FANs 121, 125Temperature Controls SectionAProduct BulletinA19AUC, A19BUCIssue Date1091©1991 Johnson Controls, Inc.1Code No. LIT-121035Part No. 3544, Rev. ITypes A19AUC, A19BUC Fixed DifferentialThermostat For Hazardous LocationApplicationThe A19AUC and A19BUCthermostats are designed foruse in locations whereflammable and explosivemixtures of vapors and gaseswith air or combustible dust in airare present. Listed at UL for“Hazardous Locations, Class I,Group D (NEMA 7) and Class II,Groups E, F and G (NEMA 9)”as defined in the NationalElectrical Code. The SPDTcontact unit provides open highor close high action for eitherheating or cooling applications.The thermostats are available tocover sensed temperatures from-30 to 475°F (-34 to 246°C).Closed tank fittings and bulbwells are available for immersionapplications.All Series A19 thermostats aredesigned for use only asoperating controls. Where anoperating control failurewould result in personal injuryand/or loss of property, it isthe responsibility of theinstaller to add devices(safety, limit controls) orsystems (alarm, supervisorysystems) that protect against,or warn of, control failure.Features•Dependable and precisesnap-acting contactsenclosed in a dust protectedcase and the liquid filledsensing element are fieldproven.•Unaffected by barometricpressure and cross ambienttemperature problems for“repeat” accuracy.•SPDT contacts for use oneither heating or coolingapplications.•UL Listed, CSA Certified for“Hazardous Locations.”General DescriptionThe temperature sensingelements are liquid filled,providing uniform differentialthroughout the selectedadjustment range. Remote bulbelements are regularly suppliedwith a 6 foot. (1.8 m) capillary.Requests for other constructionvariations should be sent toCustomer Service.The range adjustment changesthe cut-in and cutout pointsalike. The differential isnonadjustable.Fig. 1 -- A19BUC thermostatwith air bulb.Fig. 2 -- Interior view of theA19AUC with clamp on bulb.These thermostats are suitablefor installation in hazardouslocations as defined in theNational Electrical Code, wherethe atmosphere may contain thefollowing:1.Certain vapors and gases.2.Dust such as aluminum,magnesium or theircommercial alloys.3.Carbon black, coal or cokedusts.4.Flour, starch or grain dusts.Specifications2 A19AUC, A19BUC Product BulletinOptional ConstructionsPacking NutPart FTG13A-600R is availablefor closed tank applicationswhere the temperature does notfall below -35°F (-37°C) orexceed 250°F (121°C).Maximum liquid pressure limit is150 PSIG (1034 kPa). Forapplications where thetemperature or liquid pressureexceeds these limits, specifyStyle 4 element with all metalpacking nut as an integral part ofthe control.Ordering InformationTo order, specify the ProductNumber only. If the ProductNumber is not available, specify:1.Type Number.2.Range required.3.Type of bulb, clamp-on orcoiled.4.Capillary length, if otherthan 6 feet.5.Specify bulb well partnumber if required.6.Specify Part NumberFTG13A-600R packing nutassembly, if required.InstallationMountingControls are normally mountedto a flat surface by two mountingholes 3/8 in. in diameter. (SeeDimension Drawing.) For closedtank applications without a bulbwell assembly, Part FTG13A-600R packing nut assembly maybe supplied on -30 to 50°F and20 to 80°F ranges only. SeeFig. 3 for sequence ofinstallation.!CAUTION: Turn off liquidsupply and relieve pressurebefore installing orremoving the bulb or bulbwell.Place parts over support tubesection of the element, placingbulb into tank (be sure tank isfirst drained so liquid level isbelow tank opening). Screwpacking nut into the adapter withthe retaining washers andpacking in place as shown.To install models with bulb well,first install bulb well into tank.Remove bushing from bulb welland slide over capillary. (SeeFig. 4.) Replace bushing intobulb well, gently pushing bulbinto position in bottom of well.Tighten set screw in end ofadapter to hold bulb in position.!CAUTION: Do not dent ordeform the sensitive bulb ofthis control. A dent ofdeformation will change thecalibration and cause thecontrol to cycle at atemperature lower than thedial setting.A19AUC, A19BUC Product Bulletin 3Wiring!CAUTION: Disconnect thepower supply beforeconnecting the wiring orremoving the cover to avoidpossible electrical shock ordamage to the equipment.On multipole units, morethan one circuit may haveto be disconnected. Keepthe assembly tightly closedwhile circuits are alive.Note: Use terminal screwsfurnished (8-32 x 1/4 in. binderhead). Substitution of otherscrews may cause problems inmaking proper connections.Follow the equipmentmanufacturer’s wiring diagramswhen supplied. The knob andcover must be removed to makewiring connections. Make allwiring connections using copperconductors only, and inaccordance with the NationalElectrical Code and localregulations.Wiring terminals are color codedto simplify wiring. The redterminal is common. The red toyellow circuit closes ontemperature increase, and thered to blue circuit opens ontemperature increase. Usecopper conductors only. Do notbind the adjusting knob whenthe cover is replaced.Checkout ProcedureBefore leaving the installation,observe at least three completeoperating cycles to be sure thatall components are functioningcorrectly.Repairs and ReplacementField repairs must not be made.For a replacement thermostat,contact the nearest JohnsonControls distributor.4 A19AUC, A19BUC Product BulletinPerformance specifications appearing herein are nominal and are subject toaccepted manufacturing tolerances and application variables.Controls Group507 E. Michigan StreetP.O. Box 423Printed in U.S.A.Milwaukee, WI 53202Next >