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Sequence of Operation - EHA 7.5, 15, 22.5, 30, 45, 60 kW - Y and G, J, M
NOTE: This sequence of operation is for all Electric
Heat kW ratings Y through J voltages. Each step of op
eration is numbered and can be followed in sequence
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 electric heat
elements HE1 through HE6. Each element is protected
by fuse F3, F42, F43, or F44.
2- Heating demand initiates at W2 in thermostat or when
the unit goes into defrost mode.
3- 24VAC W2 signal is routed from the thermostat through
TB1 to P2-2. After S15 N.C. primary limit and S19 sec
ondary limit is proved, the electric heat contactor K15 is
energized.
4- N.O. contacts K15-1 close allowing the first bank of ele
ments to be energized.
5- Relay K9 is energized. N.O. contacts K9-2 close ener
gizing K16.
6- N.O. contacts K16-1 close allowing the second bank of
elements to be energized.
END OF SECOND STAGE HEAT:
7- Heating demand is satisfied. Terminal W2 in the ther
mostat is de-energized or defrost cycle is completed.
8- Electric heat contactor K16 is de-energized.
9- The second set of electric heat elements are de-ener
gized.
10- Electric heat contactor K15 is de-energized.
11- The first set of electric heat elements are de-energized.
