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Sequence of Operation -EHO 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 HE7. Each element is protected
by fuse F3.
SECOND STAGE HEAT:
2- Heating demand initiates at W1 in thermostat.
3- 24VAC W2 signal is routed through from the thermo
stat to TB1. After S15 N.C. primary limit and S20 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 K9-1 close ener
gizing timer DL2.
6- After a 30-second delay, DL2 closes energizing con
tactor K16.
7- N.O. contacts K16-1 close allowing the second bank of
elements to be energized.
END OF SECOND STAGE HEAT:
8- Heating demand is satisfied. Terminal W1 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.
11- Electric heat contactor K15 is de-energized.
12- The first set of electric heat elements are de-ener
gized.
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