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GAS CONNECTIONS
NOTE: The 425 HN is supplied with a gas pressure
regulator that must be installed on the heater before
attaching the gas supply line. See fig. 5. Failure to install
the gas regulator as shown in figure 5 will be a violation
of CSA certification of the unit. The regulator supplied
with the heater is preset for the gas shown on the rating
plate to the correct pressure. It is an appliance level
regulator designed for (low inlet) pressure (less than 1/
2 Psig or 15” W.C.)
DO NOT connect to an unregulated or high pressure
propane line or to a high pressure commercial natural
gas line.
GAS LINE SIZING
-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 425 HN regulator. 1/2” Black Iron
pipe up to 10 feet, 3/4” Black Iron pipe up to 40 feet and
1” Black Iron pipe up to 150 feet distances. Flex line tubing
is NOT recommended, but if used then oversize it.
-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 425 HN regulator. For semi-
rigid copper piping: 5/8” up to 20 feet and 3/4” up to 60
feet distances. For Black Iron piping: 1/2” up to 45 feet
and 3/4” up to 160 feet distances. Flex line tubing is NOT
recommended, but if used then oversize it.
THESE FIGURES ARE FOR 425 HN SUPPLY ONLY, ALL
OTHER APPLIANCES IN THE BUILDING WILL NEED TO
BE INCLUDED IN THE PIPE SIZING.
National Fuel Gas Code requires that a sediment trap (drip
leg) be installed on gas appliances not so equipped. The
drip leg must be accessible and not subject to freezing
conditions. Install in accordance with the recommendations
of the serving gas supplier.
WARNING: The heater must be disconnected from
the gas supply piping system during any pressure testing of
that system at test pressures in excess of 0.5 psig.
The water heater must be isolated from the gas supply piping
system by closing the manual shutoff valve during any
pressure testing of the gas supply piping system at test
pressures equal to or more than 0.5 psig.
The water heater, including the pressure regulator provided
with it, must not be operated at 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 and regulator must be
checked for safe operation. Make sure that the regulator
vent is protected against blockage.
When your connections are made, check for gas leaks at
all joints (not just the ones you made). Apply some soapy
water to all gas fittings and gas valve. Soap bubbles are a
sign of a leak.
NOTE: Do not apply soap solution to the pilot or pilot orifice
area. If you have a leak, shut off the gas. After verifying that
required gaskets are in place, 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.
Fig. 5 - Installation of Gas Pressure Regulator
GAS INLET PIPE
PRESSURE TAP
PRESSURE REGULATOR
(with directional arrow on
reverse side pointing
upward)
The pressure regulator provided with the heater is adjusted
to deliver the proper gas pressure (as indicated on the rating
plate and in the manual for altitude up to 2000 feet (660
meters) above sea level. On appliances being installed above
2000 ft (660 meters) elevation, the inlet gas pressure should
be set at installation to the value shown below.
PLASTIC VENT CAP
draft diverter outlet must be connected to an unobstructed
vent of the same size, or larger.
In Canada, CAN/CGA-B149 Installation Code for detailed
requirements
In U.S.A., ANSI Z223.1 - NFPA 54, National Fuel Gas
Code for detailed requirements.
The vent connection for the 425 HN is 5 inches. However,
for installations at high altitude (over 2000 feet above sea
level) a six inch vent is required. A 5" by 6" vent adaptor
must be affixed to the flue collar of the 425 HN with at
least two screws. See fig. 4.
WARNING: Failure TO INCREASE THE VENT SIZE
TO SIX INCHES AND/or assure that the manifold pressure
is set to proper value listed for applications at high altitudes
will cause unsafe venting, asphyxiation, and will void CSA
Certification.
Altitude Natural Gas Liquid Propane
inches W.C: inches W.C:
0' - 2.000 ft 5.7" 10.5"
2.000 ft - 4.500 ft 4.6" 8.4"
Above 4.500 ft consult your local gas provider.
MAXIMUM INLET GAS FLOW PRESSURE SETTING
Fig. 4 - Vent Adaptor for High Altitude Installations
5” X 6” ADAPTOR
USED ON HIGH ALTITUDE
NOTE: The gas pressures specified below refer to
pressures taken at the pressure tap on the gas inlet pipe
just above the regulator (See Fig 5). These readings
should be taken while the heater is operating at full input
— i.e. maximum water flow with the temperature dial
selector turned all the way clockwise.