Appendix D: Heat/Cool Option - Fuji Electric PXZ Series Operation Manual

Wiring and Setting:
1. Choose the correct current sensing
transformer based on the maximum
current usage of the heater.
0 - 30 Amps (part # CTL-6-SF)
0 - 50 Amps (part # CTL-12-S36-8F)
2. Thread the hot lead going to the heater through the donut of the
current sensing transformer. Connect the wires of the current
sensing transformer to the current sensing transformer input termi-
nals in the back of the controller.
3. Set Heater Break alarm setpoint parameter "Hb". With the current
sensing transformer connected and the heater in operation, output
energized, change the Heater Break Alarm setting from the maxi-
mum current setting for the particular current sensing transformer
being used to a lower value. Allow 3 secs. or more between setting
changes. Continue lowering the setting until the relay is energized
and the "HB" status indicator is lit. This is the maximum current
usage of the heater. Using the same procedure, find the maximum
current usage of the heater minus one zone. Set the setpoint in
between the two current readings. In this way, the operator knows
if one or more zones fail because the current sensed will only be
below the Heater Break Alarm setting if one or more zones fail.
Power Supply
Main
Output
Current Sensing Transformer
Input Sensor
Heater
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Connection to PXZ
(Polarity not important)
Hot lead to Heater
8 4
9
5 15
Alarm Output
7 16
+ –
17
18 1 2
APPENDIX D
Heat/Cool Option
With the Heat/Cool Option, the PXZ can control a temperature appli-
cation with one input at one main setpoint using two outputs, a heat-
ing output and a cooling output. By using a heating and cooling out-
put, a process is able to quickly bring the temperature to setpoint in
both directions and to limit the amount of overshoot. The larger the
deviation from setpoint, the more output applied to the system on both
the heating and cooling sides. Heat/Cool control is a very effective
way of controlling exothermic processes, processes that generate
their own heat, or processes where ambient temperature is not ade-
quate or fast enough in returning a process back to setpoint.
The two outputs on the PXZ are independent and sent to two different
output devices. The PXZ can be equipped with two of the same or
two different output types. Output #2 can be relay, SSR/SSC driver, or
4-20mA DC, regardless of what Output #1 is. Both output types must
be specified when ordering.
The PXZ controls the cooling side with three additional parameters,
TC-2, COOL, and DB. Each is explained below:
TC-2 Cycle Time (Output #2): Because Output #2 is not
necessarily the same as Output #1, the cycle time may
be different
CooL Proportional Band Coefficient for Cooling: Because the
cooling power may not necessarily be the same as the
heating power, the cooling proportional band may need
to be different from that of the heating proportional
band.
db Deadband/Overlap: Deadband is that area where
neither outputs are energized. Overlap is that area
when both outputs are energized. This function lets
you decide where you want the heating action to stop
and the cooling action to begin.
Notes:
1. The Heat/Cool Option is available on the PXZ-5, 7, and 9 con-
trollers only. Output #2 type can be the same or different than
Output #1 type (Relay, SSR/SSC driver, or 4-20mA DC)
2. Integral and Derivative Times are the same for both the heating
and cooling sides of a process with PID control because the
response frequency or time constant of the system does not
change at main setpoint when cooling is added.
3. The Proportional Band for heating and cooling are almost always
different. Rarely does the same amount of cooling output remove
the same percentage of process error as the heating output does.
The Cooling Proportional Band must be manually and separately
tuned.
4. If the heating side is set for On/Off control, the cooling side will be
set for On/Off control also. Regardless of what the COOL parame-
ter is set for, if the Proportional Band is set to zero, the Heating
Proportional Band and the Cooling Proportional Band will always
be zero or On/Off.
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