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17
2.11 Gas line sizing
B It is strongly recommended that the Natural Gas pipe
be Black Iron pipe the entire distance from the
outside meter to the inlet of the gas connection. ¾”
Black Iron pipe up to 20 feet (6.1m) and 1” Black Iron
pipe up to 70 feet (21.34m) distances. Flex line is
NOT recommended, but if used, then oversize the
diameter of the flex pipe, keep the length to a
minimum and try to keep the flex line as straight as
possible.
B It is strongly recommended that the LP Gas pipe be
semi-rigid copper or Black Iron pipe from the outside
regulator to the inlet of the gas connection. For semi-
rigid copper piping: 5/8” up to 10 feet (3.05m) and
¾” up to 30 feet (9.14m) distances. For Black Iron
piping: ½” up to 20 feet (6.1m) and ¾” up to 80 feet
(24.38m) distances. Flex line is NOT recommended,
but if used, then oversize the diameter of the flex
pipe, keep the length to a minimum and try to keep
the flex line as straight as possible.
National Fuel Gas Code requires that a sediment trap
(drip leg) be installed on gas appliances not so
equipped. Also, a manual gas shut off valve must be
installed on the gas supply line within close proximity of
the water heater and be visible from the water heater.
The water heater must not be piped with gas supply
pressures in excess of 0.5 psig. If overpressure has
occurred, such as through improper testing of the gas
lines or malfunction of the supply system, the gas valve
must be checked for safe operation.
When connections are made, check for gas leaks at all
joints. Apply some soapy water to all gas fittings. Soap
bubbles are a sign of a leak.
2.12 Measuring gas pressure
2.12.1 Connecting Manometer
B Shut off gas.
B Remove front cover and locate inlet gas pressure
measuring point (see Fig. 24).
B Loosen screw inside test point fitting (do not remove)
and connect manometer tube on test point.
2.12.2 Static Pressure Test
B Turn gas supply back on.
B Operate all other gas appliances on same gas piping
system at maximum output.
B Record static gas pressure reading in table 5.
2.12.3 Operating Pressure Test
B ON/OFF switch in position OFF (0).
B Press and hold "Program" (M) button and turn ON/
OFF switch to ON position.
Fig. 23
B As soon as '188' is displayed, release "Program"
button and the display should read P2.
B Press , until P1 appears.
Note: While in this mode the appliance will run
constantly at maximum power and allow maximum water
flow.
B Turn on high volume of hot water flow (at least 6
gpm) and heater will ignite.
B Record operating gas pressure reading in table 5.
Gas pressures lower than 5" W.C. for Natural Gas or
11" W.C. for LPG will result in insufficient degree rise
to the hot water being used, and must be corrected.
See Gas Connections, chapter 2.10.
Fig. 24 Gas pressure measuring (left tapping)
i
THESE FIGURES ARE FOR GWH-635-
ES SUPPLY ONLY, ALL OTHER
APPLIANCES IN THE BUILDING MUST
BE INCLUDED IN THE PIPE SIZING.
Warning: The heater must be
disconnected from the gas supply
piping system during any pressure
testing of that system at test pressures
equal to or more than 0.5 psig.
Danger: If you have a leak, shut off the
gas. Tighten appropriate fittings to stop
leak. Turn the gas on and check again
with a soapy solution. Never test for gas
leaks using a match or flame.