A.O. Smith XWH 150 Service Handbook

Commercial gas water heaters

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Service Handbook

COMMERCIAL GAS WATER HEATERS

FOR MODELS:

XWH 150 THRU 800

INSTALLATION CONSIDERATIONS - PRE SERVICE CHECKS -

CONSTRUCTION - OPERATION & SERVICE - TROUBLESHOOTING

500 Tennessee Waltz Parkway

Ashland City, TN 37015

SERVICING SHOULD ONLY BE PERFORMED BY A QUALIFIED SERVICE TECHNICIAN

PRINTED IN THE U.S.A. 1119

100274940_2000534998_Rev B

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Page 1 Service Handbook COMMERCIAL GAS WATER HEATERS FOR MODELS: XWH 150 THRU 800 INSTALLATION CONSIDERATIONS - PRE SERVICE CHECKS - CONSTRUCTION - OPERATION & SERVICE - TROUBLESHOOTING 500 Tennessee Waltz Parkway Ashland City, TN 37015 SERVICING SHOULD ONLY BE PERFORMED BY A QUALIFIED SERVICE TECHNICIAN PRINTED IN THE U.S.A.
Page 2: Table Of Contents
TABLE OF CONTENTS INTRODUCTION ..................2 Qualiﬁ cations ..................2 Service Warning ...................2 Service Reminder .................2 Tools Recommended ................2 INSTALLATION CONSIDERATIONS ............3 Instruction Manual ................3 Closed Water Systems .................3 Thermal Expansion ................3 Air Requirements ..................3 Contaminated Air ..................3 PLEASE READ BEFORE PROCEEDING..........4 Handling Ceramic Fiber Materials ............4 USER INTERFACE MODULE (UIM)/ TOUCH SCREEN DISPLAY ..5 CONTROL INPUTS ...................6...
Page 3: Introduction
INTRODUCTION This Service Handbook covers the water heater Model and Series numbers listed on the front cover only. The instructions and illustrations contained in this service handbook will provide you with troubleshooting procedures to verify proper operation and diagnose and repair common service problems. QUALIFICATIONS QUALIFIED INSTALLER OR SERVICE AGENCY Installation and service of this water heater requires ability equivalent to that of a Qualiﬁ...
Page 4: Installation Considerations
INSTALLATION CONSIDERATIONS This section of the Service Handbook covers some of the critical installation requirements that, when overlooked, often result in operational problems, down time and needless parts replacement. Costs to correct installation errors are not covered under the limited warranty. Ensure all installation requirements and instructions contained in the Instruction Manual that came with the water heater have been followed prior to performing any service procedures.
Page 5: Please Read Before Proceeding
PLEASE READ BEFORE PROCEEDING Installer – Read all instructions, including this Service Handbook and the XP Water Heater Instruction Manual, before installing. Perform steps in the order given. Have this water heater serviced/inspected by a qualiﬁ ed service technician at least annually. Failure to comply with the above could result in severe personal injury, death or substantial property damage.
Page 6: User Interface Module (Uim)/ Touch Screen Display
USER INTERFACE MODULE (UIM)/ TOUCH SCREEN DISPLAY A. O. Smith XP Tank Temperature 71°F LCD Touch Status Icons Operating Setpoint 184°F Screen Display Status: Ignition MENU DISABLE HELP Main Menu Enable / Disable / Reset Help Menu Button Figure 1. User Interface Module (UIM)/ Touch Screen Display Servicing should only be performed by a Qualiﬁ...
Page 7: Control Inputs
CONTROL INPUTS GAS PRESSURE SWITCH DHW THERMOSTAT LOW VOLTAGE FLOW SWITCH CONNECTION BOARD TANK SENSOR SEQUENCER / BUILDING MANAGEMENT SYSTEM LOW WATER CUTOFF O-TEMP HEAT EXCHANGER SWITCH INLET TEMPERATURE CONTROL BOARD SENSOR OUTLET TEMPERATURE SENSOR FLUE GAS SENSOR AIR PRESSURE SWITCH DAMPER PROVING SWITCH FLAME SENSOR BLOCKED CONDENSATE...
Page 8: Control Outputs
CONTROL OUTPUTS ALARM BELL LOW VOLTAGE DAMPER RELAY CONNECTION BOARD RUN TIME CONTACTS SEQUENCER / BUILDING MANAGEMENT SYSTEM BUILDING RECIRCULATION CONTROL BOARD PUMP WATER HEATER PUMP IGNITER BLOWER GAS VALVE TOUCH SCREEN DISPLAY AIN ADAPTER CABLE Figure 3. UIM Control Outputs Servicing should only be performed by a Qualiﬁ...
Page 9: General Operation
GENERAL OPERATION HOW THE WATER HEATER OPERATES The XP water heater uses an advanced stainless steel heat exchanger and an electronic control module that allows fully condensing operation. The blower pulls in gas and air and pushes ﬂ ue products out of the water heater through the heat exchanger and ﬂ...
Page 10: Sequence Of Operation
SEQUENCE OF OPERATION Table 1. Sequence Of Operation OPERATION TOUCH SCREEN DISPLAY The control will turn on the water heater pump A. O. Smith XP (always ON except in Setpoint Adjustment). The Tank Temperature 92°F ﬂ ow switch and/or LWCO must close. Operating Setpoint 93°F Status: Standby...
Page 11 Table 1. Sequence Of Operation (Continued.) OPERATION TOUCH SCREEN DISPLAY If ﬂ ame is not detected after the sparking ends A. O. Smith XP (approximately 5 seconds), the control will perform Tank Temperature 90°F a postpurge, then start another prepurge cycle Operating Setpoint 93°F and try to light the burner again.
Page 12: Touch Screen Display Menu Access
TOUCH SCREEN DISPLAY MENU ACCESS Table 2. Menus From The Touch Screen Display OPERATION TOUCH SCREEN DISPLAY The home screen of the User Interface Module Touch A. O. Smith XP Screen Display shows Tank Temperature, Operating Tank Temperature 92°F Setpoint, Unit Status, MENU option, ENABLE/ DISABLE option and HELP option.
Page 13 Table 2. Menus From The Display Panel (Continued.) OPERATION TOUCH SCREEN DISPLAY Press the HELP options to get additional information Help Menu related to Operating Instructions, Status Icon Legend, Operating States etc. Operating Instructions > Status Icon Legend > Operating States >...
Page 14: Touch Screen Display Parameter Access
TOUCH SCREEN DISPLAY PARAMETER ACCESS The Home Screen for the Touch Screen Display shows the MENU button to access additional user and installer screens. Parameters that can be accessed are indicated by a ' > ' to the right of the screen. Table 3.
Page 15: Parameter Table
PARAMETER TABLE This table lists User Interface Module control parameters and where to access them. Table 4. UIM Parameters MENU ACCESS LOCATION/ USER ACCESS INSTALLER ACCESS PARAMETER NAME DISPLAY MODIFY DISPLAY MODIFY Temperatures Temperatures> Tank Setpoint Temperatures> Differential Temperatures> Setpoint Offset Display Display Settings>...
Page 16 Table 4. UIM Parameters (Continued.) MENU ACCESS LOCATION/ USER ACCESS INSTALLER ACCESS PARAMETER NAME DISPLAY MODIFY DISPLAY MODIFY Lead/Lag Lead/Lag> Address Lead/Lag> Type Lead/Lag> Max Setpoint Lead/Lag> Min On/Off Time Lead/Lag> Min Next On Time Lead/Lag> DHW Size (Slave X) Economy Economy Mode/Clock >...
Page 17: Viewabale And Changeable Control Parameters
VIEWABALE AND CHANGEABLE CONTROL PARAMETERS Before changing parameters, note the settings so that the unit can be returned to its original operating parameters. TEMPERATURE Tank Setpoint By installing a tank sensor, the UIM control can perform the tank thermostat function. The UIM control automatically detects the presence of this sensor, and generates a DHW call for heat when the tank temperature drops below the tank setpoint differential (Tank Setpoint Differential parameter), and ﬁ...
Page 18: Circulation Pumps
CIRCULATION PUMPS DHW Pump Delay The DHW pump delay parameter sets the length of time the DHW pump (if connected) will run after a DHW demand has been satisﬁ ed. This parameter is adjustable by the installer by accessing the DHW Pump Delay parameter.
Page 19: Lead/Lag
Setpoint at Min Volts When programmed for BMS control through the 0 - 10V BMS input or through ModBus and the BMS Type is programmed as SETPOINT, the set point represented by the Volts at Minimum parameter is set by the Set Point at Maximum Volts parameter.
Page 20: Economy Mode/Clock
Max Setpoint This parameter determines the set point used by the individual water heaters in a Lead/Lag. When a water heater is commanded to ﬁ re by the Leader water heater, it will attempt to achieve this temperature at its outlet. The Leader water heater will limit the modulation of the water heaters in order to hold the temperature at the tank sensor to the user set point.
Page 21: Short Cycling
SHORT CYCLING Short Cycling Time Once a water heating demand has been satisﬁ ed, a set amount of time must elapse before the control will respond to a new water heating demand. The control will block the new heat demand and short cycling will be shown in the display until the time has elapsed or the water temperature drops below the Short-Cycling Differential parameter.
Page 22: Maintenance
MAINTENANCE MAINTENANCE SCHEDULES Table 5. Service And Maintenance Schedules SERVICE TECHNICIAN OWNER MAINTENANCE (SEE THE FOLLOWING PAGES FOR INSTRUCTIONS) Check water heater area DAILY General: • Address reported problems • Inspect interior; clean and vacuum if necessary; • Clean condensate trap and ﬁ ll •...
Page 23: Maintenance
MAINTENANCE Follow the service and maintenance procedures given throughout this service handbook and in component literature shipped with the water heater. Failure to perform the service and maintenance could result in damage to the water heater or system. Failure to follow the directions in this service handbook and component literature could result in severe personal injury, death, or substantial property damage.
Page 24 The condensate trap must be ﬁ lled with water during all times of water heater operation to avoid ﬂ ue gas emission from the condensate drain line. Failure to ﬁ ll the trap could result in severe personal injury or death. Check all piping for leaks Eliminate all system or water heater leaks.
Page 25 Inspect ignition and ﬂ ame sense electrodes 1. Remove the ignition and ﬂ ame sense electrodes from the water heater heat exchanger access cover. 2. Remove any deposits accumulated on the ignition/ ﬂ ame sense electrode. If the electrodes cannot be cleaned satisfactorily, replace with new ones.
Page 26 Check ﬂ ame signal 1. At high ﬁ re the ﬂ ame signal shown on the display should be at least 10 microamps. 2. A lower ﬂ ame signal may indicate a fouled or damaged ﬂ ame sense electrode. If cleaning the ﬂ ame sense electrode does not improve, ground wiring is in good condition, and ground continuity is satisfactory, replace the ﬂ...
Page 27 Table 6. Heat Exchanger Cleaning Kits COMPONENT MODEL KIT NUMBER PART NUMBER DESCRIPTION 100140243 Rear Refractory Cover 100162565* Nylon 4" Wheel Brush* 150 - 400 100157627 100162566 3mm Allen Wrench 100162568 1/4" x 24" Drill Extension 100140243 Rear Refractory Cover 100162565* Nylon 4"...
Page 28: Troubleshooting
TROUBLESHOOTING Label all wires prior to disconnection when servicing controls. Wiring errors can cause improper and dangerous operation. Always disconnect power to the water heater before servicing. Failure to comply could result in severe personal injury, death, or substantial property damage. Never jumper (bypass) any device except for momentary testing as outlined in the Troubleshooting chart.
Page 29: Troubleshooting Chart - Not Visible On Display
5. The water heater is shipped with three (3) spare fuses in a plastic bag attached to the control module cover. 6. If necessary, replace open fuse (F3 is .80 amps, F2 is 3.15 amps, and F1 is 5 amps). Note: Fuses F1, F2 and F3 are all slow blow fuses.
Page 30: Troubleshooting Chart - Noisy System
TROUBLESHOOTING CHART - NOISY SYSTEM Table 9. Troubleshooting Chart - Noisy System FAULT CAUSE CORRECTIVE ACTION • Refer to Gas Connections section of the - Supply gas problem. Natural XP Water Heater Instruction Manual for gas pressures should be between detailed information concerning the gas 4 inches w.c.
Page 31: Troubleshooting Chart - Fault Messages Displayed
TROUBLESHOOTING CHART - FAULT MESSAGES DISPLAYED Table 10. Troubleshooting Chart - Fault Messages Displayed on UIM FAULT CAUSE CORRECTIVE ACTION Gas Pressure SW • Measure the supply gas pressure to determine cause of failure. Natural gas pressures should be between 4 - 14 inches w.c.
Page 32 Table 10. Troubleshooting Chart - Fault Messages Displayed on UIM (Continued.) FAULT CAUSE CORRECTIVE ACTION Air PS/HEX Temp SW Either the air pressure APS: switch contacts are open, • Check the wiring connections to the O-temp heat exchanger switch. Wires should be connected switch has opened or the to the common and normally closed A.
Page 33 Table 10. Troubleshooting Chart - Fault Messages Displayed on UIM (Continued.) FAULT CAUSE CORRECTIVE ACTION Flame Fail: Ignition The gas valve is shutoff. • Check wiring harness connection at The unit has failed to prove the gas valve and at the main control main burner ignition after board.
Page 34 Table 10. Troubleshooting Chart - Fault Messages Displayed on UIM (Continued.) FAULT CAUSE CORRECTIVE ACTION Flame Fail: Running The unit was running and • Check wiring harness connection at lost the ﬂ ame signal. This the gas valve and at the main control condition occurred four (4) board.
Page 35 Table 10. Troubleshooting Chart - Fault Messages Displayed on UIM (Continued.) FAULT CAUSE CORRECTIVE ACTION Flame Sequence • Check supply voltage for proper polarity. • Check external wiring for voltage A. O. Smith XP feedback. Tank Temperature 64°F • Check the ﬂ ame rod and make sure Operating Setpoint 185°F The ﬂ...
Page 36 Table 10. Troubleshooting Chart - Fault Messages Displayed on UIM (Continued.) FAULT CAUSE CORRECTIVE ACTION Outlet MRHL • Verify that the system is full of water and that all air has been properly purged from the system. • Verify that the water heater is piped properly into the system.
Page 37 Table 10. Troubleshooting Chart - Fault Messages Displayed on UIM (Continued.) FAULT CAUSE CORRECTIVE ACTION Inlet Sensor Short • Check the Inlet Sensor and its associated wiring. Repair or replace the sensor or wiring if damaged. • Measure the resistance of the sensor A.
Page 38 Table 10. Troubleshooting Chart - Fault Messages Displayed on UIM (Continued.) FAULT CAUSE CORRECTIVE ACTION Flue Sensor • Check the ﬂ ue sensor is properly connected. • Replace sensor if necessary. • Measure the resistance of the sensor A. O. Smith XP and compare the resistance to Table Tank Temperature 118°F...
Page 39: Checking Temperature Sensors
CHECKING TEMPERATURE SENSORS The water heater temperature sensors (inlet water, outlet water, system water, and ﬂ ue) are all resistance type devices. The following tables show the correct values for the sensors at various temperatures. Use an ohmmeter to read the resistance of the sensor at a known temperature. If the resistance of the sensor does not closely match its corresponding table, replace the sensor.
Page 40: Combustion Analysis Procedure
COMBUSTION ANALYSIS PROCEDURE Note: The combustion analysis procedure must only be performed by a qualified service technician. 1. Turn the main power off to the water heater by placing the “On/Off” switch in the OFF position. 2. Remove the ﬂ ue temperature sensor from the ﬂ ue pipe connection. Note: Combustion measurements will be made at this point.
Page 41: Gas Valve Adjustment Procedure
GAS VALVE ADJUSTMENT PROCEDURE If adjustment of the gas valve is deemed necessary, use the following procedures: (Note: The procedures in this section are model speciﬁ c.) Models 150 - 285 Locate the throttle adjustment screw on the side of the venturi valve (See Figure 9). Using a screwdriver, turn the screw a 1/4 turn clockwise to decrease CO levels or a 1/4 turn counterclockwise to increase CO levels.
Page 42 Model 500 Locate the throttle adjustment screw on top of the gas valve, see Figure 11. Using a screwdriver, turn the screw a 1/4 turn counterclockwise to increase CO levels or a 1/4 turn clockwise to decrease CO levels. After one adjustment on the valve, follow the Combustion Analysis Procedure on Page 39 of this Service Handbook to measure the combustion.
Page 43 NOTES Servicing should only be performed by a Qualiﬁ ed Service Technician...
Page 44 COMMERCIAL GAS WATER HEATERS For additional information contact: A. O. Smith Corporation 500 Tennessee Waltz Parkway Ashland City, TN 37015 Tech Support: 800-527-1953 Parts: 800-433-2545 www.hotwater.com Copyright © 2019 A. O. Smith Water Heater Company, All rights reserved.

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