32
SYSTEM OPERATION
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 DRG0361DL00001S
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