A.O. Smith T-M50 ASME Service Manual Download Page 9

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T-M50 / T-M50 ASME Service manual

Ver. 1.05

CONFIDENTIAL

6. Wiring diagram

BK:BLACK

P:PURPLE

LB:LIGHT BLUE

BL:BLUE

G;GREEN

Y:YELLOW

O:ORANGE

BR:BROWN

Thermostat

Inlet
thermistor

Output
thermistor

Mixing
thermistor

B K

G FI

T r a n s -
f o r m e r

1
2

3
4
5
6

B R

120 VAC

10A

Ground

B K

B R

Ground

Air-fuel
ratio rod

Ground

Flame
rod

1 2 3 4 5 6

O F F

1 2 3 4 5 6

O F F

SV1

SV2

SV3

Re mo te
co nt rol ler

Parent

W
W

I G

Ground

Inlet
thermistor

Output
thermistor

Mixing
thermistor

B K

1
2

3
4
5
6

Air-fuel
ratio rod

Ground

Flame
rod

SV1

SV2

SV3

F M

Igniter
rod

I G

Heater

B L

B K

Water
Control
valve

B K

B K
B K

B K

B K
B K

B K

B L

B K

B L
B L

B L

B K

B K R

B L

L B

B K

B L

L B

B K

Gas
Porpor-
tional
Valve

Flow
Sensor

B K

B K R

Hi-

limit

B L

O.H.C.F

B L

F M

B L

Hi-

limit

B L

O.H.C.F

B L

Flow
Sensor

Left side unit

Right side unit

Surge
box

B K

MAX button

MIN button

Increase button

Decrease button

Burning lamp

Communication

lamp (right)
Communication

lamp (left)
Multi-system

on line lamp

Lower bank of

dipswitches

Upper bank of

dipswitches

7 Seg LED

Pump test run

Error call

button

Burning lamp

port

Pump

port

Button to check

unit number

Priority SW

Alarm

contact

Draft switch

Dipswitches

MAX button

MIN button

Increase button

Decrease button

Dipswitches

Gas
Porpor-
tional
Valve

Igniter
rod

L
L

TM-RE30

Summary of Contents for T-M50 ASME

Page 1: ...ASME Service manual Ver 1 05 1 CONFIDENTIAL T M50 T M50 ASME On Demand Water Heater Service manual T M50 A O Smith Water Products Company 500 Tennessee Waltz Parkway Ashland City TN 37015 Toll Free 1...

Page 2: ...ents in the interior view 6 5 Schematic diagram 8 6 Wiring diagram 9 7 Wiring diagram checkpoints for diagnosis 10 8 Resistance values of the temperature thermistors 12 9 Operational flow chart 13 10...

Page 3: ...Temperature dipswitch setting 100 F 115 F 120 F 135 F 145 F 155 F 165 F 185 F Bypass valve Yes Water control Thermistors 3 thermistors In Out Mixing Available remote controller TM RE30 PCB Model Centr...

Page 4: ...137 3mm HOT 4 3 8 110 8mm GAS 7 5 8 194 3mm COLD 4 100mm 120 VAC 6 3 4 171 3mm 120 VAC 1 2 12 5mm 2 1 2 6 2 1 m m 5 7 8 150mm HOT 15 381mm 8 203mm 2 9 7 8 7 5 9 mm GAS COLD HOT 7 3 8 186mm 4 100mm 4 3...

Page 5: ...T M50 T M50 ASME Service manual Ver 1 05 5 CONFIDENTIAL 3 Interior view 1 4 4 5 5 2 2 6 7 6 7 8 8 9 10 11 12 1 2 13 14 15 16 16 1 7 18 18 19 19 21 2 2 23 2 3 24 25 26 3 27 5 30 20 20 29 31 28 3 1 5 30...

Page 6: ...M32 EM302 LP model 4 Manifold assembly with gas valve assembly 114 EM303 NA model 5 Fan motor 416 EKK25 T K3 T K3 Pro T K3 SP T H2 DV OS T K4 IN OS T D2 IN OS T M32 6 Flame rod 103 EKK0E T K3 T K3 Pro...

Page 7: ...Hi limit switch 403 EKN34 T K3 T K3 Pro T K3 SP OS T H2 DV OS T D2 IN OS T M32 19 Overheat cut off fuse 402 EK333 T K3 T K3 Pro T K3 SP OS T KJr2 IN OS T K4 IN OS T D2 IN OS 20 Heater101 426 EX002 T...

Page 8: ...s and flames appear inside the burner chamber 6 Water circulates through the heat exchanger and is heated up to the set temperature 7 Using thermistors to measure temperatures the computer modulates t...

Page 9: ...K B K Y G O O G Y B K B K W W B L BK B K R R BL BL G G R B L Y O W P P P P P P P P G WR B K W R WR B K R W B L L B G O R W B K Y W B K W BK B L L B G O R BK W BK W W B K B K W W W W W W W Gas Porpor...

Page 10: ...to 1 9 k Orange blue at COM SV2 78 to 100 VDC during operation 1 3 to 1 9 k C Gas valves Red blue at COM SV3 78 to 100 VDC during operation 0 9 to 1 7 k C1 Hi Limit switch Blue Blue Less than 1 VDC an...

Page 11: ...uel ratio rod Yellow AFR rod Between AFR rod and the computer board More than 0 5 A during operation I Flame rod Orange Flame rod Between flame rod and the computer board More than 1 A during operatio...

Page 12: ...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 21 1 05 0 92 0 81 Temperatur...

Page 13: ...ows out Left OHCF melted above 430 F Left AFR rod failure Left Abnormal burning 121 blink 121 blink 991 blink 391 blink BV modulates Flow temp 321 blink Left InTH OPEN or SHORT 331 blink Left MiTH OPE...

Page 14: ...AFR rod 20 10 7 Heat exchanger 21 10 8 Flow sensor 22 10 9 Water Control valve 23 10 10 Thermistors 25 10 11 Hi limit switch 26 10 12 Overheat cutoff fuse 27 10 13 Freeze protection heaters 28 10 14 C...

Page 15: ...ustion 2 Dust or soot deposit on the burner surface 3 Cracks of the burners 4 Gas leakage from the burners Effects on the water heater if burners fails 1 Unexpected combustion 2 Unstable flame conditi...

Page 16: ...per gas flow from the manifold which can 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 l...

Page 17: ...er 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 inspection connecti...

Page 18: ...ection 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 Blue Light bl...

Page 19: ...rror 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 conne...

Page 20: ...ater will not initiate the ignition process The 721 error code will display 2 The fan motor speed cannot be modulated properly under abnormal flame conditions which can result in excessive CO emission...

Page 21: ...place 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 de...

Page 22: ...sensor fails Ignition sequence does not start water heater will not initiate any operation Error codes when the flow sensor fails 441 only within Easy link and Multi unit systems Diagnostic 1 Visual i...

Page 23: ...ion 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 Fail...

Page 24: ...n 13 0 to 16 0 VDC Orange Brown ON 12 5 to 16 0 VDC OFF 0 to 1 VDC Function Red Brown 0 position 1 VDC less The water control valve contains the flow adjustment valve and the bypass valve 5 3 8 137mm...

Page 25: ...heater 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...

Page 26: ...m the heat 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 h...

Page 27: ...instantly The 111 or 121 error code will display Failure event 1 Unable to detect the excessively high temperatures within the water heater Effects on the water heater if the overheat cutoff fuse fai...

Page 28: ...s Ceramic heaters do not activate allowing water contained in the heat exchanger to freeze up possibly causing the heat exchanger to burst Error codes when hears fails N A Diagnostic 1 Visual inspecti...

Page 29: ...e computers fail 1 Unable to control proper combustion during operation 2 Unable to detect correct signals from any all water heater sensors 3 Unable to control water valves which may cause output tem...

Page 30: ...g computer Effects on the water heater if the computer board fails When the central computer board fails the control from central computer board and or communication to the multi unit controller TM MC...

Page 31: ...ects 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 component...

Page 32: ...ect electrical leakage within the water heater 2 OFF failure the water heater does not receive any power from the GFI which means the water heater cannot operate Error codes when the GFI fails N A Dia...

Page 33: ...r 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 34: ...n 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 under...

Page 35: ...ilure 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 o...

Page 36: ...of remote wires Normal 11 to 25 VDC between white black No display on temperature remote controller even when remote is turned on 7 Fault of PCB of remote control 1 Check for normal voltage at termin...

Page 37: ...as 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 altitude elevation of area of where the water heater installed 5...

Page 38: ...Fluctuation of hot water temperature 7 Fault of Water control valve Normal 0 09 to 0 2 k between red black J Error Code Malfunction description Cancellation method Incorrect dipswitch setting fault T...

Page 39: ...and or Right PCB Normal 90 to 110 VAC at 7 purple purple during ignition B 3 Fault of Left and or Right PCB 1 No voltage to main gas solenoid valve MV Normal 78 to 100 VDC between COM blue 3 light bl...

Page 40: ...mal 1 3 to 1 9 k between COM blue 53 orange 3 Gas proportional valve VG0 fault Normal 1 to 15 VDC between white red during operation C H1 121 Error code is shown after three failed attempts at ignitio...

Page 41: ...connection breakage of wires and or debris on thermistor Check voltage resistance between black black 12 Refer to Section 8 for proper range of values E2 Error Code Malfunction description Cancellatio...

Page 42: ...ection breakage of wires and or debris on impeller Check voltage resistance between red black or white black H2 Error Code Malfunction description Cancellation method Fault of driving circuit for main...

Page 43: ...connection breakage of wires and or burn marks on the computer board 2 Gas solenoid valve fault SV1 SV2 and or SV3 C Error Code Malfunction description Cancellation method Fan motor fault Turn off th...

Page 44: ...l 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 Water control valve fault...

Page 45: ...breakage of wires of the gas proportional valve Normal 20 to 40 between white red H1 Error Code Malfunction description Cancellation method False flame detection Turn off the power or water supply Di...

Page 46: ...section 12 4 If not possible press and hold the INC and DEC buttons on the computer board simultaneously for more than 3 sec Diagnosis Checkpoint 991 1 Check the gas type of the water heater 2 Check...

Page 47: ...itions BTU requirements 62 12 10 Conditions that stop the T M50 from operating 63 12 11 Pump control ON OFF Conditions 64 12 12 12 13 Multi unit system ON OFF conditions Operation time for unit rotati...

Page 48: ...de 2 the right side combustion section is being fixed scroll up or down to the needed information mode of the combustion section by pressing the HOT or COLD buttons 4 Press the INFO button to fix the...

Page 49: ...nit 5 When the desired unit is fixed Fig 2 shows that unit 10 is being selecting scroll up or down to the needed combustion section of the unit by pressing the HOT or COLD buttons 6 When the desired c...

Page 50: ...to 999 11 N A Error code history displays most recent error code 12 Inlet temperature of the priority unit 0 to 999 F Error code history displays 2nd most recent error code 13 Mixing temperature of t...

Page 51: ...our unit fails on the 321 error inlet thermistor Central computer board The 7 Seg LED will flash the 3 digit error code one digit at a time The 7 Seg LED will display 3 2 1 and will continually repeat...

Page 52: ...link system will display the error code on its 7 Seg LED in exactly the same way as if it were only a single Unit So in this example the 7 Seg LED on Unit 2 will display 3 2 1 just like in the single...

Page 53: ...troller will display 232 on its screen in its entirety The first 2 indicates that Unit 2 has the error The 32 indicates the first two digits of the 321 error code Multi unit controller TM MC01 The Uni...

Page 54: ...he 7 seg LED will light in a circular 0 pattern one segment at a time B Displaying error code history 1 Briefly press the Error call button do not hold down the button 2 If the T M50 has had prior err...

Page 55: ...Are there any obstructions in the intake air and or exhaust Damper sticking Vent Flaps installed on the Terminator Snow build up around Terminator Installed in a closet No Ventilation or lack of comb...

Page 56: ...Diagnostic Mode Section 12 1 The relationship between the AFR stage and the 101 and 991 error codes 16 15 6 0 Gas type LPG Natural gas Installation Outdoor Indoor Direct vent Outdoor Indoor Direct ve...

Page 57: ...tion OFF position 1 FM FM speed is increased automatically See section 12 15 6 FM speed Disable Default 2 N A N A N A Default 3 N A N A N A Default 4 Allow adjustments of fan motor speed Changing the...

Page 58: ...default settings may damage the T M50 and the system Changing dipswitches Therefore doing that is not recommended unless there is a very strong reason to do so The functions of the upper dipswitch ban...

Page 59: ...0 F No Functions ON position OFF position 4 Activation of Individual operation mode See Section 12 14 Enable Default Disable 5 Direct vent setting Enable Direct vent mode Disable Default 6 Outdoor set...

Page 60: ...central computer board of all child units for at least 5 seconds 2 The 7 seg LED on the central computer board of all child units will display 0 to signify that central computer board s memory has be...

Page 61: ...F Conditions For Every pump modes Conditions needed to turn ON The BTU requirement is more than 11 900 BTU h AND The water flow rate is more than 0 5 GPM Conditions needed to turn OFF The BTU requirem...

Page 62: ...1 0 1 5 2 0 2 5 3 0 3 5 4 0 ON 52 4 76 2 84 1 88 1 90 5 92 1 93 2 94 1 100 OFF 76 2 88 1 92 1 94 1 95 2 96 0 96 6 97 0 ON 67 4 91 2 99 1 103 1 105 5 107 1 108 2 109 1 115 OFF 91 2 103 1 107 1 109 1 1...

Page 63: ...ystem allows for greater reliability in operation there are a few conditions which can occur that will shut down the T M50 completely due to safety reasons These conditions are listed below Conditions...

Page 64: ...culation 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 requirement is more tha...

Page 65: ...ed to activate additional T M50 A n Where n number of currently activated T M50 s One T M50 has two combustion sections and A is dependent on the output set temperature See table below Output set temp...

Page 66: ...rate Combustion unit No GPM L min Combustion unit No GPM L min No 1 ON 0 5 1 9 No 1 2 3 4 5 6 7 8 OFF 19 72 No 1 2 ON 3 12 No 1 2 3 4 5 6 7 OFF 16 60 No 1 2 3 ON 6 24 No 1 2 3 4 5 6 OFF 13 48 No 1 2 3...

Page 67: ...thecomputerboardofthe multi unitcontroller TM MC01 Example Four units of T M50 Rotation A rotation occurs when ON OFF cycles 100 times or Hours of operation 12 hours Unit No 1 Unit No 2 Unit No 3 Unit...

Page 68: ...unit system Under normal conditions 0 5GPM When the multi unit controller fails 0 5 5 2 5GPM Minimum flow rate of the multiple system depends on the number of the units installed in the multiple syste...

Page 69: ...hod 0 0 to 2 500 ft DEFAULT Standard setting Default Left bank of dipswitches No 1 OFF No 8 OFF 1 2 500 to 4 000ft FM function the fan motor speed increased by 6 Left bank of dipswitches No 1 ON No 8...

Page 70: ...t right computer s and or the central computer board detect any error codes the alarm port terminal on the central computer board will turn ON activating the connected lamp or buzzer How to reset the...

Page 71: ...automatically turned ON under these conditions When the water heater s flow sensor detects flowing water the external fan motor will turns ON When the water heater stops burning or remote controller...

Page 72: ...icular relay to ensure that the current value through the coil will not exceed 1 amp For example To the right there is a sample of relay specifications from an arbitrary brochure You can select either...

Page 73: ...se proceed onto the next step 5 Press and hold down the MAX button on that section s computer board While holding down the MAX button press either the Increase or Decrease button to increase or decrea...

Page 74: ...red value 6 When the minimum gas pressure of the combustion unit is being adjusted the combustion of the other combustion unit must be set to MINIMUM 7 Repeat these steps for the other combustion sect...

Page 75: ...1 3 Press and hold down the MAX button on the computer board While holding down the MAX button press either the Increase or Decrease button to increase or decrease the fan motor speed respectively Fi...

Page 76: ...re met it is possible for both features to operate at the same time Ceramic heating blocks The blocks will only activate based on what the freeze protection thermostat senses The thermostat is located...

Page 77: ...freeze protection the Automatic fan motor system will deactivate if Tout Tin 3 6 F OR Tin 45 F and Tout 45 F and TMIX 45 F OR Tin 39 F and Tout 39 F and TMIX 39 F and Flow sensor detects flow rate for...

Page 78: ...heat exchanger not the water leaving the T M50 direct vent which is mixed with water from the bypass valve The automatic firing system will not activate at all unless these 2 minutes have elapsed Whe...

Page 79: ...tect the temperature of the system accurately The central computer board makes the pump work every two minutes during the freeze protection operation A Activation conditions all 3 conditions must occu...

Page 80: ...se When the all water 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 M50 Unscrew the drain plugs to drain all the water out of the T M...

Page 81: ...113 708 702 710 712 713 711 714 113 711 113 113 716 416 705 707 706 708 704 418 703 709 715 701 719 113 720 721 714 113 113 717 722 723 13 Components diagrams Case assembly Computer board assembly Th...

Page 82: ...7 707 707 102 121 119 118 707 707 109 112 106 111 105 113 113 104 103 108 107 113 110 101 114 115 116 113 113 117 707 707 102 121 119 118 707 707 109 112 106 111 105 113 113 104 103 108 107 113 110 10...

Page 83: ...Part 447 the T M50 and the T M50 ASME share the same components 3 132 133 136 135 137 402 401 403 404 406 407 408 409 410 411 113 412 413 414 415 113 416 405 402 401 403 404 406 407 408 409 410 411 11...

Page 84: ...406 430 434 3 433 425 438 437 436 435 113 411 420 419 427 426 418 420 428 421 419 419 426 427 411 411 411 419 431 411 418 430 Water way assembly 419 420 419 411 424 406 407 419 411 425 427 448 407 406...

Page 85: ...2 W Washer 101 EM445 Burner assembly 102 EKN74 Igniter T K3 T K3 Pro T K3 SP OS T H2 DV OS T KJr2 IN OS T K4 IN OS T D2 IN OS T M32 103 EKK0E Flame rod T K3 T K3 Pro T K3 SP OS T H2 DV OS T K4 IN OS T...

Page 86: ...T D2 IN OS 116 EKK2K Manifold gasket B T K3 T K3 Pro T K3 SP OS T H2 DV OS T KJr2 IN OS T K4 IN OS T D2 IN OS 117 EKK1B Igniter plate T K3 T K3 Pro T K3 SP OS T H2 DV OS T KJr2 IN OS T K4 IN OS T D2...

Page 87: ...ro T K3 SP OS T H2 IN OS T D2 DV OS T M32 404 EW00A Screw M3X6 405 EKK2T Output thermistor T K3 T K3 Pro T H2 DV OS T D2 IN OS T M32 406 EKH30 Fastener 4 11 T K3 T K3 Pro T H2 DV OS T D2 IN OS T M32 4...

Page 88: ...Connecting pipe 423 EM290 Left cold pipe for T M50 424 EKK38 Inlet thermistor T K3 T K3 Pro T H2 DV OS T D2 IN OS T M32 425 EX001 Heater 502 426 EX002 Heater 101 T H2 DV OS T M32 427 EK031 Heater fix...

Page 89: ...EZM18 O ring P18 FKM T M32 447 EM370 Connecting pipe for T M50 ASME 448 EM456 Left cold pipe for T M50 ASME 449 EM459 Left hot pipe for T M50 ASME 450 EM458 Right hot pipe for T M50 ASME 451 EM457 Ri...

Page 90: ...oller terminal 715 EM167 Wire cramp 60 T K3 T K3 Pro T K3 SP OS T H2 DV OS T KJr2 IN OS T K4 IN OS T D2 IN OS T M32 716 EM269 Left PCB fixing plate 717 EM270 Right PCB fixing plate 718 EM296 Transform...

Page 91: ...Changes Date 1 00 First edition 11 26 07 1 01 Revised by the R D and Takagi Japan 03 04 08 1 02 Revision of wrong information in section 12 14 07 02 08 1 03 Revised by the R D and Takagi Japan 08 11...

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