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Thermal Expansion
Property Damage Hazard
- Avoid water heater damage.
o Install thermal expansion tank or device if necessary,
• Contact qualified installer or service agency.
NOTE: Expansion tanks are preocharged with a 40 psi air
charge, mfthe intact water pressure is higher than 40 psi, the
expansion tank's air pressure must be adjusted to match
that pressure, but must not be higher than 80 psi.
Water supply system may, because of such events as high line
pressure, frequent cut-offs, and the effects of water hammer
have installed devices such as pressure reducing valves, check
valves, back flow preventers, etc., to control these types of
problems. When these devices are not equipped with an
internal by-pass, and no other measures are taken, the devices
cause the water system to be closed. As water is heated, it
expands (thermal expansion) and closed systems do not allow
for the expansion of heated water.
The water within the water heater tank expands as it is heated
and increases the pressure of the water system. If the relieving
point of water heater's temperature-pressure relief valve is
reached, the valve will relief the excess pressure. The
temperature-pressure relief valve is not intended for the
constant relief of thermal expansion, This is an unacceptable
condition and must be corrected.
It is recommended that any devices installed which could create
a closed system have a by-pass and/or the system have an
expansion tank or device to relieve the pressure built by thermal
expansion. Thermal expansion tanks are available from Sears
stores and through the Sears Service Centers. Contact the
local plumbing inspector, water supplier and/or the Sears
Service Center for assistance in controlling these situations,
see Figure 26.
Therma! Expansion Tank Specifications
Tank Dimensions
Mode_ Capacity in Inches
Number iln Gallons Diameter Length
153.331020 2 8 (203 ram) 12-3/4 (323 mm)
153.331050 5 11(279 mm) 14-3/4 (375 mm)
Pipe
Fitting
On Tank
3/4" Mate
3/4" Mate
Expansion Tank Sizing Chart
Water Heater Capacity (Gallons)
h[et*
Water
Pressure
40psi
50psi
60psi
70psi
80psi
30 40 50 66 80
Expansion 2 2 2 5 5
Tank 2 2 2 5 5
Capacity 2 2 5 5 5
Needed 2 2 5 5 5
2 5 5 5 5
WATER HEATER (3)
(VERTICAL MOUNTING)
WATER HEATER
COLD WATER
INLET HTTING
HOT COLD
FLOOR, CEILING JOBST, ETC,
(3)
PRESSURE
REDUCING
VALVEWITH
(1_ BY-PASS
EXPANSION J
TANK :_
t
INLETCOLD
WATER SHUT=OFF
ALTERNATE RECOMMENDED INSTALLATION
(HORIZONTAL MOUNTING)
F_GURE2&
Strange Sounds
Possible noises due to expansion and contraction of some
metal parts during periods of heat-up and cool-down do not
represent harmful or dangerous conditions.
Condensation causes sizzling and popping within the burner
area during heating and cooling periods and should be
considered normal. See Condensation section.
Draft Hood Operation
Check draft hood operation by performing a worst case
depressurization of the building. With all doors and windows
closed, and with all air handling equipment and exhaust fans
operating such as furnaces, clothes dryers, range hoods and
bathroom fans, a match flame should still be drawn into the
draft hood of the water heater with its burner firing. If the flame
*Highest recorded inlet water pressure in a 24 hour period or
regulated water pressure.
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