A.O. Smith DB/DW-720-1810 General Maintenance, Relief Valve, Venting Maintenance, Deliming

GENERAL MAINTENANCE

These boilers are designed to give many years of efficient and satisfactory service when properly operated and maintained. To assure continued good performance, the following recommendations are made.

The area around the unit should be kept clean and free from lint and debris. Sweeping the floor around the boiler should be done carefully. This will reduce the dust and dirt which may enter the burner and pilot air passages, causing improper combustion and sooting.

THE FLOW OF COMBUSTION AND VENTILATION AIR TO THE BOILER MUST NOT BE OBSTRUCTED.

THE BOILER AREA MUST BE KEPT CLEAR AND FREE FROM COMBUSTIBLE MATERIALS, GASOLINE AND OTHER FLAMMABLE VAPORS AND LIQUIDS.

Any safety devices including low water cutoffs used in conjunction with this boiler should receive periodic (every six months) inspection to assure proper operation. A low water cutoff device of the float type should be flushed every six months. All relief valves should be inspected and manually operated at least twice a year. More frequent inspections may be necessary depending on water conditions.

Periodic checks, at least twice a year, should be made for water and/or gas leaks.

More frequent inspections may be necessary depending on water conditions.

The boiler mounted gas and electrical controls have been designed to give both dependable service and long life. However, malfunction can occur, as with any piece of equipment. It is therefore recommended that all components be checked periodically by a qualified serviceman for proper operation.

RELIEF VALVE

The safety relief valve should be opened at least twice a year to check its working condition. This will aid in assuring proper pressure relief protection. Lift the lever at the top of the valve several times until the valve seats properly and operate freely.

DANGER

THE WATER PASSING OUT OF THE VALVE DURING CHECKING OPERATION MAY BE EXTREMELY HOT. BEFORE OPERATING RELIEF VALVE MAKE SURE DRAIN LINE IS INSTALLED TO DIRECT DISCHARGE TO A SAFE LOCATION SUCH AS AN OPEN DRAIN, TO AVOID SCALDING OR WATER DAMAGE.

WARNING

SHOULD OVERHEATING OCCUR OR THE GAS SUPPLY FAIL TO SHUT OFF, TURN OFF THE MANUAL GAS CONTROL VALVE TO THE APPLIANCE.

VENTING MAINTENANCE

Qualified servicers should follow this procedure when the boiler’s external heating surfaces and vent pipe need cleaning.

CAUTION

DO NOT USE A NYLON BRUSH OR OTHER STATIC CREATING MATERIAL TO CLEAN DUST AND CARBON DEPOSITS FROM HEATING SURFACES AND VENT.

SUCH DEPOSITS ARE FLAMMABLE AND MAY BE IGNITED BY STATIC ELECTRICITY. USE A METAL BRUSH TO MINIMIZE THE DANGER OF EXPLOSION

1.Turn off the electrical power, main manual gas shutoff and pilot valves.

•Allow boiler parts to cool before disassembly.

2.Remove the internal flue collector and vent pipe running to the chimney.

•Check parts and chimney for obstructions and clean as necessary.

3.Remove burners from boiler and other metal parts as required to clean as necessary.

•Refer to parts list supplied with this manual for disassembly aid.

4.Clean and reinstall the parts removed in steps 2 and 3.

•Be sure the vent pipe has a minimum upward pitch of one quarter inch per foot of length and is sealed as necessary.

5.Restore electrical power and gas supply to boiler.

•Check for gas leaks and proper boiler and vent operation.

HEAT EXCHANGER

PREVENTIVE MAINTENANCE

In most water supply systems some solids exist. As the water is heated, these tend to drop out depositing as scale or lime. This scale is relatively easy to remove before the unit becomes clogged.

WARNING

Lime accumulation can reduce the life of the equipment, reduce efficiency and waste fuel. Boiler failure due to lime or scale build- up voids the warranty.

See section on CIRCULATING PUMP to ensure you have selected the proper size pump for your situation.

DELIMING

The amount of calcium carbonate (lime) released from water is in direct proportion to water temperature and usage. The higher the water temperature or water usage, the more lime deposits are dropped out of the water. This is the lime scale which forms in pipes, boilers and on cooking utensils.

The usage of water softening equipment greatly reduces the hardness of water. However, this equipment does not always remove all of the hardness (lime). For this reason it is recommended that a regular schedule for deliming be maintained.

Figure 29 shows typical piping arrangement for gravity deliming of lime deposits. For systems using recirculating deliming pumps contact your A. O. Smith distributor.

Lime build-up may be seen when viewing the interior of the inlet/ outlet manifold through the pressure relief valve tapping.

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