Appendix D: Heat/Cool Option - Fuji Electric PXV3 SERIES Operation Manual

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 set-
ting from the maximum 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 proce-
dure, find the maximum current usage of the heater minus one
zone. Set the
setpoint in
Power Supply
between the
two current
readings. In this
way, the opera-
tor knows if one
or more zones
fail because the
current sensed
Main
will only be
Output
below the
Heater Break
Alarm setting if
one or more
Current Sensing Transformer
zones fail.
Heater
APPENDIX D
Heat/Cool Option
With the Heat/Cool Option, the PXW can control a temperature applica-
tion with one input at one main setpoint using two outputs, a heating
output and a cooling output. By using a heating and cooling output, 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 heat-
ing and cooling sides. Heat/Cool control is a very effective way of con-
trolling exothermic processes, processes that generate their own heat,
or processes where ambient temperature is not adequate or fast
enough in returning a process back to setpoint.
The two outputs on the PXW are independent and sent to two different
output devices. The PXW can be equipped with two of the same or two
different output types. Output #2 can be relay, SSR driver, or 4-20mA
DC, regardless of what Output #1 is. Both output types must be speci-
fied when ordering.
The PXW controls the cooling side with three additional parameters,
TC-2, COOL, and DB as explained in the programming section.
TC2 Cycle Time (Output #2): Because Output #2 is not nec-
essarily 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
be different from that of the heating proportional band.
4
8
9
15
5
Alarm Output
7 16
+ –
17 18 1
2
Input Sensor
db Deadband/Overlap: Deadband is that area where neither
outputs are energized. Overlap is that area when both out-
puts 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 PXW-5, 7, and 9 con-
trollers only. Output #2 type can be the same or different than
Output #1 type (Relay, SSR 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.
5. If the cycle times of one or both outputs are long and the process
dynamic, there is a good chance that both outputs will be cycling
on and off at the same time around main setpoint. This is evident if
one or both outputs are relays.
6. Autotune is not effective on the cooling side of Heat/Cool control.
Autotune the controller for heat only and then manually tune the
cooling parameters.
Wiring and Setting
1. Make sure that your PXW has the correct output type installed for
Output #2. Verify that the TC2, COOL, and DB parameters are indi-
cated in the primary (setpoint) menu.
2. Wire your cooling load to the Output #2 terminals located on the
back of your PXW controller.
3. In the secondary (system) menu, program the correct code for
Heat/Cool action. See Table of Output Type Codes.
4. In the primary (setpoint) menu, program TC2, the cycle time for
Output #2. The table below is a general guide to TC2 settings.
Output#2 Type
Relay
SSR Driver (pulsed DC)
4-20mA DC
5. Autotune or manually tune the PID parameters of your PXW con-
troller. Autotune will work for the heating PID parameters but not on
the cooling parameters. You must manually tune the cooling para-
meters.
6. With the heat side tuned, manually set the COOL parameter or
Proportional Band Coefficient for Cooling. If the cooling output is
22
Setting(Secs)
30
2
Not indicated or 0