VSX SERIES STEAMER - ELECTRICAL OPERATION
Page 32 of 80
Electro Mechanical - Low level Cut-Off & Differential Control
The steamer is equipped with three water level sensing probes (high, low and low level cut-off), a differential
level control (1G1GO) and a low level cut-off control (1D1DO). The low-level cut-off is an additional control that
is identical to the differential level control but serves as the safety backup to shut off the heat source in case the
water level drops below the low level cut-off (LLCO) probe. The differential level control maintains the water level
between the low and high water level probes.
Each control is powered by input voltage (120VAC) on terminals 1 and 2 which also connect to the primary side
of the internal transformer. The transformer secondary (300VAC) will provide power to the internal contactor coil
through a series path going from one side of the secondary winding, through the contactor coil, through the water
level control probe, through the water in the boiler and to the boiler for ground. The other side of the transformer
secondary is attached to the probe that directs power to the other side of the internal contactor coil.
When the main power switch is turned ON, both water level controls are energized. The boiler fill solenoid is then
energized through the normally closed contacts (terminals 3 & 4) on the differential level control and water
begins filling the boiler.
When the water level reaches the low level cut-off (LLCO) probe, the internal contactor coil on the low water
level control is energized. With the contacts on terminals 7 & 8 now closed, the heat source is then energized.
The internal contactor coil will remain energized until the water level in the boiler drops below the LLCO probe.
When the water level reaches the low level (LL) probe, power to terminal 7 on the differential level control will be
present but no switching occurs.
After the water level reaches the high level (HL) probe, the differential control contactor coil is energized and the
normally closed contacts on terminals 3 & 4 open, which de-energizes the boiler fill solenoid and stops the flow of
water into the boiler. The internal contactor coil will have a locking path through contacts 7 & 8 to the low level
probe to keep the coil energized after the water level drops below the high level probe.
When the water level drops below the low level (LL) probe, the internal contactor coil is de-energized, returning
contacts 3 & 4 back to their normally closed state and energizing the boiler fill solenoid to refill the boiler. The
water level must then fill to the high level probe again, to energize the internal contactor coil. The differential
control will toggle ON and OFF during a cooking cycle as needed.
