Specifications

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Safety
Excessive Temperatures
The T&P valve will also acvate when the water
temperature exceeds 210°F. Acvaon of the T&P valve
for excessive temperatures will result in a large amount of
water being discharged and could indicate a problem with
the control circuit. This problem should be corrected at
once in order to prevent scalding injuries.
Gas water heaters are equipped with an energy cuto
(ECO) switch. It is designed to shut o the gas supply to
the unit if the water temperature exceeds about 190°F.
The ECO is a single use switch and requires complete
replacement of the enre thermostat if acvated.
Electric water heaters have a high limit control switch,
shown above, which will shut o power to the elements if
water temperatures exceed about 170°F. This switch can
be reset by rmly pushing the red reset buon located on
the thermostat.
When a series of short draws of hot water are used
from the tank, usually 3 gallons or less, it can arcially
increase the number and frequency of heang cycles. With
each draw, cool water enters the boom of the tank. The
lower thermostat senses a change in temperature
acvang the lower element or burner. Since a short draw
of water does not completely remove all the hot water in
the top of the tank, increasing the number of heang
cycles adds more temperature to water in the top of the
tank. This is called stacking.
Electric water heaters are not as subject to stacking as gas
water heaters because, on short draws all the heat
produced by the heang element is transferred to the
water in the boom 1/3 of the tank and mixes with the
surrounding water. For this reason, electric water heaters
usually do not stack more than about 5°F.
Gas water heaters can stack up to 30°F. Heat from the
burner is transferred through the ue at the top of the
water heater as well as through the boom head.
Repeated short draws accompanied by short heang
cycles allow the ue to overheat water in the top of the
tank without the thermostat sensing it.
Stacking increases the chance of scald injuries. A mixing
valve greatly reduces the chance of a scalding injury due to
stacking by automacally adjusng the proporon of cold
to hot water as water is drawn from the tank. In homes
where children, elderly people or the disabled are present,
a mixing valve is recommended for general use xtures.
Submerged Water Heaters
When a water heater has been submerged in water, such
as during a ood, it must be replaced. The operang
controls can no longer be considered funconally safe. The
insulaon surrounding the unit will have become
saturated and cannot be fully dried out. This will cause the
outer surface of the tank to corrode creang
potenally unsafe operang condions.