Install Instructions

20
DANGER
HOT WATER TEMPERATURES REQUIRED FOR AUTOMATIC
DISHWASHER AND LAUNDRY USE CAN CAUSE SCALD BURNS
RESULTING IN SERIOUS PERSONAL INJURY AND/OR DEATH.
THE TEMPERATURE AT WHICH INJURY OCCURS VARIES
WITH THE PERSON’S AGE AND TIME OF EXPOSURE. THE
SLOWER RESPONSE TIME OF CHILDREN, AGED OR DISABLED
PERSONS INCREASES THE HAZARDS TO THEM. NEVER
ALLOW SMALL CHILDREN TO USE A HOT WATER TAP, OR TO
DRAW THEIR OWN BATH WATER. NEVER LEAVE A CHILD OR
DISABLED PERSON UNATTENDED IN A BATHTUB OR SHOWER.
THE WATER HEATER SHOULD BE LOCATED IN AN AREA
WHERE THE GENERAL PUBLIC DOES NOT HAVE ACCESS
TO SET TEMPERATURES.
It is recommended in domestic hot water applications that lower
water temperature be used to avoid the risk of scalding. It is further
recommended, in all cases, that the water temperature be set for
the lowest temperature which satises the user’s hot water needs.
This will also provide the most energy efcient operation of the
heater and minimize scale formation in the heat exchanger, thus
prolonging the life of the heater.
SETTING THE WATER HEATER TEMPERATURE AT 120°F
(49°C) WILL REDUCE THE RISK OF SCALDS. Some states
require settings at specific lower temperatures. The table
below shows the approximate time-to-burn relationship for
normal adult skin.
Water Temperature
°F (°C)
Time for 1st Degree Burn
(Less Severe Burns)
Time for Permanent Burns
2nd & 3rd Degree
(Most Severe Burns)
110 (43) (normal shower temp.)
116 (47) (pain threshold)
116 (47) 35 minutes 45 minutes
122 (50) 1 minute 5 minutes
131 (55) 5 seconds 25 seconds
140 (60) 2 seconds 5 seconds
149 (65) 1 second 2 seconds
154 (68) instantaneous 1 second
(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15, 1978)
Table 7
USE ANTI-SCALD VALVE(S) in the hot water system to reduce
the risks of scalding at points of use such as lavatories, sinks and
bathing facilities.
CAUTION
IN THE EVENT OF ELECTRIC POWER FAILURE, DO NOT
ATTEMPT TO OPERATE THE HEATER.
CHECKING AND ADJUSTING THE INPUT
The maximum inlet gas pressure must not exceed the value
specified by the manufacturer (10.5” W.C. - natural gas,
13.0” W.C. - propane gas). The minimum value listed on the Rating
Plate is for the purposes of input adjustment.
1. Turn the gas valve control knob to “OFF”, (See page 19).
2. Attach a pressure gauge or a manometer to the outlet pressure
tap, gure 13 and refer to table 3 for correct manifold pressure.
3. Fire the heater by turning the gas valve control knob to “ON”.
4. Use this formula to “clock” the meter. Be sure that other gas
consuming appliances are not operating during this interval.
3600
T x H = Btuh
T = Time (in seconds) to burn one cubic foot of gas.
H = Heating value of gas (in Btu’s per cubic foot of gas).
Btuh = Actual heater input (in Btuh).
EXAMPLE: (Using HW-120M heater)
T = 31.5 seconds/ft
3
H = 1050 Btu/ft
3
Btuh = ?
3600 x 1050 = 120,000 (compare with ratings in Table 2).
31.5
Should it be necessary to adjust the gas pressure to the burners
to obtain the full input rate, the steps below should be followed.
5. Remove the regulator adjustment sealing cap, g. 13, and adjust
the pressure by turning the adjusting screw with a screwdriver.
• Clockwise
to increase gas pressure and input rate.
• Counterclockwise
to decrease gas pressure and input
rate.
DO NOT turn the adjusting screw in past the point of little or no
manifold pressure change or fully bottom the adjusting screw.
6. “Clock” the meter as in step 4 above.
7. Repeat steps 5 and 6 until the specied input rate is achieved.
8. Turn the gas valve control knob to “OFF”. Replace the regulator
adjustment sealing cap and remove the pressure gauge or
manometer from the outlet pressure tap. Using an allen wrench,
replace the set screw in the outlet pressure tap.
9. Turn the gas valve control knob to “ON”.
If gas pressure regulator cannot be equipped to give the full input
rating with sufcient gas pressure at the valve, contact A.O. Smith
Technical Services.
IMPORTANT
UNDER NO CIRCUMSTANCES SHOULD THE GAS INPUT
EXCEED THE INPUT SHOWN IN TABLE 2. OVERFIRING COULD
RESULT IN DAMAGE OR SOOTING OF THE HEATER.
When the heater is operating at full capacity, or full gas input, it
should consume 1 cu. ft. of gas in approximately the amount of
time indicated in table 8.
TABLE 8 — TIME REQUIRED TO CONSUME 1 CUBIC FT. OF GAS
(Heater operating at full input or full capacity.
Does not apply to high altitude installations.)
Heating Total Time Required (Seconds)
Value
MODEL
Type of (Btu/
Gas Cu. Ft.)
HW-120M HW-160M HW-200M HW-225M
Natural 1050 31.5 23.6 19.0 16.8
Propane 2500 78.3 56.3 45.2 - - -