lp-672 Rev. 000 Rel. 002 Date 10.3.18
37
Part 8 - Gas Connections
FIRE AND/OR EXPLOSION HAZARD
To avoid serious injury or death, the gas line installation and the gas line inlet pressure test must be done by a licensed professional.
Ensure the gas on which the water heater will operate is the same type specified on the rating plate (natural gas or LP gas). This water
heater must be converted into propane operation unless specifically manufactured for use with propane. Follow Gas Conversion Manual
instructions (separate document). Propane ready water heaters have the suffix “LP” after the model serial number. Failure to follow these
instructions could result in property damage, personal injury, or death.
Make sure the gas line pressures are within normal limits. Pressures outside normal limits can result in poor performance and hazardous
operating conditions. Failure to do so could result in property damage, personal injury, or death.
A. Gas Pipe Sizing Tables
1. Gas Pipe Sizing
This information is for reference use only. Refer to gas pipe manufacturer specifications for actual delivery capacity. The DOE standard for
Natural Gas is 1100 BTU/ft
3
. Contact the local gas supplier for actual BTU/ft
3
rating.
2. Natural Gas Pipe Sizing
The following table lists maximum capacity of pipe in cubic feet of gas per hour for gas pressures of 14” or less and a pressure drop of 0.5
inches water column, based on a 0.60 specific gravity for natural gas.
Pipe Size (in.)
Length of Pipe (Feet)
BTU’s Per
Hour x 1,000
Schedule 40
Metallic Pipe
(0.60 Specific
Gravity,
0.5 WC
Pressure Drop)
10
20
30
40
50
60
80
100
150
200
3/4
360
247
199
170
151
137
117
104
83
71
1
678
466
374
320
284
257
220
195
157
134
1 1/4
1390
957
768
657
583
528
452
400
322
275
1 1/2
2090
1430
1150
985
873
791
677
600
482
412
2
4020
2760
2220
1900
1680
1520
1300
1160
928
794
3
11300
7780
6250
5350
4740
4290
3670
3260
2610
2240
4
23100
15900
12700
10900
9660
8760
7490
6640
5330
4560
Table 18 - Natural Gas Delivery Capacity - Refer to ANSI Z223.1 - National Fuel Gas Code, Latest Edition
3. LP (Liquid Propane) Gas Pipe Sizing
Contact gas supplier to size pipes, tanks, and 100% lockup gas pressure regulator. Adjust propane supply regulator provided by the gas
supplier for 14 inches w.c. maximum pressure.
B. Gas Connection Requirements
1. The gas connection fitting on the water heater is ¾” NPT.
NOTE:
The pipe size must not be less than ¾”.
2. The supply line must be sized for the maximum output of the water heater being installed. If there are additional gas appliances from
the main supply line, measure the size of the supply line according to the COMBINED total maximum BTUH draw for the appliances as
if they were operating at the same time.
3. Measure the length of the gas supply line from the gas meter to the water heater. Water heater must be installed downstream of the
gas meter to ensure adequate gas supply. Use the tables in this manual or refer to the gas line manufacturer’s sizing information to
determine the correct supply pipe size.
4. The National Fuel Gas Code (NFPA 54) requires that a sediment trap (drip leg) be installed in the gas line on appliances not so equipped.
The drip leg must be accessible, a minimum of 3” in length, and not subject to freezing conditions. See Figure 40.
UNION
SEDIMENT TRAP
MANUAL SHUT OFF
BALL VALVE
Figure 40 - Gas Line with Shut-Off and Sediment Trap Detail
5. A manual gas shut-off valve should be installed in the gas
supply line close to the water heater. See Figure 40 for detail.
6. To facilitate any future maintenance, it is also recommended
that an approved gas union fitting be installed in the supply
line between the shut-off valve and the ¾” NPT connection on
the water heater.
7. Use a manometer to test the gas pressure to make sure it
meets the minimum standards and does not exceed the
maximum standards of the water heater.
8. Leak test the gas line pipe before placing the water heater in
operation. Only use approved leak detector liquid solutions
to check for leaks.
9. Do not operate the water heater until all connections have been completed and the heat exchanger is filled with water.
