VHX SERIES STEAMER - ELECTRICAL OPERATION
F24700 (October 2001)Page 41 of 68
ELECTRICAL OPERATION
WATER LEVEL CONTROLS
Low Level Cut-Off & Different i al Control
The steamer is equipped with three water lev el
sensing probes (high, low and low level cut-of f) and
a single water level control boar d (solid state). The
water level control board perf orms two functions: 1)
Provide low level c ut -off protection to shut of f the
heat source in case the water level drops below the
low level cut-off (LLCO) probe. 2) Perform as a
differential level control to maintain the water level
between the low and high water level probes.
The water level control (W LC) has input voltage
(120VAC) across terminals 11 and 12 which powers
the primary side of the transf ormer. On one side of
the transformer secondary, power is prov i ded to the
control by a series path through chassis ground
(terminal 10). The other side of the transformer
secondary (12VAC) is attached to the probe that
directs power to the other side of board relay coi ls
(LLCO and HL) and to the Inverse Latching Rel ay
(ILR) electronic circui t on the board. As water enters
the boiler, it becomes part of the water level
control’s circuit. W hen t he water level in the boiler
reaches a probe, that circuit is com pl eted.
The inverse latching relay of the board is de-
energized, leaving the ILR- 1 ( N .O.) and I LR- 2 ( N. C.)
contacts in their shelf state.
When the main power switch is turned ON, power i s
supplied to the WLC board which energizes the hi gh
level (HL) relay, cl oses HL-3 normally open
contacts, and illuminates the HL relay LED. With the
HL-3 contacts closed, the boiler fill solenoid is
energized and water begins filling the boiler.
When the water level reac hes the l ow level cut-off
(LLCO) probe, the LLCO relay is energized and
illuminates the LLCO LED. With the LLCO-2
contacts closed the heat source is then energized.
The LLCO relay will remain energized and its LED
will stay lit until the water level in the boiler drops
below the LLCO probe. NOTE: Auxiliary control(s)
in the heating circuit m ust al so be satisfied before
heating can start.
When the water level reac hes the l ow level (LL)
probe, power to terminal 2 on the W LC board is
present but no switching occurs.
After the water level r eac hes the hi gh level (HL)
probe, the inverse latching rel ay of the board is
energized and locked through the low lev el probe
(LL) and ILR-1 contacts. With I LR-2 contacts open,
this de-energizes the HL relay and the HL LED goes
out. With the HL-3 contact s open, the boiler fill
solenoid is de-energized, stopping the fl ow of water
into the boiler.
When the water level drops bel ow the l ow level (LL)
probe, power is removed from t he inverse latching
relay, the HL relay energizes through ILR-2 and HL
contacts change state. The fill solenoid is energized
through HL-3 to refill the boiler and the HL LED is lit.
The HL relay and LED will toggle ON and OFF
during a cooking cycle as needed.