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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 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.
Thermal Expansion Tank Specifications
Mode!
Number
153.331020
153.331050
Tank
Capacity
in Gallons
2
5
Dimensions Pipe
in inches Fitting
Diameter Lenoth On Tank
18 {203 ram) I2-3/4 {323 ram) 3/4" Mate
11(279 ram) I4-3/4 (375 ram) 3/4" Mate
Expansion Tank Sizing Chart
Water Heater Capacity (Gallons)
inlet*
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
*Highest recorded inlet water pressure in a 24 hour period or
regulated water pressure.
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.
WATERHEATER (3)
H_T r'nRr_ _" COLDWATER PRESSURE
....... _[_.._,_ iNLET FITTING *'_REDUCING
! BY-PASS
PRESSURE GAUGE INLET COLD
WATERSHUTOFF
RECOMMENDEDiNSTALLATiON
-- -- -- (VERTICALMOUNTING)
WATER HEATER
COLD WATER
iNLET FiTTiNG FLOOR, CEILING JOIST, ETC.
)k II Jl
r__ HOT COL C .,_---- STRAPPING
J f
PRESSURE GAUGE iNLET COLD
WATER SHUT-OFF
ALTERNATE RECOMMENDEDINSTALLATION
(HORIZONTALMOUNTING)
FIGURE 26.
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
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