Vulcan-Hart MHB24G, VHX24G5 manual High Limit, Cycling

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VHX SERIES STEAMER - SERVICE PROCEDURES AND ADJUSTMENTS

boiler shell, remove and clean the Aux LLCO probe.

a.Replace the probe and check resistance again. If resistance is still present, install a new probe.

b.Replace lead wire on probe and repeat steps "2) thru 4)" to verify proper operation.

PRESSURE SWITCHES

4.The cycling pressure switch will maintain the steam pressure setting in the boiler by cycling the main burner ON and OFF.

High Limit

Adjusting the High Limit pressure switch from a cold startup is the preferred condition of the boiler. On the initial cold startup, the highest overshoot pressure (drift) is achieved after the burner cycles OFF for the first time. If the boiler is already operating, the pressure setting can still be made after following the procedures outlined below.

WARNING: THE FOLLOWING STEPS REQUIRE POWER TO BE APPLIED TO THE UNIT DURING THE TEST. USE EXTREME CAUTION AT ALL TIMES.

Remove the cover from the pressure switch control box to access the two pressure switches. The pressure switch near the front is the cycling pressure switch and the one beside it is the high limit pressure switch.

Cycling

1.If the boiler is already operating, proceed to step 2. If the boiler is not already operating, start the boiler as outlined under "CABINET BASE BOILER" in "STEAMER OPERATION".

2.Turn one of the cooking compartment timers ON to exhaust steam from the boiler.

3.Monitor the boiler pressure gauge for several cycles and note the pressures at which the burner comes ON and goes OFF.

A.The main burner should come ON at 8 PSI and go OFF at 10 PSI. If the readings differ, adjust the pressure settings as described below.

1)Two pressure adjustment screws extend through the top of the switch case. The screw directly above the right side pointer raises or lowers both the cut-out (OFF) and the cut-in (ON) set points simultaneously, without affecting the differential.

The screw directly above the left side pointer raises or lowers the cut-in (ON) set point and changes the differential.

2)Turn the adjustment screw above the right side pointer to obtain the proper cut-out (OFF) setting first, then adjust the other screw to obtain the proper cut-in (ON) setting.

a.A clockwise rotation increases the pressure setting while a counterclockwise rotation decreases the pressure setting.

1.The high limit pressure switch should be adjusted to allow a maximum pressure in the boiler of 14.5 to 15.0 PSI. Before making adjustments to the high limit pressure setting, the 13 PSI pressure relief valve (PRV- left side) must be temporarily disabled. This will allow a high enough pressure in the boiler to properly set the switch.

A.The suggested methods to prevent the valve from releasing pressure are:

1)Use a wooden block, a hand tool or other object to hold the valve plunger down.

2)Use a metal wire threaded through the hole in the valve handle and tie the pressure relief valve handle to the piping below it.

3)If neither of the two methods keep the valve fully closed without leaks, an alternate method is:

a.Turn the power switch OFF and allow the boiler to blowdown.

b.Remove the discharge piping from the valve outlet and insert a pipe plug for temporary use only.

2.Turn the power switch ON and allow the boiler to completely fill.

A.High Pressure and Low Water indicator lights (amber) come ON.

3.When water in the boiler reaches the minimum level, the green light on the reset switch will come ON.

A.Press the reset switch on the front control panel to reset the High Pressure and Low Water safety controls.

1)Ignition sequence starts, main burner lights and water in the boiler begins to heat.

4.Monitor the boiler pressure gauge and note the pressure at which the high limit switch opens.

NOTE: In front of the boiler there is an additional

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F24700 (October 2001)

 

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Contents VHX24G Shown VHX Boiler Base Series High Efficiency GAS SteamersTable of Contents VHX Series Steamers Installation Maintenance Cleaning IntroductionGeneral Boiler Control Styles Electrical Water Conditioning SpecificationsSystem Water SupplySpecial ToolsGas Supply StandardVHX Series Steamers Operation Steamer OperationCabinet Base Boiler Cooking Compartment ControlsBoiler Blowdown Steamer Shut OFF Ignition Control Module Component FunctionVHX Series Steamers Component Function Blowdown/DrainPressure Relief Valve Steam Header AssemblyWater Level Water Inlet Valve manualSteam Supply Manifold Compartment Pressure SwitchSteam Solenoid Valve Manifold Pressure GaugeCabinet Base Boiler Controls Removal and Replacement of PartsVHX Series Steamers Removal and Replacement of Parts Component LocationsCabinet Base Boiler Controls Water Level Controls Main or Auxiliary Llco Relay BoardCooking Compartment Controls Water Level Gauge Assembly Pressure SwitchesBoiler Assembly Boiler Fill and Cold Water Condenser Solenoid Valves Pilot GAS Valve Main GAS ValveComplete Burner Assembly Burner Head AssemblyHeat Exchanger VHX Series Steamers Removal and Replacement of Parts Cooking Compartment Doors RemovalGasket Handle Latch AssemblyInspection Service Procedures and AdjustmentsClean-Out BoilerDescaler Cathodic Protector Water Level Probe Housing BlowdownTest Water Level ControlsAuxiliary Low level Cut-Off Control Cycling High LimitSmall increments Fill and Cold Water Solenoid ValvesBoiler BLOWDOWN/DRAIN Solenoid Valve Inline Water Strainer CleaningMain Burner Ignition Checks Pressure Switch AdjustmentGAS 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 Terminals Ignition Control Module ChecksSpark Verification Test Cooking Compartment Doors Intake Shut-Off Valve Adjustment Steam FlowDoor Sealing Adjustment Cooking CompartmentVHX Series Steamer Electrical Operation Door Latch AdjustmentLow Level Cut-Off & Differential Control Electrical OperationAuxiliary Low Level Cut-Off LED Legend Board Layout and LED LegendAux Water Level Satisfied State B Boiler Operational Status LED IndicatorReset Engaged State C Initial Conditions State aBurner ON, Boiler Heating to generate steam State E Air Pressure Switch Satisfied State DK32 Close K51 CloseHL-LED Sequence of OperationNEW Style Controls Boiler Initial Fill and PreheatN14, N16, N17 go out N9, N10, N11, N12, N13 go outBoiler Blowdown/drain Water Refill After Initial FillVHX Series Steamer Electrical Operation Cooking Compartment Controls This page Intentionally Left Blank Models Built After 5/25/00 New Style Boiler Controls SchematicsVHX 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
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