Gas Piping; Gas Line Leak Testing; Purging - A.O. Smith 104 Series Instruction Manual

GAS PIPING

Conta t your lo al gas servi e ompany to ensure that adequate
gas servi e is available and to review appli able installation odes
for your area
Size the main gas line in a ordan e with Table 8 The gures shown
are for straight lengths of pipe at 0 5 in W C pressure drop, whi h is
onsidered normal for low pressure systems Note Fittings su h 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
S hedule 40 Steel or Wrought Iron Pipe is the preferred material
for the gas line of this water heater It is imperative to follow the
sizing re ommendations 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 in h gage) supply gas pressure
Exposure to higher supply pressure may
gas valve whi h ould result in re or explosion If overpressure
has o urred su h as through improper testing of gas lines or
emergen y malfun tion of the supply system, the gas valve must be
he ked for safe operation Make sure that the outside vents on the
supply regulators and the safety vent valves are prote ted against
blo kage These are parts of the gas supply system, not the heater
Vent blo kage may o ur during i e storms
TABLE 8. MAXIMUM CAPACITY OF PIPE IN
CUBIC FEET OF GAS PER HOUR
(Based upon a Pressure Drop of 0 5 in h Water Column and
0 6 Spe i Gravity Gas and max gas pressure of 5 psig)
NOMINAL IRON PIPE SIZE (INCHES)
LENGTH
IN FEET
1/2 3/4 1
10 175 360 680
20 120 250 465
30 97 200 375
40 82 170 320
50 73 151 285
60 66 138 260
70 61 125 240
80 57 118 220
90 53 110 205
100 50 103 195
125 44 93 175
150 40 84 160
175 37 77 145
200 35 72 135
It is important to guard against gas valve fouling from ontaminants in
gas ways Su h fouling may ause improper operation, re or explosion
If opper supply lines are used they must be internally tinned and
erti ed for gas servi e Before atta hing the gas line, be sure that
all gas pipe is lean on the inside
To trap any dirt or foreign material in the gas supply line, a sediment
trap must be in orporated in the piping (see Figure 20) The sediment
trap must be readily a essible and not subje t to freezing onditions
Install in a ordan e with re ommendations of serving gas suppliers
Refer to the latest version of the National Fuel Gas Code
To prevent damage, are must be taken not to apply too mu h torque
when atta hing gas supply pipe to gas valve inlet
ause damage to the
1 1/4 1 1/2 2 2 1/2 3
1,400 2,100 3,950 6,300 11,000 23,000
950 1,460 2,750 4,350 7,700
770 1,180 2,200 3,520 6 250
660 990 1,900 3,000 5,300
580 900 1,680 2,650 4,750
530 810 1,520 2,400 4,300
490 750 1,400 2,250 3,900
460 690 1,300 2,050 3,700
430 650 1,220 1,950 3,450
400 620 1,150 1,850 3,250
360 550 1,020 1,650 2,950
325 500 950 1,500 2,650
300 460 850 1,370 2,450
280 430 800 1,280 2,280
Apply joint ompounds (pipe dope) sparingly and only to the male
threads of pipe joints Do not apply ompounds to the rst two threads
Use ompounds resistant to the a tion of lique ed petroleum gases
GAS METER SIZE – NATURAL GASES ONLY
Be sure the gas meter has suf ient apa ity to supply the full rated
gas input of the water heater as well as the requirements of all other
gas red equipment supplied by the meter If gas meter is too small, ask
the gas ompany to install a larger meter having adequate apa ity
GAS PIPING AND SEDIMENT TRAP INSTALLATION

GAS LINE LEAK TESTING

4
15,800
12 800
10,900
9,700
8,800
8,100
7,500
Any time work is done on the gas supply system perform a leak test
7,200
to avoid the possibility of re or explosion
6,700
1 For test pressures ex eeding 1/2 psi (3 45 kPa) dis onne t the
6,000
water heater and its Main Gas Shutoff Valve from the gas supply
5,500
piping system during testing, see Figure 20 The gas supply line
must be apped when dis onne ted from the water heater
5,000
4,600
2 For test pressures of 1/2 psi (3 45 kpa) or less, the water heater
need not be dis onne ted, but must be isolated from the supply
gas line by losing the Main Gas Shutoff Valve during testing
3 Coat all supply gas line joints and onne tions upstream of the
water heater with a non- orrosive soap and water solution to
test for leaks Bubbles indi ate a gas leak Do not use mat hes,
andles, ame or other sour es of ignition for this purpose
4 Repair any leaks before pla ing the water heater in operation

PURGING

Gas line purging is required with new piping or systems in whi h air
has entered
Purging should be performed per the urrent edition of NFPA 54 the
National Fuel Gas Code
22
FIGURE 20.
Fire and Explosion Hazard
Use joint compound or Teflon tape
compatible with propane gas.
Leak test before placing the water
heater in operation.
Disconnect gas piping and main gas
shutoff valve before leak testing.
Install sediment trap in accordance
with NFPA 54.