A.O. Smith T-H2S-DV, Troubleshooting Manual

Page 1: ...2 000 A O Smith Water Products Company 500 Tennessee Waltz Parkway Ashland City TN 37015 Toll Free 1 877 737 2840 Outdoor models 520 Outdoor T H2 DV 320 Outdoor T H2S DV Direct Vent Indoor models 520 Indoor T H2 DV 320 Indoor T H2S DV http waterheatertimer org Troubleshoot Rheem Tankless water heater html ...

Page 2: ...oblems 9 Error Codes 13 Procedures 22 Verifying proper Dipswitch settings 22 Draining the unit 23 Cleaning the filter 23 Checking for a Cross Connection 24 Check for Reverse Connection 24 Check gas supply pressure 24 Purge the gas line of air 24 Adjusting manifold pressure 25 Resetting the computer board 26 Checking the OHCF 26 6 MAINTENANCE 27 Rod Assembly 27 Burner Rod Assembly 28 Heat Exchanger...

Page 3: ... F 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 Out Mixing Exhaust 3 thermistors In Out Mixing 4 thermistors In Out Mixing Exhaust 3 thermistors In Out Mixing Operation Remote controller model Part 9007603005 TM RE30 PCB model T H2 Part 319143 126...

Page 4: ... the procedures consult with the technical service department or the local service agent IMPORTANT Installation and service must be performed by a qualified installer for example a licensed plumber or gas fitter Otherwise the warranty will be void The installer service agent licensed professional is responsible for correctly installing or servicing your water heater and for compliance with all nat...

Page 5: ...epending on the set temperature 2 OPERATION a The proportional gas valve will modulate based on the amount of hot water demanded and the temperature rise needed The fan speed will modulate as well to create an efficient burn b You will notice that only partial sections of the burner will be lit This is normal operation there are three sections on the burner assembly and the computer controls the a...

Page 6: ...ting length maximums Table 2 Diameter Max No of Elbow Max Vertical Horizontal Total Vent Length 3 2 25 ft 4 5 50 ft The venting may consist of Schedule 40 PVC CPVC ABS or Category III Stainless Steel In Canada Plastic venting requires ULC S636 Certified materials Direct Vent combustion air intake is very important o Install the Direct Vent air intake opening in an area that is free of airborne deb...

Page 7: ...less water heater requires a inch connection to the cold water inlet and hot water outlet Tankless water heaters all require a Pressure only relief valve PRV on each individual unit rated for 150 psi with a discharge capacity of at least the rated gas input of the water heater 199 000 BTU h to be installed per local code Install a CSA AGA approved isolation valve on each heater on all three inlets...

Page 8: ...hardness or 70 140ppm one must be installed If there is no water softener installed existing installations will gradually accumulate scale buildup on the heat exchanger and cause a leak Heat exchanger leaks due to hard water scale are not covered under the warranty NEW INSTALLATIONS Is this installation a few years old or brand new o A unit that has worked properly for a while but is now strugglin...

Page 9: ... Check for cross plumbing between cold water lines and hot water lines See the Procedures section p 24 for instructions Unit may be hard water scaled The scale acts as an insulator preventing the heat exchanger from transferring heat to the water Contact a service agent The unit may not be receiving enough gas o The gas supply valve may not be fully open o The gas line may be sized improperly o Th...

Page 10: ...ot or chattering Check the directional indicator on the pump flange Check the sizing of the pump a minimum flow of 2 gpm is required Check gas supply o Verify the gas supply lines are sized for the maximum Btu h demand as indicated in the Proper Installation section p 6 of this guide If the gas supply line is shared with other appliances it should be sized to account for those appliances as well T...

Page 11: ...reaker or wire nut IT TAKES A LONG TIME TO GET HOT WATER AT THE FIXTURES The time it takes to deliver hot water from the unit to your fixtures depends on the length of piping between the two The longer the distance or the bigger the pipes the longer it will take to get hot water If this is the case and you would like to receive hot water to your fixtures quicker you may want to consider a hot wate...

Page 12: ...water cross connection o Open Pressure Relief Valve Water flow should stop If not unit is plumbed in backwards Clean the filter p 23 If the fan never initiates check for a fouled water flow sensor p 34 EASY LINK SYSTEM SETUP MULTIPLE HEATER SETUP Unit Numbering o Refer to the installation manual for proper setup o The master unit will always be assigned number 1 The remaining units will be randoml...

Page 13: ...if installed displays a 3 digit number which signifies which unit has the error and what the error code is Table 3 Error Codes Error Symptom Error Symptom Error Symptom 031 Incorrect Dipswitch Settings 391 Air fuel Ratio Rod Failure 661 Abnormal Water Bypass Valve 101 Warning for 991 Error Code 441 Flow Sensor 701 Proportional Valve Computer 111 Ignition Failure 510 Abnormal Main and Solenoid Gas ...

Page 14: ... in the OFF position right and the communication wires will be attached to the slave in out plugs ERROR CODE 101 ABNORMAL COMBUSTION 1 Blockage in the airway Check the following areas a Venting length obstruction Birds nests trash etc b Backflow preventer installed backwards c Heat exchanger d Fan 2 Check the manifold pressure p 25 Adjust the manifold pressure to the correct values if necessary 3 ...

Page 15: ...romised For procedures on how to check whether the OHCF is intact refer to p 26 If the OHCF has been compromised contact the technical service department for further assistance 6 If flame comes on for only 1 2 seconds before going out clean the flame sensor p 27 7 Check the igniter for a spark The spark may be viewed through the sight glass located next to the igniter and flame sensor a A strong b...

Page 16: ...chnical service department ERROR CODE 311 OUTPUT THERMISTOR 1 Check that the wire connections are secure and free of burns or cuts The output thermistor is located on the heat exchanger on the right side 2 Check the resistance value it should be about 9 0kΩ at room temperature about 74 F 3 Clean the thermistor a Drain the unit of water See p 23 b Remove the fastener holding the output thermistor a...

Page 17: ... 4 If the error code persists replace the thermistor ERROR CODE 341 EXHAUST THERMISTOR 1 Check that the wire connections are secure and free of burns or cuts The exhaust thermistor is embedded at the top center of the unit above the heat exchanger 2 Check the resistance of the thermistor The value should be about 10 75kΩ at room temperature about 74 F 3 Clean the thermistor a Remove the screw hold...

Page 18: ...fied limits Too high of an inlet gas pressure may cause the main gas valve to jam or could be damaged ERROR CODE 551 ABNORMAL SOLENOID GAS VALVE Driving circuit fault for the solenoid gas valve 1 If the hot water is shut off but flames are still visible through the sight glass immediately shut off gas and power to the unit and contact the technical service department 2 Check the wire connections t...

Page 19: ...fan c Locate and remove the four Phillips head screws around the fan motor to the combustion chamber box d The fan motor should be free to be removed e If signs of water or debris are evident water may have damaged the fan motor requiring replacement 5 If the 621 error code still appears after all items have been checked the PCB may need replacement ERROR CODE 631 ABNORMAL EXTERNAL PUMP This error...

Page 20: ...alve may need to be replaced if the valve cannot be cleaned ERROR CODE 701 PROPORTIONAL GAS VALVE COMPUTER 1 Turn off the power supply 2 The proportional valve is located at the bottom of the gas valve assembly with a red and white wires connecting to it 3 Check all wire connections and make sure they are secure and free of burns or cuts 4 Inspect the PCB for connection breakage of wires and or bu...

Page 21: ...in a multiple heater setup where there is a miscommunication between master and slave units for Easy Link systems 2 This error code will only be displayed on the master heater 3 This error indicates that the master unit has lost communication with the indicated heater 4 Verify that there is power to the unit that has lost communication 5 See the Installation Manual for proper communication cable s...

Page 22: ...ipswitches No Function ON position OFF position 1 Gas type Propane Disable 2 Natural Gas Disable 3 N A N A N A Default 4 Allow adjustments of fan motor speed Similar procedure to changing manifold pressure Enable Disable Default 5 FM FM FM Fan motor for combustion No 5 OFF position ON position No 6 OFF position 0 6 ON position 12 18 Fan motor for exhaust Indoor models only No 5 OFF position ON pos...

Page 23: ...2 Turn off power to the unit and then turn on again 3 Wait 30 seconds and then turn off power to the unit yet again 4 Close the cold water inlet shutoff valve 5 Open all hot water taps in the house or open the pressure relief valve to remove the initial pressure When the residual water flow has ceased close all hot water taps 6 Unscrew the drain plugs hot water outlet drain plug and cold water inl...

Page 24: ...shuts down due to lack of gas and then shut the faucet off Ignore any error codes that may occur at this time 3 Remove the screw for the pressure port located on the gas inlet shown on the right 4 Connect a manometer to the pressure port 5 Slowly re open the manual gas valve Check to see that there are no gas leaks 6 Open some of the fixtures that use the highest flow rate to turn on the unit 7 Ch...

Page 25: ...procedures Adjusting the manifold pressure can cause unexpected combustion conditions during operation which can cause a health hazard damage the 520 T H2 or 320 T H2S and or shorten its lifespan Therefore changing the manifold pressure is not recommended unless there are very strong reasons to do so e g high elevation installations and with the consultation of the Technical Service Department 1 S...

Page 26: ...the end of the OHCF with an ohmmeter If there is continuity the OHCF is still intact Reconnect the plug If there is no continuity the OHCF has been compromised If compromised contact the technical service department for further assistance 5 If an ohmmeter is not available jump the plug connection on the opposite side of the OHCF with a wire paper clip or other metal material 6 Restore power and te...

Page 27: ...etup The 3 digit LED on the PCB should not be lit 3 FRONT COVER Remove the front cover It is held on by two screws on the top corners of the tankless unit 4 ROD ASSEMBLY a Locate the black yellow and orange wires located in the center of the unit b Remove the three Phillips head screws holding the panel in place c Pull the assembly out Caution all pieces are separate Be careful to not lose the sig...

Page 28: ... Remove the front cover 5 COMPUTER BOARD a Remove the three screws all wire clip connections and move the computer board out of the way b Disconnect the three rods on the front face of the burner flame sensor orange wire AFR yellow wire and igniter black wire 6 MANIFOLD PLATE GAS VALVE ASSEMBLY a Remove the manifold plate screws They are wide pan head Philips screws located on the edges of the sta...

Page 29: ...sed please contact the technical service department for further assistance b Thoroughly saturate the burner with the cleaning solution from the top down through the slots as well as the openings in the front of the burner until the burner is soaking wet c Let the burner sit for 5 minutes d Remove the burner from the solution Set the burner in a sink in its normal upright position and wash the burn...

Page 30: ... white crusty solid buildup in the heat exchanger please contact the technical service department for further instruction 12 SENSORS a Clean the flame sensor and AFR with sandpaper thoroughly to a bright finish It is important to be very gentle with the sensor rods while cleaning them as they will easily bend out of place Their original position relative to the burner needs to be unaltered in orde...

Page 31: ...together a Degreaser in a pump action bottle b Sheet of 100 Grit Sandpaper c 2 Philips Screw Driver d Needle Nosed Pliers e Duct Tape f Flashlight g Air Compressor h Old Towels at Least Three 2 PREPARE THE UNIT a POWER Disconnect power to your unit b GAS Shut off the gas supply to the unit c WATER Drain the unit Refer to p 23 for instructions 3 REMOVE PC BOARD MANIFOLD GAS ASSEMBLY BURNER a Follow...

Page 32: ...drain clip on the left b Remove the two clips below the water control valve 8 REMOVE THE HEAT EXCHANGER a Remove the seven screws from the perimeter of the secondary heat exchanger front plate Bend the tab on the left to slide the plate out b FOR DV MODEL remove the 5 screws from the back of the combustion chamber connecting it to the exhaust fan air intake c The heat exchanger should be free to r...

Page 33: ... Plastic pressure port v Hi Limit switch vi Hot water thermistor 10 REASSEMBLE Reassemble the unit in reverse order Key points to remember a All wires must be reconnected Keep wires dangling out in front of the unit never push them toward the back where they are not visible you will forget about them b Inspect all of the gaskets c Be aware of the various O rings on the gas and water valves along w...

Page 34: ... above the flow sensor by pushing on the tabs to pop them off one on each side of the flow sensor 5 CHECKING THE FLOW SENSOR a Check for functionality Flow rate is determined by an impeller that spins as fluid runs through it b Blow into the inlet of the flow sensor Listen for the spinning impeller it should spin freely for a few seconds If it comes to rest abruptly or doesn t spin at all it needs...

Page 35: ... closing the incoming outgoing water isolation valves C and D b Connect hoses pump to the drain ports of the isolation valves Outlet of the pump to valve B and another hose from Valve A to the bucket 4 PUMP a Fill the bucket with 5 gallons of diluted solution Dilution ratio depends on the cleaning solution used b Place the pump into the bucket if it is submersible or use an inlet hose into the buc...