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CLOSED WATER SYSTEMS
Water supply systems may, because of code requirements or such
conditions as high line pressure, among others, have installed
devices such as pressure reducing valves, check valves, and back
flow preventers. Devices such as these cause the water system to
be a closed system.
THERMAL EXPANSION
As water is heated, it expands (thermal expansion). In a closed
system the volume of water will grow when it is heated. As the
volume of water grows there will be a corresponding increase in
water pressure due to thermal expansion. Thermal expansion can
GENERAL
Check the water heater model and rating plate information against
the characteristics of the branch circuit electrical supply. Do not
connect the heater to an improper source of electricity.
Voltage applied to the heater should not vary more than +5% to -10%
of the model and rating plate marking for satisfactory operation.
Do NOT energize the branch circuit for any reason before the water
heater tank is filled with water. Doing so may cause the heating
elements to fail.
The factory wiring is attached to a terminal block on the unit. The
branch circuit is connected to the block through an opening provided
on the heater. Factory terminal block has 500 MCM maximum
copper wire size capacity in each opening. If apparent field wire
size is over 500 MCM multiple terminal blocks will be furnished.
If other opening sizes are desired they should be specified when
unit is ordered.
The installation must conform with these instructions and the
local code authority having jurisdiction and the requirements of
the power company. In the absence of local codes, the installation
must comply with the current editions of the National Electrical
Code, NFPA 70 or the Canadian Electrical Code CSA C22.1.
BRANCH CIRCUIT
The branch circuit wire size should be established through
reference to the NEC (National Electrical Code) or other locally
approved sources in conjunction with the water heater amperage
rating.. Wire rated at 75°C should be used. For convenience,
portions of the wire size tables from the Code are reproduced in
Table 1. It is suggested the electrician size the branch circuit at
125 percent of the heater rating and further increase wire size as
necessary to compensate for voltage drop in long runs. Voltage
drop should not exceed 3% at the water heater.
HEATER CIRCUITS
The water heater's electrical components are pictured and identified
by the Features and Components illustrations on pages 9 and 10.
The model and rating plate illustration identifies the heater electrical
characteristics. The heater has two electrical circuits:
Control Circuit: 120V circuit containing all safety and control devices.
The control circuit operates the contactors in the power circuit.
Power Circuit: High voltage, single or three phase circuit that carries
the heating element load.
The following section and pages describe the water heater circuits
and includes wiring diagrams.
cause premature tank failure (leakage). This type of failure is not
covered under the limited warranty. Thermal expansion can also
cause intermittent temperature-pressure relief valve operation:
water discharged from the valve due to excessive pressure build
up. This condition is not covered under the limited warranty. The
temperature-pressure relief valve is not intended for the constant
relief of thermal expansion.
A properly sized thermal expansion tank must be installed on all
closed systems to control the harmful effects of thermal expansion.
Contact a local plumbing service agency to have a thermal expansion
tank installed.
ELECTRICAL
13
These ampacities relate only to conductors described
in Table 310-13 of the NEC. For ambient temperatures
over 30°C, see Correction Factors, Note 13 in the NEC.
TABLE 1. BRANCH CIRCUIT WIRE SIZE.
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