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CHP16/20 Y and G VOLTAGE SEQUENCE OF OPERATION
Operation Sequence
Cooling:
1- Line voltage energizes transformer T1. Transformer
T1 provides 24VAC power to all unit controls and therĆ
mostat.
2- Latch relay K6 controls operation of reversing valve L1
during normal operartion (contacts K10-2 control reĆ
versing valve during defrost). Latch relay K6 operates
as follows:
a- 24VAC from Y1 cooling demand applied to K6
SET" coil closes K6-1 and switches K6-2 (contacts 6-8
close and 6-4 open). Contacts 6 and 8 remains closed
when power is removed.
b- 24VAC from W1 heating demand applied to K6 REĆ
SET" coil opens K6-1 and switches K6-2 (contacts 6-8
open and 6-4 close). K6-1 and K6-2 remain in this posiĆ
tion when power is removed.
3- Cooling demand energizes Y1 and G in the thermostat.
Y1 energizes K6 relay SET" coil. K6-1 and K6-2 imĆ
mediately switch. G energizes indoor blower relay K3.
4- When K6-1 closes, reversing valve L1 is energized.
When K6-2 switches (contacts 6-8 close), contactor K1
is energized.
5- K1-1 closes to energize compressor and the condensĆ
er fan.
6- K3-2 switches to energize the blower on high speed.
K3-1 switches to power the economizer (if equipped).
Dampers open to minimum position.
Heating:
7- 1st. stage heating demand energizes W1 in the therĆ
mostat. W1 energizes transfer relay K8 and K6 relay
RESET" coil. K6-1, K6-2 and K8-1 all switch immediĆ
ately.
8- When K8-1 switches indoor blower relay K3 is enerĆ
gized.
9- When K6-1 opens, reversing valve L1 is de-energized.
When K6-2 switches (terminals 6-8 open and 6-4
close), compressor contactor K1 and de-frost board
CMC1 are energized.
10-K1-1 closes to energize the compressor and condensĆ
er fan.
11- K3-2 switches to energize the blower on high speed.
K3-1 switches to power the economizer (if equipped).
Dampers open to minimum position.
12-Additional heating demand W2 is directed to optional
electric heat (not shown).
Defrost Mode:
13-During heating operation, when outdoor coil temperaĆ
ture drops below 35ºF 4ºF, the defrost thermostat
closes.
14-After 30, 60 or 90 minutes of heating demand (dependĆ
ing on how the conrtrol is pre-set) CMC1 checks for deĆ
frost demand by closing a set of relay contacts conĆ
nected to terminal OUT. Terminal OUT remains enĆ
abled for 14 1 minutes. If defrost temperature therĆ
mostat S6 is closed when terminal OUT is enabled, deĆ
frost relay K4 and outdoor fan relay K10 are allowed to
energize and defrost begins.
15-When K4 energizes, K4-1 opens and K4-2 and K4-3
close.
16-When K10 energizes, K10-1 and K10-2 immediatley
switch.
17-When K4-1 opens internal timer is reset to zero.
18-When K4-2 closes, W1 is shunted to W2 to energize
optional electric heat.
19-When K4-3 closes, defrost relay K4 and outdoor fan
relay K10 are latched in until defrost terminates.
20-When K10-1 opens, the outdoor fan is de-energized.
21-When K10-2 switches, reversing valve L1 is energized.
22-Defrost is terminated when relay K4 loses power. K4
can lose power two ways.
1) If defrost is not satisfied after 14 1 minutes, CMC1
(terminal OUT) internal relay contacts open, K4 is de-
energized and defrost is terminated.
2) If S46 opens before 14 minutes has elapsed, K4
and K10 are de-energized and defrost is terminated.
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