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less than the Setpoint, the rate infl uence is de ter mined by
how close the result is to the Setpoint; close yields larg er
infl uence, further yields small er in fl u ence.
Therefore, per the above, the values programmed for Pro-
portion Limit Open/Close and Rate Limit Open/Close de-
termine the sensitivity of the level control. Smaller val ues
generally yield greater response for the same level change
in the Level control Period. Also, the small er the value
programmed for the Level Con trol Period, the more often
an output signal is applied to the Variable Orifi ce Actua-
tor. With Flash memory Card version C.MLM.01.06.xxx
and later or C.MLM.04.02.xxx, the duration of the open
and close pulse applied to the Valve Actuator is in de -
pen dent of the selected Period Setpoint. It is a fi xed per-
centage of 3.5 seconds. Previously, it was a per cent age
of the Period Setpoint. Therefore, longer Pe ri ods would
pro duce longer output pulses for the same error, resulting
in unstable operation under certain con di tions.
The orifi ce valve movement is animated on the Re frig er ant
Level Control Screen as follows: when 0-20% open, shown
fully closed; 20 - 40% open, shown as 20% open; 40 - 60%
open, shown as 40% open; 60 - 80% open, shown as 80%
open; 80 - 100% open, shown as 100% open.
FIG. 51 – REFRIGERANT LIQUID LEVEL SENSOR
YORK INTERNATIONAL
MANUAL OPERATION
The Orifi ce Actuator can be manually controlled from the
Keypad using the Refrigerant Level Control Screen after
logging in at SERVICE access level. Open, Close, Hold
and Auto keys are used to control the Variable Or i fi ce.
Using the Open, Close and Hold keys, the Vari able Ori-
fi ce can be placed in a fi xed position. Pressing the Auto
key returns Level Control to Automatic op er a tion.
ACTUATORS
New production units use a Belimo actuator that op er ates
from 24VAC. If the OptiView Control Center is retrofi t
to an existing chiller, the chiller could be equipped with
a Bar ber-Coleman actuator that op er ates from 115VAC.
The interface for both actuators is shown in Fig. 52. The
description of the operation of both ac tu a tors is in the
"I/O Board" section of this book.
FORM 160.54-M1(503)
14
LD04091
93
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