A.O. Smith DB/DW-720-1810 warranty System Installation, LOW Water Cutoff, Tank Temperature Control

Thereafter, during the heating season, lubricate the three oil cups at least once every four months. Combination heating/cooling systems or water heating (Cer-temp) systems should be lubricated every four months year-round.

Use 2 or 3 teaspoonfuls in bearing oil cups, fig. 9, and 10 or 12 drops in the motor oil cups. Use No. 20 non-detergent motor oil.

Follow the same oiling procedure if a replacement circulator is installed into the system.

LOW WATER CUTOFF

A low water cutoff is a safety device which is installed in the boiler piping to prevent the boiler from firing in the event of inadequate water levels in the boiler system.

Where required by local code, this optional device is to be installed in the boiler piping at a level above that of the heat exchanger.

A float type or an electronic probe type low water cutoff may be used. The manufacturers installation instructions must be followed.

A hot water boiler installed above radiating level or as required by the Authority having jurisdiction, must be provided with a low water cutoff device at the time of boiler installation.

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 water heater and minimize scale formation.

SETTING THE WATER TEMPERATURE AT 120°F (49°C) WILL REDUCE THE RISK OF SCALDS. Some states require settings at specific lower temperatures. Table 6 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 second
150°F (65°C)		About 1-1/2 seconds
140°F (60°C)		Less than 5 seconds
130°F (55°C)		About 30 seconds
120°F or less (49°C)		More than 5 minutes
	TABLE 6

USE ANTI-SCALD VALVE(S) in the hot water system to reduce the risks of scalds at points of use such as lavatories, sinks and bathing facilities.

TANK TEMPERATURE CONTROL

The water temperature in the storage tank is controlled by the Tank Temperature Control. The sensing element is mounted inside the hot water storage tank, see fig. 24.

A change in water temperature in the storage tank lower than the Tank Temperature Control setting will cause the sensor to close its contacts and consequently, energize the boiler.

If the Tank Temperature Control is out of calibration, replace it with a new one; do not attempt to repair this control.

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.

The tank temperature control is adjustable from 100°F to 220°F (38°C to 104°C). It is recommended that lower water temperatures be used to avoid the risk of scalding. It is further recommended, in

SYSTEM INSTALLATION

GENERAL

If the system is to be filled with water for testing or other purposes during cold weather and before actual operation, care must be taken to prevent a downdraft entering the boiler or freezing air from contacting the system. Failure to do so may cause the water in the system to freeze with resulting damage to the system. Damage due to freezing is not covered by the warranty.

Good practice requires that all piping, etc., be properly supported.

CONVENTIONAL SPACE HEATING INSTALLATION

Modern fin type boilers are exceptionally fast heating units. The low water volumes in relation to firing rates require special attention to water flow rates for smooth, efficient operation. These considerations for the A. O. Smith copper heat exchanger boilers are covered below.

Refer to page 5 for tables on these units showing “flow rate vs. pressure drop and temperature rise”.

Figure 10 shows a typical installation of the boiler.

A system with several flow controlled zones, or with a 3-way mixing valve system which could present a flow rate to the boiler of less than that required for a maximum of 50°F (10°C) temperature rise at the minimum firing rate, should be designed with compensating bypasses at the boiler.

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