A.O. Smith VB/VW- 1000, VB/VW- 750 instruction manual Inputs to MCB

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Inputs to MCB

TEMPERATURE SENSORS:

Temperature probes (MCB - outlet and either inlet or tank are required): The MCB accepts analog temperature inputs from up to three sensors (inlet, outlet, and tank).

MRHL (Manual Reset HIGH LIMIT): The MRHL is a hi-limit switch located inside the outlet probe. It is a normally closed switch that opens if the probe is exposed to a temperature higher than the trip point. Once tripped, the control system needs to be manually reset.

Thermostat input (MCB - optional): This input is set up to work with an externally connected thermostat that provides a contact closure. If this input is closed and everything else is in the proper state, a “call for heat” condition will be initiated. These leads should be shorted together when a thermostat is not being used. If it is desired that the thermostat control the temperature of the boiler, the operating setpoint of the system should be set higher than the temperature that the thermostat is controlling. This will allow the thermostat to control the boiler. When the thermostat closes, a call for heat will be generated until the thermostat determines that the required temperature has been reached.

AirPressureSensors(openconditionindicatesfault):

Blocked Inlet (MCB - required) Normally closed switch that activates if the air inlet is blocked 3/4 or more during operation.

Blocked Flue (MCB - required): Normally closed switch that opens if the flue becomes blocked during operation.

Blower Prover (MCB - required): Normally open switch that closes when the air pressure produced by the blower is above the set point.

GasPressureSensors(openconditionindicatesfault):

Low Gas (MCB - required): Normally open switch that closes when the gas pressure rises above the trip level. This input is enabled/ disabled by a dip switch on the MCB

Hi Gas (MCB - required): Normally closed switch that opens if the gas pressure exceeds a set value. This input is enabled/disabled by a dip switch on the MCB.

Water Level Sensor (open condition indicates fault):

Low Water Cut Off (MCB - optional): Normally open switch that closes when water reaches preset level. This input is enabled/ disabled by a dip switch on the MCB.

Water Flow Sensor:

Flow (MCB - required): Normally open switch that closes when flow exceeds a set value.

Flame Sensor:

Flame (MCB - required): Returns a signal to the microprocessor if flame is detected on the burner. If the flame rod is missing or shorted, the flame will not be detected.

OUTPUTS FROM MCB

Relay Contact Output:

Alarm (MCB - 24VAC - optional): Provides electrical power to operate an external alarm. This can be an audio device (i.e., Sonalert), a visual device (lamp), or any other device that will operate with the voltage and current level provided.

Pump (MCB - 120VAC - required on systems that do not have an external pump): Provides electrical power to directly operate a pump or the coil of an externally connected contactor.

Blower (MCB - 120VAC - required): Variable speed blowers utilize the high blower output only.

Igniter (MCB - 120VAC - required): Provides power to operate the HSI igniters.

Gas Valve (MCB - 24VAC - required): Provides power to activate the gas valve. The gas valve cannot be activated when the MRHL contacts are open.

Low Water Cut Off (MCB - 24VAC - optional): Directly connected to the 24VAC line to provide power to operate an external LWCO device.

MCB AND PDB INDICATOR LAMPS AND FUSES

A green LED is mounted on the PDB to indicate when line voltage is applied (the PDB also contains a yellow and red LED, and a test/ run jumper that are used during installation to verify proper power connections). A red LED on the MCB is used to indicate when the 24VAC input fuse has blown.

Yellow LEDs are located near the microcontrollers on the MCB. These LEDs are “heartbeat indicators,” and blink approximately twice per second to indicate that the microcontrollers are running.

MCB JUMPERS

The MCB has two jumpers. JP1 on the MCB is used to terminate the external communications line. It is normally left off and installed when the external cable is very long.

IGNITERS

The EMC modulation system operates with Silicon Carbide Igniters

MCB - Ten Position Dipswitch:

Dipswitch configurations are READ ONLY ON POWER UP. These switches are only to be set at the factory or by authorized trained personnel! Once set the boiler will operate according to the chosen options. If a switch is changed, power must be cycled before the change will take effect. The status of all dipswitches can be observed on the system status screen on the UIM.

TABLE 13. - MCB/FCB Dipswitches:

Dipswitch Function

 

 

Switch Position

 

 

 

Hot Water Boilers

Hydronic Heating Boiler

Switch 1: Selection of the type of boiler application:

On

=

VW

Off

=

VB

Switch 2: Trials for ignition:

On

=

3

Off

=

1

Switch 3: IRI Gas Valve Not Available:

 

 

 

 

 

 

Switch 4: Controlling Probe:

On

=

Tank (Remote)

Off

=

Inlet

Switch 5: Powered Venter:

On =

Yes

Off =

No

Switch 6: Low Water Cut Off: (LWCO)

On =

Yes

Off =

No

Switch 7: Low Gas Pressure

On =

Yes

Off =

No

Switch 8: Modulation:

On

 

 

 

 

 

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Contents Models Safe INSTALLATION, USE and Service General Safety Dimension and capacity data GAS and Electrical CharacteristicsRecovery Capacities Capacity and Flow dataContents IntroductionField Installed Components PrecautionsHigh Altitude Installations Grounding InstructionsControl Components Temperature Probes Water Temperature Limit ControlsON/OFF Switch Circulating PumpPanels and Covers Required AbilityLocation VB HOT Water Heating BOILERS, are shipped with a 50 psiLeveling Installtion ClearancesChemical Vapor Corrosion Air Requirements Breathing Hazard Carbon Monoxide GasOutdoorAir Through Two HorizontalDucts Outdoor Air Through Two OpeningsOutdoor Air Through One Opening Outdoor Air Through Two Vertical DuctsAir From Other Indoor Spaces Termination Clearances Sidewall Power Vent Power VentTermination Clearances Sidewall Direct Vent Direct VentConnecting Vent to Boiler Special Installation ConsiderationsVenting System Using AL 29-4C Venting Supports Vertical Installation RequirementsHorizontal Installtion Requirements Vertical Termination Direct Vent Installation Requirements BELOW. Keep Clear of ALL ObstructionsDirect Vent Horizontal Direct Vent Using TWT with Vertical Intake Hot Water Heating Hydronic Equipment System installationGeneral Hard Water Conditions Remote Probe Installation ProcedureInternal Contaminants Thermal Expansion Closed SystemGas Connections Gas Supply Line SizingTypical PRIMARY, Secondary Piping ONE VF Model VW HOT Water Supply Boiler with Vertical Tank ONE VF Model VW HOT Water Supply Boiler with Horizontal Tank Wiring Suggested Pipe Size For Multiple Gas Appliances Natural Gas Suggested Pipe Size For Multiple Gas Appliances Propane GasWiring Diagram Connection DiagramPage VB/VW-500, 750 & 1000 Schematic Diagram Operation Filling and Purging of Heating Boiler InstallationFilling Hot Water Supply Boiler Installation Purging Gas LineWater Temperature Regulation Risk of ScaldsMCB Three position Dipswitch MCB Ten Position DipswitchMCB/FCB Dipswitches Lighting & Operation Instructions for Models VB/VW 500, 750 High Fire Setting Natural GAS AdjustmentSetting of the Test Mode PropaneInputs to MCB Temperature Setpoints System Control Algorithm Operating SequenceUIM Operating Procedures OperatingSetpointAdjustmentProcedure Description of FCB control statesHighLimitDifferentialSetpointAdjustment Procedure Fault Messages and Troubleshooting Guide UIM LED’sTroubleshooting Ignition System Fault Displayed Description Red LED LockoutMain Burner Preventative maintenanceTroubleshooting Gas Valve Combustion Air Filter Burner MaintenanceRelief Valve Blower CompartmentTube Cleaning Procedure Mechanical Removal of Deposits Venting MaintenanceHeatExchangerPreventativeMaintenance Replacement PartsPage Page Page Limited Warranty Tennessee Waltz Parkway, Ashland City, TN Phone

VB/VW- 1000, VB/VW- 750 specifications

A.O. Smith is a renowned name in the water heating industry, and their VB/VW-750 and VB/VW-1000 models reflect the cutting-edge advancements in both design and functionality. These commercial water heaters stand out due to their innovative features and robust characteristics, making them ideal solutions for various applications in commercial settings.

The VB/VW-750 and VB/VW-1000 models are designed with high efficiency in mind. They utilize advanced heat transfer technology that maximizes energy use, translating to significant savings on utility bills. These units are engineered to deliver consistent hot water supply, essential for businesses such as restaurants, hotels, and manufacturing facilities where extensive hot water demands are necessary.

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Maintenance and serviceability are key characteristics of these models. They feature easy access to critical components, allowing for quick inspections and repairs. This design consideration minimizes downtime, which is crucial for any business reliant on continuous hot water supply.

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