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Gas Supply
INSTALLATION INSTRUCTIONS
Determining the required pipe size.
The gas system is designed to operate at a certain
maximum pressure drop. A pressure drop greater
than what is permissible can cause operational
issues with the gas appliances. The National Fuel
Gas Code (NFPA 54, ANSI Z223.1 2012) allows for
three pressure drop levels, a 0.3 inch W.C., (see
table 2); a 0.5 inch W.C., (see table 3) and a 3.0 inch
W.C., (see table 4) pressure drop for natural gas.
Only a 0.5 inch W.C. pressure drop is allowable with
Propane (see table 5). For Canadian installations the
maximum allowable pressure drop is 0.5 inch W.C.,
(see table 3).
Measure the inlet gas pressure to the system using
a manometer. For Natural Gas, if the inlet pressure
is less than 8.0 inches W.C. then use Table 2 or 3
for your gas pipe sizing. Table 4 can only be used if
the inlet gas pressure is 8.0 inches W.C. or greater.
Table 4 cannot be used for Canadian installations.
The gas piping system consists of a main trunk
line that runs from the meter/regulator and branch
lines that run from the trunk line to the individual
appliances. A branch may carry gas for more than
one appliance.
The trunk line must be sized to carry the entire load
of all the gas appliances on the system. As with
determining the meter/regulator size, total the BTU
of all the appliances together and divide that by the
heating value of the fuel (for natural gas the average
is 1,024 or 2,546 for propane). This will give you the
total cubic feet per hour of gas required for the trunk
line. Measure the total length of the line Refer to
Table(s) 2, 3, or 4 and find the number closest to but
higher than the total cubic feet per hour requirement
calculation. This will tell you the minimum size that
the trunk line must be.
Each branch line must be sized to carry the load
of the appliance(s) attached to it. If more than one
appliance is on a branch total the BTU and as with
the trunk line divide that by the heating value of the
fuel. Refer to Table(s) 2, 3, or 4 and find the number
closest to but higher than the total cubic feet per
hour requirement calculation for the branch and
appliance(s). This will tell you the minimum size for
that branch line and appliance.
Final Considerations
If this water heater is replacing an existing water
heater, it is important to verify the capacity of the gas
system. Check the capacity of the meter/regulator,
and verify the pipe lengths and sizes.
An improperly sized gas system will cause
operational issues with this water heater. Other
appliances on the gas system may be affected as
well.
Flexible Gas Connectors may be used however the
BTU capacity of the connector must be checked.
Each connector has a capacity label on it, verify
that the connector has a BTU capacity greater than
that of the water heater. An undersized flexible gas
connector will cause operational issues with this
water heater.
Half-inch gas lines are permissible provided the gas
system meets certain requirements. First, the gas
pressure on the system must be 8.0 inch W.C. or
greater. Second the capacity of the pipe as outlined
in Table 4 is followed. If the existing pipes are too
small it could cause a pressure drop greater than 3.0
inch W.C. and will cause operational issues with this
water heater as well as other gas appliances on the
system.
Gas Supply
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