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Sequence of Operation -EHA 7 / 30kW - Y and G, J, M
NOTE: This sequence of operation is for all Electric
Heat kW ratings and Y through J voltages. Each step
of operation is numbered and can be followed in se-
quence on the diagrams. Operation for G, J, and M
voltages will be the same.
HEATING ELEMENTS:
1 - Terminal Strip TB3 is energized when the unit discon-
nect closes. TB3 supplies line voltage to Heat Contac-
tors K15 and K16, which supplies voltage to HE1
through HE6. Each element is protected by fuse F3.
FIRST STAGE HEAT:
2 - Heating demand initiates at W1 in thermostat.
3 - 24VAC is routed through TB34 to the main control
module A55. After A55 proves N.C. primary limit S15
and secondary limit S20, the electric heat contactor
K15 is energized.
4 - N.O. contacts K15-1 closes allowing the first bank of
elements to be energized.
SECOND STAGE HEAT:
5 - With the first stage heat operating, an additional heat-
ing demand initiates at W2 in the thermostat.
6 - 24VAC is routed through the main control module A55,
which in turn energizes the electricheat contactor K16.
7 - N.O. contacts K16-1 close allowing the second set of
elements to be energized.
END OF SECOND STAGE HEAT:
8 - Heating demand is satisfied. Terminal W2 in the ther-
mostat is de-energized.
9 - Electric heat contactor K16 is de-energized.
10- The second set of electric heat elements are de-ener-
gized.
END OF FIRST STAGE HEAT:
11- Heating demand is satisfied. Terminal W1 in the ther-
mostat is de-energized.
12- Electric heat contactor K15 is de-energized.
13- The first set ofelectric heat elements arede-energized.
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