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COMMERCIAL
Service Handbook
VF Boiler
Variable Fire Boiler
Domestic Hot Water/Hydronic Heating
M O D E L S C O V E R E D
VW and VB 500, 750, and 1000 Models
Series 100 and 101
Visit the “Information Central” link of
www.hotwater.com for a listing of
available Service Handbooks.
For additional information contact:
A. O. Smith Water Products Company
A Division of A. O. Smith Corporation
500 Tennessee Waltz Parkway
Ashland City, TN 37015
1-800-527-1953
www.hotwater.com
Part No. TC-099 Part No. T
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A. O. SMITH WATER PRODUCTS COMPANY VF BOILER SERVICE MANUAL Technical Training Department ©2007 CONTENTS Introduction....................................................................... 2 41 Troubleshooting - Error Messages.................................. Qualifications.................................................................... 2 42 Display Is Blank................................................................ Service Warning.......................................................
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VF BOILER SERVICE MANUAL INTRODUCTION This Service Manual is designed to aid in servicing and troubleshooting A. O. Smith VF boilers. Models VW/VB 500 - 1000 - series 100/101 boilers are covered in this manual. The instructions and illustrations contained in this service manual will provide you with troubleshooting procedures to verify proper operation and diagnose and repair common service problems. Important Service Reminder When performing any troubleshooting step outlined in this service
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VF BOILER SERVICE MANUAL Tools Required • Instruction Manual that came with the boiler. • Hand tools common to installation and service of commercial water heaters and boilers. • TORX® T40 or 5mm hex wrench - for setting gas mixture at gas valve. • 3mm or 7/64in hex (allen) wrench - for setting gas mixture at gas valve. • Two - U tube manometers (preferably) or gas pressure gauges. U tube manometers can be used to accurately measure supply gas pressures. However, their resolution is insufficie
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VF BOILER SERVICE MANUAL EMC 5000 MODULATION CONTROL SYSTEM This portion of the service manual will cover the EMC 5000 Modulation Control system (EMC - Energy Management Control). The EMC 5000 control system includes several components: a UIM (User Interface Module), a MCB (Modulation Control Board), and a PDB (Power Distribution Board). The EMC 5000 Control System can control single stage, multiple stage, and modulating boilers and water heaters. This service manual should be used as a ref
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VF BOILER SERVICE MANUAL UIM - USER INTERFACE MODULE - OVERVIEW The UIM is an assembly that consists of several electronic components. The main circuit board in the assembly is the UIB (User Interface Board) which houses the communications port. The UIB relays user input and data to and from the MCB, controls the LCD, and activates the LEDs. Mounted to the UIB is a TSB (Touch Sensor Board) containing the touch sensor pads that are the user input buttons. There is a LCD module mounted to the
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VF BOILER SERVICE MANUAL UIM - USER INTERFACE MODULE - STATUS LIGHTS System Status LEDs LCD display 4 line x 20 character Firing Rate Status 5 Touch Sensitive User Input Buttons System Status LED Lights The three “System Status” LED lights on the upper right portion of the UIM convey current operational and diagnostic information. The red Service LED will be continuously illuminated for soft lock-outs and flashing on and off for hard lock- outs. Soft lock-outs will automatically reset afte
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VF BOILER SERVICE MANUAL UIM - USER INTERFACE MODULE - USER INPUT BUTTONS System Status LEDs LCD display 4 line x 20 character Firing Rate Status 5 Touch Sensitive User Input Buttons Select Button is used to: • Enter menu screens. • Activate adjustment mode for various settings. The [ > ] will be flashing slowly to the left of the menu item when the adjustment mode is active. • Confirm and store new values and settings in memory. • Reset the control when in a lock-out condition. Menu Button is
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VF BOILER SERVICE MANUAL UIM - USER INTERFACE MODULE - CHANGING SETTINGS The sequence of UIM screen displays below is an example of how to navigate the menus to change the Operating Set Point. Screen Display 1: shows the temperatures screen. This is the default display screen the UIM comes to rest at after approximately 60 seconds without any user input. The Menu button is touched once to enter the Menus screen containing 9 different sub menus. Screen Displays 2 - 4: show the first four line
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VF BOILER SERVICE MANUAL UIM - USER INTERFACE MODULE - MENU SCREENS At the top center of the UIM panel is the display LCD. This LCD is used to provide information to the user through menu activated screens. Within each of the screens, helpful context sensitive information can be displayed at any time by touching the “Help” button. Touching the help button once more returns the user to the previous screen. The 10 available screens are: Menu Screen: Displayed when the “Menu” button is touched.
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VF BOILER SERVICE MANUAL UIM - USER INTERFACE MODULE - MENUS Log & System Info Screen: This screen displays the following: • Elapsed hours of operation (Total time system has been powered up). • Number of running minutes (Number of minutes system has been in the run mode). • Number of heating cycles. • kBtu rating of the boiler. • Software revision of the CCB (MCB), FCB, and Config Key (see explanation on page 25). There are no adjustable user inputs available from this screen. Current Error Sc
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VF BOILER SERVICE MANUAL PRINCIPLES OF OPERATION VF boilers do not have a gas orifice. The blower “pulls” gas from the gas valve into a Venturi attached to the suction (inlet) side of the blower (page 12). As the speed of the blower is increased the vacuum in the Venturi is also increased and more fuel gas and combustion air is supplied to the burner. This is the basic principle of how a VF boiler modulates firing rate. VFD and Blower Operation VF boilers have a small circuit board (Daughter
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VF BOILER SERVICE MANUAL PRINCIPLE OF OPERATION (CONT) Venturi Operation - Gas Train A Venturi is connected to the inlet side of the combustion blower on VF Boilers. The gas line from the outlet of the gas valve connects to the Venturi. The Venturi contains a cone shaped restrictor that constricts the air passage to the blower. As air enters the constriction point it’s velocity increases. A pressure drop occurs at this point and creates a negative (vacuum) pressure in the cavity between the
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VF BOILER SERVICE MANUAL PRINCIPLE OF OPERATION (CONT) Blower Speed Verification - Hall Effect Sensor The MCB (page 25) initiates blower operation by closing the VFD enable/disable circuit AND sending a 1-10 VDC speed instruction to the VFD (page 11) to energize the blower and to modulate blower speed. The MCB monitors actual blower speed (rpm) to verify the speed dictated by the instruction has been achieved and to change the instruction as necessary. Actual blower speed information is rel
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VF BOILER SERVICE MANUAL PRINCIPLE OF OPERATION (CONT) Config Key - Blower Speed Programming The Config Key is an 18” long cable with a plug on one end and an EEPROM memory chip sealed at the other. The Config Key plugs into the J23 socket on the MCB Daughter Board (see pages 25 and 34). The memory chip contains blower speed programming data specific to the input Btu/hr and fuel type for each VF boiler. VF boilers are available in natural and propane gas and in three input Btu/hr sizes; 500,
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VF BOILER SERVICE MANUAL SEQUENCE OF OPERATION Call For Heat is Activated EMC 5000 Control System MCB board applies power to pump relay compares the temperature read Pump Is Energized from controlling probe (Inlet or remote Tank/Loop) to the Boiler enters Service Mode Operating Set Point. and locks out. UIM displays Flow Switch Closes Contacts NO No Flow If the temperature read is less than Error message the Operating Set Point minus YES Stage 1 Differential AND the Enable/Disable (the
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VF BOILER SERVICE MANUAL SEQUENCE OF OPERATION (CONT) Previous Page MCB Energizes Ignitor NOTE Ignition State – 18 Seconds The events shown in this flow chart are in sequential order. The EMC Boiler enters Service Mode 5000 is a multi-task control that MCB Senses Minimum and locks out. UIM displays performs some functions NO Igniter Stg1 simultaneously. Only key events are 2.7 AC Amps Through Ignitor shown in order to provide a general Error message understanding of how the control YES
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VF BOILER SERVICE MANUAL START UP PROCEDURE Prior To Start Up In addition to normal supplies and hand tools necessary for installing and servicing water heaters and boilers the following tools and test equipment should be on hand. See the tool requirements page 3. • A combustion analyzer capable of measuring draft pressure, CO, and CO2 or O2. • True RMS Digital Multi Meter DMM capable of reading AC volts, DC volts, ohms, DC micro amps µA, and frequency Hz. • AC amp meter. • TORX® T40 or 5mm h
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VF BOILER SERVICE MANUAL START UP PROCEDURE (CONT) Start Up Procedure 1. Before starting the boiler, please review the boilers Instruction Manual supplied with the boiler. Ensure the water piping, gas line, controls, and venting have been installed per the instruction manual. Further information on water piping and controls is on pages 61 - 67 in this service manual. 2. Ensure the gas train shut off valve (see the image on page 23) in the boiler’s gas train is open. 3. Purge all air from the
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VF BOILER SERVICE MANUAL START UP PROCEDURE (CONT) Adjusting Manifold Gas 13. Set the boiler to Max Mode (Firing Modes - page 17). Check combustion readings using combustion analyzer. Compare CO2 readings taken to the high fire CO2 table below. If combustion readings are not in accordance with the high fire CO2 table adjust as follows: Remove the flat, round, blue plastic cap from the top of the boiler’s 24 VAC gas valve. Using a 3mm (7/64”) hex wrench, turn the high fire adjustment screw u
