Vulcan-Hart MHB24E, ML-126857, ML-126853, VHX24E5 Sequence Of Operation, Initial Fill and Preheat

VHX SERIES STEAMER - ELECTRICAL OPERATION

SEQUENCE OF OPERATION

Refer to schematic diagram AI1385 for the electrical sequence of operation.

Initial Fill and Preheat

1.Conditions.

A.Boiler connected to correct supply voltage and is properly grounded.

1)Supply voltage transformer energized and 120VAC is output from transformer secondary.

2)120VAC to compartment controls and one side of the power switch.

B.Power switch off.

C.Cycling pressure switch closed.

D.High limit pressure switch closed.

E.Cold water condenser (CWC) thermostat open.

F.Automatic blowdown/drain valve (A.B.D.) open and boiler empty.

G.Water supply valve(s) on.

2.Turn power switch on.

A.Automatic blowdown/drain valve (N.O.) is energized and closes.

B.Water level control (WLC) energized.

1)High level (HL) relay energized, HL-3 N.O. contacts close.

a.Boiler fill solenoid energized, water begins filling the boiler (fill time 4-11 min.).

2)LLCO-1 N.O. contacts remain open.

3)HL LED lit.

C.Auxiliary water level control (AUX WLC) energized.

1)AUX LLCO-1 N.O. contacts remain open.

D.120VAC to common relay terminal on K1(1) N.O., K3(1) N.O., K3(1) N.C., K3(2) N.O. , K4(1) N.O., K4(1) N.C contacts.

E.Low Water light lit thru K3(1) N.C.

F.High Pressure light lit thru K4(1) N.C.

G.K2 energized through the high limit pressure switch (N.C.).

1)K2 contacts K2(1) N.O. & K2(2) N.O. close, no power transferred.

H.120VAC to common terminal on AUX LLCO-1 contacts.

I.120VAC to common terminal on WLC LLCO-1 contacts thru cycling pressure switch (N.C.).

3.Water level reaches LLCO probe for the main water level control and AUX LLCO probe for the auxiliary water level control.

A.LLCO relay on water level control energizes, LLCO-1 contacts (N.O.) close

1)LED on board lights.

2)Cycling contactors B & D energized. Heating elements remain de- energized until manual reset switch pressed.

B.AUX LLCO relay on AUX water level control energizes, AUX LLCO-1 contacts (N.O.) close.

1)LED on board lights.

2)K1 is energized thru AUX LLCO-1 N.O. contacts.

a.K1(1) N.O. and K1(2) N.O. close.

b.Ready light on manual reset switch lit thru K1(1) N.O. contacts.

NOTE: The LLCO and AUX LLCO relays will remain energized and LLCO LED’S will remain lit until the water level drops below the LLCO probes or the power switch is turned off.

NOTE: The manual reset switch could be pressed to energize the heating elements but it’s preferred to let the boiler fill the to the high level before continuing.

4.Water reaches LL (low level) probe.

5.Water reaches HL (high level) probe.

A.Boiler fill solenoid is de-energized.

B.HL LED goes out.

6.Manual reset switch pressed.

A.K3 is energized.

NOTE: Relay K3 remains energized through K3(1) N.O. latching circuit.

1)K3(1) N.O. contacts close and K3(1) N.C. contacts open.

2)Low water light goes out.

3)K3(2) N.O. contacts close.

a.120VAC to common side of K4(2) N.O. contacts.

B.K4 is energized.

NOTE: Relay K4 remains energized through K4(1) N.O. latching circuit.

Page 33 of 48 F25154 (February 2004)