Xylem EPR IM Electric heater-circulator unit EPR (obsolete) - Manual (Page 22)

Instruction manual Laing Electric heater circulator unit
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Indirect domestic hot water heating with the Electric heater-circulator
EPR
Indirect domestic hot water heating
During the heating period the heating of the domestic hot water normally
is performed by the domestic hot water heater that is essentially a heat
exchanger. When hot water is needed, the water from the hydronic heating
circuit is conveyed through this heat exchanger by activating the hot water
heater priority circuit control. This means that the circulator for the heating
circuit is shut off and the charging circulator for the domestic hot water heater
is switched on. In addition the temperature of the boiler will be increased to
the temperature necessary to heat the domestic hot water.
However, this system can only be operated economically during the hea-
ting period. Outside the heating period it is uneconomical to run the boiler
just for heating of the domestic hot water. Therefore it is customary, to have
an electric heating element beside the heat exchanger within the boiler that
heats the domestic hot water outside the heating period.
This method is problematic when the water is extremely corrosive or when
the water is hard. It is possible that the heating elements survive only a few
month in such a situation.
In these cases it is advantageous to heat the hot water heater outside the
heating period also with electricity but indirectly via the Electric heater-circu-
lator EPR that is ideal for this application.
By adding an additional printed circuit the Electric heater-circulator EPR
can easily be integrated into existing controls.
Starting operation of the domestic hot water heating and adaptation to
seasonal change
To start the Electric heater-circulator the constant temperature has to be set
to the desired value, normally about 158°F. The circulator then has to be swit-
ched to time delay (close jumper 5) for the switching sequence of the heating
elements D, which means, jumper 1, and 3 must be open, jumper 4 has to
be closed. Now the Electric heater-circulator is ready for operation.
To change to the heating season when the boiler is in operation, the main
switch has to be shut off while outside the heating season the main switch
has to be turned on. In this latter case the heating of the domestic hot water
is performed by the Electric Heater-circulator. Even outside the heating period
the boiler control has to stay operational.