A.O. Smith HW-120M Hard Water, Closed Water System, Water Line Connections, Water Potable Heating

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Your local code authority may have other specific relief valve requirements not covered in this section.

THE PURPOSE OF A RELIEF VALVE IS TO AVOID EXCESSIVE PRESSURE OR TEMPERATURE INTO THE STEAM RANGE, WHICH MAY CAUSE SCALDING AT FIXTURES, TANK EXPLOSION, SYSTEM OR HEATER DAMAGE.

TO AVOID SCALDING OR WATER DAMAGE, A DRAIN LINE MUST BE CONNECTED TO A RELIEF VALVE TO DIRECT DISCHARGE TO A SAFE LOCATION. A DRAIN LINE MUST NOT BE REDUCED FROM THE SIZE OF THE VALVE OUTLET AND IT MUST NOT CONTAIN ANY VALVES BETWEEN THE HEATER AND THE RELIEF VALVE OR THE RELIEF VALVE AND THE DRAIN LINE EXIT. IN ADDITION, THERE SHOULD NOT BE ANY RESTRICTIONS IN A DRAIN LINE NOR SHOULD IT BE ROUTED THROUGH AREAS WHERE FREEZING CONDITIONS MIGHT OCCUR. DO NOT THREAD OR CAP THE DRAIN LINE EXIT. RESTRICTING OR BLOCKING A DRAIN LINE WILL DEFEAT THE PURPOSE OF THE RELIEF VALVE AND MAY CREATE AN UNSAFE CONDITION. INSTALL A DRAIN LINE WITH A DOWNWARD SLOPE SUCH THAT IT NATURALLY DRAINS ITSELF.

Recommended locations of relief valves are shown in the installation diagrams.

HARD WATER

Where hard water conditions exist, water softening or the threshold type of water treatment is recommended. This will protect the dishwashers, coffee urns, water heaters, water piping and other equipment. When water softening or water treatment is not practical, a comparatively easy method of periodic lime removal from the heater may be employed by installing gate valves, drain valve and acid fill opening as shown in PREVENTIVE MAINTENANCE section of this manual.

CLOSED WATER SYSTEM

A closed system will exist if a back-flow prevention device (check valve), pressure reducing valve, or other similar device is installed in the cold water line between the water heater and the street main (or well). Excessive pressure may develop due to the thermal expansion of heated water causing premature tank failure or intermittent relief valve operation. This is not a warranty failure. An expansion tank may be necessary in the cold water supply to alleviate this situation. Contact the local plumbing authority.

WATER LINE CONNECTIONS

This manual provides detailed installation diagrams for typical methods of application. See piping diagrams.

• Cer-Temp 80 Recovery System (for one temperature water).

These diagrams will serve to provide the installer with a reference for the materials and method of piping necessary for installation. It is essential that all water and gas piping, vent connections, electrical wiring and check and flow regulating valves be installed as shown on the diagrams.

Consult the installation diagrams for appropriate locations to install the safety flow switch(es), drain valves, thermometers, relief valves and the circulating pump(s). Apply suitable pipe thread sealing compounds to only the male threads of parts to be connected. If any of these parts are being replaced in a functioning system, remember to shut off the manual gas and control valve(s) and close off the water inlet(s). Open a nearby faucet to relieve pressure and drain the heater and/or system before attempting to install the new parts.

Check the diagrams thoroughly before starting installation to avoid errors and minimize time and material costs.

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 heater 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.

WATER (POTABLE) HEATING

1.All piping components connected to this unit for space heating applications shall be suitable for use with potable water.

2.Toxic chemicals, such as those used for boiler treatment, shall NEVER be introduced into this system.

3.This unit may NEVER be connected to any existing heating system or component(s) previously used with a non-potable water heating appliance.

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Contents Models HW-120M, 160M, 200M, 225M Commercial GAS Copper Heat Exchanger Water HeaterROUGH-IN-DIMENSIONS Heater Performance DataGeneral Safety Information Table of ContentsForeword Chemical Vapor Corrosion High Altitude InstallationsGrounding Instructions Liquid Petroleum ModelsThermal Balancer FeaturesAutomatic GAS Shutoff Control Intermittent Ignition Control ModuleCirculating Pump Tank Temperature ControlSafety Flow Switch Intermittent Ignition Control Module I.I.DSafety Flow Switch Settings Drain Valve Not SuppliedInstallation Instructions Relief Valve Proper Vent Pipe InstallationVenting Confined SpaceWater Line Connections Hard WaterClosed Water System Water Potable HeatingPiping Diagrams Page Page Sizing GAS Supply Line GAS ConnectionsCorrect GAS GAS Supply Pipe Sizes in InchesElectrical Information Page Filling OperationGeneral Purging of GAS LineFor Your Safety Read Before Operating Operating Instructions for I.I.D. ModelsChecking and Adjusting the Input Over 170F 77CD. Pilot Burner Service InformationPilot and Main Burner Maintenance Main Burner for HW HeatersThermal Balancer Schematic Diagram Protector SwitchProtector Switch Continuity Test Inspecting the Heat Exchanger Venting SystemReplacement Parts Preventive MaintenanceElectrical Service GAS Pressure RegulatorHeavy Lime Deposits Deliming SolventsRemoving Light Deposits Deliming the HW Water HeaterRemoving Silicate CheckoutSystem Operation No Spark AT Pilot Burner YESSpark AT Pilot Burner but Pilot will not Light Replace pilot burner Replace ignition ModulePilot Burner Lights but Main Burner does not Light MV & MV/PV?Conditions and Exceptions Service and Repair ExpensesClaim Procedure Limitations on Implied Warranties

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.
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