Anti-Reset Windup (Suffix Letter F) Operation; Remote Set Point (Suffix Letter M) Operation; Auto/Manual Station (Suffix Letter E); Operation - Emerson Fisher KC Series Instruction Manual

Instruction Manual
Form 5207
April 2007
RESET
VALVE
RESET PROPORTIONAL
BELLOWS BELLOWS
19A5000−A
A3237-2 / IL
Figure 4-7. Reset-Rate Schematic
Anti-Reset Windup (suffix letter F)

Operation

Anti-reset windup is available on all 4195KB and KC
Series controllers and is designated by the letter F in
the type number. The differential relief valve
operates when the difference between the
proportional bellows pressure and the reset bellows
pressure reaches a predetermined value. Anti-reset
windup reduces overshoot of the process pressure
that can result from a large or prolonged deviation
from set point.
Remote Set Point (suffix letter M)
Operation
The capability to adjust the controller set point from
a remote location is available with all 4195KB and
KC Series controllers. This option is designated by
the letter M in the type number.
A control pressure is applied to the capsular element
within the remote set point assembly. The expansion
4195KA, KB, KC, and KS Controllers
RELAY OUTPUT
PRESSURE
RATE
VALVE
GAIN
LIMITER
and contraction of the capsule moves the set point
indicator via connecting linkage. Increasing the
control pressure to the capsule increases the set
point setting and decreasing the control pressure
reduces the set point setting.

Auto/Manual Station (suffix letter E)

Operation
A controller with the auto/manual station (designated
by the suffix letter E in the type number) has piping
on the output side of the relay as shown in figure
4-8. Supply pressure to the relay is also applied to
the manual loader. The manual loader, functioning
as a regulator, applies pressure to one side of the
plastic tube and to the auto/manual switch. Output
pressure from the relay registers on the other side of
the plastic tube as well as in the auto/manual switch.
When the auto/manual switch is in the MANUAL
position, the manual loader output is channeled
through the auto/manual switch and becomes the
controller output. When the auto/manual switch is in
the AUTO position, the relay output is channeled
through the switch to become the controller output.
Before the auto/manual switch is operated, the relay
output must equal the manual loader output to avoid
bumping the process. Adjusting the set point varies
the pressure on the left-hand side of the plastic tube.
Adjusting the manual loader knob varies the
pressure on the right-hand side. When the pressures
are equal, the metal ball is centered in the tube and
it is held in place by a small magnet. A pressure
imbalance forces the ball to one end of the tube
where it forms a seal, blocking air flow through the
tube.

External Feedback Operation

External feedback is available for all 4195KB Series
controllers. Controllers with this option have an
external connection on the bottom of the controller
case as shown in figure 2-5. This connection breaks
the positive feedback (reset) loop inside the
controller and brings it outside as shown in figure
4-9. The connection allows the positive feedback
loops of two controllers (primary and secondary) to
be tied together when the controllers are used in an
override application. When connected, the
secondary controller tracks the primary controller,
minimizing reset windup.
4-13