Checking and Adjusting the Input, Over 170F 77C

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 satisfies the user’s hot water needs. This will also provide the most energy efficient operation of the boiler and minimize scale formation in the heat exchanger, thus prolonging the life of the boiler.

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.

Temperature	Time to Produce 2nd & 3rd
Setting	Degree Burns on Adult Skin
Over 170°F (77°C)	Nearly instantaneous
160°F (71°C)	About 1/2 seconds
150°F (66°C)	About 1-1/2 seconds
140°F (60°)	Less than 5 seconds
130°F (54°)	About 30 seconds
120°F (49°C) or less	More than 5 minutes
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 18).

2.Attach a pressure gauge or a manometer to the outlet pressure tap, figure 14 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/ft3

H = 1050 Btu/ft3

Btuh = ?

3600	x 1050 = 120,000 (compare with the ratings in
31.5	Table 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, fig. 14, 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 specified 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 sufficient gas pressure at the valve, re-orifice the main burners.

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		- - -

HW-120M, 225M, 200M, 160M specifications

A.O. Smith is renowned for its range of advanced water heaters, and the 160M, 200M, 225M, and HW-120M models stand out as some of the most reliable and innovative options available. These water heaters are designed to deliver exceptional performance, energy efficiency, and user-friendly features, making them ideal for various residential and commercial applications.

The A.O. Smith 160M model boasts a robust design that ensures longevity and efficiency. It has a 160-gallon capacity, providing ample hot water for households with high demand. This model incorporates insulation technology that minimizes heat loss, contributing to energy savings and reduced utility bills. Additionally, it features a durable exterior that is resistant to rust and corrosion.

The 200M model takes performance a step further with a higher capacity of 200 gallons, making it suitable for larger homes or businesses. This model is equipped with advanced components, including a high-efficiency burner and a powerful thermocouple that ensures reliable heating. The 200M also includes user-friendly controls that allow for precise temperature settings and easy operation.

Next in line is the A.O. Smith 225M, which offers an impressive 225-gallon capacity. This model is designed for heavy-duty usage and features a reinforced tank to withstand high pressure. The 225M is also equipped with state-of-the-art flame retention technology that optimizes fuel use, enhancing the overall efficiency of the unit. This ensures that customers not only get hot water when needed but also experience considerable savings on energy costs.

Finally, the HW-120M model is a compact solution that does not compromise on performance. With a capacity of 120 gallons, it is ideal for smaller households or spaces where water heating needs are moderate. The HW-120M includes features such as an LED display for easy temperature monitoring and an integrated safety system that prevents overheating.

All these models utilize advanced technologies such as electronic ignition and enhanced insulation materials, contributing to a reduction in energy consumption and maintenance needs. The combination of these features makes A.O. Smith appliances a smart choice for consumers looking for efficiency, reliability, and performance. With a strong commitment to craftsmanship and innovation, A.O. Smith continues to set the standard in water heater technology, ensuring customers enjoy reliable hot water access while promoting energy efficiency.

Over 170°F (77°C)

CHECKING AND ADJUSTING THE INPUT

TABLE 8 — TIME REQUIRED TO CONSUME 1 CUBIC FT. OF GAS

MODEL

HW-120M, 225M, 200M, 160M specifications