A.O. Smith ATO-240H-N Service Manual

Gas Tankless Water HeaterTMSuitable for potable water heating and space-heating Please refer to local codes for space-heating compliance.540 (T-H3) mo

10 PageInstallaonInstallaon ManualThe pipe cover protects the plumbing pipes to the water heater from unexpected adjustments. This pipe cover is f

11 PageWARNING FOR INSTALLATIONSFOR YOUR SAFETY, READ BEFORE INSTALLATION:Do not install the heater where water, debris or flammable vapors may get i

12 PageHIGH-ALTITUDE INSTALLATIONSCheck the elevation where your water heater is installed. Set DIPswitches shown in the table below depending on th

13 PageVENTING INSTRUCTIONSFor the 240 Indoor (T-H3J-DV), 340 Indoor (T-H3S-DV) and 540 Indoor (T-H3-DV) models-General-TheIndoormodelsmustbeven

14 Page-DIPswitch settings for Vent length-4" ventingVent length240 Indoor (T-H3J-DV) 340 Indoor (T-H3S-DV) 540 Indoor (T-H3-DV) (Upper bank of

15 Page-Exhaust vent (ABS, PVC, CPVC, or polypropylene vent)-TheIndoormodelscanbeventedwithABS,PVC,CPVC,orpolypropylene(temperaturerat

16 Page-Two-pipe, direct-vent illustraons-For details of the optional items, refer to the Installation manual for each optional item.<Howtoinst

17 Page-Single pipe with room-air intake illustraons-For details of the optional items, refer to the Installation manual for each Optional item.<

18 Page-Exhaust vent (Stainless steel vent)-ThisisaCategoryIVapplianceandmustbeventedaccordingly.Theventsystemmustbesealedairtight.

19 Page-Direct-vent and single vent Illustraons-<Howtoinstallstainlesssteelventwiththeindoormodels>• Regardingtheclearancesfromt

2 PageCONTENTSInstallation Manual　SPECIFICATIONS ...

20 Page-Vent terminaon clearances-Canada U.S.ADirect-vent and other than Direct-ventDirect- ventOther than Direct-ventAClearance above grade, veran

21 Page-For sidewall terminaons-For multiple sidewall exhaust terminations (e.g. Multi-Unit Systems), an exhaust termination must be at least 1 ft.

22 Page-For rooop terminaons-3 ft (914 mm) minExhaust gasIntake air1 ft (305 mm) min1 ft (305 mm) min2 ft (610 mm) min1 ft (305 mm) min1 ft (305 mm

23 PageGAS SUPPLY AND GAS PIPE SIZING-General-• The minimum and maximum inlet gas pressures are:• Inlet gas pressures that fall outside the range

24 Page-Natural Gas Supply Piping-Maximum delivery Capacity of Cubic Feet of Gas per Hour of IPS Pipe carrying Natural Gas with 0.60 Specific Gravit

25 Page-Measuring inlet gas pressure-The water heater cannot perform properly without sufficient inlet gas pressure. Below are instructions on how t

26 Page-Pressure relief valve-The water heater has a high-temperature shutoff switch built in as a standard safety feature (called a Hi-Limit switch)

27 Page-Condensate Drain Connecons-The water heater is a high efficiency condensing water heater that produces condensate (acidic water). The acidi

28 PageELECTRICAL CONNECTIONSAll Indoor models come with a power plug instead of a junction box. The following procedure is for outdoor models only.

29 PageTEMPERATURE REMOTE CONTROLLER-Outdoor models only--INSTALLATION-<MountingandWiringtheRemoteController>1. Takeoffthe“Back plate”

3 PageInstallaon ManualInstallation ManualCONGRATULATIONSCongratulations and thank you for choosing our tankless water heater. Before use, we reco

30 Page3. Tightenthetwo"Fork terminals" beneath the two "Remote controller terminal" screws on the back of the main bod

31 Page540 (T-H3) models9008172005 (TM-RE40)Connect other end to these terminals240 (T-H3J) and 340 (T-H3S) models9008172005 (TM-RE40)Connect other

32 PageEASY-LINK SYSTEM(Available on the 540 (T-H3) models only)The 540 (T-H3) models water heaters can be connected with allowable heaters (see the

33 Page2. Select one unit to be the “PARENT” unit.3. “PARENT” unit : Locate the two banks of DIPswitches at the bottom left of the computer b

34 Page(C) Examples of incorrect settings and /or connections CASE 1: Wrong DIPswitch setting on the "PARENT" unit CASE 2: Wrong

35 PageCASE 3: Wrong connections between the "CHILD-1" unit and the "CHILD-2" unit• If you connect the “PARENT” connector of the

36 PageMULTI-UNIT SYSTEMMultiple 540 (T-H3) models can be combined for a Multi-Unit System, along with the multi-unit controller (Part 9008300005 (TM

37 PageAPPLICATIONS-Space-Heang Applicaons--Recirculaon-*The recirculation pump is to be controlled by:-Dual-set aquastat (recommended w/timer)*Th

38 Page-Dual-purpose hot water heang-(Domestic and Space Heating):Diagrammatic layout of radiant heating and domestic water heater per mass. code.

39 PageINITIAL OPERATIONInialial operaonInstallaon ManualIF YOU SMELL GAS:• Do not try to start the water heater.• Do not touch any electric s

4 PageSpecicaonsInstallaon ManualSPECIFICATIONS*40 psi or above is recommended for maximum flow.** The Manifold Pressure is the factory setting a

40 PageOwner's GuideCONGRATULATIONSCongratulations and thank you for choosing our tankless water heater. Before use, we recommend that you read

41 PageOPERATING SAFETYFOR YOUR SAFETY READ BEFORE OPERATINGA. This water heater does not have a pilot. It is equipped with an ignition device that

42 PageDANGERVapors from flammable liquids will explode and catch fire causing death or severe burns. Do not use or store flammable products su

43 PageNormal OperaonOwner's GuideNORMAL OPERATIONTEMPERATURE CONTROLLER and REMOTE CONTROLLERTheillustraonbelowshowsanexampleofthec

44 PageTEMPERATURE SETTINGS-Set temperature-TEMPERATURE TABLE OF CONTROLLERNormal OperaonOwner's Guide°F 100 105 110 115 120* 125 130 135 140°

45 PageADDITIONAL FEATURESYou can get some information about the water heater condition by pressing the "INFO" button. For more informat

46 PageTEMPERATURE SETTINGS ON THE PCB(WITHOUT REMOTE CONTROLLER)There are 2 preset temperatures (120 °F (49 °C) and 140 °F (60 °C)) that you can se

47 PageFLOW• This unit comes equipped with heating blocks to protect it against damages associated with freezing.• For this freeze protection sys

48 PageMAINTENANCE AND SERVICE• Cleanthecold-waterinletfilter.(RefertotheUnitDrainingandFilterCleaningSectioninthispage.)• Be sure

49 PageTROUBLESHOOTINGGENERALPROBLEM SOLUTIONSTEMPERATURE and AMOUNT OF HOT WATERIt takes long time to get hot water at the fixtures.• The time it t

5 PageINTRODUCTION• This manual provides information necessary for the installation, operation, and maintenance of the water heater.• The model des

50 PagePROBLEM SOLUTIONSWATER HEATERUnit does not ignite when water goes through the unit.• Is the flow rate over 0.5 GPM (1.9 L/min)? (p. 43)• Che

51 PageERROR CODES-General-• The units are self-diagnostic for safety and convenience when troubleshooting.• If there is a problem with the install

52 Page-Fault Analysis of Error Codes-If the error code is displayed on the computer board of the water heater or remote controller and/or temperatur

53 PageTroubleshoongOwner's GuideRemoteGreen LEDMalfunctiondescriptionDiagnosis391Two Times Air-fuel ratio rod failure• Check for connection/b

54 PageCOMPONENTS DIAGRAMIndoor modelsOutdoor modelsCase assembly Temperature remote controller72472372205605205200300700205000670400505270270400

55 Page540 (T-H3) models240 (T-H3J) and340 (T-H3S) modelsComputer board assemblySurge box assembly121713703706063709053703711701713103709402707708714

56 PageComponents DiagramOwner's GuideBurner assembly1011041151061071081101091117111120620530537090534011031050650541131141027081191511180550511

57 PageComponents DiagramOwner's GuideWater Way assembly402460456461458404417407454405457406410455408458454462CD052059052409417Water outlet se

58 PagePARTS LISTItem # DescriptionPart #240, 340 and 540 modelsT-H3J, T-H3S and T-H3 models001 Case assembly for Indoor models

59 PageParts ListOwner's GuideItem # DescriptionPart #240, 340 and 540 modelsT-H3J, T-H3S and T-H3 models116117118Pressure portCombustion cham

6 PageSAFETY GUIDELINESSAFETY DEFINITIONGENERAL 1. Follow all local codes, or in the absence of local codes, follow the most recent edition of the

60 PageParts ListOwner's GuideItem # DescriptionPart #240, 340 and 540 modelsT-H3J, T-H3S and T-H3 models462463464465Fastener“16-25A”Fastener

61 PageOUTPUT TEMPERATURE CHARTChart is based on properly sized gas line240 (T-H3J) modelsOutput Temperature ChartOwner's Guide340 (T-H3S) mod

62 Page1. The manufacturer warrants this product against defects in materials or workmanship as described in this document if installed within the

63 Page•  Freezedamagethatoccurswithouttakingproperpreventivemeasuresasdescribedintheinstallation manual.• 

64 Page68A161-1

7 PageINSTALLATIONGENERAL1. Follow all local codes, or in the absence of local codes, follow the most recent edition of the National Fuel Gas Code:

8 PageINCLUDED ACCESSORIESOPTIONAL ITEMS• Installation and service must be performed by a qualified installer (for example, a licensed plumber or ga

9 PageMaintain all clearances around the water heater.CLEARANCESInstallaonInstallaon ManualINCLUDED ACCESSORIESModel Top Bottom Front Back Sides2