Page 81
A19 diagram with B9 diagram
ECH16-185/255/275/300 75kW 208/230V Operating Sequence
Operation Sequence: A19 Section and B9 Sections
(75kW 208/230V electric heat wired to CHA16-1853)
1- 1st stage heating demand closes W1. W1 energizes pilot relay K77. K771 closes.
2- When K771 closes, heating pilot relay K9 is energized. K91 switches and K93 closes.
K92 close to enable K19.
3- When K91 switches, indoor blower contactor K3 is energized (and optional power exhaust
fan relay K65 is enabled when K32 cotacts close).
4- When K93 closes, electric heat contactor K15 and time delay DL2 are both energized.
K151 closes and DL2 begins timing. After 30 seconds, DL2 closes.
5- When K151 closes, heating elements HE1 are energized. All elements are arranged in a
Delta" configuration for 208/230V operation.
6- When DL2 closes, contactor K16 is energized.
7- When K16 is energized, heating elements HE2 are energized.
8- Additional heating demand W2 energizes pilot relay K49. K49-1 closes.
9- When K491 closes, pilot relay K19 is energized. K191 closes and DL4 is energized. After 30
seconds, DL4 closes.
10- When DL4 closes, contactor K17 and time delay DL5 are both energized. K171 closes and
DL5 begins counting. After 30 seconds, DL5 closes.
11- When K171 closes, heating elements HE3 are energized.
12- When DL5 closes, contactor K18 and time delay DL18 are both energized. K181 closes
and DL18 begins counting. After 30 seconds, DL18 closes.
13- When K181 closes, heating element HE4 is energized.
14- When DL18 closes, contactor K75 is energized.
15- When K751 closes, heating elements HE5 are energized.
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