Case Circuit Control Software Overview; Valve Control - Emerson Site Supervisor User Manual
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5.27.2 Case Circuit Control
Software Overview
There are six different versions of case control soft-
ware in the Retail Solutions case control family:
• CC-100P - This version controls temperature in a
case using a pulse modulated valve, which is pulsed
ON for a percentage of a fixed amount of time to
achieve the necessary refrigerant flow.
• CC-100LS - This version controls temperature in a
case using a liquid-side stepper valve. This valve is
capable of various positions in between 0% and
100%. As a result, the CC-100 is capable of supply-
ing the exact refrigerant flow necessary to achieve
the case setpoint.
• CC-100H - This version controls temperature in a
case using a suction-side evaporator pressure regu-
lator (EEPR). This valve is capable of various posi-
tions in between 0% and 100%. As a result, the CC-
100 is capable of providing the exact suction pres-
sure necessary to achieve the case setpoint.
• CS-100 - This controller uses suction-side evapora-
tor suction regulators (ESRs) to control suction
pressure for an entire circuit. Unlike the CC-100,
which controls only one case, the CS-100 controls
all cases on an entire circuit.
• EC-2s - The EC-2 is a liquid-side pulse valve case
controller that doubles as a case temperature and
information display. Unlike the CC-100, it is
designed to be mounted on the front of the case, and
has a push-button front panel interface for program-
ming and viewing status. (The EC-2 29x version
controls the refrigeration solenoid valve to allow
the passage of refrigerant to the TXV valve,
whereas the 39x version controls a pulse valve on
the liquid side of the evaporator to regulate super-
heat.)
• CCBs - An I/O Network-based controller used pri-
marily in old RMCC installations. Like the CC-100
family, the CCB was available in several different
models that controlled liquid pulse, liquid stepper,
suction stepper, and suction lineup.
NOTE: There are several variations of the
EC-2. Contact Retail Solutions at 1-800-829-
2724 for more information.
5.27.2.1
Valve Control
The CC-100 is capable of supporting two types of
valves: pulse and stepper. The CC-100 uses PID control to
Case Control Circuits
vary the aperture rates of both valves between 0% and
100% as required by their temperature control algorithms
(see Section 5.27.3, below).
Pulse Valves
A pulse valve is a device capable of being in only two
states: fully open or fully closed. To achieve the necessary
percentage of refrigerant flow, CC-100s repeatedly
"pulse" these valves open for a percentage of an interval
called the valve period (which defaults to six seconds).
For example, to achieve a 20% valve output in a CC-
100 with a valve period of six seconds, a pulse valve
would be opened for 20% of six seconds (or 1.2 seconds)
and closed for the remaining 80% of the valve period (4.6
seconds). This same six-second sequence will repeat for as
long as the CC-100 calls for a 20% valve output.
Stepper Valves
Stepper valves are devices that may opened to many
different positions between fully closed (0%) and fully
open (100%). Stepper valves usually have hundreds or
thousands of "steps" in between fully closed and fully
open. To achieve the desired opening percentage, the CC-
100 moves the valve the required number of steps.
To properly control a stepper valve, the CC-100 must
know the operating characteristics of the valve, such as its
maximum steps per second change rate, the total number
of steps between 0% and 100%, and its hysteresis rate (the
number of steps required for the valve to change direc-
tion).
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Software Overview
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