Troubleshooting Guide Non‐Condensing Models On‐Demand Water Heater Troubleshooting Guide 110 Indoor (T‐KJr2‐IN) 310 Indoor (T‐K4‐IN) 510 Indoor (T‐D2‐IN) 110 Outdoor (T‐KJr2‐OS) 310 Outdoor (T‐K4‐OS) 510 Outdoor (T‐D2‐OS) A.O.
Troubleshooting Guide Table of Contents Troubleshooting Guide 1. SPECIFICATIONS.……………………………………………………………………………..……………………3 2. INTRODUCTION.…………………………………………………………………………………..………………4 3. NORMAL OPERATION…………….………………………………………………………………………..…..5 Activation………………………………………………………………………………………………….5 Operation..………………………………………………………………………………………………..5 Shutdown……….………….………….……………………………………………………………..…..5 4. INSTALLATION….…………………………………………………………………………….…………………….6 Venting…………….………………………………………………………………………………..…..
Troubleshooting Guide 1.
Troubleshooting Guide 2. INTRODUCTION This manual provides the necessary information for troubleshooting the 110 (T‐KJr2), 310 (T‐K4), 510 (T‐ D2) tankless water heaters. It will be effective in helping your troubleshooting needs as long as the instructions are followed in the intended order. Here is how to use this manual: • • • • • First refer to the Installation Manual as the primary source of information. Refer to it along side this manual throughout the troubleshooting process.
Troubleshooting Guide 3. NORMAL OPERATION Becoming familiar with how a tankless water heater normally operates may help to figure out what is wrong with it. Assuming it is properly installed with appropriate gas, water, and electric connections, the following is how it should operate: 1) ACTIVATION a. A hot water tap is opened enough that the flow sensor detects a flow rate through the heater greater than the activation point of 0.75 gpm. b. The fan activates after flow is detected. c.
Troubleshooting Guide 4. INSTALLATION 1. Follow all local codes, or in the absence of local codes, follow the most recent edition of the National Fuel Gas Code: ANSI Z223.1/NFPA 54 in the USA or CAN/CSA B149.1 Natural Gas, Propane Installation Code in Canada. 2. All gas water heaters require careful and correct installation to ensure safe and efficient operation. This manual must be followed exactly. Read the “Safety Guidelines” section in the installation manual. 3.
Troubleshooting Guide 5. TROUBLESHOOTING 5.1 PRELIMINARY CHECKLIST Check all of these basic items before proceeding onto any other section: • GAS/WATER/ELECTRIC: o The gas supply valve should be fully open. o Verify the correct gas type is being used, NG or LP. o The water supply valve should be fully open. o The unit should be connected to a 120 VAC 60 Hz power supply. This can be verified by observing the computer board 3‐digit LED display. If it is not lit, the computer board is not being powered.
Troubleshooting Guide 5.2 TROUBLESHOOTING ‐ GENERAL PROBLEMS Proceed to the Error Codes section if an error code is identified. For other common problems that do not involve an error code, see if the following items help: The water is not hot enough. The water is too hot. Temperature fluctuates when a fixture is opened. Unit does not ignite when water goes through it. It takes a long time to get hot water at the fixtures. The fan motor is still spinning after operation has stopped.
Troubleshooting Guide • • The flow adjustment valve could be obstructed due to hard water scale or debris, causing lower than expected water flow. Verify water flow with a graduated container or with the remote temperature controller, if one is installed. The output thermistor could be compromised. This component may be checked by entering the Diagnostics Mode on a remote controller, if one is installed.
Troubleshooting Guide UNIT DOES NOT IGNITE WHEN WATER GOES THROUGH IT • • • • • • • • Is the flow rate over 0.75 gpm? See if the unit initiates when you increase demand of water being drawn through the unit (e.g. opening up more hot fixtures). Check that the gas line is open and is purged of air (p. 22). Check that the filter on the cold water inlet is clean (p. 21). Check for reverse connection and cross connection (p. 21).
Troubleshooting Guide UNIT HAS POWER, GAS, AND WATER BUT DOES NOT TURN ON • • • For new unit installs, check to make sure the unit is not plumbed in backwards. o Shut off cold water feed only. o Open nearest hot water tap. Water flow should stop. If not there is a cold water cross connection. o Open Pressure Relief Valve. Water flow should stop. If not unit is plumbed in backwards. Clean the filter (p. 21). If the fan never initiates, check for a fouled water flow sensor (p. 31).
Troubleshooting Guide 5.3 TROUBLESHOOTING ‐ ERROR CODES • • • All units are self diagnostic for safety and convenience when trouble shooting. If there is a problem with the installation or the unit, it will display a numerical error code on the Remote Controller (if installed), on the 7‐Seg LED on the computer board (510 (T‐D2)), or the flashing red LED (110 (T‐KJr2), 310 (T‐K4)) to communicate the source of the problem. Consult the following chart for the cause of each error code.
Troubleshooting Guide ERROR CODE 031 [510 (T‐D2)], ONE FLASH/03 [110 (T‐KJR2), 310 (T‐K4)] INCORRECT DIPSWITCH SETTINGS 1) Turn off the power supply. 2) Remove front cover and locate the dipswitches on the center of the computer board. 3) Check the dipswitch settings on the left and right banks. Refer to p.19 for the correct dipswitch positions. a. Gas type is a common dipswitch error. b. Most other switches should be on default setting UNLESS the particular setup requires otherwise. c.
Troubleshooting Guide 3) 4) 5) 6) 7) 8) gas meter. b. For propane units, colder periods of the day result in a cold regulator and may cause this problem. Verify that the gas supply pressure is within specifications when the heater is in standby and when the heater is running. Check that the clear plastic tube connecting the proportional gas valve to the combustion chamber is attached. The overheat cutoff fuse (OHCF) may have been compromised.
Troubleshooting Guide ERROR CODE 311 [510 (T‐D2)], TWO FLASHES/31 [110 (T‐KJR2), 310 (T‐K4)] 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. 21. b. Remove the fastener holding the output thermistor and pull out the sensor probe.
Troubleshooting Guide ERROR CODE 391 [510 (T‐D2)], TWO FLASHES/39 [110 (T‐KJR2), 310 (T‐K4)] AIR‐FUEL RATIO ROD FAILURE 1) Check that the wire connections are secure and free of burns or cuts. 2) Check that the clear plastic tube connecting the proportional gas valve to the combustion chamber is attached. 3) Clean the AFR (p. 25). Figure 10 ERROR CODE 441 [510 (T‐D2)] FLOW SENSOR Part of an Easy‐Link system (510 (T‐D2) only), the master unit signaled for an additional heater to activate and it did not.
Troubleshooting Guide ERROR CODE 611 [510 (T‐D2)], FOUR FLASHES/61 [110 (T‐KJR2), 310 (T‐K4)] ABNORMAL FAN MOTOR 1) Turn off power supply. 2) Check fan motor wiring for any breakages, burn marks on the PC board, or moisture. If moisture is found, allow connection to completely dry before turning power back on. 3) Check fan housing for water. If found, please dry the fan, then test heater. 4) To remove the fan motor. a. Turn off the power supply. b. Move the computer board out of the way. c.
Troubleshooting Guide ERROR CODE 721 [510 (T‐D2)], SIX FLASHES/72 [110 (T‐KJR2), 310 (T‐K4)] FALSE FLAME DETECTION 1) First and foremost, shut off all gas and power to the unit. The problem could be the flame sensor, but if it isn’t, this is a very dangerous situation. 2) Contact the Technical Service Department for further assistance.
Troubleshooting Guide 5.4 TROUBLESHOOTING ‐ PROCEDURES Verifying proper Dipswitch settings… p.19 Draining the unit………………………………p.21 Cleaning the filter…………………………….p.21 Checking for a Cross Connection………p.21 Check for Reverse Connection………….p.21 Check gas supply pressure………………. p.21 Purge the gas line of air………………….. p.22 Adjusting manifold pressure…………….p.22 Resetting the computer board………… p.23 Checking the OHCF…………………………. p.
Troubleshooting Guide Upper bank of dipswitches Lower bank of dipswitches Figure 16 Table 4 – 510 (T‐D2) Dipswitch Settings: UPPER BANK No. Function ON position OFF position 1 Gas type Propane Disable 2 Natural Gas Disable 3 Allow adjustments of fan motor speed Enable Disable (Default) 4 FM+, FM++, FM+++ Indoor 510 (T‐D2‐IN) No.4 5 OFF position ON position No.5 OFF position 0% +6% ON position +12% +18% Outdoor 510 (T‐D2‐OS) No.4 OFF position ON position No.
Troubleshooting Guide DRAINING THE UNIT: 1) 2) 3) 4) 5) Close the manual gas shut off valve. Turn off power to the unit, and then turn on again. Wait 30 seconds, and then turn off power to the unit, yet again. Close the cold water inlet shutoff valve. 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.
Troubleshooting Guide 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 activate. 7) Check the inlet gas pressure. Appropriate pressures are listed in the specification page at the front of this manual. PURGE THE GAS LINE OF AIR: 1) 2) 3) 4) The unit should not be running during this procedure. Turn off power to the unit. Turn the gas valve to the off position (perpendicular to the gas line).
Troubleshooting Guide ADJUSTING MANIFOLD PRESSURE: The manifold gas pressure of the tankless unit can be adjusted by the following procedure. WARNING Adjusting the manifold pressure can cause unexpected combustion conditions during operation, which can cause a health hazard, damage the tankless unit, and or shorten its lifespan. Therefore, changing the manifold pressure is not recommended unless there are very strong reasons to do so (e.g.
Troubleshooting Guide CHECKING THE OVERHEAT CUTOFF FUSE (OHCF): 1) Locate the white OHCF which wraps around the heat exchanger. 2) Find the white clip at the end of the two blue braided wires coming from the OHCF. 3) Unplug the connection. 4) Test for continuity at 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.
Troubleshooting Guide 6. MAINTENANCE Become familiar with the components before attempting these procedures, utilizing the Installation Manual and referencing the component schematic on the last few pages of the manual. Safety is the most important part of this guide. These procedures must be done by a licensed competent technician. A.O. Smith is not liable for the actions of the technician if he/she fails to adhere to any or all safety procedures, specifically in regards to electrical and gas safety.
Troubleshooting Guide CLEANING THE COMBUSTION COMPONENTS Procedure for cleaning the fan, burner, Flame Sensor and AFR, as used by all Service Representatives. 1) TOOLS ‐ Gather the following materials together: a. Degreaser in a pump action bottle, Sandpaper, Philips Screw Driver, Needle‐Nosed Pliers, Duct Tape, Flashlight, Air Compressor, Shop Vacuum, 3x Towels 2) POWER ‐ Disconnect power to your unit by either unplugging it from the wall outlet, or by the circuit breaker, depending on the setup.
Troubleshooting Guide 6) BURNER ASSEMBLY ‐ Now proceed to remove the burner assembly. a. Remove the five wide pan head Philips screws holding the burner to the combustion chamber. There are three at the top of the burner. There are two at the bottom of the burner to the back of the combustion chamber. b. Disconnect the rod assembly: Orange flame sensor, Yellow AFR, Black igniter wire c. Remove the burner. It may be hard to take out, so try the following: i.
Troubleshooting Guide 9) COMBUSTION CHAMBER ‐ Inspect the combustion chamber with a bright flashlight. a. Remove the exhaust venting from top of the unit for the DV model b. Place one towel at the bottom of the combustion chamber, protecting the discharge of the fan (fan port), as well as drape another towel covering the square opening of the combustion chamber (to prevent airborne debris) c. Turn on the shop vacuum and vacuum all of the dirt from the combustion chamber. d.
Troubleshooting Guide REPLACING THE HEAT EXCHANGER There are many possible causes of a heat exchanger failure: • Contaminated air with a high level of dust, lint, sand, grease, aerosols or other contaminants, can become airborne and enter the air intake. The contaminants build up within the fan and burner assembly causing abnormal flame conditions due to lack of combustion air, damaging many components of the unit. • Scale can build up from very hard water.
Troubleshooting Guide 5) FAN a. The fan is held in by two screws. They face the bottom of the heater, and can be reached by two holes in the bottom of the case with a long screwdriver. b. Slide it left to release it from the grooves. 6) WATERWAYS a. If the unit has not been drained at this point, now is the time to do so. Refer to the Draining the Unit procedure in the troubleshooting procedures section. b. Disconnect the waterway clips pictured at the right. c.
Troubleshooting Guide CHECKING THE FLOW SENSOR If the tankless unit is properly connected to water, gas, and power supplies but the fan motor does not initiate when water is run through it, the flow sensor is most likely not working properly and not telling the PC Board to initiate. 1) TOOLS ‐ Gather the following materials together: a. Degreaser in a pump action bottle b. #2 Philips Screw Driver c. Flashlight d. Old Towels, at least three 2) PREPARE THE UNIT – a.
Troubleshooting Guide DESCALING THE UNIT Hard water is a severe problem for the copper coils inside heat exchangers. Heat exchanger failure due to scale buildup from hard water conditions is NOT covered by warranty. It is highly suggested that a scale inhibitor be installed before the cold water inlet after this procedure is done. 1) TOOLS ‐ Gather the following materials together: a. Pump: The pump should provide a minimum of 1GPM through the heater b.
