Installation Requirements; Gas Pressure Requirements; Supply Gas Line; Supply Gas Regulator - A.O. Smith 101 Series Instruction Manual

gas pressure reQuirements

taBle 4
*mANiFOLD PrESSUrE
moDEL
NATURAL GAS
bTH 300
4" W. C. (1.0 kPa)
bTH 400
4" W. C. (1.0 kPa)
bTH 500
4" W. C. (1.0 kPa)
* manifold gas pressure; reading can only be taken while gas is flowing. reading taken should be ± 0.3" W. C. of the listed value. These water heaters are certified for
use without modification for altitudes up to 10,000 feet. For elevations above 10,000 feet (3,048 meters) see High Altitude installations on page 52.
† minimum supply gas pressure; readings are taken while gas is not flowing (static pressure) AND while gas is flowing (dynamic pressure). Supply pressure must never
fall below the minimum values. Supply gas pressures should be measured with all gas fired appliances connected to a common main firing at full capacity. if supply
pressure drops more than 1.5" W. C. as gas begins to flow the supply gas system (gas line/regulator) may be restricted or undersized. See Table 5 and the Supply
Gas regulator requirements below. See Supply Gas Line installation on page 37 and Supply Gas regulator installation on page 38 for sizing and installation instructions
also.
‡ maximum supply gas pressure; reading are taken while gas is not flowing (static pressure) AND while gas is flowing (dynamic pressure). Supply pressure must never
exceed this maximum value.

supply gas line

The high efficiency water heaters covered in this manual require
an adequate volume of fuel gas for proper operation. A lack of
fuel gas volume can lead to ignition failure, rough starting and
rough operation. increasing the supply gas pressure DoES
NoT necessarily increase the volume of gas supplied to the
water heater and must remain below the maximum supply gas
pressures shown in Table 4.
The minimum supply gas line sizes shown in Table 5 must be
observed on all installations to help insure an adequate volume
of fuel gas is provided. Do NoT use flexible gas piping.
Supply gas lines serving more than one appliance may require
larger sizes than what is shown in Table 5. See Gas Line Sizing
on page 37.
minimum supply gas line siZe
taBle 5
moDEL *NATURAL GAS
bTH 300 1 1/4" NPT
bTH 400 1 1/4" NPT
† bTH 500 1 1/2" NPT
† Note that BTH 500 natural gas models require a 1 1/2" minimum supply gas
line size. Depending on the installed equivalent length, and/or the number
of appliances connected, the supply gas line size may have to be increased
beyond the minimum required sizes shown in this table - see Gas Line Sizing
on page 37.

supply gas regulator

The high efficiency water heaters covered by this manual require
a supply gas regulator to be installed in the supply gas line serving
the water heater for proper operation. Supply gas regulators are
required on high and low pressure gas supply systems.
note: On multiple water heater installations each water heater
shall have its own dedicated supply gas regulator installed in the
supply gas line serving the water heater.
Supply gas regulators must be rated at or above the input Btu/
hr rating of the water heater they supply. Supply gas regulators
shall have inlet and outlet connections not less than the minimum
supply gas line size for the water heater they serve as shown in
Table 5. The maxitrol 325-7L or equivalent is recommended.
See Supply Gas Regulator Installation on page 38.

installation reQuirements

†miNimUm SUPPLy PrESSUrE
PRoPANE GAS NATURAL GAS
10" W. C. (2.49 kPa) 5.2" W. C. (1.29 kPa)
10" W. C. (2.49 kPa) 5.2" W. C. (1.29 kPa)
10" W. C. (2.49 kPa) 5.2" W. C. (1.29 kPa)
PRoPANE GAS
1 1/4" NPT
1 1/4" NPT
1 1/4" NPT
PRoPANE GAS
11" W. C. (2.74 kPa)
11" W. C. (2.74 kPa)
11" W. C. (2.74 kPa)

power supply

The water heaters covered in this manual require a 120 VAC,
1Ø (single phase), 60Hz, 15 amp power supply and must also
be electrically grounded in accordance with local codes or, in the
absence of local codes, with the National Electrical Code, ANSi/
NFPA 70 or the Canadian Electrical Code, CSA C22.1.
power fluctuations and electrical noise
The water heater's control system requires a source of stable
clean electricity for proper operation. Connecting the water heater
to a branch circuit that is subject to fluctuations in voltage level or
electrical line noise such as Emi (electro magnetic interference)
or rFi (radio frequency interference) may cause erratic control
system operation and malfunction.
A high quality power supply filter/suppressor such as the kleen
Line model SELF/T-10 Series SC-L or equivalent must be
installed if the above conditions exist. Call the technical support
phone number listed on the back cover of this manual for more
information.
note: malfunctions caused by the power supply and the costs
to install power supply filters are not covered under the limited
warranty.
dedicated power wiring and Breakers
Dedicated power supply wires, ground wiring and dedicated
circuit breakers often prevent electrical line noise and should be
considered when installing the water heater.
polarity sensitiVe
The control system on the water heaters covered in this manual
is polarity sensitive; electronic flame sensing requires correct
polarity. The control system is programmed to monitor the
incoming power supply. if the Hot and Neutral wires in the 120
VAC power supply are reversed, the control system will declare
a Fault condition and lock out, heating operation will be disabled
until the power supply is correctly wired. The control system will
display the "AC reversed" Fault message on the LCD.
See Electrical Wiring on page 39 for installation instructions.
13
‡mAximUm SUPPLy PrESSUrE
NATURAL GAS PRoPANE GAS
10" W. C. (2.49 kPa) 12" W. C. (2.99 kPa)
10" W. C. (2.49 kPa) 12" W. C. (2.99 kPa)
10" W. C. (2.49 kPa) 12" W. C. (2.99 kPa)