Manuals / A.O. Smith / Household Appliance / Water Heater

A.O. Smith 28 30 50 60 service manual Appliance’s heating cycle

Models: 28 30 50 60

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7.4The appliance’s heating cycle

ON Ê

13:45 Thursday 63ÉC

Tset 65ÉC

HEAT DEMAND

Figure 7.8 Frost protection cuts in


ON	Ê Ê
13:45 Thursday		63ÉC
	Tset 65ÉC
PRE PURGE
Figure 7.9 Pre-purge


ON	Ê Ê Ê
13:45 Thursday		63ÉC
	Tset 65ÉC
PRESSURE SWITCH
Figure 7.10 Pressure switch


ON	Ê	Ê
13:45 Thursday		63ÉC
	Tset 65ÉC
GLOW PLUG
Figure 7.11 Pre-glow

The appliance’s heating cycle

The appliance’s heating cycle is activated as soon as the measured water temperature (Tnet) falls below the threshold value (Tset). This threshold value depends on the currently selected appliance operating mode. For example, if the appliance is in the “OFF mode” (frost protection), then this value is 5°C. If the appliance is in the “ON mode”, then this threshold value is selectable, for example, 65°C.

The heating cycle runs in turn through the following states:

1.HEAT DEMAND;

2.PRE-PURGE;

3.PRESSURE SWITCH;

4.PRE-GLOW;

5.IGNITION;

6.RUNNING;

7.POST-PURGE.

The complete cycle is explained in the example set out below assuming the appliance is operating in mode ON.

nRemark

The same heating cycle applies to the other operating modes.

Once the appliance starts, it will run through 8 steps:

1.The water temperature drops below the set temperature of (for example) 65°C. The ThermoControl detects a heat demand and starts the heating cycle.

-The W icon is activated.

-The message HEAT DEMAND appears.

2.Following the heat demand, the fan is powered up and the pre-purge begins. This lasts about 15 seconds. During this phase, any residual gases are removed.

-The S icon is activated.

-The message PRE PURGE appears.

3.During the pre-purge, the pressure switch closes.

-The D icon is activated.

-The message PRESSURE SWITCH appears.

4.After some time, the pre-purge ceases and the ThermoControl reduces the speed of the fan to the rotational speed for ignition. This is followed by the pre-glow of the glow igniter.

-The S and D icons are dimmed.

-The O icon is activated.

Release R.1.3 UK

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A.O. Smith 28 30 50 60 service manual Appliance’s heating cycle

Contents

Release R.1.3 UK Your installer More information CopyrightTrademarks LiabilityPage Gis Table of contentsStarting up and shutting down Filling and drainingControl panel Status of the applianceMaintenance Service programTroubleshooting Maintenance frequencyIndex AppendicesIntroduction What to do if you smell gas RegulationsAbout the appliance Introduction Target groups Maintenance Forms of notationSymbol Target group RemarkChapter Target groups Description Overview of thisDocument Overview of this documentGis Functioning of the appliance Introduction Functional description of the applianceIntroduction Water temperature protection Gas control Pressure switch Ionisation rodAppliance’s heating cycle Protection for the appliance 3 Fan Water temperature protectionPressure switch Gas controlIonisation rod Safety of the instal- lationUnvented installation Vented installationIntroduction Packaging Environmental conditions InstallationWorking clearances Humidity and ambient temperatureMaximum floor loading Water compositionWorking clearances Environmental conditionsPlan and elevation of the appliance Technical specificationsUnit BFC DimensionsTechnical specifications Dime Description BFC NsionVAC G30-30 mbar butane Installation diagramGas data GeneralUnvented InstallationCondensation drainage Water connections, Unvented Cold water sideHot water side Circulation pipeSee din Figure Water connections, VentedGas connection See paragraph ’3.6.4 Condensation drainage’Dimension BFC Air supply and flue gas dischargeAir supply and flue gas discharge Concentric wall flue terminal Specification DescriptionConcentric roof flue terminal Concentric roof flue terminal specificationsElectrical connection PreparationPreparation Mains voltage Electrical connection Mains voltageProgram-controlled pump Extra on mode switch Tank onIsolating Transformer Continuous pumpAppliance Connecting extra error signal Alarm OUTChecking the supply Pressure and burner Checking the supply pressure and burner pressureMain menu Conversion to a different gas category Conversion to a different gas categoryRemove the burner as complete assembly Check the burner and supply pressure see paragraph 13 Conversion of gas controlInstallation Filling the appliance Filling the appliance Filling unvented installationsFilling vented installations Filling and drainingFilling and draining Installation diagrams F d cDraining the appliance Draining unvented installationsDraining vented installations Draining the applianceGis Introduction Operating Control panelControl panel Explanation of the icons ON/OFF switch of ThermoControlNavigation buttons PC connectionOperating modes Error conditions Service condition Status of the applianceIntroduction Operating modes Status of the appliance Error conditionsService condition Service conditionGis Shutting down Open the gas valve see ’ .1 Installation diagrams’Starting up and shutting down Introduction Starting upStarting up and shutting down Shut the appliance down for a brief period OFF modeDisconnect the appliance from the mains Shut the appliance down for a longer periodAppliance’s heating cycle Appliance’s heating cycle12 Ignition Notational convention for menu-related instructions Main menuSwitching into on mode Setting the water temperature Setting the water temperature via Setpoint MenuSetting water temperature during on mode Week programme Introduction Starting up and shutting down the week programChanging the appliance’s standard week program Remark Setting the switch-on time Setting switch-off timeExample Week programme Setting the water temperatureSetting program-controlled pump Adding times to a week program20 Period added Deleting times from a week program23 week program options Programming an extra period Extra periodSettings Setting menu languageSettings Displaying appliance specifications Remark Setting day and time46 Main menu Gis Service program Setting the hysteresisDisplaying the error history Displaying the appliance history Setting the pump on/offSetting the service interval Service programSetting the display contrast Setting the display contrastSetting the backlight time Setting the display scroll speedService program Troubleshooting General errorsDisplayed errors Symptom Cause Solution Remark Gas smell Gas leak Troubleshooting table for general errorsSymptom Cause Solution Remark Display is off See appendix ’A.2 Electrical diagram BFC’Water leakage Water Troubleshooting table for displayed errorsSymptom Cause Solution Remark Explosive ignition Insufficient or no hotS05 blocking error S02 blocking errorS03 blocking error S04 blocking errorS13 blocking error S14 blocking errorS15 blocking error F02 lock out error Phase-sensitive. See ’3.10 Electrical connection’Appliance specifications’ How to bleed air from the gas line, and measure the supply ’3.9 Air supply and flue gas discharge’ F06 lock out errorF07 lock out error F08 lock out errorF10 lock out error Error F09 remains active in the event that the waterRelease R.1.3 UK Release R.1.3 UK E04 blocking error C04 blocking errorE01 blocking error E03 blocking errorDetermining service interval Maintenance frequencyMaintenance frequency Remark Preparation for maintenance MaintenanceStarting up Maintenance Water-side mainte- nance Introduction Descaling and cleaning the tankCleaning condensation water discharge Cleaning the burnerRemark Finalising mainte- nance Cleaning the orificeCleaning heat exchanger 12.4.3Warranty Certificate Warranty Certificate Week program card AppendicesAppendices Electrical diagramWeek program card Release R.1.3 UK Index IX IndexIX Index 0306