Service Manual

10
SEQUENCE OF OPERATION
Sequence of Operation- Double Element, Simultaneous Operation, 3 Phase.
1
2
1
Line voltage is applied across terminals L1
& L3 of upper thermostat. Line voltage also
extends to terminal L1 of lower thermostat.
Also, line voltage is applied to terminal L3
of lower thermostat. ECO in both upper &
lower thermostat is closed, so there is
voltage at terminal L4 of both thermostats
and to one side of both upper & lower
elements.
ECO
Closed
Thermostat closed
at terminal T2
2
Tank is cold therefore both thermostats
are closed at terminal T2 (calling for heat).
This completes the circuit through the
thermostats and allows current to flow
through the elements.
ECO
Closed
at terminal T2
3
3
When either thermostat is satisfied, it will
open at terminal T2, interrupting current
flow through the corresponding element. As
both thermostats satisfy, the system will be
in stand-by mode waiting for the next call
for heat. Thermostats will operate
independent of the other.
Thermostat open
at terminal T2
Thermostat open
at terminal T2
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