OVERVIEW
The Zonex Systems CAPL-4 is a combination staging and capacity control
device in one. It can stage an economizer and up to four compres-
sors and up to four stages of heat. The CAPL-4 monitors the leaving air
temperature and stages the cooling or heating to maintain the leaving air
temperature within a fixed range. Controlling the staging based on the
leaving air temperature ensures the supply will always match the load.
This is essential with a zoning system, since the load varies sub-
stantially as the number of zones calling varies.
Cool mode
– When there is a cool call, if the leaving air is above the
cool cut-in temperature, the CAPL-4 turns on the next stage compressor
after a time delay. If the air gets too cold, it turns off the last stage
compressor after that compressor has run a minimum of four minutes.
As long as there is a cool call, when a compressor turns off it will stay off
for a minimum of four minutes and when a compressor turns on it will
run a minimum of four minutes. This prevents short cycling and
ensures sufficient compressor oil return. When the cool call is
removed, all compressors are immediately turned off.
Heat mode
– If the leaving air is below the heat cut-in temperature, it
turns on the next heat stage after a time delay. If the air gets too warm,
it turns off the last heat stage after a time delay. When the heat call is
removed, all heat stages turn off immediately.
OPERATION
The following sequence of operation assumes the cool cut-out setpoint is
48 and the heat is 150 degrees Fahrenheit. For any other cut-out settings,
add or subtract the difference to the values stated. Example: If your actu-
al cool cut-out is 50 degrees, add 2 degrees to each temperature val-
ue stated under the Cooling Call section. All temperatures are in degrees
Fahrenheit.
COOLING CALL
(cool setpoint 48): As long as there is a cooling call
(YIN energized), the following will occur.
ECONOMIZER:
As long as there is a cooling call the economizer, if available, is enabled
and outside air is supplied based on enthalpy.
COMPRESSOR STAGING ON:
If the
leaving air is 58° or greater
, the next compressor will turn
on within four minutes. As long as the air temperature remains within
this range the next higher compressor will stage on every four minutes.
COMPRESSOR STAGING OFF:
If the
leaving air is between 48 and 52°
, the highest compressor
stage on will shut off within four minutes. As long as the air temperature
remains within this range the next highest running compressor will stage
off every four minutes.
If the
leaving air is 48° or less
then all compressors will turn off after
the last compressor running has run for at least four minutes.
NO STAGING:
If the
leaving air is equal to or greater than 52 and less than 58°
then no compressor staging will occur.
HEATING CALL
(heat setpoint 150). As long as there is a heating call
(WIN energized), the following will occur.
HEAT STAGING ON:
If the
leaving air is 130° or less
, the next heat stage will turn on
within four minutes. As long as the air temperature remains within this
range the next higher heat stage will turn on every four minutes.
HEAT STAGING OFF:
If the
leaving air is between 145 and 150°
the highest heat stage on
will shut off within four minutes. As long as the air temperature remains
within this range the next highest heat will stage off every four minutes.
If the
leaving air is 150° or greater
then all heat stages will turn off.
COMPONENTS
The CAPL-4 consist of the following:
A. Digital Display
– Three digit LED. Normally displays the leaving air
temperature of the HVAC unit. When the UP/DN buttons are pressed, the
cut-out setpoints are displayed. Refer to the Setpoint Calibration section
for reading and adjusting the setpoints.
B. Microcontroller
– Activates and controls outputs based upon leav-
ing air temperature comparison with programmed setpoints. Occasion-
ally software upgrades may become available. If so, the CAPL-4 software
can be field upgraded by changing this microcontroller.
CAPACITY CONTROLLERS – CAPL-4
Y1 IN Y1 Y2 Y3 Y4 G
R C
+
-
W1 IN W1 W2 W3 W4
W1 W2 W3 W4
Y1 Y2 Y3 Y4 G
E
C
O
N
O
UP
DN
SW1
ON
R4
B
F
G
D
I
H
A
C
E
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