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12
Gas Piping Checks
CAUTION
To prevent property damage or personal injury
due to fire, the following instructions must
be preformed regarding gas connections and
pressure testing:
•
The unit and its gas connections must be
leak tested before placing in operation.
Because of the danger of explosion or fire,
never use a match or open flame to test for
leaks. Never exceed specified pressures for
testing. Higher pressure may damage gas
valve and cause overfiring which may result
in premature heat exchange failure.
•
This unit and its shut-off valve must be
disconnected from the gas supply during
any pressure testing of that system at test
pressures in excess of ½ PSIG (3.48 kPa).
•
This unit must be isolated from the gas
supply system by closing its manual shut-off
valve during any pressure testing of the gas
supply piping system at test pressures equal
to or less than ½ PSIG (3.48 kPa).
WARNING
To avoid property damage or personal injury, be
sure there is no open flame in the vicinity during
air bleeding.
There will be air in the gas supply line after testing for leaks
on a new installation. Therefore, the air must be bled from
the line by loosening the ground joint union until pure gas
is expelled. Tighten union and wait for five minutes until all
gas has been dissipated in the air. Be certain there is no
open flame in the vicinity during air bleeding procedure.
The unit is placed in operation by closing the main
electrical disconnect switch for the unit.
PROPANE GAS INSTALLATIONS
WARNING
To avoid property damage, personal injury
or death due to fire or explosion caused by
a propane gas leak, install a gas detecting
warning device. Since rust can reduce the level
of odorant in propane gas, a gas detecting
warning device is the only reliable way to detect
a propane gas leak. Contact a local propane
gas supplier about installing a gas detecting
warning device.
IMPORTANT NOTE: Propane gas conversion kits
must be installed to convert units to propane gas.
NOx screens must be removed before converting
to LP. Remove burner assembly and pull NOx
screens from each burner tube. When all the
screens are out, reassemble the burner assembly
without the screens.
All propane gas equipment must conform to the safety
standards of NFPA 58 - Liquefied Petroleum Gas Code.
For satisfactory operation, propane gas pressure must be
within 9.7 - 10.3 inches w.c. for high fire at the manifold
with all gas appliances in operation. Maintaining proper
gas pressure depends on three main factors:
1. Vaporization rate, which depends on (a) temperature
of the liquid, and (b) wetted surface area of the
container or containers.
2. Proper pressure regulation.
3. Pressure drop in lines between regulators, and
between second stage regulator and the appliance.
Pipe size required will depend on length of pipe run
and total load of all appliances.
Tanks and Piping
Complete information regarding tank sizing for
vaporization, recommended regulator settings and pipe
sizing is available from most regulator manufacturers and
propane gas suppliers.
Since propane gas will quickly dissolve white lead or most
standard com mercial compounds, special pipe dope must
be used. Shellac base compounds resistant to the actions
of liquefied petroleum gases such as Gasolac
®
, Stalactic
®
,
Clyde’s
®
or John Crane
®
are satisfactory.
See the following figure for typical propane gas piping.
200 PSIG
Maximum
5 to 15 PSIG
(20 PSIG Max.)
Continuous
11" W.C.
Second Stage
Regulator
First Stage
Regulator
Typical propane gas piping
Roof Top Location and Installation
The gas supply piping location and installation for roof
top units must be in accordance with local codes or, in
the absence of locals codes, with ordinances of the latest
edition of the National Fuel Gas Code ANSI Z223.1/NFPA
54.
Summary of Contents for AHRI 210
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