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T3EH 072/150, 10−15 kW Y Voltage − Sequence of Operation
Heat Call TSA / TPA
1. W1 (W2 in TPA) heat demand energizes the econo-
mizer relay K43 and heat relay K9. K43−1 closes ener-
gizing blower relay K3.
2. K3−1 closes energizing indoor blower B3. K9−1
closes energizing contactor K15.
3. K15−1 closes and assuming primary limit S15 and secon-
dary limit S20 are closed, heating elements HE1 and HE2
are energized.
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