TC 816 Operation Manual
THERMON…The Heat Tracing Specialists
®
Page 36 of 42
Operation Manual 0503 E TC 816
4.3.3
Parameter P18:
CTR MODE
This Parameter is:
•
Valid for Temperature Controller Zones
- Zones 1 through 16
- unit in: not applicable
•
Not valid for
Limiter Zones
•
Not valid for
Current Zones
Parameter P18 determines the TC 816 control mode (
CTR MODE
). Possible control modes are:
•
PID control:
The temperature controller Zone controls according to PID (Proportional Integral &
Differential) control algorithm for accurate, fast and smooth temperature
maintenance. The parameters for this algorithm are set with:
Parameter
P19:
Proportional
band
(
P HEAT
)
Parameter P20: Integration time (
I HEAT
)
Parameter
P21:
Differential
time
(
D HEAT
)
•
APC control:
The temperature controller Zone controls according to APC (Ambient Proportional
Control) algorithm.
This algorithm is used for frost protection heat tracing circuits allowing huge energy
savings. Ambient temperature is measured by a single ambient temperature sensor
connected to an AF TIT Tracing Input module for Temperature. Every temperature
controller Zone which is assigned to the ambient temperature input Zone (by
parameter
P26
SENSOR #
) will be proportionally controlled between:
Parameter P22: Lowest ambient temperature for which the heat tracing circuit is
designed
(
APC MIN T
)
and
Temperature set point of the present circuit.
•
ON/OFF control: The temperature controller Zone controls as a mechanical thermostat with a
hysteresis.
The heat tracing is switched ON at:
maintenance temperature set point (in the circuit display) + ½ of the hysteresis
The heat tracing is switched OFF at:
maintenance temperature set point (in the circuit display) - ½ of the hysteresis
The
hysteresis
is
set
with:
Parameter
P24:
Hysteresis
(
HYSTER
)
Adjustment thresholds: 0 =
PID control
1 =
APC control
2 =
ON/OFF control
Default value:
0
Note:
In case
Parameter P18 (
CTR MODE
) is set to ON/OFF control it is recommended to set parame-
ter P12 (
ON DELAY
) to “0” (zero).
