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E–ECB29-12.5CB, -15CB – 208/230V SINGLE PHASE – SEQUENCE OF OPERATION
FIRST STAGE HEAT
1- When there is a call for heat, W1 of the thermostat
energizes the electric heat relay K32 with 24VAC.
2- When K32-1 closes, the blower is energized on
heating speed and economizer heat relay K43 is
energized (see 208/230VAC CB schematic).
3- Assuming the N.C. primary (S15) and secondary
(S20) limit switches are closed, electric heat ele-
ment HE1 is energized.
SECOND STAGE HEAT
(remove jumper between W2 and R)
4- When K32-2 closes, the unit is ready for a second
stage heat demand. W2 of the thermostat sends a
second stage heat demand, energizing the electric
heat relay K33 with 24VAC.
5- When K33-1 and K33-2 close, assuming the N.C.
primary (S15) and secondary (S20) limit switches
are closed, electric heat elements HE2 and HE3
are energized.
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