22
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 3. The
fi
gures 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.
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 VALVES ARE PROTECTED AGAINST BLOCKAGE.
THESE ARE PARTS OF THE GAS SUPPLY SYSTEM, NOT THE HEATER.
VENT BLOCKAGE MAY OCCUR DURING ICE STORMS.
TABLE 9 - GAS SUPPLY LINE SIZES (IN INCHES)*
MAXIMUM CAPACITY OF PIPE IN
CUBIC FEET PER HOUR
LENGTH
IN
FEET
NOMINAL IRON PIPE SIZE (INCHES)
1/2"
3/4"
1"
1 1/4" 1 1/2"
2"
2 1/2"
3"
4"
10
175
360
680
1400
2100
3960
6300
11000
23000
20
120
250
465
950
1460
2750
4360
7700
15800
30
97
200
375
770
1180
2200
3520
6250
12800
40
82
170
320
660
990
1900
3000
5300
10900
50
73
151
285
580
900
1680
2650
4750
9700
60
66
138
260
530
810
1520
2400
4300
8800
70
61
125
240
490
750
1400
2250
3900
8100
80
57
118
220
460
690
1300
2050
3700
7500
90
53
110
205
430
650
1220
1950
3450
7200
100
50
103
195
400
620
1150
1850
3250
6700
125
44
93
175
360
550
1020
1650
2950
6000
150
40
84
160
325
500
950
1500
2650
5500
175
37
77
145
300
460
850
1370
2450
5000
200
35
72
135
280
430
800
1280
2280
4600
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
fi
rst
two threads. Use compounds resistant to the action of lique
fi
ed
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 suf
fi
cient capacity to supply the full
rated gas input of the water heater as well as the requirements of
all other gas
fi
red 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 speci
fi
ed 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.
Do not subject the combination gas valve to inlet gas
pressures of more than 14.0” W.C. (3.48 kPa) - natural gas.
A service regulator is necessary if higher gas pressures are
encountered.
Gas pressure speci
fi
ed in Table 10, refer to
fl
ow pressure taken at
pressure tap of automatic gas valve while heater is operating.
TABLE 10
MANIFOLD GAS PRESSURE IN INCHES
OF WATER COLUMN (ALL MODELS*)
TYPE OF GAS
NATURAL
PROPANE
3.5 (0.87 kPa)
10.0 (2.48 kPa)
