Unit installation

6
• Do not cover the temperature & pressure relief valve.
•
Do not cover the instruction manual. Keep it on the side of the
water heater or nearby for future reference.
•
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 ORIFICE IN ACCORDANCE
WITH SECTION 8.1.2 OF THE NATIONAL FUEL GAS CODE
(ANSI Z223.1). FOR CANADIAN INSTALLATIONS CONSULT
CANADIAN INSTALLATIONS CODES AND CAN/CSA B149.1
OR .2. FAILURE TO REPLACE THE ORIFICE 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 (610m). For elevations above 2000
feet (610), ratings must be reduced at the rate of 4% for each
1000 feet (305m) 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 (1219m), 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 (121.9m): 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 (1829m) the correct input rating should be 91,200 Btuh (26.7
Kwh).
CANADIAN REQUIREMENTS
Appliances with inputs up to and including 400,000 BTU must be
factory equipped with orifices for operation at specific elevations.
Standard (sea level) orifices permit operation up to 2000' (610m)
elevation. For operation between 2000' (610m) and 4500' (1370m)
specify "HIGH ALTITUDE OPERATION" when ordering the
heater(s). For operation above 4500' (2370m) 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 also reduced and should be
compensated for in the sizing of the equipment for application.
FEATURES
HIGH LIMIT SWITCH (E.C.O.)
The dual bulb controller (fig. 2) contains the high limit (energy
cutoff) sensor. The high limit switch interrupts main burner gas
flow should the water temperature reach 205
°
F (96°C).
In the event of high limit switch operation, the appliance cannot
be restarted unless the water temperature is reduced by at least
20
0
F (11°C) and the high limit reset button on front of limit control
(fig. 2) is depressed.
Continued manual resetting of high limit control, preceded by
higher than usual water temperature is evidence of high limit switch
operation. The following are possible reasons for high limit switch
operation.
• A malfunction in the thermostatic controls would allow the gas
valve to remain open causing water temperature to exceed
the thermostat setting. The water temperature would continue
to rise until high limit switch operation.
Contact your dealer or servicer if continued high limit switch
operation occurs.
DUAL-BULB THERMOSTAT
(COVER REMOVED)
FIGURE 2
Continued pilot outage preceded by higher than usual water
temperature is evidence of high limit switch operation. Contact
your dealer or servicer to determine the reason for operation.
ELECTRONIC IGNITION CONTROL
Each heater is equipped with a Honeywell ignition module. The
solid state ignition control, fig.3, ignites the pilot burner gas by
creating a spark at the pilot assembly. Pilot gas is ignited and
burns during each running cycle. The main burner and pilot
gases are cut off during the OFF cycle. Pilot gas ignition is proven
by the pilot sensor. Main burner ignition will not occur if the pilot
sensor does not first sense pilot ignition.