Contactors; Transformer - Bradford White VR-150-(kW) Installation And Service Manual

A main power terminal block is provided for field connection of the branch power supply to the electric
water heater. All internal power circuits to the immersion heating elements are connected to the load side
of the main terminal block. The line side of the terminal block has individual lug type connections
properly sized for the recommended copper field wire size.
FUSE AND FLUE BLOCKS:

CONTACTORS:

CONTROL CIRCUIT TRANSFORMER:
A transformer is used to reduce the line voltage to 120 VAC for
internal control operation. The transformer is fused on both the
primary and secondary side. The common side of the secondary
control circuit is grounded. The VA rating of the control circuit
transformer is based on the load of the various components in the
water heater control circuit.
When appliance amperage exceeds 120Amps, each internal
power circuit is fused for safety. Each power circuit to an
immersion element is fused at a maximum of 48 amps. Power
circuits may be fused at lower current levels as needed to
balance current on three phase units. The power circuit fuses are
held by a spring loaded fuse block rated for the voltage specified
to operate the water heater.
The control circuit is also fused on both the primary and
secondary sides of the control circuit transformer.
The power to the immersion electric heating elements
is switched by a definite purpose magnetic contactor.
The contactor is supplied with 120 VAC from the
control circuit when the immersion thermostat senses
a drop in stored water temperature below the desired
set point. A magnetic coil in the contactor is
energized to complete the electrical circuit supplying
power to the immersion heating elements. When the
thermostat is satisfied, the contactor coil is de-
energized and power to the heating elements is
turned off.
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