A.O. Smith T-H2-DV Page 48 Service Manual Download

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T-H2-DV/T-H2-OS Service Manual

Ver. 1.01

CONFIDENTIAL

Error Code

Malfunction description

Cancellation method

341

Disconnected/short-circuited exhaust thermistor
(T-H2-DV only)

Turn off the power or water supply

Diagnosis

Checkpoint

1 Exhaust thermistor fault

(Refer to section 10-13)

Visual inspection: connection/breakage of wires and/or debris on
thermistor.
Check voltage/resistance between white & white (#52).
Refer to Section 8 (B) for proper range of values.

Error Code

Malfunction description

Cancellation method

391

Disconnected AFR rod

Turn off the power or water supply

Diagnosis

Checkpoint

1 AFR rod fault

(Refer to section 10-7)

Visual inspection: connection/breakage of wires, soot on it.

Error Code

Malfunction description

Cancellation method

441

Flow sensor failure (Easy-Link system only)

Turn off the power or water supply

Diagnosis

Checkpoint

1 Flow sensor failure

(Refer to section 10-10)

Visual inspection: connection/breakage of wires and/or debris on impeller.
Check voltage/resistance between (red & black) or (white & black)

Summary of Contents for T-H2-DV

Page 1: ...CONFIDENTIAL T H2 DV T H2 OS On Demand Water Heater Service Manual Flash Water Heater Model T H2 DV Flash Water Heater Model T H2 OS A O Smith Water Products Company 500 Tennessee Waltz Parkway Ashla...

Page 2: ...atic diagram 11 6 Wiring diagram 12 7 Wiring diagram checkpoints for diagnosis 13 8 8 A Resistance values of the temperature thermistors B Resistance values of the temperature Exhaust thermistors 15 1...

Page 3: ...to 185 F default 120 F Temperature on the unit settings 100 F 105 F 110 F 115 F 120 F 125 F 135 F 140 F 145 F 150 F 155 F 160 F 165 F 170 F 175 F 185 F Bypass valve Yes Thermistors 4 thermistors In O...

Page 4: ...2mm 18 1 2 470mm 7 1 4 183 8mm 6 3 8 1 6 1 5 mm 18 1 2 470mm 6 1 4 161 5mm 3 1 2 90mm 12 1 2 320mm 1 2 12 5mm GAS 6 153 6mm HOT 7 1 4 182 1mm COLD 8 5 8 220 6mm HOT 5 5 8 142 2mm 120VAC 8 1 2 216 3mm...

Page 5: ...1 1 4 29 2mm 120VAC 2 1 4 58 2mm GAS 4 5 8 116 8 mm HOT 5 1 2 142 2mm 2 5 1 2 6 4 9 m m 1 2 12 5mm GAS 6 153 6mm HOT 7 1 4 182 1mm COLD 8 5 8 22 0 6mm 18 1 2 470mm 3 1 2 90mm 12 1 2 320mm 4 1 2 115mm...

Page 6: ...T H2 DV T H2 OS Service Manual Ver 1 01 6 CONFIDENTIAL 3 Interior view T H2 DV 20 32 16 10 18 24 11 15 3 19 37 38 17 33 5 8 27 6 7 21 23 30 31 9 1 13 25 2 22 4 12 14 28 29 26 26 35 35 34 36...

Page 7: ...T H2 DV T H2 OS Service Manual Ver 1 01 7 CONFIDENTIAL T H2 OS 1 3 4 5 6 27 7 8 9 2 11 13 15 16 17 19 20 21 22 23 24 25 29 28 10 12 33 37 38 26 18 35 34 35 26 14 36...

Page 8: ...inlet 411 EM404 T M32 6 Water outlet 435 EKJ02 T M32 7 Mixing thermistor 418 EX00H T M32 8 Inlet thermistor 422 EKK38 T K3 T K3 Pro T D2 IN OS T M50 T M32 9 Output thermistor 433 EKK2T T K3 T K3 Pro...

Page 9: ...106 EKK0E T K3 T K3 Pro T K3 SP OS T K4 IN OS T D2 IN OS T M50 T M32 23 Flame rod 106 EKK0E T K3 T K3 Pro T K3 SP OS T K4 IN OS T D2 IN OS T M50 T M32 24 Igniter rod 108 EKK0F T K3 T K3 Pro T K3 SP O...

Page 10: ...m Takagi Part Common parts For other models 32 Exhaust thermistor assembly 706 EKH6E 33 Inlet drain plug water filter 409 EX006 T M50 T M32 34 Flat heater 453 EX13P 35 3 array heater 454 EX13R 36 Case...

Page 11: ...istors to measure temperatures the computer modulates the gas and water valves to ensure proper output water temperatures 8 When the tap is closed the T H2 DV or T H2 OS shuts down T H2 DV controls fa...

Page 12: ...1 2 3 4 5 6 O F F 7 8 2 1 W Y O R Gas Propor tional Valve W R W R BK R W Flow Sensor B K W R Hi limit switch for exhaust Exhaust thermistor W W W R YG W BK BR R O Y G W BK BL Water Control valve Ignit...

Page 13: ...90 to 110 VAC B2 Igniter Purple Purple 90 to 110 VAC C Gas valves Light blue blue at COM MV 78 to 100 VDC during operation 0 9 to 1 3 k Green blue at COM SV1 78 to 100 VDC during operation 1 3 to 1 9...

Page 14: ...White red 1 to 15 VDC during operation and 20 to 40 H2 Flow sensor Red Black 4 to 5 5 VDC White Black GND 1 to 4 VDC 1 200pulse min I Air fuel ratio flame rod Yellow AFR rod Between AFR rod and the c...

Page 15: ...23 76 19 08 15 43 12 56 10 28 8 47 7 02 5 85 4 90 4 12 Temperature F 122 131 140 149 158 167 176 185 194 203 212 C 50 55 60 65 70 75 80 85 90 95 100 Resistance k 3 49 2 96 2 53 2 16 1 86 1 60 1 39 1 2...

Page 16: ...4 12 19 50 15 87 13 00 10 71 8 87 7 39 6 19 5 21 Temperature F 122 131 140 149 158 167 176 185 194 203 212 C 50 55 60 65 70 75 80 85 90 95 100 Resistance k 4 41 3 74 3 19 2 73 2 35 2 03 1 76 1 53 1 33...

Page 17: ...ailure 031 blink 321 blink 701 blink 510 blink 611 blink Fan motor stop operation 721 blink False flame Igniter OFF Reignition Success OuTH OPEN or SHORT Fan motor fault MV OFF SV2 OFF GPV OFF SV1 SV3...

Page 18: ...0 7 AFR rod 25 10 8 Heat exchanger 26 10 9 Secondary heat exchanger 27 10 10 Flow sensor 28 10 11 Water control valve 30 10 12 Thermistors 31 10 13 Exhaust thermistor 32 10 14 Hi limit switch 33 10 15...

Page 19: ...Dust or soot deposit on the burner surface 3 Cracks on the burners 4 Gas leakage from the burners Effects on the water heater if burners fails 1 Unexpected combustion 2 Unstable flame conditions and...

Page 20: ...an cause poor combustion in the combustion chamber In this case the AFR rod will detect an improper flame condition and computer will take safety measures 2 Gas leakage from the manifold Error codes w...

Page 21: ...The water heater does not function properly 2 Failure to ignite or abnormal ignition 3 Unstable combustion conditions Error codes when the fan motor fails 101 111 121 611 991 Diagnostic 1 Visual insp...

Page 22: ...st gas temperature Error codes when the fan motor fails 621 T H2 DV only 941 T H2 DV only Diagnostic 1 Visual inspection connection breakage of wires or dust causing electrical shortage 2 Voltage chec...

Page 23: ...n connection breakage of wires 2 Listen for clunk sounds from the gas valves opening right after fan motor initiates 3 Check voltages and resistance of coils proper range of values shown below Color N...

Page 24: ...or code s will display 2 The water heater will not initiate the ignition process The 721 error code will display Error codes when the flame rod fails 111 121 721 Diagnostic 1 Visual inspection connect...

Page 25: ...121 error code s will display 2 The water heater will not initiate the ignition process The 721 error code will display 3 The fan motor speed cannot be modulated properly under abnormal flame conditi...

Page 26: ...to detect this event and immediately stop the water heater from operating 3 Abnormal sounds during combustion Error codes when the heat exchanger fails N A Diagnostic 1 Visual inspection soot deposits...

Page 27: ...Leaking exhaust gas Effects on the water heater if the secondary heat exchanger fails 1 Water leakage from the secondary heat exchanger 2 Exhaust gas leakage 3 Abnormal sounds during combustion Error...

Page 28: ...f flow sensor fails Ignition sequence does not start T H2 DV T H2 OS will not initiate any operation Error codes when the flow sensor fails 441 Within Easy link systems only Diagnostic 1 Visual inspec...

Page 29: ...on The function of the bypass valve 4 Prevents water from flowing through the heat exchanger when water heater is not in operation to protect the heat exchanger The function of the two way valve Failu...

Page 30: ...and bypass valve Color Number of wires Blue Brown 13 0 to 16 0 VDC Orange Brown ON 12 5 to 16 0 VDC OFF 0 to 1 VDC Red Brown 0 position 1 VDC less The water control valve contains the flow adjustment...

Page 31: ...eater will have temperature fluctuations in hot water Error codes when thermistors fails 311 Output 321 Inlet 331 Mixing Diagnostic 1 Visual inspection connection breakage of wires and or debris on th...

Page 32: ...istance values are just off the 341 error codes will display Error codes when exhaust thermistor fails 341 T H2 DV only Diagnostic 1 Visual inspection connection breakage of wires and or debris on imp...

Page 33: ...t exchanger exceeds 194 F 90 C Note The mixing and output thermistors always act as backup hi limit detectors to detect excessively high water temperatures in the heat exchanger 2 The water heater is...

Page 34: ...exhaust fails 1 Unable to shut down the water heater if the exhaust gas temperature in the exhaust chamber exceeds 151 F 66 C 2 The water heater is always shut down immediately after the ignition pro...

Page 35: ...antly The 111 121 or 711 error code will display Failure events 1 Unable to detect the excessively high temperatures within the water heater Effects on the water heater if the overheat cutoff fuse fai...

Page 36: ...age needed to heat up Effects on the water heater if heater fails Ceramic heaters do not activate allowing water contained in the heat exchanger to freeze up possibly causing the heat exchanger to bur...

Page 37: ...Effects on the water heater if the computer board fails A component s may not operate within the water heater In most cases of computer board failure the whole the water heater does not operate at al...

Page 38: ...ts on the water heater if transformer fails 1 The water heater does not operate due to lack of power from transformer 2 A failed transformer can cause electrical damage to other electrical components...

Page 39: ...cannot ignite during the ignition process and the 111 or 121 error codes will display 2 No effects on the water heater however the durability of the igniter wears down Error codes when Igniter fails...

Page 40: ...tection thermostat fails 1 The freeze protection heaters will always be ON causing heat damage to components inside the water heater 2 The freeze protection heaters will never be able to turn on even...

Page 41: ...ure of the absorber Effects on the water heater if the Surge box fails 1 Unable to protect the computer board if high voltage gets applied to the unit The computer board can short out stopping all ope...

Page 42: ...F 6 Disconnection short circuit grounding of remote wires Normal 11 to 25 VDC between 7 Fault of PCB of remote control 1 Check for normal voltage at terminal It takes long time to get hot water at the...

Page 43: ...ut of the flue Abnormal sound from water heater 1 Check the gas type of the water heater 2 Check how long the water heater has been installed and in use 3 Check the installation place 4 Check the alti...

Page 44: ...l 13 0 to 16 0 VDC between blue brown Normal ON 12 5 to 16 0 V OFF 0 to 1 V between orange brown Normal 1 VDC less 0 position between red brown J 7 Fault of Water control valve Normal 0 09 to 0 2 k be...

Page 45: ...ck the igniter Refer to section 10 20 Visual inspection connection breakage of wires and or observed weak spark 1 Cracks soot on igniter rod 2 Improper gap between burner igniter rod Normal gap 0 16 4...

Page 46: ...During operation more than 1 A through the flame rod wire orange I 8 Check if hi limit switch is properly functioning Error Code Malfunction description Cancellation method 121 Error code is shown af...

Page 47: ...utput thermistor fault Refer to section 10 12 Visual inspection connection breakage of wires and or debris on thermistor Check voltage resistance between black black 12 Refer to Section 8 A for proper...

Page 48: ...Section 8 B for proper range of values K1 Error Code Malfunction description Cancellation method 391 Disconnected AFR rod Turn off the power or water supply Diagnosis Checkpoint 1 AFR rod fault Refer...

Page 49: ...l 78 to 100 VDC between COM blue 73 red during operation Visual inspection of PCB connection breakage of wires and or burn marks on the computer board 2 Gas solenoid valve fault MV SV1 SV2 and or SV3...

Page 50: ...r burn marks on the computer board G1 Error Code Malfunction description Cancellation method 621 Exhaust fan motor fault T H2 DV only Turn off the power or water supply Diagnosis Checkpoint 1 PCB and...

Page 51: ...pump Turn off the power Diagnosis Checkpoint 1 Check whether the pump connected to PCB works properly Error Code Malfunction description Cancellation method 651 Water control valve fault Flow adjustme...

Page 52: ...0 to 1 V Normal 1 V Less than 0 position Visual inspection PCB connection breakage of wires and or burn marks on the computer board J Error Code Malfunction description Cancellation method 701 1 PCB f...

Page 53: ...between blue blue C2 2 PCB and or gas valve fault Refer to section 10 5 10 18 Visual inspection PCB connection breakage of wires and or burn makes on the computer board C Error Code Malfunction descri...

Page 54: ...ressure in the water heater 6 Check if the exhaust fan motor works properly 7 Check if the set temperature is higher than 140 F 60 C and the system is recirculation Recirculation system with high temp...

Page 55: ...y link system 71 12 8 B Pump control ON OFF conditions BTU requirements 72 12 9 Multi unit system ON OFF conditions 73 12 10 Operation time for unit rotation 74 12 11 12 12 Individual unit operation i...

Page 56: ...please refer to the table on p 59 and p 61 for the proper mode In the tables on p 58 to p 60 say the followings d1 to d18 p 59 to p 60 Unit information of Individual T H2 DV or T H2 OS h1 to h15 p 61...

Page 57: ...e HOT or COLD buttons Fig 1 shows mode 5 being selected When selecting information please refer to the table on p 58 and p 59 for the proper mode 3 Press the INFO button to select the mode and the inf...

Page 58: ...sy link system of T H2 DV or T H2 OS s a maximum of four T H2 DV or T H2 OS s can be linked together 4 Press the INFO button to select the desired unit 5 When the desired unit is selected and fixed sc...

Page 59: ...on 0 Ratio of hot water and cold water d10 0 to 999 10 0 to 999 Error code history displays most recent error code d11 Error code history displays most recent error code 11 Error code history displays...

Page 60: ...output from Computer board d29 0 to 999 1000 BTU h 29 0 to 9 999 100 BTU Actual output of Unit d30 0 to 999 1000 BTU h 30 0 to 9 999 100 BTU Integrating flow of Unit d31 0 to 999 10000 gallon 31 0 to...

Page 61: ...next rotation occurs h7 0 to 720 minutes After 720 the next rotation occurs ON OFF cycles during current rotation h8 0 to 100 cycles After 100 the next rotation occurs h8 0 to 100 cycles After 100 the...

Page 62: ...hite If no voltage is detected going into the computer board the fuse box or transformer might have malfunctioned or been damaged If 100 VAC is measured going into the computer board and the water hea...

Page 63: ...ior error codes the 3 digit 7 seg LED will display the most recent error code first Pressing the button again will display the 2nd most recent error code and so on Computer saves a maximum of 12 error...

Page 64: ...r sticking Vent Flaps installed on the Terminator Snow build up around Terminator Installed in a closet No Ventilation or lack of combustion air 6 If installed in laundry room check the burner and hea...

Page 65: ...higher than the normal value the FM speed is increased If the AFR value is lower than the normal value the FM speed is decreased These values are read with the front cover close Measure the values af...

Page 66: ...Individual operation mode See Section 12 11 Enable Default Disable 5 6 Pump mode 7 The number of priority unit in a T H2 DV or T H2 OS Two priority units One priority unit Default 8 Deactivation of t...

Page 67: ...peed is increased automatically See section 12 12 Fan motor for combustion No 5 OFF position ON position No 6 OFF position 0 6 ON position 12 18 Fan motor for exhaust T H2 DV only No 5 OFF position ON...

Page 68: ...he computer board of all child units for at least 5 seconds 2 The 3 digit 7 seg LED on the computer board of all child units will display 0 to signify that the computer memory has been erased of its p...

Page 69: ...ter ON OFF Conditions Conditions needed to turn ON The BTU requirement is more than 14 880 BTU h AND The water flow rate is more than 0 5 GPM Conditions needed to turn OFF The BTU requirement is less...

Page 70: ...temperature F Flow rate GPM 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 100 ON 40 5 70 2 80 2 85 1 88 1 90 1 91 5 92 6 OFF 52 4 76 2 84 1 88 1 90 5 92 1 93 2 94 0 115 ON 55 5 85 2 95 2 100 1 103 1 105 1 106 5 10...

Page 71: ...ctions enable the re circulation pump to be controlled by the following conditions ON OFF Conditions Re circulation mode Energy conserving re circulation mode Conditions that activate the pump The BTU...

Page 72: ...example Set temperature Tset 120 F Flow rate 2 5 GPM Condition needed to turn the pump ON 120 Tin 2 5 500 14 880 Tin 108 1 F Condition needed to turn the pump OFF 120 Tin 2 5 500 14 880 Tin 108 1 F C...

Page 73: ...F C GPM L min 100 120 38 49 3 4 13 125 130 52 54 3 2 12 140 60 2 9 11 145 150 63 65 2 6 10 155 185 68 85 2 4 9 2 Condition required to reduce the number of activated T H2 DV or T H2 OS s A In the cas...

Page 74: ...12 hours of operation NOTE The priority unit is the unit that turns on first when there is a hot water demand When there is a black out and or cut off for over 50 minutes priority unit will switch bac...

Page 75: ...r normal conditions 0 5GPM When the parent unit fails 0 5 4 2 0GPM Minimum flow rate of the easy link system depends on the number of the units installed in the easy link system The set temperature of...

Page 76: ...fan motor speed increased by 3 6 T H2 OS Left bank of dipswitches No 5 ON No 6 OFF 2 4 000 to 5 000ft FM function the fan motor speed increased by 12 T H2 DV the fan motor speed increased by 7 3 T H2...

Page 77: ...nk of dipswitches See section 12 5 for dipswitch settings NOTE Changing the temperature display unit on the PCB does not change the unit of the TM RE30 display To convert between C and F displays on t...

Page 78: ...s are always monitoring exhaust gas conditions in order to prevent heat damage to PVC Plastic venting If the exhaust gas temperature exceeds 140 F these components will enable the unit to safely stop...

Page 79: ...1 amp For example To the right there is a sample of relay specifications from an arbitrary brochure You can select either the 120 VAC or 240 VAC relay because their current values are less than 1 A 1...

Page 80: ...V T H2 OS computer detects any error codes the alarm port terminal on the T H2 DV T H2 OS computer will activate the connected lamp or buzzer How to reset the operation Clear the current error code Re...

Page 81: ...ctivate its operation If presence of a gas leak is detected immediately shut off the T H2 DV or T H2 OS and inspect the tube manifold connection otherwise proceed onto the next step 5 Press and hold d...

Page 82: ...e or decrease the manifold gas pressure respectively Figure 3 Refer to the manometer to verify that pressure has been set to desired value 6 After gas pressure has been set deactivate the T H2 DV or T...

Page 83: ...oller display mode 3 fan motor speed by entering the Diagnostics mode Refer to Section 12 1 3 Press and hold down the MAX button on the computer board While holding down the MAX button press either th...

Page 84: ...for combustion 10 0 5 0 1 0 0 1 0 5 0 10 0 Fan motor for exhaust 6 3 0 6 0 0 6 3 6 Figure 1 Left bank of dipswitch settings Figure 2 T H2 DV T H2 OS Computer board 1 2 3 4 5 6 7 8 FM N O 9 10 Unit MAX...

Page 85: ...clusive because they focus on different areas of the T H2 DV or T H2 OS As long as each particular feature s activation requirements are met it is possible for both features to operate at the same tim...

Page 86: ...Yes 46 F and above 37 F and below YES Ceramic heating blocks The blocks will only activate based on what the freeze protection thermostat senses The thermostat is located on the intake port for T H2 D...

Page 87: ...display P on its three 7 seg LED however the TM RE30 remote controllers will not display anything on its screen In order to detect the temperature of the system accurately The computer makes the pump...

Page 88: ...ot be in combustion forced combustion or FM adjustment modes press and hold the Increase button for at least 5 seconds or longer to enter Diagnostic Mode 4 Scroll through the needed information mode P...

Page 89: ...ater flow has ceased close all hot water taps 6 Have a bucket or pan to catch the water from the drain plugs of the T H2 DV or T H2 OS Unscrew the drain plugs to drain all the water out of the T H2 DV...

Page 90: ...H2 OS s parts are the same as the T H2 DV The T H2 OS doesn t have fan motor for exhaust No 124 Case assembly T H2 OS T H2 DV 01 5 00 7 0 5 4 0 06 70 3 0 52 00 4 7 0 2 15 2 00 5 0 16 0 51 0 08 00 9 0...

Page 91: ...or assembly No 716 and exhaust fan motor wire No 720 Computer board assembly 1 01 102 103 1 04 1 05 106 10 7 1 08 1 09 1 10 1 11 112 11 4 11 6 117 11 8 11 9 120 121 122 123 151 152 1 52 1 52 152 710 1...

Page 92: ...y assembly 456 152 4 59 4 60 461 1 52 152 T H2 OS T H2 DV A 401 4 02 403 404 407 408 409 4 10 41 1 4 12 41 3 414 415 416 417 418 419 420 41 4 421 422 423 424 425 428 414 4 29 4 14 436 430 432 433 419...

Page 93: ...EKK22 Fastener T M32 010 EKH23 Condensate drain port 011 EKH5K Duct 012 EKH4G Duct gasket A 013 EKH4K Duct gasket B 014 EKH73 Duct cover plate 015 EKH5C Case assembly OS 016 EKH61 Front cover OS 051...

Page 94: ...2 IN OS T M50 111 EKH5G Damper 112 EKK2N Urethane tube T K3 T K3 Pro T K3 SP T K4 IN OS T D2 IN OS 113 EKK2D Pressure port T K3 T K3 Pro T K3 SP T K4 IN OS T D2 IN OS T M50 T M32 114 EKK25 Fan motor T...

Page 95: ...tion plate Left 128 EK042 O ring P20 NBR T K3 T K3 Pro T K3 SP OS T KJr2 IN OS T K4 IN OS T D2 IN OS T M50 150 EW012 Screw M4 8 151 EW00D Pan screw M4 8 152 EW003 Screw M4 10 153 EW00H Pan screw M4 12...

Page 96: ...ng P6 FKM 418 EX00H Mixing thermistor T M32 419 EZF04 O ring P4 FKM 420 EZF16 O ring P16 FKM 421 EKH74 Cold pipe 422 EKK38 Inlet thermistor T K3 T K3 Pro T D2 IN OS T M50 T M32 423 EKH32 Water control...

Page 97: ...3 EKK24 Fastener 14 22 T K3 T K3 Pro T K3 SP OS T KJr2 IN OS T K4 IN OS T D2 IN OS 444 EX13H Thermistor fixing plate 445 EKH5N Secondary heat exchanger plate 446 EKH6X Secondary heat exchanger 447 EKH...

Page 98: ...wire DV 705 EKH6V Gas valve wire 706 EKH6E Exhaust thermistor assembly 707 EKH6J Thermistors wire 708 EKK12 Proportional gas valve wire T K3 T K3 Pro T D2 IN OS 709 EKH6F Pump and multi cable 710 EKH...

Page 99: ...T H2 DV T H2 OS Service Manual Ver 1 01 99 CONFIDENTIAL 15 Revisions Version Description of changes Date 1 00 First edition 10 09 09 1 01 Revised by the R D and Japan 11 01 10...

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