A.O. Smith VF VB 1000, Service Handbook

Page 1: ...riable Fire Boiler Domestic Hot Water Hydronic Heating VF Boiler 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 Service Handbook Part No TC 099 Printed in the U S A 040...

Page 2: ...ck Control Panel Layout MCB Modulation Control Board PDB Power Distribution Board 2 2 2 3 4 4 6 7 8 9 11 11 12 13 14 15 17 19 20 23 24 25 35 Troubleshooting Error Messages Display Is Blank Error Messa...

Page 3: ...rvice 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 r...

Page 4: ...owever 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 su...

Page 5: ...ental 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 preventi...

Page 6: ...e right of the LCD 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 ra...

Page 7: ...ter 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 disp...

Page 8: ...d to Touch once to display helpful information about the current menu screen Touch a second time to return to previous screen Touched from the main menu screen and the UIM displays general information...

Page 9: ...he lower right corner this indicates there are more menu items below the four lines currently being displayed Up arrows appear on the top right corner when there are more menu items above Screen Displ...

Page 10: ...inputs available from this screen System Status Screen This screen is used to view the status of switch inputs and output states An asterisk is displayed next to the label when the status is True the...

Page 11: ...still valid When cleared it is moved to the Error History Screen The system will automatically jump to this screen when an error is detected It will also go to this screen upon power up if an error wa...

Page 12: ...precisely by modulating the frequency Hz of the power supplied to the blower motor VFD output to the blower is a 3 Phase power supply Three conditions must be met before the VFD will start the blower...

Page 13: ...city of air flowing through the Venturi is also increased This further increases the vacuum created by the Venturi and more fuel gas is pulled from the gas valve This increases the firing rate input B...

Page 14: ...speed See the images below Example If the MCB has sent an 4 3 VDC instruction to the VFD to run the blower at 2500 rpm and the actual rpm relayed back from the Hall Effect sensor indicates the blower...

Page 15: ...om the Config Key into it s own internal memory The MCB then uses the data to modulate blower speed by sending 1 10 VDC instructions to the VFD page 11 Modulating blower speed also modulates the firin...

Page 16: ...at is activated Call For Heat is Activated High Blower Prover Switch Contacts Verified Open Boiler enters Service Mode and locks out UIM displays Blower Prov Stg1 Error message NO Blower Is Energized...

Page 17: ...neously 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 SERVICE NOTE VF boilers utilize two flam...

Page 18: ...p with the User Settings menu and press the Select button Scroll down to Mod Mode menu item and press the Select button again The cursor starts flashing on and off slowly indicating adjustment of this...

Page 19: ...eclare a fault This will verify that the pump flow switch igniter VFD variable frequency drive gas valve blower and low high blower prover switches are all functioning 8 Drill a 7 16 hole in the side...

Page 20: ...gas valve Using a TORX T40 or a 5mm hex wrench carefully turn the low fire adjustment screw under the cap clockwise to increase or counterclockwise to decrease gas flow and achieve the desired CO2 lev...

Page 21: ...ivalent to 10 linear feet of pipe on VF boilers If the boiler is in an equipment room with a door to the outdoors temporarily disconnect the intake air pipe and prop open the equipment room door Take...

Page 22: ...Mode Firing Modes page 17 Start the boiler and check the three parameters listed below during the three operating states given above DC voltage sent by the MCB at the VFD page 11 Actual blower rpm as...

Page 23: ...urge Mode Approx RPM 5000 5000 5000 Blower Speed Ignitor Warm Up Period Approx RPM 2200 2200 2200 Blower Speed Min Mode 25 Approx RPM 800 1200 1250 Blower Speed Max Mode 100 Approx RPM 2500 4100 4500...

Page 24: ...below Service Note If the actual pressures observed during the test above are considerably different higher pressures closer to a positive pressure closely inspect all fittings and flanges in the gas...

Page 25: ...is running See the Sequence of Operation on page 15 Note which sensing ports are used The two sensing ports on each pressure switch are differentiated with the letters L and H embossed on the switch b...

Page 26: ...he UIM pages 4 and 14 menu screens on VF boilers it is referred to as the CCB Some UIM menu screens show the term FCB flame control board The FCB is a portion of the MCB that controls ignition It is n...

Page 27: ...ng and connection information shown in this service manual are in reference to how the EMC 5000 controls and circuit boards connect on VF boilers This service manual should be used as a reference for...

Page 28: ...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 lin...

Page 29: ...hed 24 VAC control circuits with a maximum amp rating of 1 amp When these optional components are used the MCB must be configured to recognize and enable the components by setting the SW1 dip switches...

Page 30: ...20 VAC hot wire Pin 2 120 VAC neutral wire Pin 3 Ground J18 Socket Silicon Carbide igniter power Pin 1 Igniter 120 VAC hot wire Pin 2 Igniter 120 VAC neutral wire F2 Fuse N A on VF boilers if fuse is...

Page 31: ...tch 4 Controlling probe On Tank Loop Remote Off Inlet Switch 5 Power vent kit N A set to off On Yes Off No Switch 6 Low water cut off present On Yes Off No Switch 7 Low gas pressure switch present On...

Page 32: ...res from this socket are routed to the junction box on the back of the boiler Dedicated field wiring and conduit must be routed between the Tank Loop probe and the junction box The remote Tank Loop te...

Page 33: ...ed daisy chained together in this way For a boiler to be seen on the network it s default network address of 0 must be changed to a number between 1 and 31 in the User Settings menu from the UIM Each...

Page 34: ...ust be configured correctly dip switch 3 does not affect operation on VF boilers Switch 1 Spare On Off Switch 2 High gas pressure switch is optional this switch must be set to Off if there is not a hi...

Page 35: ...he MCB will read 0 rpm even though the blower is running The control system would then lock out and display the Ignition Speed error message The MCB contains a resistor for the VFD enable disable circ...

Page 36: ...wer supply protection Wiring and connection details given here reference 100 101 Series VF boilers The wiring and connection information given in this document is in reference to how the EMC 5000 cont...

Page 37: ...er NEMA standards using a 30 amp dedicated circuit breaker The power supply must be in a dedicated conduit Hot wires neutral wires and ground wires must not be shared with any other appliances includi...

Page 38: ...e on board remote pump relay connected to TB1 terminal board on the PDB page 36 For 120 VAC outputs between 5 and 20 FLA use an external relay starter and supply 120 VAC pump power through the 20 amp...

Page 39: ...s 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 Pin 10 24 VAC Hot to S...

Page 40: ...3 Earth Ground to MCB J1 Socket Pin 4 120 VAC Hot to VFD Input Terminals page 11 Pin 5 120 VAC Neutral to VFD Input Terminals page 11 Pin 6 Earth Ground to VFD Input Terminals page 11 Pin 7 Spare 120...

Page 41: ...n LEDs should be illuminated and the red LED should be off If any other combination of LEDs are illuminated refer to the table below for the problem indicated and what corrective action must be taken...

Page 42: ...y the flow switch flow switch contacts are closed an asterisk will appear in front of the Flow menu item Flow Things to check before servicing Using the Instruction Manual that came with the boiler as...

Page 43: ...nd install a new comm cable standard Cat 5 net work cable Plug UIM comm cable into other internal comm port on the MCB page 32 Closely inspect communication ports on MCB and UIM for damage or wear pag...

Page 44: ...on Plug UIM comm cable into the other internal comm port on the MCB see page 32 Check comm cable to the UIM Turn off power and Install a new different comm cable standard Cat 5 network cable Inspect b...

Page 45: ...g to perform this step thoroughly often results in needless down time unnecessary parts replacement and customer dissatisfaction Ensure the Config Key is securely plugged into the J23 socket on the MC...

Page 46: ...nsformer if rating is less than 100 VA Secure power to boiler temporarily disconnect load wiring from secondary coil on transformer Turn power back on and check voltage at sec ondary coil if secondary...

Page 47: ...m this step thoroughly often results in needless down time unnecessary parts replacement and customer dissatisfaction VB Models No Factory Pump Check for power at the pump motor if the pump has power...

Page 48: ...fore performing the check repair procedures here New boiler installations in older systems Check for restrictions in the water lines accu mulated lime to and from the boiler System lines can become re...

Page 49: ...se See pages 13 and 34 Close visual inspection of J24 plug socket con nection on MCB Daughter Board Ensure plug socket connect is in good condition and making good contact See page 34 Remove end cap f...

Page 50: ...p or failing to perform this step thoroughly often results in needless down time unnecessary parts replacement and customer dissatisfaction SW1 dip switch 8 is in the off position this dip switch must...

Page 51: ...nnecessary parts replacement and customer dissatisfaction 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 acti vated c...

Page 52: ...e manual always consider the wiring and connectors between components Perform a close visual inspection of all wiring and connectors to a given component before replacement Ensure wires were stripped...

Page 53: ...switches close on a fall in pressure the pressure sensed must be in a vacuum Operational Note See blower prover switch information on page 24 and the Sequence of Operation on page 15 Ensure the sensin...

Page 54: ...er failure during the heating cycle or if the pressure sensed by the switch rises above the switches activation pressure for any reason The normally open contacts on both Blower Prover switches close...

Page 55: ...all in pressure the pressure sensed must be in a vacuum Operational Note See blower prover switch information on page 24 and the Sequence of Operation on page 15 Determine if High BPS is causing the l...

Page 56: ...ence of Operation on page 15 Pressure Reading Test Take a manifold gas pressure reading See page 23 for how to perform this test Allow the boiler to operate until the Pre purge cycle com pletes and th...

Page 57: ...a normally closed switch Check all wiring between the Blocked Flue Switch and the MCB J5 socket pins 5 6 page 28 Closely inspect the J5 socket plug repair replace anything worn or damaged Disconnect t...

Page 58: ...es on pages 20 23 View the burner through the view port near the igniter on the top of the combustion chamber during the ignition trial period If the burner is igniting but the flame goes out in a few...

Page 59: ...en results in needless down time unnecessary parts replacement and customer dissatisfaction Check igniter amperage during igniter warm up period If amp draw is less than 3 0 amps replace the igniter E...

Page 60: ...re power to the boiler Remove the gas pressure test plug at the outlet of the boiler s 24 VAC gas valve Install a barbed hose adapter fit ting in this test port Connect a U tube or digital manometer t...

Page 61: ...ng 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 d...

Page 62: ...dependently or work with an external supervisory control utilizing the Enable Disable circuit 2 The Enable Disable circuit page 65 must be closed Two wires are provided in the wiring junction box on t...

Page 63: ...s A change in temperature causes a corresponding change in electrical resistance ohms The EMC 5000 control system interprets the probe resistance as temperature VF boilers have two factory installed t...

Page 64: ...to temperature sensed by the Controlling Probe When the temperature sensed at the Controlling Probe drops below the Operating Set Point minus the Stage 1 Differential AND the Enable Disable circuit pa...

Page 65: ...programmed for more than 20 F above Operating Set Point but not for less The Operating Set Point cannot be raised higher than 20 F below the Automatic High Limit Hi Limit set point Keep this in mind...

Page 66: ...conduit page 68 The external control can then enable disable the boiler by closing or opening its contacts When the external control opens it s contacts the boiler is disabled and goes through a norm...

Page 67: ...d by an EMS control equipped with it s own Tank Loop temperature sensor Supervisory functionality such as occupied unoccupied and or freeze protection can be programmed in EMS systems to enable or dis...

Page 68: ...r systems DO NOT connect the cold water make up line to the boiler return inlet piping as this will make maintaining 120 F minimum inlet water temperature more difficult Bypass Lines Bypass lines shou...

Page 69: ...icated conduit Flame Sensors 2 High and Low fire 5 A DC micro amps current typical Flame detection failure occurs under 2 5 A Igniter Silicon Carbide 40 to 70 ohms cold 3 0 to 4 0 AC amps typical mini...

Page 70: ...level is low High Speed Combustion Blower 120 VAC 50 60 Hz 3A MCB J15 Socket Low Speed Combustion Blower 120 VAC 50 60 Hz 3A MCB J15 Socket Hot surface igniter Silicon Carbide 120 VAC 50 60 Hz must p...

Page 71: ...t circulate time Selectable 45 90 180 seconds or continuous VW MODELS DEFAULT SETTING ADJUSTABLE RANGE Oper Setpnt Operating Setpoint 145 F 63 C 70 F to 190 F Stage1 Diff Operating Setpoint Differenti...

Page 72: ...fall in pressure It is used to detect that the blower is running during the heating cycle Connects to J17 socket on MCB see pages 24 and 28 Low Gas Pressure Switch This is a normally open pressure sw...

Page 73: ...C only Connects to internal communications port on MCB see page 32 VFD Variable Frequency Drive A component that varies the power supply s frequency Water Flow Switch This is a normally open paddle ty...

Page 74: ...ation 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 Tennesse...