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T3EH ELECTRIC HEAT SEQUENCE OF OPERATION (refer to gure 10) – 2 STAGE HEAT
First Stage Heat Call
Heat Pumps (ELXP) - W1 heat demand operates the heat pump in heating mode.
Air Conditioners (ELXC) - W1 heat demand energizes the K9 heat relay.
K9−1 closes energizing K15 contactor.
K15−1 closes energizing heating elements HE1 and HE2 assuming primary limit S15 and secondary limit S20 are closed.
Second Stage Heat Call
Air Conditioners (ELXC) − W2 heat demand energizes K19 contactor.
K19−1 closes, energizing one side of contactor K16 which energizes one side of K32 relay.
K32−1 closes energizing K16 contactor.
K16−1 closes, energizing heating elements HE3 and HE4 assuming primary limit S15 and secondary limit S20 are
closed.
Heat Pumps (ELXP) – W2 heat demand energizes K9 and K19 relays.
K9−1 closes energizing K15 contactor.
K15−1 closes energizing heating elements HE1 and HE2 assuming primary limit S15 and secondary limit S20 are closed.
K19−1 closes, energizing one side of contactor K16 which energizes one side of K32 relay.
K32−1 closes energizing K16 contactor.
K16−1 closes, energizing heating elements HE3 and HE4 assuming primary limit S15 and secondary limit S20 are
closed.
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