Gas Piping
Contact your local gas service company to ensure that adequate gas service is available and to review applicable installation codes for your area.
Size the main gas line in accordance with Table 9. The figures shown are for straight lengths of pipe at 0.5 in. W.C. pressure drop, which is considered normal for low pressure systems. Note: Fittings such as elbows, tees and line regulators will add to the pipe pressure drop. Also refer to the latest version of the National Fuel Gas Code.
Schedule 40 Metallic Pipe is the preferred material for the gas line of this water heater. It is imperative to follow the sizing recommendations in the latest version of the National Fuel Gas Code if Corrugated Stainless Steel Tubing (CSST) is used as the gas line for this water heater.
THE HEATER IS NOT INTENDED FOR OPERATION AT HIGHER THAN 14.0” W.C.- NATURAL GAS, (1/2 POUND PER SQUARE INCH GAGE) SUPPLY GAS PRESSURE. EXPOSURE TO HIGHER SUPPLY PRESSURE MAY CAUSE DAMAGE TO THE GAS VALVE WHICH COULD RESULT IN FIRE OR EXPLOSION. IF OVERPRESSURE HAS OCCURRED SUCH AS THROUGH IMPROPER TESTING OF GAS LINES OR EMERGENCY MALFUNCTION OF THE SUPPLY SYSTEM, THE GAS VALVE MUST BE CHECKED FOR SAFE OPERATION. MAKE SURE THAT THE OUTSIDE VENTS ON THE SUPPLY REGULATORS AND THE SAFETY VENT VALVESARE PROTECTEDAGAINST BLOCKAGE. THESE ARE PARTS OF THE GAS SUPPLY SYSTEM, NOT THE HEATER. VENT BLOCKAGE MAY OCCUR DURING ICE STORMS.
TABLE 9 - GAS SUPPLY PIPE LENGTH (FEET)
| Schedule 40 metallic | 500,000 btu/hr input rate |
| Maximum Equivalent Pipe Length (Feet) |
| pipe nominal dia. |
| Natural Gas | Propane |
| | |
| 3/4" | - | 10 |
| | 1" | 10 | 40 |
| 1 | 1/4" | 60 | 150 |
| 1 | 1/2" | 150 | 350 |
| | 2" | 200 | 400 |
| 2 | 1/2" | 200 | 400 |
Natural Gas: 0.60 Specific Gravity, 0.50"W.C. pressure drop
Propane Gas: 1.50 Specific Gravity, 0.50"W.C. pressure drop
IT IS IMPORTANT TO GUARD AGAINST GAS VALVE FOULING FROM CONTAMINANTS IN THE GAS WAYS. SUCH FOULING MAY CAUSE IMPROPER OPERATION, FIRE OR EXPLOSION.
IF COPPER SUPPLY LINES ARE USED THEY MUST BE INTERNALLY TINNED AND CERTIFIED FOR GAS SERVICE. BEFORE ATTACHING THE GAS LINE, BE SURE THAT ALL GAS PIPE IS CLEAN ON THE INSIDE.
TO TRAP ANY DIRT OR FOREIGN MATERIAL IN THE GAS SUPPLY LINE, A DIRT LEG (SOMETIMES CALLED SEDIMENT TRAP OR DRIP LEG) MUST BE INCORPORATED IN THE PIPING (SEE FIG. 21). THE DIRT LEG MUST BE READILY ACCESSIBLE AND NOT SUBJECT TO FREEZING CONDITIONS. INSTALL IN ACCORDANCE WITH RECOMMENDATIONS OF SERVING GAS SUPPLIERS. REFER TO THE LATEST VERSION OF THE NATIONAL FUEL GAS CODE.
To prevent damage, care must be taken not to apply too much torque when attaching gas supply pipe to gas valve inlet.
Apply joint compounds (pipe dope) sparingly and only to the male threads of pipe joints. Do not apply compounds to the first two threads. Use compounds resistant to the action of liquefied petroleum gases.
BEFORE PLACING THE HEATER IN OPERATION, CHECK FOR GAS LEAKAGE. Use soap and water solution or other material acceptable for the purpose in locating the leaks. DO NOT USE MATCHES, CANDLES, FLAME OR OTHER SOURCES OF IGNITION FOR THIS PURPOSE.
DISCONNECT THE HEATER AND ITS MANUAL GAS SHUTOFF VALVE FROM THE GAS SUPPLY PIPING SYSTEM DURING ANY SUPPLY PRESSURE TESTING EXCEEDING 1/2 PSIG. GAS SUPPLY LINE MUST BE CAPPED WHEN DISCONNECTED FROM THE HEATER. FOR TEST PRESSURES OF 1/2 PSIG OR LESS THE APPLIANCE NEED NOT BE DISCONNECTED, BUT MUST BE ISOLATED FROM THE SUPPLY PRESSURE TEST BY CLOSING THE MANUAL GAS SHUTOFF VALVE.
GAS PIPING AND DIRT LEG INSTALLATION
FIGURE 21
Purging
Gas line purging is required with new piping or systems in which air has entered.
PURGING SHOULD BE PERFORMED BY PERSONS EXPERIENCED IN THIS TYPE GAS SERVICE. TO AVOID RISK OF FIRE OR EXPLOSION, PURGE DISCHARGE MUST NOT ENTER CONFINED AREAS OR SPACES WHERE IGNITION CAN OCCUR. THE AREA MUST BE WELL VENTILATED AND ALL SOURCES OF IGNITION MUST BE INACTIVATED OR REMOVED.
GAS METER SIZE — NATURAL GASES ONLY
Be sure the gas meter has sufficient capacity to supply the full rated gas input of the water heater as well as the requirements of all other gas fired equipment supplied by the meter. If gas meter is too small, ask the gas company to install a larger meter having adequate capacity.
Gas Pressure Regulator
The gas pressure regulator is built into the gas valve and is equipped to operate on the gas specified on model and rating plate. The regulator is factory adjusted to deliver gas to burner at correct water column pressure allowing for a nominal pressure drop through the controls.
The minimum gas supply pressure for input adjustment must not be less than 4.5” W.C. (1.12 kPa) for natural gas or 11.0"W.C. (2.74 kPa) for propane gas.
Do not subject the combination gas valve to inlet gas pressures of more than 14.0” W.C. (3.48 kPa). A service regulator is necessary if higher gas pressures are encountered.
The manifold gas pressure specified in Table 10 refers to the gas pressure measured at the pressure tap of the automatic gas valve when the burners are firing.
TABLE 10 - MANIFOLD GAS PRESSURE IN INCHES OF WATER COLUMN (ALL MODELS*)
TYPE OF GAS
NATURAL | PROPANE |
3.5 (0.87 kPa) | 10.0 (2.49 kPa) |
