A.O. Smith TWI 35-130 Security of the water temperature, Gas control, 4 Fan, Air pressure switch

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2.4.2Security of the water temperature

The safety switch or ECO (Energy Cut-Off) switches off the device when the water temperature exceeds 95 ºC. As soon as the temperature has sufﬁciently dropped, the ECO is reset automatically. Contact the installation engineer if the ECO repeatedly switches off the device.

2.4.3Gas control

The electronic control opens the gas control allowing supply of gas to the burner. The gas control has two valves as a safety device. Both valves shut off the gas supply.

2.4.4Fan

The fan (10) ensures optimum air supply during the heat demand. In view of safety, the fan makes sure that the combustion chamber is purged before ignition takes place. This is called pre-purging.

2.4.5Air pressure switch

The air pressure switch guarantees discharge of ﬂue gasses and supply of air during pre-purging and operation of the device. The air pressure switch is typically open. When the pressure difference is sufﬁcient, the pressure switch closes. If, however, a disturbance occurs, the pressure switch opens again and the heating cycle is interrupted. The table gives the trip points for each device.

Remark

The trip point of the pressure switch cannot be adjusted.

Trip point of the pressure switch

Device

Pressure difference

TWI 35-130

700 Pa

TWI 45-190

370 Pa

2.4.6Ionisation detection

The electronic control uses the hot surface igniter for ﬂame detection by means of ionisation detection. The electronic control closes the gas valve as soon as it observes that there is no ﬂame while gas is ﬂowing.

Instruction manual TWI 35-130 G/TWI 45-190 G

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Contents 35-130 45-190 Your installer Page Page Copyright 2007 A.O. Smith Water Products Company Page Operation of the device InstallationErrors MaintenanceWarranty certiﬁcate Table of contentWhat to do when you smell gas Regulations IntroductionAbout the device Target groups IntroductionChapter Target groups Description Installation This chapter contains the terms of warranty Warranty certiﬁcateIntroduction This chapter will cover in the given order Operation of the deviceOperation of the device Heating cycleSecurity of the device Introduction 4 Fan Security of the water temperatureAir pressure switch Gas controlUnvented installation Vented installation3 T&P valve Packaging InstallationInstallation Working area Dimension Description TWI Dimensions of the deviceDescription Unit TWI Dimension Description TWIVented Condensation drainage Cold water sideHot water side Circulation pipingRequirements for ﬂue gas discharge material Air supply and ﬂue gas discharge IntroductionDevice types Practical example of concentric ﬂue gas discharge Example Device types DescriptionConcentric connections Device Diameter Maximum length Maximum num Ber of 90 bendsSubject Description SpeciﬁcationsPractical example of parallel ﬂue gas discharge Example Parallel connectionsDevice Diameter Maximum running length BendDevice with parallel ﬂue gas discharge material Preparation Electrical connectionConnector block Isolating transformer Check and adjust the CO2-value Connect the mains voltageGas control Checking procedureAdjust the CO2-value Conversion to another gas category Conversion to another gas category Unvented FillFill vented installations Fill the device Fill unvented installationsDrain Installations Drain unventedDrain vented Start up Opening the gas valve 3.5 Connections diagramStart up Electrically isolate Shut downIntroduction You can For a short timeShut down Errors Introduction Distinction is made between General errorsErrors visible on the control Symptom Cause Solution Remark Gas smell Water leakageExplosive ignition Hot water Symptom Cause Solution Remark Insufﬁcient or noLight pulses Cause Solution Remark Troubleshooting table for errors visible on the controlSee 12.2 Electrical circuit diagram Light pulses Cause Solution Remark SL3TWI Introduction Prepare maintenance MaintenanceMaintenance 11.3 Conditions Warranty certiﬁcate11.1 Warranty general 11.2 Warranty tankSmith Warranty certiﬁcate11.6 Claims 11.7 ObligationsAnnex Annex Electrical circuit diagramWiring Annex Connect IndexIndex User WarrantyPage 0308 489 R1.0