SEQUENCE OF OPERATION
Sequence of Operation:
600V Surface Mounted Thermostats (w/Contactors).
Line voltage is applied across ter minals of fuse block
or a terminal block. Line voltage continues down and
connects to terminals L1, L2 & L3 of one or more
contactors.
A) Contactor is open (no call for heat), so there is no
voltage across terminal T1, T2 & T3
of contactor.
B) The contactor is controlled by the control circuit
consisting of the surface mounted thermostat,
ECO (hi limit) and contactor coil.
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1
2
Contactor
Fuse Block
Line Voltage
When the thermostat calls for heat , contacts close
inside the thermostat completing the circuit through
the ECO and energizing the contactor coil.
The system has two distinctcircuits.
1. Power circuit - Line Voltage (600V)
2. Control Circuit - 120V
The energized contactor coil causes the contactor to
close, energizing the elements from term inals T1, T2
& T3 of the contactor.
3
When the temperature setting of th e thermostat is
reached, the contacts in the thermostat open. This
interrupts current flow through t he control circuit de-
energizing the contactor coil.
4
The de-energized contactor coil causes t he contactor
to open, interrupting current fl ow through the
elements. The heater is now in stand-by waiting for
the next call for heat.
5
Heating Elements
High Limit
59T
Transformer
60VA
59T
Notice in the wiring diagram at right that each row of
elements is equipped with a surface mounted
thermostat on the highest element in the row. These
thermostats are individually wired in series to the
contactor whose line voltage corre sponds to the same
row of elements. Each thermostat and contactor
combination are wired to the high limit (ECO) device
in parallel. This allows for ea ch row of elements to be
powered “ON” independent of the other element rows.
However, the high limit (ECO) is wired in series so
that voltage can be interrupted to the entire control
circuit if the ECO senses that the tank water has
become overheated.
6
6 Element Configuration Shown
(9 Elements Possible)
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