AAON RL-240 - Manual (Page 34)

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A factory installed pressure tap on the outlet
end of the gas valve can be used to verify a
manifold pressure of 3.5” w.c. for natural
gas, or 10.5” w.c. for propane. For two
stage gas valves, the low stage setting
should be set at 1.1” w.c. for natural, 5.0”
w.c. for propane. For modulating heaters,
the safety shut-off valve would be set
following the instructions above, then from
a provided pressure tap in the gas train
immediately preceding the burner manifold
the modulating valve is set maintain a
maximum of 3.5” w.c. and a minimum
of 0.4” w.c.
Gas Pressure Regulator & Overpressure
Protection Device
A gas pressure regulator must be installed if
natural gas supply pressure to the unit is
greater than 10.5” w.c. and if propane gas
supply pressure is greater than 13” w.c.
Regulators must comply with the latest
edition of the Standard for Line Pressure
Regulators, ANSI Z21.80/CSA 6.22.
Both a gas pressure regulator and
overpressure protection device (OPD) must
be installed if gas supply pressure to the unit
is greater than 2 psi (55.4” w.c.) and less
than 5 psi (138.4” w.c.), in compliance with
ANSI Z21.80/CSA 6.22. For proper heater
operation, pressure to the regulator MUST
NOT be greater than 5 psi (138.4” w.c.).
Piping Supports
Gas supply piping must be supported
directly at the connection to the unit and at
intervals listed in the following table with
metal straps, blocks, or hooks. Piping should
not be strained or bent.
Table 5 - Piping Support Intervals
Pipe Size
Support
Intervals
1/2” to 3/4” Every 6 ft
3/4” to 1”
Every 8 ft
1-3/4” or Larger (Horizontal) Every 10 ft
1-1/4” or Larger (Vertical) Every Floor
Additional Gas Piping Considerations
Local codes will usually require a field
provided and installed manual main shutoff
valve and union external the unit. Main
shutoff valve should be labeled. A field
provided 1/8” NPT pressure tap is required
to be installed in the piping just upstream of
the shutoff valve for test gage connection to
allow checking of the gas supply pressure at
the unit. A drip leg should be installed near
the unit connection to trap sediment and
condensate. Pipe joint compounds used on
all gas piping connections should be
resistant to liquid petroleum gases.
Leak Testing
All components of gas supply system,
including manual shut off valves and the
piping in the interior of the unit, should be
leak tested with a soap solution before
operating the appliance and at least on an
annual basis thereafter.
Do not use open flame or other
source of ignition for leak testing. Fire
or explosion could result causing
property damage, personal injury, or
death.
DANGER
Heater should be disconnected from
the gas supply piping during pressure
testing of the supply piping system
with pressures in excess of ½ psi. Gas
valves can be damaged if subjected to
more than ½ psi.
CAUTION