Lennox CHP20-060

Page 62
ECH16-15/20/25kW P VOLTAGE
1
2
3
45
6
7
ECH16 15 / 25kW P VOLTAGE SEQUENCE OF OPERATION
NOTE - Call for heat is first stage heat for CHA16 units and second stage heat for CHP16/20 units.
1- On a call for heat, relay K43 is energized. K43-1 closes
immediately.
2- When K43-1 closes, heat relays K15, K16 and K17 are
energized. K15-1, K16-1 and K17-1 close immediately.
3- When K43-2 closes, nothing happens as indoor blower
is already energized from first stage heat call.
4- When K15-1 closes, 15kW: heating element HE1 is enĆ
ergized.
When K15-1 closes, 20kW or 25kW: heating element
HE1 and HE2 are energized.
5- When K16-1 closes, 15kW: heating element HE2 is enĆ
ergized.
When K16-1 closes, 20kW or 25Kw: heating element
HE3 and HE4 are energized.
6- When K17-1 closes, 15kW: heating element HE3 is enĆ
ergized.
When K17-1 closes, 20kW or 25kW: heating element
HE5 and HE6 are energized.
7- When heating demand is satisfied, heat relay K43 is
de-energized. All heating elements de-energized imĆ
mediately.