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Start Up Conditions
Thermal Expansion
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
Tank
Model
Capacity
Number
In Gallons Diameter
153.331020
2
8 (203 mm) 12-3/4 (323 mm) 3/4" Male
153.331050
5
11 (279 mm) 14-3/4 (375 mm) 3/4" Male
Expansion Tank Sizing Chart
Inlet*
Water
Pressure
Expansion
40psi
Tank
50psi
Capacity
60psi
Needed
70psi
80psi
*Highest recorded inlet water pressure in a 24 hour period or
regulated water pressure.
TROUBLESHOOTING GUIDE
Dimensions
Pipe
in Inches
Fitting
Length
On Tank
Water Heater Capacity (Gallons)
30
40
50
66
2
2
2
5
2
2
2
5
2
2
5
5
2
2
5
5
2
5
5
5
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.
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.
80
5
Draft Hood Operation
5
5
Check draft hood operation by performing a worst case
5
depressurization of the building. With all doors and windows
5
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
23
FIGURE 26.
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