Closed System/Thermal Expansion; Locating The Solar Water Heater; Water Piping - A.O. Smith Cirrex SUN-80 Instruction Manual

WARNING: The temperature-pressure relief valve should be
manually opened once a year. Caution should be taken to ensure that
(1) no one is in front of or around the outlet of the temperature-
pressure relief valve discharge line, and (2) the water manually
discharged will not cause any bodily injury or property damage
because the water may be extremely hot.
If after manually operating the valve, it fails to completely reset and
continues to release water, immediately close the cold water inlet
to the water heater, follow the draining instructions, and replace
the temperature-pressure relief valve with a new one.
WARNING: If the temperature-pressure relief valve on the water
heater weeps this may be due to thermal expansion. The water
supply serving this solar water heater may have a check valve
installed. Contact the water supplier or local plumbing contractor
on how to control this situation. Do not plug the temperature-
pressure relief valve.

CLOSED SYSTEM/THERMAL EXPANSION

Most public water systems in North America are required to
prevent water flowing from points of use (residences, businesses,
etc.) back into the supply system in order to maintain water quality.
To accomplish this, back flow preventers such as check valves,
are installed in the water line going to each point of use. Typically
the back flow preventer will be installed at the water meter or
inside a building where the supply line enters the building. This
device allows water to flow into the residence but does not allow
it to flow back into the water supply. This creates what is known
as a "Closed System". As water is heated by the water heater,
the water in the system attempts to expand, but has nowhere to
go resulting in an increase in pressure. This increase in pressure
in the system may cause the temperature-pressure relief valve to
open to relieve the pressure. Water will drip from the temperature
and pressure relief valve. Premature tank failure will result if this
condition is not corrected. To prevent this condition, a properly-
sized thermal expansion tank should be installed in the cold
water supply to the water heater. Failure to install a properly
Figure 3.
sized expansion tank in a closed system will void the warranty
on the water heater in the event of tank failure. It is important
to follow the thermal expansion tank manufacturers' installation
instructions and to adjust the expansion tank pressure to match
the water supply pressure. Contact a plumbing service agency
or your retail supplier regarding the installation of a thermal
expansion tank.

LOCATING THE SOLAR WATER HEATER

If you have a choice of where to install the solar water heater,
these ideas may help you decide.
1. Put the solar water heater indoors as close as possible to where
you use the most hot water. This water heater is not
intended for outdoor installation.
2. It is handy to have a floor drain, tub or sink nearby. That will
make it easy to drain water from the water heater. It is also a
good place to end the drain line of the temperature-pressure
relief (T & P) valve.
3. The solar water heater or the pipes and the connections may,
in time, leak. Put the water heater in a place where a water
leak will not damage anything.
4. You must not put the water heater in an area where it might
freeze. You must turn off the electricity to the water heater
before you drain it, to protect the heating elements.
5. Make sure that you are able to reach the drain valve and all
access panels when the water heater is in place. This will make
it easy to service the water heater.
6. The water heater must be level before you begin the piping.
WATER HEATERS EVENTUALLY LEAK. The installation of the
water heater must be accomplished in such a manner that if the
tank or any connections should leak, the flow of water will not
cause damage to the area adjoining the water heater or to lower
floors of the structure. When such locations can't be avoided, a
suitable drain pan should be installed under the water heater. Such
a pan should be no greater than 1-1/2 (45mm) inches deep, have
a minimum length and width of at least two inches (51mm) greater
than the water heater dimensions and must be piped to an
adequate drain.

WATER PIPING

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