Gas Piping; Purging; Gas Pressure Regulator - A.O. Smith BTN 120 THRU 400/A Series Installation And Operaion Manual

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 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.
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 7 - GAS SUPPLY LINE SIZES (IN INCHES)*
MAXIMUM CAPACITY OF PIPE IN
CUBIC FEET PER HOUR
LENGTH NOMINAL IRON PIPE SIZES (INCHES)
IN
FEET 1/2" 3/4" 1" 1 1/4" 1 1/2"
10 175 360 680 1400 2100 3960
20 120 250 465 950
30 97 200 375 770
40 82 170 320 660
50 73 151 285 580
60 66 138 260 530
70 61 125 240 490
80 57 118 220 460
90 53 110 205 430
100 50 103 195 400
125 44 93 175 360
150 40 84 160 325
175 37 77 145 300
200 35 72 135 280
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. 10). 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.
WARNING
2" 2 1/2" 3"
6300 11000 23000
1460 2750 4360 7700 15800
1180 2200 3520 6250 12800
990 1900 3000 5300 10900
900 1680 2650 4750
810 1520 2400 4300
750 1400 2250 3900
690 1300 2050 3700
650 1220 1950 3450
620 1150 1850 3250
550 1020 1650 2950
500 950 1500 2650
460 850 1370 2450
430 800 1280 2280
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.
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
4"

PURGING

9700
8800
Gas line purging is required with new piping or systems in which
8100
air has entered.
7500
7200
6700
6000
PURGING SHOULD BE PERFORMED BY PERSONS
5500
EXPERIENCED IN THIS TYPE GAS SERVICE. TO AVOID RISK
5000
OF FIRE OR EXPLOSION, PURGE DISCHARGE MUST NOT
4600
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
21
DO NOT USE
FIGURE 10
CAUTION