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VL SERIES STEAMER - ELECTRICAL OPERATION
Pa
g
e 40 of 88
Electro Mechanical - Low level Cut-Off &
Differential Control
The steamer is equipped with three water level
sensin
g
probes (hi
g
h, 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 hi
g
h water level probes.
Each control is powered by input volta
g
e (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 throu
g
h a series path
g
oin
g
from one side of the secondary windin
g
,
throu
g
h the contactor coil, throu
g
h the water level
control probe, throu
g
h the water in the boiler and to
the boiler for
g
round. The other side of the
transformer secondary is attached to
g
round.
When the main power switch is turned ON, both
water level controls are ener
g
ized. The boiler fill
solenoid is then ener
g
ized throu
g
h the normally
closed contacts (terminals 3 & 4) on the differential
level control and water be
g
ins fillin
g
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 ener
g
ized. With the contacts
on terminals 7 & 8 now closed, the heat source is
then ener
g
ized. The internal contactor coil will
remain ener
g
ized 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 switchin
g
occurs.
After the water level reaches the hi
g
h level (HL)
probe, the differential control contactor coil is
ener
g
ized and the normally closed contacts on
terminals 3 & 4 open, which de-ener
g
izes the boiler
fill solenoid and stops the flow of water into the
boiler. The internal contactor coil will have a lockin
g
path throu
g
h contacts 7 & 8 to the low level probe to
keep the coil ener
g
ized after the water level drops
below the hi
g
h level probe.
When the water level drops below the low level (LL)
probe, the internal contactor coil is de-ener
g
ized,
returnin
g
contacts 3 & 4 back to their normally
closed state and ener
g
izin
g
the boiler fill solenoid to
refill the boiler. The water level must then fill to the
hi
g
h level probe a
g
ain, to ener
g
ize the internal
contactor coil. The differential control will to
gg
le ON
and OFF durin
g
a cookin
g
cycle as needed.