Service Manual

Page 13
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Power Circuit Description
The Power Circuit Wiring Diagram illustrates the electrical connections from the incoming power supply through
the contactors to the heating elements. The power circuits are available with internal circuit fusing and without
internal circuit fusing.
As it would be impractical to show all wired configurations in this service manual, a reference wiring diagram is
illustrated below to aid in the understanding of the power circuit operating sequence. Service providers must refer
to the water heaters power circuit wiring diagram attached to the inside panel of the control cabinet for the specific
connections of the water heater being serviced.
The power circuit components and supporting information that appear on the wiring diagram include the following:
 Field wiring connection via terminal block or other connection point;
 Fuse block with amperage ratings displayed (when provided);
 Contactors with amperage ratings displayed;
 Electrical elements with voltage and wattage ratings displayed;
 Water heaters total amperage draw is displayed.
Power Circuit Sequence
Line voltage is applied across terminals of a 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 as explained on pages 10 & 11.
The control circuit senses a call for heat and
energizes the operating coil within the
contactor.
The energized contactor coil causes the contactor
to close energizing the elements from terminals
T1, T2 & T3 of the contactor.
Line voltage from
service panel
Line voltage to
control circuit
When the temperature setting of the thermostat
is reached, the contacts in the thermostat open.
This interrupts current flow through the control
circuit de- energizing the contactor coil.
The de-energized contactor coil causes the
contactor to open, interrupting current flow
through the elements.
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