Auxiliary Low Level Cut-Off | Vulcan-Hart MHB24G, VHX24G5 specification

VHX SERIES STEAMER - ELECTRICAL OPERATION

Auxiliary Low Level Cut-Off

This control serves as a safety backup to the main water level control (WLC) board to meet CSD-1 code requirements. The operation of the auxiliary control is identical to the low level cut-off (LLCO) function of the main WLC board but performs a single function: 1) Provide auxiliary low level cut-off protection to shut off the heat source in case the water level drops below the low level cut-off (LLCO) probe. A single LLCO probe, identical to the LLCO probe on the main WLC board, is connected to the auxiliary control.

The auxiliary water level control (WLC) has input voltage (120VAC) across terminals 11 and 12 which powers the primary side of the transformer. On one side of the transformer secondary, power is provided to the control by a series path through chassis ground (terminal 10). The other side of the transformer secondary (12VAC) is attached to the control that directs power to the other side of the internal relay (LLCO). As water enters the boiler, it becomes part of the auxiliary water level control’s circuit. When the water level in the boiler reaches the LLCO probe, the circuit is completed.

When the main power switch is turned ON, power is supplied to the auxiliary WLC board but no switching occurs. Also, the low water level indicator light (amber) on the boiler base control panel comes on.

When the water level reaches the low level cut-off (LLCO) probe, the LLCO relay is energized (LLCO-2 close) and the LLCO LED lights up. The LLCO relay will remain energized and its LED will stay lit until the water level in the boiler drops below the LLCO probe.

When the boiler stops filling, press the manual reset switch on the boiler base control panel. This turns off the low water light, energizes the combustion blower and allows the ignition cycle to begin.

F24700 (October 2001)		Page 42 of 68

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Vulcan-Hart MHB24G, VHX24G5 manual Auxiliary Low Level Cut-Off

Contents

VHX Boiler Base Series High Efficiency GAS Steamers VHX24G Shown Table of Contents VHX Series Steamers Installation Maintenance Cleaning IntroductionGeneral Boiler Control Styles Water Supply Water Conditioning SpecificationsSystem Electrical Standard ToolsGas Supply Special Cooking Compartment Controls Steamer OperationCabinet Base Boiler VHX Series Steamers Operation Boiler Blowdown Steamer Shut OFF Blowdown/Drain Component FunctionVHX Series Steamers Component Function Ignition Control Module Water Inlet Valve manual Steam Header AssemblyWater Level Pressure Relief Valve Manifold Pressure Gauge Compartment Pressure SwitchSteam Solenoid Valve Steam Supply Manifold Component Locations Removal and Replacement of PartsVHX Series Steamers Removal and Replacement of Parts Cabinet Base Boiler Controls Cabinet Base Boiler Controls Water Level Controls Main or Auxiliary Llco Relay BoardCooking Compartment Controls Water Level Gauge Assembly Pressure SwitchesBoiler Assembly Pilot GAS Valve Main GAS Valve Boiler Fill and Cold Water Condenser Solenoid Valves Burner Head Assembly Complete Burner Assembly Heat Exchanger VHX Series Steamers Removal and Replacement of Parts Cooking Compartment Doors RemovalGasket Latch Assembly Handle Boiler Service Procedures and AdjustmentsClean-Out Inspection Water Level Probe Housing Blowdown Descaler Cathodic Protector Water Level Controls Test Auxiliary Low level Cut-Off Control High Limit Cycling Fill and Cold Water Solenoid Valves Small increments Inline Water Strainer Cleaning Boiler BLOWDOWN/DRAIN Solenoid Valve Pressure Switch Adjustment Main Burner Ignition Checks GAS Manifold Pressure Adjustment VHX Series Steamer Service Procedures and Adjustments AIR Pressure Switch Adjustment GAS Pilot Pressure Adjustment Pressure Readings Inches W.C GAS Manifold Pressure Adjustment Ignition Control Module Checks Terminals Spark Verification Test Cooking Compartment Intake Shut-Off Valve Adjustment Steam FlowDoor Sealing Adjustment Cooking Compartment Doors Door Latch Adjustment VHX Series Steamer Electrical Operation Electrical Operation Low Level Cut-Off & Differential Control Auxiliary Low Level Cut-Off Board Layout and LED Legend LED Legend Initial Conditions State a Boiler Operational Status LED IndicatorReset Engaged State C Aux Water Level Satisfied State B K51 Close Air Pressure Switch Satisfied State DK32 Close Burner ON, Boiler Heating to generate steam State E Initial Fill and Preheat Sequence of OperationNEW Style Controls Boiler HL-LED N9, N10, N11, N12, N13 go out N14, N16, N17 go out Water Refill After Initial Fill Boiler Blowdown/drain VHX Series Steamer Electrical Operation Cooking Compartment Controls This page Intentionally Left Blank Schematics Models Built After 5/25/00 New Style Boiler Controls VHX Series Steamer Electrical Operation Models Built Before 5/25/00 Old Style Boiler Controls Cooking Compartment Controls Wiring Diagrams VHX Series Steamer Electrical Operation Models Built Before 5/25/00 Old Style Boiler Controls VHX Series Steamer Electrical Operation Cooking Compartment Controls Troubleshooting VHX Series Steamer TroubleshootingBoiler Base Controls Symptom Possible Causes Adjustments Boiler blowdown solenoid valve clogged and not fully closing Boiler Base Procedures and Adjustments VHX Series Steamer Condensed Spare Parts List VHX Series Steamer Condensed Spare Parts ListNEW Style Controls only VHX24G, VHX24G5, MHB24G