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SECTION II: GENERAL INFORMATION (cont .)
TEmpERATURE CONTROL
A solar controller (not provided) shall be used in conjunction with the solar water heater to
run all solar components in the heating system. The solar controller will be connected to
two thermistors that monitor lower and upper tank temperature. In some cases, only one
thermistor (near the bottom of the tank) will be used. The proper temperature setting for
domestic hot water use is 120°F/49°C.
The solar water heater is equipped with a backup electrical heating element and adjustable
thermostat. The thermostat is located behind the access cover on the side of the water heater.
If the solar system cannot satisfy the user demand, the electric element will energize and heat
the water until the thermostat is satisfied. An ECO (electrical cut-off) is included as part of
the temperature control and is designed to cut off power to the heating element in the event
the water in the tank reaches 180°F. The ECO is a safety feature on the water heater and
cannot be adjusted. In the event that the ECO opens, the control must be manually reset with
the stored water temperature below 180°F.
The thermostat is factory set at 120°F. See Table 6 for thermostat letter and temperature
relationships. If hotter water is required a tempering device or anti-scald device must be
installed at the domestic hot water outlet of the heater or at the point of use. Table 3 details
the approximate relationship of water temperature and time with regard to scald injury. It
is important for the user to understand the necessity of tempering or anti-scald devices when
using hotter water in domestic water heating systems.
CAUTION: Hot water in excess of 120
°
F can cause scalding!
DHT recommends
a tempering valve or anti-scald valve be installed and used according to
the manufacturer’s directions to prevent scalding. Many state and local codes now require
installation of these devices. The tempering valve
or anti-scald valve will ensure potable water
temperatures at the desired set point with a higher
degree of accuracy.
APPROXIMATE
TEMPERATURE/TIME
RELATIONSHIPS TO
SCALDING
120°F
More than 5 minutes
125°F
1
1
⁄
2
to 2 minutes
130°F
About 30 seconds
135
°F
About 10 seconds
140°F
Less than 5 seconds
145°F
Less than 3 seconds
150°F
About 1
1
⁄
2
seconds
155°F
About 1 second
Table 3:
Scald Temperature/Time Relationships
