A.O. Smith 200M, 225M, HW-120M, 160M Protector Switch, Inspecting the Heat Exchanger Venting System

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PILOT BURNER USED ON I.I.D. SYSTEMS

FIGURE 15

PROTECTOR SWITCH

(Coil High Limit - All Heaters)

If the protector switch, fig 2, should shut off unit, check for the following conditions:

1.No water in heater.

2.Restricted water flow through the heater.

3.Excessive liming.

4.Improper wiring (automatic gas shutoff control acting as primary control).

5.Pump failure.

After correcting failure condition, remove the protector switch cover and depress reset button. Button will not reset until water temperature in heater coil is down to 2000F. Restart heater, following the “OPERATING INSTRUCTIONS FOR I.I.D. MODELS” , PAGE 18.

PROTECTOR SWITCH CONTINUITY TEST

Do not depress the protector switch reset button prior to testing. The leads from the switch are removed at the point farthest from the switch.

Attach the leads from a test flashlight to the switch leads.

The Model N22T test kit (combination flashlight and continuity tester) is manufactured by the Ray-O-Vac Company, Madison, WI and available through your local suppliers.

With the flashlight turned on, the lamp should light. If the lamp lights, the protector switch circuit is closed and in proper working order. If the lamp does not light, the reasons could be:

1.Protector switch contacts open.

•Depress reset button on switch (switch cannot be reset until water temperature in the heater coil drops below 2000F). Lamp should light.

2.Defective protector switch or bad leads.

•If lamp does not light when reset button is depressed, attach the test flashlight leads to the protector switch terminals. If lamp does not light, switch is defective and must be replaced.

•If lamp does not light, the leads are bad and must be repaired or replaced.

TANK TEMPERATURE CONTROL

The tank temperature control is the primary operating control of the system. The sensing element is mounted on the hot water storage tank. A change of temperature lower than the control setting will cause the element to activate the electrical switch and start the heater.

If control is out of calibration, replace control.

AUTOMATIC GAS SHUTOFF CONTROL

The automatic gas shutoff control, fig. 1, is an automatic device which is wired in series with the gas valve and intermittent ignition control module.

The control settings are fixed at 1950F (90.5°C) cut-out and 1900F (87.7°C) cut-in. Reduced water flow due to lime scale accumulation is one cause of frequent automatic gas shutoff control operations. Refer to “PREVENTIVE MAINTENANCE” section for deliming instructions. If this non-adjustable control is out of calibration, replace control.

THERMAL BALANCER

Figure 16 shows the internal wiring of the thermal balancer. The device may be tested after disconnecting the four leads from their respective terminals on the unit.

1.Apply a test light to the yellow and red leads:

•The lamp should light as the contact in this circuit is normally closed when the resistor is cool.

2.Apply the light to the black and yellow leads.

•The lamp should not light as the contact in this circuit is normally open when the resistor is cool.

3.Remove the test light.

4.Apply 120 volts to the white and red leads which power the 1900 ohm resistor.

•After warming period, the contacts of the thermal balancer should change position.

5.Remove the 120 volt power source.

6.Apply the test light as described in steps 1 and 2.

•While the resistor is still warm, the lamp indications should be the opposite as described above. If this is not the case, replace the thermal balancer.

THERMAL BALANCER SCHEMATIC DIAGRAM

FIGURE 16

INSPECTING THE HEAT EXCHANGER

AND VENTING SYSTEM

Every 6 months, inspect the venting system (including the chimney) for blockages which will retard free draft and points of flue gas leakage. Remove any obstructions and replace any damaged or deteriorated vent pipe.

Check the heat exchanger to be sure it is not blocked by dirt or soot. It is not sufficient to only look through the flue outlet with the draft hood removed. Examination should also be made using a mirror and light through the burner opening, viewing the entire bottom area of the exchanger.

Qualified servicers should follow this procedure when the heater’s external heating surfaces need cleaning.

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Contents Commercial GAS Copper Heat Exchanger Water Heater Models HW-120M, 160M, 200M, 225MHeater Performance Data ROUGH-IN-DIMENSIONSTable of Contents General Safety InformationForeword Grounding Instructions High Altitude InstallationsChemical Vapor Corrosion Liquid Petroleum ModelsAutomatic GAS Shutoff Control FeaturesThermal Balancer Intermittent Ignition Control ModuleSafety Flow Switch Tank Temperature ControlCirculating Pump Intermittent Ignition Control Module I.I.DDrain Valve Not Supplied Safety Flow Switch SettingsInstallation Instructions Venting Proper Vent Pipe InstallationRelief Valve Confined SpaceClosed Water System Hard WaterWater Line Connections Water Potable HeatingPiping Diagrams Page Page Correct GAS GAS ConnectionsSizing GAS Supply Line GAS Supply Pipe Sizes in InchesElectrical Information Page General OperationFilling Purging of GAS LineOperating Instructions for I.I.D. Models For Your Safety Read Before OperatingOver 170F 77C Checking and Adjusting the InputPilot and Main Burner Maintenance Service InformationD. Pilot Burner Main Burner for HW HeatersProtector Switch Continuity Test Protector SwitchThermal Balancer Schematic Diagram Inspecting the Heat Exchanger Venting SystemElectrical Service Preventive MaintenanceReplacement Parts GAS Pressure RegulatorRemoving Light Deposits Deliming SolventsHeavy Lime Deposits Deliming the HW Water HeaterCheckout Removing SilicateSystem Operation YES No Spark AT Pilot BurnerReplace pilot burner Replace ignition Module Spark AT Pilot Burner but Pilot will not LightMV & MV/PV? Pilot Burner Lights but Main Burner does not LightClaim Procedure Service and Repair ExpensesConditions and Exceptions 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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