Supply Gas Line Installation - A.O. Smith BTH-120 Instruction Manual

supply gas line installation

Contact your local gas utility company to ensure that adequate
gas service is available and to review applicable installation
codes for your area.
Be sure that the gas meter has sufficient capacity to supply the
rated gas input of the water heater as well as the requirements
of all other gas fired equipment supplied by the meter. If the
gas meter is undersized, the gas company will have to install a
properly sized gas meter.
Fire and Explosion Hazard
Do not use water heater with any gas
other than the gas shown on the rating
label.
Excessive gas pressure to gas valve can
cause serious injury or death.
Turn off gas lines during installation.
Contact a qualified installer or service
agency for installation and service.
make sure gas supplied is same type listed on the water heater's
rating label.
The water heaters covered in this manual are not intended for
operation at higher than 10.5" W. C. (2.62 kPa) for natural gas and
14.0" W. C. (3.49 kPa) for propane gas supply pressure, see Table
3 on page 12. The water heaters covered in this manual require
supply gas regulators to maintain required supply gas pressure.
Exposure to higher gas supply pressure may cause damage to the
gas controls which could result in fire or explosion. If overpressure
has occurred such as through improper testing of gas lines or
malfunction of the supply system the water heater's gas valve
must be checked for safe operation by a Qualified Service Agency.
Ensure supply regulator vent lines and the safety vent valves are
protected against blockage. These are components of the gas
supply system, not the water heater. Vent blockage may occur
during ice storms.
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.
REGULATED GAS
SUPPLY LINE
MAIN GAS
SHUTOFF VALVE
TEE FITTING
SEDIMENT TRAP
PIPE CAP
Ensure all gas pipe is clean on the inside before installation. To
trap any dirt or foreign material in the gas supply line a sediment
trap must be installed as shown in Figure 52. The sediment trap
must be readily accessible and not subject to freezing conditions.
Install in accordance with the recommendations of the local gas
utility company.
figure 52
gas line siZing
Depending on the developed equivalent length and/or the number
of appliances connected to a common main, the size of supply gas
lines may have to be increased.
Size the supply/main gas line(s) in accordance with Table 8 or
Table 9. The values given in Table 8 and Table 9 are for straight
lengths of iron pipe at 0.5" W. C. (125 Pa) pressure drop, which
is considered normal for low pressure systems. Note that fittings
such as elbows and tees will add to the pipe pressure drop.
Schedule 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 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.
supply gas line siZing u. s. units
taBle 8
lENGTH NOrmAL IrON PIPE SIZES (INCHES)
IN INPUT IN THOUSANDS BTU/Hr
FEET 1/2" 3/4"
10 175 360
20 120 250
30 97 200
40 82 170
50 73 151
60 66 138
70 61 125
80 57 118
90 53 110
100 50 103
125 44 93
150 40 84
175 37 77
200 35 72
supply gas line siZing metric units
taBle 9
lENGTH NOrmAL IrON PIPE SIZES (INCHES)
IN
mETERs 1/2" 3/4"
3.0 51 105
6.1 35 73
9.1 28 59
12.2 24 50
15.2 21 44
18.3 19 40
21.3 18 37
24.4 17 35
27.4 16 32
30.5 15 30
38.1 13 27
45.7 12 25
53.3 11 23
61.0 10 21
39
1" 1 1/4" 1 1/2"
680 1400 2100 3960
485 950 1460 2750
375 770 1180 2200
320 660 990 1900
285 580 900 1680
260 530 810 1520
240 490 750 1400
220 460 690 1300
205 430 650 1220
195 400 620 1150
175 360 550 1020
160 325 500
145 300 460
135 280 430
INPuT IN kW
1" 1 1/4" 1 1/2"
199 410 615 1160
142 278 428
110 225 346
94 193 290
83 170 264
76 155 237
70 143 220
64 135 202
60 126 190
57 117 182
51 105 161
47 95 146
42 88 135
40 82 126
2"
950
850
800
2"
805
644
556
492
445
410
381
357
337
299
278
249
234