Vulcan-Hart VSX24D Service Manual page 31

VSX SERIES STEAMER - ELECTRICAL OPERATION
Solid State - Auxiliary Low Level Cut-Off
This control serves as a safety backup to the main
water level control (WLC) board to meet Cal-Code
and 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. On CSD-1 models, the low water
level indicator light (amber) on the boiler control box
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
button on the boiler control box. On CSD-1 models,
this energizes the low water relay, turns off the low
water light and energizes the heat source auxiliary
control. On Cal-Code models, this closes and locks
the manual reset switch contacts to energize the
heat source auxiliary control.
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