A. O. SMITH WATER PRODUCTS COMPANY VF BOILER SERVICE MANUAL Technical Literature Department ©2008 CONTENTS Introduction....................................................................... 2 Troubleshooting - Error Messages................................. 41 Qualifications.................................................................... 2 Display Is Blank................................................................ 42 Service Warning.............................................................
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.
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. • One - U tube manometer for measuring supply gas pressure. • One (optionally two) digital Manometers range -15.00 to +15.00" W.C., resolution 0.01" W.C.
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.
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.
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 lockouts.
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.
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.
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.
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.
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.
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.
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.
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 BOILER SERVICE MANUAL SEQUENCE OF OPERATION Call For Heat is Activated EMC 5000 Control System compares the temperature read from controlling probe (Inlet or remote Tank/Loop) to the Operating Set Point.
VF BOILER SERVICE MANUAL SEQUENCE OF OPERATION (CONT) Previous Page NOTE The events shown in this flow chart are in sequential order. The EMC 5000 is a multi-task control that performs some functions simultaneously. Only key events are shown in order to provide a general understanding of how the control operates. Event timings can vary depending on actual conditions. MCB Energizes Ignitor Ignition State – 18 Seconds MCB Senses Minimum 2.
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.
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.
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 Max Mode CO2 table below. If CO2 readings are not within this range adjust as follows: Remove the flat, round, blue plastic cap from the top of the boiler’s 24 VAC gas valve.
VF BOILER SERVICE MANUAL POOR COMBUSTION - IGNITION PROBLEMS If the high and/or low fire CO2 combustion readings are not in accordance with the tables shown on page 19, the CO readings are high, or if the boiler is experiencing ignition failure or rough starting perform the following procedures: Adequate Combustion - Proper Venting 1. Ensure there is an adequate supply of fresh air for combustion and the boiler is vented properly. DO NOT OVERLOOK THIS STEP.
VF BOILER SERVICE MANUAL POOR COMBUSTION - IGNITION PROBLEMS (CONT) Burner Inspection 2. Remove the burner and inspect the burner for any signs of damage or debris inside. If the burner is damaged or contaminated with debris - replace the burner. Check all gaskets in the burner/blower assembly for wear or damage. Replace any worn or damaged gaskets. Firing Rate - Modulation Performance 3. The firing rate on VF boilers is modulated or controlled by blower speed (see pages 11 through 14).
VF BOILER SERVICE MANUAL POOR COMBUSTION - IGNITION PROBLEMS (CONT) VFD Operating Parameters Approximate MCB/VFD operating parameters for natural gas models are shown in the first table below. Parameters for propane models are shown in the second table. When combustion is poor, the firing rate of the boiler or blower speed is in question, or the boiler is experiencing rough starts or ignition failure compare the values given here to actual readings taken during the various operating states shown.
VF BOILER SERVICE MANUAL POOR COMBUSTION - IGNITION PROBLEMS (CONT) Manifold Gas Pressure Check 5. Attach Digital manometer to one of the manifold gas pressure taps on gas line between the boiler’s 24 VAC gas valve outlet and the gas inlet on the Venturi as shown in the images below. Recommend UEI model EM200 or equivalent. Manifold gas pressure on VF boilers is a negative (vacuum) pressure. The lower the pressure (deeper the vacuum) the higher the firing rate will be.
VF BOILER SERVICE MANUAL CONTROL PANEL LAYOUT The illustration below shows the control panel on VF boilers. Blower Prover Switches VF boilers are equipped with High and Low blower prover switches or BPS. Both are normally open air pressure switches. Both close on a fall in pressure (a negative/vacuum pressure). The contacts of both must be open at the beginning of each heating cycle. The High BPS is only used when the boiler is in the Pre/Post Purge operating states (blower at 5000 rpm).
VF BOILER SERVICE MANUAL MCB - MODULATING CONTROL BOARD - OVERVIEW MCB / CCB / FCB Terminology Explanation MCB and CCB are separate terms that refer to the same circuit board which is the main controller for the EMC 5000 control system on VF boilers. MCB stands for “modulating control board,” CCB stands for “central control board.” In VF boiler product literature MCB is used to describe this component; in the UIM (pages 4 and 14) menu screens on VF boilers it is referred to as the CCB.
VF BOILER SERVICE MANUAL MCB - MODULATING CONTROL BOARD - OVERVIEW (CONT) The MCB circuit board is the main controller. All instructions for burner modulation and temperature control originate from this circuit board. Diagnostic and operational messages are generated by the MCB and sent to the UIM. Most of the boiler’s components, such as the igniter, blower, gas valve, and temperature probes are directly connected to one of the MCB’s 16 socket connectors.
VF BOILER SERVICE MANUAL MCB - SECTION A The upper left corner of the MCB contains the following sockets/components: Red LED (illuminated when the F1 fuse is open or missing) F1 Fuse (7.5 amp automotive fuse - 24 VAC transformer protection) J3 Socket (24 VAC power supply from transformer) • Pin 1 - 24 VAC line • Pin 2 - 24 VAC line • Pin 3 - Ground The MCB circuit board is mounted upside down on VF boilers compared to the illustrations below.
VF BOILER SERVICE MANUAL MCB - SECTION B The upper middle section of the MCB contains the following sockets/components: † J5 Socket (Inputs) J4 Socket (Outputs/Inputs) • Pin 1 - 24 VAC Flow switch • Pin 1 - Spare - not used • Pin 2 - 24 VAC Flow switch • Pin 2 - Spare - not used • Pin 3 - 24 VAC Low gas press switch • Pin 3 - Spare - not used • Pin 4 - 24 VAC Low gas press switch • Pin 4 - 24 VAC line low water cut off (optional) • Pin 5 - 24 VAC Blocked flue (exhaust) switch • Pin 5 - Low water cut off p
VF BOILER SERVICE MANUAL MCB - SECTION C The upper right corner of the MCB contains the following sockets/components: J2 Socket (Pump relay coil; IRI gas valve) • Pin 1 - 120 VAC switched hot wire to pump relay coil • Pin 2 - 120 VAC neutral wire to pump relay coil • Pin 3 - 120 VAC hot wire to IRI gas valve - N/A on VF boilers. • Pin 4 - 120 VAC neutral wire to IRI gas valve - N/A on VF boilers.
VF BOILER SERVICE MANUAL MCB - SECTION D MCB Master Control Dip Switches System configurations are made on the MCB circuit boards with dip switches. This page explains how the Master Control dip switches (SW1) are configured on the MCB. These dip switch/configuration settings can be viewed from the “Configuration Settings” menu screen on the UIM (see page 9).
VF BOILER SERVICE MANUAL MCB - SECTION E The lower left corner of the MCB contains the following sockets/components: J6 Socket (Gas valve relay - N/A on VF boilers) • Pin 1 - 24 VDC gas valve relay circuit • Pin 2 - N/A - plug is filled • Pin 3 - 24 VDC gas valve relay circuit • Pin 4 - Ground J7 Socket (Outlet probe) • Pin 1 - 24 VDC manual reset ECO • Pin 2 - 24 VDC manual reset ECO • Pin 3 - Not used • Pin 4 - 0 - 5 VDC outlet temperature probe • Pin 5 - 0 - 5 VDC outlet temperature probe • Pin 6 - Not
VF BOILER SERVICE MANUAL MCB - SECTION F This section of the MCB contains the communication or “Comm” ports: ICSP Port The ICSP port (In Circuit Serial Programming) is used for programming the MCB board. DO NOT plug any device or cable into this port. This port is used by A. O. Smith engineering personnel only. Damage caused by plugging cables/devices into this port would not be covered under warranty.
VF BOILER SERVICE MANUAL MCB - SECTION G Along the bottom edge of the MCB there is a second dip switch (SW2). This page details and explains the SW2 dip switch. There are 3 switches on SW2: switch 1 is a spare, switch 2 must be configured correctly, dip switch 3 does not affect operation on VF boilers. Switch 1 Spare On 2 High gas pressure switch present On = Yes ‡Switch 3 Number of blower speeds On = 1 speed Off Off = No †Switch Off = 2 speed †.
VF BOILER SERVICE MANUAL MCB SECTION H This section of the MCB contains a small “Daughter Board” that contains the J23 and J24 sockets. Refer to page 25 for more information. The VFD (page 11), the Hall Effect sensor (page 13) and the Config Key (page 14) connect to this Daughter Board. Service Notes: J24 Pins 1 and 2 (1-10 VDC VFD instruction) are polarity sensitive. If these two wires are not connected as shown. The VFD will not start the blower.
VF BOILER SERVICE MANUAL PDB - POWER DISTRIBUTION BOARD - OVERVIEW The PDB provides connection points for line-input (120 VAC) power, the pump, and the transformer. It distributes the line-input power and the transformer output (24 VAC) power to necessary locations. It also contains fuses for the pump and the MCB circuit board. The PDB also contains filtering circuitry for EMI/RFI (page 4) power supply protection. Wiring and connection details given here reference 100-101 Series VF boilers.
VF BOILER SERVICE MANUAL PDB - SECTION A The left side of the PDB circuit board contains a terminal strip (TB1) used to connect the 120 VAC power supply to the boiler, the pump relay, and the pump motor. VW models will have a factory mounted pump powered by the pump relay; VB models are not equipped with factory pumps. Review the output specification table (page 69) for field supplied pumps.
VF BOILER SERVICE MANUAL PDB - SECTION B The mid section of the PDB contains the fusing for the following: F1 Fuse - 10 amp 240 VAC - European Models only † F2 Fuse - 20 amp 120 VAC - Pump F3 Fuse - 3 amp 120 VAC - Transformer Primary Winding F4 Fuse - 10 amp 120 VAC - FCB 4 Power Supply - N/A on VF boilers F5 Fuse - 10 amp 120 VAC - FCB 3 Power Supply - N/A on VF boilers F6 Fuse - 10 amp 120 VAC - FCB 2 Power Supply - N/A on VF boilers F7 Fuse - 15 amp 120 VAC - MCB Power Supply F1 Fuse - 10 Amp - 240 V
VF BOILER SERVICE MANUAL PDB - SECTION C The upper right corner of the PDB contains the following: J2 Socket (24 VAC Outputs) • Pin 1 - 24 VAC Hot to MCB J3 Socket • Pin 2 - 24 VAC Return to MCB J3 Socket • Pin 3 - Ground to MCB J3 Socket • Pin 4 - 24 VAC Hot to Stage 2 FCB - N/A on VF boilers. • Pin 5 - 24 VAC Return to Stage 2 FCB - N/A on VF boilers. • Pin 6 - N/A • Pin 7 - N/A • Pin 8 - 24 VAC Hot to Stage 3 FCB - N/A on VF boilers. • Pin 9 - 24 VAC Return to Stage 3 FCB - N/A on VF boilers.
VF BOILER SERVICE MANUAL PDB - SECTION D The lower right corner of the PDB contains the J3 Socket and the JP1 jumper. The J3 Socket is described here the JP1 jumper is described on page 40.
VF BOILER SERVICE MANUAL PDB - POWER SUPPLY TEST The lower right corner of the PDB also contains two jumpers and three power supply status LED lights. With power applied the green DS2 LED should always be lit. The JP1 jumper is used to activate a power supply test function. The JP2 and JP3 jumpers are used for manufacturing purposes only. Power Test Procedure: Turn power off to the boiler at the breaker or disconnect switch. Disconnect the wiring plugs at J1, J2, and J3 Sockets on the PDB.
VF BOILER SERVICE MANUAL ERROR MESSAGES - TROUBLESHOOTING The EMC 5000 control system performs exhaustive self diagnostics and displays detected fault conditions on the UIM (page 6). There are approximately 80 different error messages. Troubleshooting procedures for the most common error messages are covered in this service manual. A more complete list of error messages is in the boiler’s Instruction Manual.
VF BOILER SERVICE MANUAL ERROR MESSAGES DISPLAYED MESSAGE CONDITION/INDICATES UIM Display Is Blank CHECK/REPAIR • Ensure the on/off switch is on and working replace switch if defective. Boiler is turned off 120 VAC power supply problems 24 VAC power supply problems Blown Fuses Defective transformer Wiring or plug/socket connection problems UIM communication cable problems • Ensure 7.5 amp fuse on MCB is not blown/missing - replace fuse (see page 27).
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Display Fail” CHECK/REPAIR • Plug UIM comm cable into the other “internal” comm port on the MCB. (see page 32) Communication between the MCB and UIM has been interrupted - the MCB is having trouble communicating with the UIM. • Check comm cable to the UIM. Turn off power and Install a new/different comm cable (standard Cat 5 network cable).
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES CHECK/REPAIR “Config Key CRC” • Data read from the Config Key by the MCB was not properly confirmed at power up. Ensure the Config Key is securely plugged into the J23 socket on the MCB circuit board (see pages 14 and 34). • Turn power off to the boiler for 1 minute and then turn power back on. Press the Select button on the UIM to clear any error messages.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Low AC Voltage” Power supply polarity is reversed. Line voltage to boiler is less than 90 VAC. “Low 24 VAC” CHECK/REPAIR • Ensure power supply polarity is not reversed and boiler is properly grounded. • Perform Power Supply Test Procedure (page 40) - correct any problems indicated by test.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “No Flow” Pump IS NOT Running (If pump is running proceed to the next page) Normally open contacts on factory mounted flow switch are not closing or are not remaining closed after the pump is energized. CHECK/REPAIR VB Models - No Factory Pump • Check for power at the pump motor - if the pump has power but will not start - replace/ repair pump.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “No Flow” Pump is Running CHECK/REPAIR • New boiler installations in older systems; Check for restrictions in the water lines (accumulated lime) to and from the boiler. System lines can become restricted with lime and sediment accumulation over time and sometimes must be replaced on older systems. • New boiler installations in older systems; Ensure existing water lines to and from the boiler are properly sized.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES CHECK/REPAIR “Sequence Err” • Ensure all wiring to VFD is connected properly. and in good condition. See pages 11 and 34. Enable/disable circuit wires to VFD disconnected. 1-10 VDC instruction wires to VFD disconnected. 1-10 VDC instruction wires to VFD reversed polarity. MCB failing to send 1-10 VDC instruction to VFD. • Check for 1-10 VDC instruction on VFD low voltage terminal strip. See page 11.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES CHECK/REPAIR “Blower Prov Stg1” Blower IS NOT Starting • SW1 dip switch #8 is in the off position, this dip switch must be in the “on” position (page 30). (If the blower is starting proceed to the “Blower Prov Stg1” Blower Is Starting tables) • Turn off power to boiler and disconnect the wires to both BPS (BPS = Blower Prover Switches) - check for continuity between the “Com” and N.O. terminals on both BPS.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Blower Prov Stg1” Blower IS NOT Starting CHECK/REPAIR • Ensure all wiring is reconnected to the VFD and all plugs are securely plugged into the MCB/ PDB. With power on and a call for heat activated check for a 1-10 VDC instruction from the MCB at VFD low voltage terminals “0V” and “AI1” - see VFD connections on page 11.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Blower Prov Stg1” Blower IS NOT Starting CHECK/REPAIR • (If the blower is starting proceed to the “Blower Prov Stg1” Blower Is Starting tables) IMPORTANT SERVICE NOTE: BEFORE performing any of the check/repair procedures in the right column of this table; review the VFD and Blower Operation section in this manual on page 11.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Blower Prov Stg1” Blower Is Starting CHECK/REPAIR • Ensure the sensing tubes are connected to the “L” sensing ports on both BPS (BPS = Blower Prover Switches) see the control panel layout and pressure switch information on page 24. • Ensure all BPS sensing tubes are not kinked and are properly connected.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Blower Prov Stg1” Blower Is Starting (If the blower is not starting go to the “Blower Prov Stg1” Blower Is Not Starting tables) Helpful Troubleshooting Note: The state of the contacts for the Low BPS can be viewed in real time using the System Status Menu. An asterisk will appear next to the “BlwLo Prv” menu item when the switch contacts are closed. The asterisk is not present when the switch contacts are open.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Blower Prov Stg1” Blower Is Starting (If the blower is not starting go to the “Blower Prov Stg1” Blower Is Not Starting tables) Helpful Troubleshooting Note: The state of the contacts for the High BPS can be viewed in real time using the System Status Menu. An asterisk will appear next to the “BlwHi Prv” menu item when the switch contacts are closed. The asterisk is not present when the switch contacts are open.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Blower Prov Stg1” Blower Is Starting (If the blower is not starting go to the “Blower Prov Stg1” Blower Is Not Starting tables) CHECK/REPAIR Pressure Reading Test • Three conditions can cause this error message when the blower is starting: Normally Open Low Blower Prover or High Blower Prover pressure switch contacts are not closing during the pre or post purge operating states - or within 5 minutes of call for heat be
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Blocked Flue” CHECK/REPAIR • Turn off power and disconnect the wires to the Blocked Flue (Exhaust) Switch, see page 24 for location. Check for continuity between the terminals of switch with an ohm meter. If there IS NOT continuity through the switch contacts replace the switch (this is a normally closed switch). • Check all wiring between the Blocked Flue Switch and the MCB J5 socket pins 5 & 6 (page 28).
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Flame Stg1” Flame or ignition failure. Error message displayed after 1 or 3 losses of flame or after 1 or 3 failed trials for ignition. EMC 5000 control system will lock-out after 1 or 3 trials depending on the SW1 #2 dip switch setting on the MCB circuit board. (see page 30) CHECK/REPAIR • Ensure the supply gas shut off valve to the boiler and the gas train shut off valve (see image on page 23) are both open.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Flame Stg1” (cont) Flame or ignition failure. Error message displayed after 1 or 3 losses of flame or after 1 or 3 failed trials for ignition. EMC 5000 control system will lock-out after 1 or 3 trials depending on the SW1 #2 dip switch setting on the MCB circuit board. (see page 30) CHECK/REPAIR • Check igniter amperage during igniter warm up period. If amp draw is less than 3.0 amps replace the igniter.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Flame Stg1” (cont) CHECK/REPAIR • Ensure the 24 VAC gas valve is opening and gas is flowing through the valve: Flame or ignition failure. Error message displayed after 1 or 3 losses of flame or after 1 or 3 failed trials for ignition. EMC 5000 control system will lock-out after 1 or 3 trials depending on the SW1 #2 dip switch setting on the MCB circuit board. (see page 30) Secure power to the boiler.
VF BOILER SERVICE MANUAL ERROR MESSAGES (CONT) DISPLAYED MESSAGE CONDITION/INDICATES “Igniter Stg1” CHECK/REPAIR • MCB is not sensing minimum igniter current of 2.7 AC amps during the igniter warm up period. Closely inspect the pins in the J18 socket/plug for wear or damage. Ensure the plug and socket are properly connected and making good contact.
VF BOILER SERVICE MANUAL BOILER CONTROLS Boiler controls that are improperly installed or set up can cause serious operational and service related problems such as short cycling. This section provides information for how various controls can work together or independently to provide proper system and boiler control. Two conditions must be met for the VF boiler to start a heating cycle: 1.
VF BOILER SERVICE MANUAL BOILER CONTROLS (CONT) Primary System Control A Primary System Control is a top level “system” temperature control. A Primary System Control activates the call for heat or enables boiler operation when system temperature falls below the control’s set point and deactivates a call for heat or disables the boiler when system temperature reaches set point. The “system” is typically a storage tank (domestic hot water supply) or a hydronic loop (building heat system).
VF BOILER SERVICE MANUAL BOILER CONTROLS (CONT) Controlling Probe The Operating Set Point on the VF boiler’s EMC 5000 control system reacts to temperature sensed by the Controlling Probe. The EMC 5000 control system can be configured to use either the Inlet probe or the remote Tank/Loop probe as the “Controlling Probe.” VF boilers are designed to use the remote Tank/Loop probe as the Controlling Probe. Review the installation and configuration information on page 62.
VF BOILER SERVICE MANUAL BOILER CONTROLS (CONT) INTERNAL TEMPERATURE CONTROLS (CONT) Automatic High Limit - User Setting “Hi Limit” The Automatic High Limit is a “local” EMC 5000 User Setting that can be adjusted through the UIM (page 8). The Automatic High Limit is a temperature limiting control, it reacts to temperatures sensed at the Outlet Probe (page 62). It prevents the outlet water temperature from rising above the programmed set point.
VF BOILER SERVICE MANUAL BOILER CONTROLS (CONT) EXTERNAL CONTROLS Enable/Disable Control Circuit The Enable/Disable Control Circuit is always active. This control circuit must be “closed” to enable boiler operation. Two wires located in the junction box on the back of the boiler are provided for this circuit. From the factory these two wires are wire nutted together.
VF BOILER SERVICE MANUAL BOILER CONTROLS (CONT) EXTERNAL CONTROLS (CONT) Types of External Controls An External Control can be a Primary System Control or a Supervisory Control or both. The enable/disable circuit described on page 65 would be field wired to the external control’s dry contacts. Field control wiring must be installed in a dedicated conduit.
VF BOILER SERVICE MANUAL OPERATING TEMPERATURES Temperature rise through the boiler: 20 - 40°F. The temperature rise (ΔT = Delta T) through the boiler should be maintained between 20 40°F while firing at 100%. This flow rate maintains a balance between the harmful effects of calcium/lime accumulation (low flow rate) and velocity erosion (excessive flow rate). The ΔT will be lower when the firing rate is less than 100%. Install and throttle a flow control valve in the outlet line to achieve 20 - 40°F ΔT.
VF BOILER SERVICE MANUAL TECHNICAL SPECIFICATIONS Input Power and Circuit Protection: † Power Supply Voltage 120 VAC 108 VAC RMS minimum; 132 VAC RMS maximum. Below 90 VAC will result in lock out. “Low AC Voltage” error message will be displayed. Power Supply Requirements Dedicated 30 amp circuit breaker should be provided. Voltage across the neutral and ground wires should not exceed 1 VAC. Dedicated wiring – no shared hot, neutral or ground wires.
VF BOILER SERVICE MANUAL TECHNICAL SPECIFICATIONS Input Specifications (cont): † High Blower Prover Pressure Switch Normally Open, closes on a pressure fall at -4.8" W.C. ± 0.01 01/15/08 High BPS activation pressure changes to -5.2" W. C. †Low Blower Prover Pressure Switch Normally Open, closes on a pressure fall at -0.12" W.C.± 0.01 † Blocked Flue (Exhaust) Pressure Switch Normally Closed, opens on a pressure rise at 1.0" W.C. ± 0.1 † Normally Open, closes on a pressure rise.
VF BOILER SERVICE MANUAL TECHNICAL SPECIFICATIONS Ignition Timing: Pre-Purge - cold start 32 ± 2 seconds Pre-Purge – not cold start 10 ± 2 seconds Shutter Adjust 5 minutes Pre-Circulate 34 to 45 seconds or until flow is proven Igniter proving time 18 ± 1 seconds Inter-Purge 15 ± 2 seconds Post-Purge 25 ± 2 seconds Pump post-circulate time Selectable 45, 90, 180 seconds or continuous Default User Settings/Ranges: As shipped from the factory the SW1 dip switches (page 30) on the MCB are prese
VF BOILER SERVICE MANUAL GLOSSARY ΔT:Symbol used for “Delta T.” Engineering term to convey “temperature rise” or “difference” through a boiler or heat exchanger. IE: If the inlet water temperature to a boiler is 120°F and the outlet water temperature leaving the boiler is 140°F; the temperature rise through the boiler is 20°F, which is commonly expressed as “20° ΔT.” Blocked Flue Switch - Blocked Exhaust Switch: Two terms describing the same device.
VF BOILER SERVICE MANUAL GLOSSARY (CONT) UIB - User Interface Board: Part of the UIM assembly. Communicates with the MCB. Controls the operation of the LCD. Receives inputs from the touch switches. Activates the LED's according to commands sent from the MCB. UIM - User Interface Module:Plastic housing that holds the UIB, LCD, and TSB. Provides means to both send and receive information from the user. Only one cable to the MCB is required for communications and power. Operates on 5 VDC only.
