A.O. Smith BTR 120, Installation Operation & Maintenance

6

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Do not cover the instruction manual.  Keep it on the side of the
water heater or nearby for future reference.

•

Do not allow insulation to come within 2” (5 cm) of the burners,
to prevent blockage of combustion air flow to the burners.

•

Do not allow insulation to come within 9” (23 cm) of floor, (within
2” (5 cm) of bottom cover) to prevent blockage of combustion
air flow to the burners.

•

Do inspect the insulation blanket frequently to make sure it
does not sag, thereby obstructing combustion air flow.

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Do obtain new labels from A.O. Smith for placement on the
blanket directly over the existing labels.

HIGH ALTITUDE INSTALLATIONS

 WARNING

INSTALLATIONS ABOVE 2000 FEET (610 METERS) REQUIRE
REPLACEMENT OF THE BURNER ORIFICES IN ACCORDANCE
WITH THE NATIONAL FUEL GAS CODE (ANSI Z223.1). FOR
CANADIAN INSTALLATIONS CONSULT NATURAL GAS AND
PROPANE INSTALLATION CODE CAN/CSA-B149.1.  FAILURE
TO REPLACE THE ORIFICES WILL RESULT IN IMPROPER AND
INEFFICIENT OPERATION OF THE APPLIANCE RESULTING
IN THE PRODUCTION OF INCREASED LEVELS OF CARBON
MONOXIDE GAS IN EXCESS OF SAFE LIMITS WHICH COULD
RESULT IN SERIOUS PERSONAL INJURY OR DEATH.

You should contact your gas supplier for any specific changes
which may be required in your area.

As elevation above sea level is increased, there is less oxygen
per cubic foot of air.  Therefore, the heater input rate should be
reduced at high altitudes for satisfactory operation with the reduced
oxygen supply.  Failure to make this reduction would result in an
overfiring of the heater causing sooting, poor combustion and/or
unsatisfactory heater performance.

U.S. REQUIREMENTS

Ratings specified by manufacturers for most appliances apply
for elevations up to 2000 feet (610 m).  For elevations above
2000 feet (610), ratings must be reduced at the rate of 4% for
each 1000 feet (305 m) above sea level.  For example, if a heater
is rated at 120,000 Btuh (35 Kwh) at sea level, to rate the heater
at 4000 feet (1219 m), you subtract 4 (once for each thousand
feet) x 04 (4% input reduction) x 120,000 (original rating) from
the original rating.  Therefore, to calculate the input rating at
4,000 feet (121.9 m): 4 x .04 x 120,000 =19,200 Btuh (5.6 Kwh),
120,000 (35 Kwh) - 19,200 (5.6 Kwh) = 100,800 Btuh (29.4 Kwh).
At 6000 feet (1829 m) the correct input rating should be 91,200
Btuh (26.7 Kwh).

CANADIAN REQUIREMENTS

Appliances with inputs up to and including 400,000 BTU (117.2
Kw) must be factory equipped with orifices for operation at specific
elevations.  Standard (sea level) orifices permit operation up to
2000' (610 m) elevation.  For operation between 2000' (610 m)
and 4500' (1370 m) specify "HIGH ALTITUDE OPERATION" when
ordering the heater(s).  For operation above 4500' (2370 m)
consult factory before ordering.

Field conversion for operation at altitudes other than
that specified on the heater rating plate is not permitted.

The input reduction is primarily achieved by reducing the size of
the main burner orifices.  To do this, the main burner orifices require
replacement with orifices sized for the particular installation
elevation.  Correct orifice sizing and parts may be obtained from
A.O. Smith Water Products Company.  When ordering, be sure
to state the model number and the altitude of the location where
the water heater is being installed.

Upon completion of derating of the heater, adjustment to the gas
pressure regulator may be required.  See CHECKING THE INPUT
section in this manual for inlet and manifold pressure
requirements.

Also due to the input rating reduction required at high altitudes,
the output rating of the appliance is reduced and should be
compensated for in the sizing of the equipment for application.

FEATURES

THE ELIMINATOR

(SELF-CLEANING SYSTEM)

These units include The Eliminator (Self-Cleaning System)
installed in the front water inlet.  See figure 2. The Eliminator
must be oriented correctly for proper function.  There is a marked
range on the pipe nipple portion of the Eliminator, that must be
aligned with the top of the inlet spud. A label above the jacket
hole has an arrow that will point to the marked portion of the pipe
nipple if the orientation is correct. If the arrow does not point within
the marked range on the pipe nipple, adjust the pipe nipple to
correct.  A pipe union is supplied with the Eliminator to reduce the
probability of misaligning the Eliminator accidentally while
tightening the connection to the inlet water supply line.  Improper
orientation of the Eliminator can cause poor performance of the
heater and can significantly reduce outlet water temperatures
during heavy draws.

NOTE: The inlet tube may have 1, 3 or 7 cross-tubes.

FIGURE 2

For proper function, The Eliminator must be oriented correctly.
There is a marked range on the pipe nipple that must be aligned
with the top of the inlet spud (check for label on the appliance) to
assure proper orientation. Please check to confirm that the marked
range is in alignment with the top of the spud.  A pipe union is
supplied with The Eliminator to help eliminate the possibility of
changing the orientation by accidentally over-tightening the inlet
supply line. Improper orientation of The Eliminator may cause
temperature build-up issues or spells of colder than usual water
temperatures.

HIGH LIMIT SWITCH

The digital thermostat (Fig. 3) contains the high limit (energy cutoff)
sensor. The high limit switch interrupts main burner gas flow should
the water temperature reach 203°F (95°C).

In the event of high limit switch operation, the appliance cannot
be restarted unless the water temperature is reduced to
approximately 120°F (49°C). The high limit reset button on the
front of the control then needs to be depressed.