AO Smith Boiler TC 099 User Guide

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  
Part No. TC-099 • Printed in the U.S.A. • 0407  
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A. O. SMITH WATER PRODUCTS COMPANY  
VF BOILER SERVICE MANUAL  
Technical Training Department ©2007  
CONTENTS  
Introduction....................................................................... 2  
61  
67  
68  
71  
Troubleshooting - Error Messages..................................  
Display Is Blank................................................................  
Error Message “Display Fail”..........................................  
Error Message “No Config Key”......................................  
Error Message “Config Key CRC”...................................  
Error Message “Config Key Part”....................................  
Error Message “Low AC Voltage”....................................  
Error Message “Low 24 VAC”..........................................  
Error Message “Low Water”............................................  
Error Message “Low Gas”...............................................  
Error Message “No Flow”................................................  
Error Message “Sequence Err”.......................................  
Error Message “Ignition Speed”......................................  
Error Message “Mtr Spd < Min Spd”................................  
Error Message “Blower Prov Stg1”.................................  
Error Message “Blocked Flue”........................................  
Error Message “Flame Stg1.............................................  
Error Message “Igniter Stg1.............................................  
Boiler Controls Information.............................................  
Operating Temperatures..................................................  
Bypass Lines.....................................................................  
Technical Specifications..................................................  
Glossary............................................................................  
Qualifications.................................................................... 2  
Service Warning................................................................ 2  
Tools Required.................................................................. 3  
EMC 5000 Modulation Control System........................... 4  
UIM - User Interface Module - Overview.......................... 4  
UIM - Status Lights............................................................ 6  
UIM - Input Buttons........................................................... 7  
UIM - Changing Settings.................................................. 8  
UIM - Menu Screens.......................................................... 9  
Principles of Operation.................................................... 11  
VFD and Blower Operation.............................................. 11  
Venturi Operation - Gas Train.......................................... 12  
Blower Speed Verification - Hall Effect Sensor.............. 13  
Config Key - Blower Speed Programming...................... 14  
Sequence Of Operation.................................................... 15  
START UP PROCEDURE.................................................. 17  
Adjusting Manifold Gas.................................................... 19  
Poor Combustion - Ignition Problems............................ 20  
Manifold Gas Pressure Check......................................... 23  
Control Panel Layout........................................................ 24  
MCB - Modulation Control Board.................................... 25  
PDB - Power Distribution Board...................................... 35  
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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 manual always consider  
the wiring and connectors between components. Perform a close visual inspection of all  
wiring and connectors to and from a given component before replacement. Ensure wires  
were stripped before being crimped in a wire connector, ensure wires are crimped tightly in  
their connectors, ensure connection pins in sockets and plugs are not damaged or worn,  
ensure plugs and sockets are mating properly and providing good contact.  
Failure to perform this critical step or failing to perform this step thoroughly often results in  
needless down time, unnecessary parts replacement, and customer dissatisfaction.  
Instruction Manual  
Have a copy of the Instruction Manual that came with the boiler on hand for the model and  
series number before servicing.  
Installation information given in this service manual is not a complete installation instruction.  
Installation information covered in this service manual has a limited focus as it applies to  
servicing the boiler. This Service Manual does not replace or supersede the Instruction  
Manual that came with the boiler. Always refer to the Instruction Manual that came with the  
boiler for complete installation instructions.  
Qualifications  
Service of A. O. Smith VF boilers requires ability equivalent to that of a Qualified Service  
Agent (defined by ANSI below) in the field involved. Installation skills such as plumbing, air  
supply, venting, gas supply, electrical supply are required in addition to electrical testing  
skills. Start up and servicing of VF boilers requires combustion analysis test equipment.  
ANSI Z223.1 2006 Sec. 3.3.83: “Qualified Agency” - “Any individual, firm, corporation or  
company that either in person or through a representative is engaged in and is responsible  
for (a) the installation, testing or replacement of gas piping or (b) the connection, installation,  
testing, repair or servicing of appliances and equipment; that is experienced in such work;  
that is familiar with all precautions required; and that has complied with all the requirements  
of the authority having jurisdiction.”  
Service Warning  
If you are not licensed or certified to perform a given task do not attempt to perform any of  
the service or installation procedures outlined in this manual. If you do not understand the  
instructions given in this manual or do not feel confident in your abilities to perform a given  
task do not attempt to perform any procedures outlined in this manual.  
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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  
insufficient to be used for measuring draft, manifold gas pressure on VF boilers, or  
perform air pressure switch testing. U tube manometers or gas pressure gauges may not  
be substituted for Digital Manometers listed below.  
• Digital Manometer (s) range -20.00 to +20.00" W.C., resolution 0.01" W.C. Recommend  
UEI model EM200 or equivalent. Used to test performance of air pressure switches,  
measure draft, and measure manifold gas pressure.  
• True RMS Digital Multi Meter DMM, recommend UEI model DL289 or Fluke equivalent.  
Capable of measuring:  
„ AC/DC Voltage  
„ VAC Frequency (Hz)  
„ Ohms  
„ DC micro amps µA  
• AC amp meter- recommend UEI model DL289 or equivalent.  
• Combustion analyzer  
Capable of measuring:  
„ CO2  
„ CO  
„ Draft Pressure  
„ Exhaust Temperature  
„ Efficiency  
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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 reference for A. O. Smith VW/VB 500-1000 Series 100-101 boilers only.  
Features Include:  
EMI / RFI filtering - built into all circuit boards. (EMI = Electro Magnetic Interference, RFI  
= Radio Frequency Interference) Helps prevent or eliminate erratic operation caused by  
EMI/RFI.  
Help screens - text based operational information to help the user understand how to  
change settings and navigate the menu screens.  
Self diagnostics - text based diagnostic information (error and fault messages) on board  
to help service technicians quickly and accurately service the boiler.  
Error message log - will retain a 9 event history (plus the current event) of error  
messages with a time stamp. This will help diagnose load and/or environmental conditions  
that may be contributing to a problem with operation or a lock-out.  
Short cycling protection - if any stage logs more than 30 cycles in one hour the control  
enters a short cycle prevention condition. The boiler will continue to operate in this mode.  
The UIM will display and log a “Short Cycle Cond” error message with the yellow Standby  
system status LED flashing. The MCB will add a 180 second delay before activating any  
stage’s call for heat after the last call for heat during this operating mode.  
The short cycle protection mode can be ended (reset) by touching the Select button on the  
UIM while the error message is displayed.  
Temperature probe filtering - The inlet, outlet, and remote Tank/Loop temperature  
probes are read twice per second by the MCB and are filtered for 4 seconds. This filtering  
will help prevent rapid short cycling caused by momentary fluctuations in temperature.  
Pressure/flow switch filtering - input switches such as air pressure switches are read  
every second by the MCB and are filtered (de-bounced) for 6 seconds. This desensitizes  
the input signal and will help prevent nuisance error/fault conditions due to momentary  
fluctuations caused by wind gusts or blower speed changes. The flow switch is filtered for  
4 seconds.  
Network capability - multiple boilers can be networked together (daisy chained) with  
standard Category 5/6 network cable and given individual network addresses.  
Access/monitoring with future A. O. Smith EMS (Energy Management System)  
controller.  
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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 UIB that  
displays operational information and diagnostic messages in plain English.  
LEDs  
• Three “System Status” LED lights: Service, Standby, Running.  
Located to the right of the LCD.  
(Light Emitting Diode)  
• Firing Rate Status indicator - located in the lower right portion of  
the UIM. Four LED lights behind a green (gradient) translucent  
cover. This display indicates the approximate firing rate  
between 25% and 100%.  
LCD  
• LCD display - 4 lines, up to 20 characters per line.  
(Liquid Crystal Display)  
• 10 different screens - Menus, Temperatures, System Status,  
Control States, User Settings, Configuration Settings, Log &  
System Information, Current Error, Error History, and Reload  
Defaults (see page 9).  
Text based operational and diagnostic information.  
User Input Buttons  
Settings / Memory  
• Select - Menu - Help - Up - Down.  
• 5 touch sensitive buttons for user input. Located on the lower  
left portion of the UIM.  
• No moving parts - no pressure is required; these buttons  
activate on finger presence.  
• Non volatile memory; once new settings are confirmed  
(touching the Select button) they remain in memory.  
LCD display  
4 line x 20 character  
System Status  
LEDs  
Firing Rate Status  
5 Touch Sensitive  
User Input Buttons  
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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 after the condition that caused the error has been  
corrected or a factory programmed time period of one hour. Soft lock-outs can also be reset  
by touching the Select button while the error screen is displayed.  
Hard lock-outs can only be reset by touching the Select button while the error screen is  
displayed. Power interruptions or cycling the power on and off will not reset hard or  
soft lock-outs.  
The yellow Standby LED is illuminated whenever the system set point has been satisfied.  
The green Running LED is illuminated continuously whenever a call for heat is active.  
Firing Rate Status  
The Firing Rate Status indicator shows the current  
firing rate of the boiler between; 25 and 100%.  
The Firing Rate Status indicator will not illuminate  
unless flame is proven by one of the two flame  
sensors; high fire sensor/low fire sensor.  
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