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Start Up Conditions
THERMAL EXPANSION
Water supply systems may, because of such events as high line
pressure, frequent cut-offs, the effects of water hammer among
others, 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 the 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.
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 to relieve the pressure built by thermal expansion.
Thermal expansion tanks are available from Sears stores and
through Sears Service Centers. Contact the local plumbing
inspector, water supplier and/or the Sears Service Center for
assistance in controlling these situations.
Thermal Expansion Tank Specifi cations
Model
Tank
Number
Capacity
In Gallons
Diameter
153.331021
2
(203 mm)
153.331051
5
(279 mm)
Inlet*
Water
Pressure
Expansion
40 psi
Tank
50 psi
Capacity
Needed
60 psi
70 psi
80 psi
* 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.
TROUBLESHOOTING
Dimensions
Pipe
in Inches
Fitting
On Tank
Length
8
12-3/4
3/4" Male
(323 mm)
11
14-3/4
3/4 Male
(375 mm)
Water Heater Capacity (Gallons)
27
30
40
50
2
2
2
2
2
2
2
5
2
2
2
5
2
2
2
5
2
2
5
5
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.
Operational Conditions
SMELLY WATER
In each glass-lined water heater there is installed one anode
rod (see parts section) for corrosion protection of the tank.
Certain water conditions will cause a reaction between this rod
66
and the water. The most common complaint associated with the
anode rod is one of a "rotten egg smell". This odor is derived
5
from hydrogen sulfide gas dissolved in the water. The smell is
5
the result of four factors which must all be present for the odor
5
to develop:
5
A. A concentration of sulfate in the supply water.
5
B. Little or no dissolved oxygen in the water.
C. A sulfate reducing bacteria within the water heater. (This
harmless bacteria is non-toxic to humans.)
D. An excess of active hydrogen in the tank. This is caused by
corrosion protective action of the anode.
Smelly water may be eliminated or reduced in some water heater
models by replacing the anode rod (s) with one of less active
20
FIGURE 29
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