John Wood Commercial - 300-400K BTU - Manual (Page 36)

36
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
Turn off gas lines during installation.
Contact a qualified installer or service
agency for installation and service.
Excessive gas pressure to gas valve can
cause serious injury or death.
Do not use water heater with any gas
other than the gas shown on the rating
label.
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 10.0” W. C. (2.49 kPa) for natural gas
and 12.0” W. C. (2.99 kPa) for propane gas supply pressure, see
Table 3 on page 13. 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
PIPE CAP
SEDIMENT TRAP
(DIRT LEG)
figure 52
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
(dirt leg) 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.
gas line siZing
do not
use flexible gas piping.
Minimum required supply gas line sizes are shown in Table 4 on
page 13. 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 7 or
Table 8. The values given in Table 7 and Table 8 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.
supply gas line siZing u. s. units
table 7
lENGTH
IN
FEET
NOrMAL IrON PIPE SIZES (INCHES)
INPuT IN THOuSANDS bTu/Hr
1 1/4” 1 1/2” 2” 2 1/2” 3” 4”
10 1400 2100 3960 6300 11000 23000
20 950 1460 2750 4360 7700 15800
30 770 1180 2200 3520 6250 12800
40 660 990 1900 3000 5300 10900
50 580 900 1680 2650 4750 9700
60 530 810 1520 2400 4300 8800
70 490 750 1400 2250 3900 8100
80 460 690 1300 2050 3700 7500
90 430 650 1220 1950 3450 7200
100 400 620 1150 1850 3250 6700
125 360 550 1020 1650 2950 6000
150 325 500 950 1500 2650 5500
175 300 460 850 1370 2450 5000
200 N/A 430 800 1280 2280 4600
supply gas line siZing metric units
table 8
lENGTH
IN
METErS
NOrMAL IrON PIPE SIZES (INCHES)
INPuT IN kW
1 1/4” 1 1/2” 2” 2 1/2” 3” 4”
3.0
410 615 1160 1845 3221 6735
6.1
278 428 805 1277 2255 4626
9.1
225 346 644 1031 1830 3748
12.2
193 290 556 878 1552 3192
15.2
170 264 492 776 1391 2840
18.3
155 237 445 703 1259 2577
21.3
143 220 410 659 1142 2372
24.4
135 202 381 600 1083 2196
27.4
126 190 357 571 1010 2108
30.5
117 182 337 542 952 1962
38.1
105 161 299 483 864 1757
45.7
95 146 278 439 776 1610
53.3
88 135 249 401 717 1464
61.0
N/A 126 234 375 688 1347