you leak test with
soap, then thoroughly rinse soap from piping after
leak checks are completed.
CAUTION
Unit Size (Tons) Input (MBH) Pipe Size (In.)
2 – 5 45 – 120 3/4
Table 21.1, Minimum Gas Piping Sizes
Note: Some utility companies will require pipe sizes larger than the
minimum listed above. Local codes may require the use of a
manual main gas shut-off valve and union (field furnished),
installed in the gas line external to the unit.
Pipe Size (In.) Intervals (Ft.)
3/4 or 1 (horizontal or vertical) 8
1 1/4 or larger (horizontal) 10
1 1/4 or larger (vertical) Every floor level
Table 21.2, Gas Piping Support Intervals
Those sensitive to odors or gases from trace
amounts of residual oils should NOT be present in
the conditioned space during the start-up of a gas
fired installation.
WARNING