GAS PIPING CHECKS
CAUTION
TO PREVENT PROPERTY DAMAGE OR PERSONAL INJURY DUE TO FIRE, THE FOLLOWING INSTRUCTIONS MUST BE PERFORMED 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 1/2 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 1/2 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.
All propane gas equipment must conform to the safety standards of the National Board of Fire Underwriters (See NBFU Manual 58). Line pressure 11.3 - 14” w.c.
For satisfactory operation, propane gas manifold pressure must be within 9.7 - 10.3 inches w.c. for high fire and within
6.7- 7.3 inches w.c. low fire at the manifold with all gas appli- ances 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 commercial 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 following figure for typical propane gas piping.
First Stage | 5 to 15 PSIG | |
(20 PSIG Max.) | ||
Regulator | ||
Continuous | ||
| 11" W.C. | |
200 PSIG | Second Stage | |
Maximum | 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 ab- sence of locals codes, with ordinances of the latest edition of the National Fuel Gas Code (ANSI Z223.1).
A manual gas shutoff valve must be field installed external to the roof top unit. In addition, a drip leg must be installed near the inlet connection. A ground joint union connection is re- quired between the external shutoff valve and the unit con- nection to the gas valve to permit removal of the burner as- sembly for servicing.
1.Route gas piping to unit so that it does not interfere with the removal of access panels. Support and align piping to prevent strains or misalignment of the manifold assembly.
2.All units are furnished with standard female NPT pipe connections. Connection pipe size is 3/4" NPT. The size of the gas supply piping to the unit must be based on length of run, number of units on the system, gas characteristics, BTU requirement and available supply pressure. All piping must be done in accordance with local codes or, in the absence of local codes, with the latest edition of the National Fuel Gas Code (ANSI Z223.1).
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