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A.O. Smith AGT-705-NE Service manual

Other manuals for AGT-705-NE: Design Manual
Manual is about: On-Demand Gas Tankless Water Heater Service Manual Series 100/101 & Series 200/201

Summary of AGT-705-NE

  • Page 1

    Printed 0709 316437-001 on-demand gas tankless water heater service manual service information for single and multiple unit installations for residential, commercial, recirculation and storage tank systems. Ati-305-n gts-305-ni gt-305-ni ati-305-p gts-305-pi gt-305-pi ato-305-n gts-305-ne gt-305-ne ...

  • Page 2: Table of Contents

    Table of contents general information................................................3-5 specifications.........................................................6, 7 schematic diagrams..............................................8, 9 fault isolation......................................................

  • Page 3: General Information

    General information safety definitions this is the safety alert symbol. This symbol alerts you to potential hazards that can kill or hurt you and others. Indicates an imminently hazardous situation which, if not avoided, will result in death or serious injury. Indicates a potentially hazardous situa...

  • Page 4: General Information

    General information on-demand gas tankless water heater service manual 4 service information the on-demand water heaters must be installed according to all local and state codes or, in the absence of local and state codes, the “national fuel gas code”, ansi z223.1 (nfpa 54) - current edition. Csa am...

  • Page 5: General Information

    General information on-demand gas tankless water heater service manual 5 closed system/thermal expansion caution - property damage hazard as water is heated, it expands (thermal expan- sion). In a closed system, the volume of water will grow. As the volume of water grows, there will be a correspondi...

  • Page 6: Specifications

    Specifications model number temperature range 305 15,000 - 199,000 ng 15,000 - 190,000 lp 705/705 asme indoor (i) on-demand gas tankless water heater service manual 6 input min. - max. (btu) flow rate hot water capacity @ 45°f temp. Rise 0.6 - 5.3 gpm (2.3 - 20.1 lpm) 5.3 gpm (20.1 lpm) efficiency r...

  • Page 7: Specifications

    Specifications model number temperature range 305 indoor (i) on-demand gas tankless water heater service manual 7 input min. - max. (btu) flow rate hot water capacity @ 45°f temp. Rise 0.6 - 7.5 gpm (2.3 - 28.4 lpm) efficiency rating 84% 505 15,000 - 199,000 ng 15,000 - 190,000 lp 0.6 - 9.4 gpm (2.3...

  • Page 8: Schematic Diagrams

    Schematic diagrams outdoor model (not present on all models) (located on bracket near fan on some models) (not present on all models) on-demand gas tankless water heater service manual 8.

  • Page 9: Schematic Diagrams

    Schematic diagrams indoor model (not present on all models) (not present on all models) (located on bracket near fan on some models) on-demand gas tankless water heater service manual 9.

  • Page 10: Fault Isolation

    Fault isolation some of the checks below may need to be done by a qualified service technician. Call a service technician for any remedy that involves gas or electricity. Call a service technician if you have any doubt or reservation about performing the remedy yourself. Warning accessing operating ...

  • Page 11: Fault Isolation

    Fault isolation code fault remedy 02 no burner operation during freeze protection mode service call - check for possible freeze damage to heat exchanger. 10 air supply or exhaust blockage ensure approved venting materials are being used. Check that nothing is blocking the flue inlet or exhaust. Chec...

  • Page 12: Fault Isolation

    14 thermal fuse check gas type of unit and ensure it matches gas type being used. Check for restrictions in air flow around unit and vent terminal. Check for low water flow in a circulating system causing short-cycling. Ensure dip switches are set to the proper position. Check for foreign materials ...

  • Page 13: Electrical Diagnostic Points

    Electrical diagnostic points wire color voltage resistance connector no. Pin no.’s (sv1, sv2, sv3, pov) gas valve and modulating solenoids (main) pink - black 11 - 13 vdc 36.8 - 44.8 ohms h5 6 ~ 7 6 ~ 5 6 h w o ll e y - k c a l b ) 1 v s ( 6 ~ 4 7 h e u l b - k c a l b ) 2 v s ( 6 ~ 3 8 h n w o r b ...

  • Page 14: Electrical Diagnostic Points

    Electrical diagnostic points wire color voltage resistance connector no. Pin no.’s thermal fuse / overheat switch red - red 11 - 13 vdc below 1 ohm f6 h1 f6 ~ h12 flame rod place one lead of the meter to the flame rod and the other to ground. With the unit running, 5-150 vac should be read. Set the ...

  • Page 15: Electrical Diagnostic Points

    Electrical diagnostic points wire color voltage resistance connector no. Pin no.’s (sv1, sv2, sv3, pov) gas valve and modulating solenoids (main) pink - black 11 - 13 vdc 24 - 28 ohms h3 6 ~ 7 6 ~ 5 4 h d e r - k c a l b ) 1 v s ( 6 ~ 4 5 h e g n a r o - k c a l b ) 2 v s ( 6 ~ 3 6 h w o ll e y - k ...

  • Page 16: Electrical Diagnostic Points

    Electrical diagnostic points wire color voltage resistance connector no. Pin no.’s thermal fuse / overheat switch red - white 11 - 13 vdc below 1 ohm f6 h1 f6 ~ h12 flame rod place one lead of the meter to the flame rod and the other to ground. With the unit running, 5-150 vac should be read. Set th...

  • Page 17: Wiring Diagram

    Wiring diagram 305e/o, 305i, 505e/o, 505i color coding w :white bk:black br:brown r :red bl:blue y :yellow p :pink o :orange g :green gy:gray 1 3 br 3 1 b 1 2 o f f dip sw1 3 8 7 6 5 4 f 5 w w b 1 bk bk min max modulating valve current adjusting gas pressure f 4 w w w p w w outgoing water thermistor...

  • Page 18: Wiring Diagram

    Wiring diagram 705e/o (asme), 705i (asme) a 3 1 w 3 1 b 1 2 o f f dip sw 1 3 8 7 6 5 4 f 4 w w b 1 bk bk mi n ma x m o dula ti n g v al ve curre nt a d ju st in g ga s p re ss ur e f 3 w w w p w w ou tg o in g w at er w ater ther m isto r heat exc han g er w ate r th er m is to r y br o r w br r o y...

  • Page 19: Flushing The Heat Exchanger

    An “lc” or “00” error code indicates the unit is beginning to lime up and must be flushed. Failure to flush the appliance will cause damage to the heat exchanger. Damage caused by lime build-up is not covered by the unit’s warranty. After flushing, reset the lc fault code by turning off the power to...

  • Page 20: Warning

    Component replacement instructions ignition line six screws wire harness connector pc board (dip switches) three screws 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Remove four screws securing the front panel. Remove front panel. 4. Pull out wire harness connector at the gas ma...

  • Page 21

    Component replacement instructions 13. Install the gas manifold using 2 new packings (included in kit) between the manifold and the heat exchanger. Replace the two circular gaskets (included in kit) in the gas valve (figure 5). 14. Start the three screws that attach the gas manifold to the gas valve...

  • Page 22

    Component replacement instructions 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Remove four screws securing the front panel. Remove front panel. 4. On indoor models, remove the bracket holding the controller (1 screw). (figure 6) 5. Move aside the ignition line by pulling it ou...

  • Page 23: Warning

    Component replacement instructions figure 10 black / orange orange / orange figure 9 warning failure to correctly assemble the components according to these instructions could result in a gas leak or explosion. 12. Pull out the gas control assembly. Remove the wire harness from the 2 solenoids. 13. ...

  • Page 24

    Component replacement instructions 305e/o, 505e/o 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. 4. Remove four screws securing the front panel. Remove front panel. 5. Disconnect wire harness at the fan assembly. Disconnect the air temperature thermisto...

  • Page 25

    Component replacement instructions 305i, 505i 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. 4. Remove four screws securing the front panel. Remove front panel. 5. Disconnect wire harness at the fan assembly. Disconnect the air temperature thermistor (t...

  • Page 26

    Component replacement instructions 705e/o (asme), 705i (asme) 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. 4. Remove four screws securing the front panel. Remove front panel. 5. On indoor models, remove the bracket holding the controller (1 screw). (f...

  • Page 27

    1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. 4. Remove four screws securing the front panel. Remove front panel. 5. Remove the plastic guard covering the front of the pc board. 6. Remove the controller connections. 7. If a surge protector with termina...

  • Page 28

    Propane (lpg) natural gas (ng) sw2 setup for 505i switch no. F o f 5 6 4 3 on 1 2 switch no. F o f 5 6 4 3 on 1 2 switch no. F o f 5 6 4 3 on 1 2 switch no. F o f 5 6 4 3 on 1 2 component replacement instructions switch no. F o f 5 6 4 3 on 1 2 switch no. F o f 5 6 4 3 on 1 2 propane (lpg) natural g...

  • Page 29

    Component replacement instructions 705e/o (asme), 705i (asme) 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Remove four screws securing the front panel. Remove front panel. 4. Remove the surge protector (2 screws) 5. Remove the 2 screws connecting the pc board to the water heate...

  • Page 30: Notice

    Component replacement instructions 305e/o, 305i, 505e/o, 505i 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. Drain all water from the appliance. 4. Remove four screws securing the front panel. Remove front panel. 5. Remove 1 screw and bracket at the wat...

  • Page 31

    Component replacement instructions assemble a.Water flow sensor harness (black/yellow/red wires) b.Water flow servo harness (red/blue/brown/yellow/gray or red/blue/brown/orange/yellow/gray wires) c.Heating element 7. Pull out the water flow servo assembly and disconnect the cable harnesses. (figure ...

  • Page 32: Notice

    Component replacement instructions 505e/o, 505i 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. Drain all water from the appliance. 4. Remove four screws securing the front panel. Remove front panel. Remove fan assembly (figure 20) 5. Disconnect wire har...

  • Page 33

    Component replacement instructions 11. Remove the 4 screws attaching the water inlet to the underneath side of the water heater. A. Water flow sensor harness (black/yellow/red wires) b. Bypass servo assembly harness (white/red/yellow/orange/brown wires) c. Water flow servo harness (red/blue/brown/ye...

  • Page 34

    Component replacement instructions 705e/o (asme), 705i (asme) 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. Drain all water from the appliance. 4. Remove four screws securing the front panel. Remove front panel. 5. Remove 2 screws and 2 brackets at the...

  • Page 35

    Component replacement instructions 305e 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. Drain all water from the appliance. 4. Remove four screws securing the front panel. Remove front panel. Remove fan assembly (figure 29) 5. Disconnect wire harness at ...

  • Page 36

    Component replacement instructions 305e disconnect pc board (figure 31) 11. Remove 1 screw connecting the pc board to the heat exchanger assembly. 12. Remove the 6 screws that attach the gas manifold to the combustion chamber (part of the heat exchanger assembly). 13. Remove the 3 screws that attach...

  • Page 37: Warning

    Component replacement instructions 305e 21. Install the largest o-ring (included in kit) over the water outlet tube and the two smaller o-rings (included in kit) over the bypass servo tubes. (figure 30) 22. Remove any other attached items and install on the new heat exchanger. 23. Install the new he...

  • Page 38

    Component replacement instructions 505e/o 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. Drain all water from the appliance. 4. Remove four screws securing the front panel. Remove front panel. Remove fan assembly (figure 37) 5. Disconnect wire harness a...

  • Page 39

    Component replacement instructions disconnect pc board (figure 39) 11. Remove 1 screw connecting the pc board to the heat exchanger assembly. 12. Remove the 6 screws that attach the gas manifold to the combustion chamber (part of the heat exchanger assembly). 13. Remove the 3 screws that attach the ...

  • Page 40: Warning

    Component replacement instructions 20. Remove 2 screws above the exhaust. Pull assembly from the unit. (figure 42) 21. Install the largest o-ring (included in kit) over the water outlet tube and the two smaller o-rings (included in kit) over the bypass servo tubes. (figure 38) 22. Remove any other a...

  • Page 41

    Component replacement instructions 305i 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. Drain all water from the appliance. 4. Remove four screws securing the front panel. Remove front panel. 2 screws wire harness connection on the fan assembly solenoid ...

  • Page 42

    Component replacement instructions ignition line 6 screws (gas manifold) pc board screw 3 machine screws (gas valve) 13. Remove the 6 screws that attach the gas manifold to the combustion chamber (part of the heat exchanger assembly). 14. Remove the 3 screws that attach the gas manifold to the gas v...

  • Page 43: Warning

    Component replacement instructions 19. Remove the wire harness attachments - sensors, heating elements, fusible link brackets. Ensure that the small o-ring in the thermistor is removed. Disconnect wire harness attachments remove heat exchanger and air intake/exhaust 20. Remove 8 screws connecting th...

  • Page 44

    Component replacement instructions 26. Install the o-ring (included in kit) over the water outlet tube and the o-ring (included in kit) over the water flow servo tube. (figure 45) 27. Install the bracket over the replacement heat exchanger. Push evenly on both sides of the bracket. Attach with four ...

  • Page 45

    Component replacement instructions 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. Drain all water from the appliance. 4. Remove four screws securing the front panel. Remove front panel. Remove fan assembly (figure 56) 5. Disconnect wire harness at the f...

  • Page 46

    Component replacement instructions disconnect pc board (figure 58) 10. Remove 1 screw from the water outlet bracket. Remove the bracket by rotating and moving it up toward the bend in the tube where the diameter is smaller. 11. Remove 2 screws and 2 brackets at the bypass servo assembly. Disconnect ...

  • Page 47

    Component replacement instructions 505i remove burner and burner cover plate (figure 59) 16. Remove the 8 screws attaching the burner cover plate to the combustion chamber. Move the cover plate to the side. It is not necessary to disconnect the wire harness from the burner cover plate. 17. Remove th...

  • Page 48: Warning

    Component replacement instructions 505i remove heat exchanger and air intake/exhaust 20. Remove 8 screws connecting the assembly to the water heater casing assembly. (figures 61, 62) separate the heat exchanger from the air intake/exhaust 21. Pull out the assembly. Remove 3 brackets on the side and ...

  • Page 49

    Component replacement instructions combine the heat exchanger and the air intake/exhaust 28. Push the heat exchanger into the air intake/exhaust assembly. Attach with four screws. (figure 64) 29. Attach the cover plate over the air intake passage with 9 screws. (figure 63) install heat exchanger and...

  • Page 50

    Component replacement instructions 705e/o (asme) 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. Drain all water from the appliance. 4. Remove four screws securing the front panel. Remove front panel. 5. Disconnect wire harness at the fan assembly, the e...

  • Page 51

    Component replacement instructions 15. Remove the fan assembly (4 screws) and install it on the new heat exchanger. (figure 71) 16. Remove the flue outlet (6 screws) and install it on the new heat exchanger. (figure 72) 17. Install the largest o-ring (included in kit) over the water outlet tube and ...

  • Page 52

    Component replacement instructions 705i (asme) 1. Turn off the gas supply. 2. Turn off the 120 v power supply. 3. Turn off the water supply. Drain all water from the appliance. 4. Remove four screws securing the front panel. Remove front panel. 5. Remove the bracket holding the controller (1 screw)....

  • Page 53

    Component replacement instructions 14. Remove the 3 screws at the seal plate at the top of the water heater. Remove the seal plate and gasket. (figure 79) 15. Remove flue outlet vent (4 screws). (figure 80) 16. Remove the 4 screws connecting the heat exchanger to the back of the casing. (figure 81) ...

  • Page 54

    Component replacement instructions 24. Insert the burner and place the burner cover plate into position. Attach the burner cover plate first with 9 screws and then attach the burner with 2 screws. (figure 78) 25. Replace the electrode gasket. (figure 83) 26. Make sure that the black gasket (figure 8...

  • Page 55: Caution

    Gas pressure setting procedure 1. Remove the front panel (four screws). 2. Calibrate the low fire and high fire settings as follows: a. Remove the allen head plug and attach the manometer to the burner test point located on the gas control (figure 86 or 87). Caution do not touch the areas at or near...

  • Page 56

    Figure 89 forced low switch no. F o f 8 5 7 6 4 3 on 1 2 figure 90 forced high switch no. F o f 8 5 7 6 4 3 on 1 2 figure 91 normal switch no. F o f 8 5 7 6 4 3 on 1 2 figure 88 access plug b. Turn on the gas supply. C. Turn on the power supply. D. Flow water through the water heater at the maximum ...

  • Page 57

    Manifold gas pressure settings 100/101 and 200/201 series altitude high fire low fire high fire low fire 305e/o 2.9 0.56 4.2 0.88 505e/o 3.3 0.56 5.1 0.88 705e/o (asme) 2.8 0.65 3.8 0.80 305i 2.7 0.52 4.4 0.92 505i 3.3 0.52 5.0 0.92 705i (asme) 3.0 0.67 3.7 0.83 less than 10200 ft (3109 m) natural g...

  • Page 58: Dip Switch Settings

    0-2000 ft (0-610 m) 2001-5200 ft (610-1585 m) 5201-7700 ft (1585-2347 m) 7701-10200 ft (2347-3109 m) #2: off #2: off #2: on #2: on #3: off #3: on #3: off #3: on dip switch settings 100/101 and 200/201 series sw1 bank sw2 bank (present on replacement pc boards only) off - 305e, 305i, 505e, 505i, 705e...

  • Page 59: Notes

    Notes on-demand gas tankless water heater service manual 59.

  • Page 60

    • 500 tennessee waltz parkway • ashland, tn 37015 •.