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PLUMBING CONNECTION Summer 2017
CLASS IS IN - HOT WATER 101
T
his article explores the electric
water heater - its operation,
function, installation, and
commissioning, to a system that has
been an industry mainstay for many
years particularly in non-reticulated
natural gas areas.
OPERATION
MAINS PRESSURE
Electric water heaters are designed to
operate at mains pressure by connecting
directly to the mains water supply. If the
mains supply pressure in the area exceeds
the unit’s cold water supply parameters,
a pressure limiting valve must be fitted.
The supply pressure should be greater
than 350 kPa for true mains pressure
performance to be achieved.
ELEMENTS
Each electric storage water heater
is fitted with at least one tubular single
phase immersion element located
near the bottom of the tank, controlled
by a contact thermostat and over-
temperature energy cut out mechanism.
The elements are attached to the
cylinder by a mounting plate and sealed
with a rubber gasket and four screws.
The tube of the element sheath
is made from copper. A resistor is
connected between the sheath and the
mounting plate to produce a resistance
earthed element, reducing unwanted
dissipation of the protective anode.
∫
Single Element Models
This type of water heater has one
element with its own thermostat,
located at the base of the water heater.
It can be connected to an Off-Peak
(overnight) or time controlled supply,
Extended Off-Peak (overnight and day)
or Extended Time controlled supply, or a
Continuous/Domestic electricity supply.
∫
Twin Element Models
These have two separate elements,
Since the mid-1940s Australia has utilised mains pressure electric storage water heaters for use in
domestic and commercial applications,
Jon Palfrey
explains the best practices of installation and
commissioning.
IN HOT WATER -
JON PALFREY
each with its own thermostat and over-
temperature energy cut out mechanism.
One is located near the base of the
cylinder and designed to heat the whole
cylinder.
The other element is located part
way up the tank to serve as a “booster”
to heat only the upper portion of the
contents of the cylinder in conjunction
with the main element circuit.
During normal operation only the
bottom element supplies all the hot
water. During periods of high demand
the top (booster) element operates, to
provide an additional supply of heated
water.
NOTE:
Power must be available to the
top element circuit at all times for this
water heater to operate as designed.