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Start Up Conditions
Thermal Expansion
Property Damage Hazard
- Avoid water heater damage.
- Install thermal expansion tank or device if necessary,
• Contact qualified installer or service agency.
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 relieve 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.
WATER HEATER
COLD WATER
iNLET FiTTiNG FLOOR, CEiLiNG JOIST, ETC.
\ lIZ
HOT \COLD II II
/111--sTRAPP'No
(3)
I==== fll-lrlh PRESaURE
/ ]_ II II IN REDUCING
\ II II II / _,. VALVEWITH
"--4J---u--u--"-- (1) BY-PASS
I EXPANSION/
I Jl GAUGE iNLET COLD
I J WATER SHUT-OFF
ALTERNATERECOMMENDEDINSTALLATION
(HORIZONTALMOUNTING)
FmGURE 26A.
Thermal Expansion Tank Specifications
Tank
Model Capacity
Number In Gallons
153.331050 5
Dimensions Pipe
in Inches Fitting
Diameter Length On Tank
11(279 ram) 14-3/4(375 mm) 3/4" Male
NOTE: Expansion tanks are pre-charged with a 40 psi air
charge. If the inlet 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.
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 and Figure 26 A.
WATER HEATER (3)
(VERTICAL MOUNTING)
FIGURE 26.
Strange Sou nds
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
is not drawn toward the draft hood, shut off water heater and
make necessary air supply changes to correct.
Condensation
23
Whenever the water heater is filled with cold water, some
condensate will form while the burner is on. A water heater may
appear to be leaking when in fact the water is condensation.
This usually happens when:
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