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11-6 • E2 RX/BX/CX I&O Manual 026-1614 Rev 4 5-JAN-2013
11.3.1 Refrigeration Control
A Standard Circuit application may apply one of four
different control methods to a case circuit: the Tempera
-
ture Monitor method, the Temperature Control method,
and the Line Up(ESR)/Defrost method, and the
Lineup(MFESR)/Defrost method.
11.3.1.1 Temperature Monitor
The Temperature Monitor method does not control
case temperature. The application will read and record
case temperature inputs, but it will not make any attempt
to control temperature. The application will still initiate
and control defrost, cycle fans, and perform other neces
-
sary functions.
11.3.1.2 Temperature Control
A Standard Circuit application using the Temperature
Control method will pulse the refrigeration liquid line
solenoid OPEN and CLOSED so as to control the case
temperature to the user-defined setpoint. The application
monitors up to six different temperature sensors in the cir
-
cuit and combines them into a single value that is com-
pared to the setpoint.
11.3.1.3 Line Up(ESR)/Defrost
In Line Up ESR, circuit temperature is controlled by
an electronic evaporator pressure regulator (EEPR). The
EEPR is controlled by a PID algorithm that steps the valve
open from 0% to 100% based on how far away the circuit
temperature is from the setpoint.
This strategy requires the use of the Echelon-based
ESR8 stepper regulator output board, which has been dis
-
continued and replaced by the I/O Network-based Multi-
Flex ESR.
11.3.1.4 Line Up(MFESR)/Defrost
In Line Up MFESR, circuit temperature is controlled
by an electronic evaporator pressure regulator (EEPR).
The EEPR is controlled by a PID algorithm that steps the
valve open from 0% to 100% based on how far away the
circuit temperature is from the setpoint.
This new strategy requires the use of the I/O Network-
based MultiFlex ESR and should not be used with the
Echelon-based MultiFlex ESR.
11.3.2 Defrost Control
Defrost cycles in a Standard Circuit application may be
initiated in either of three ways: by schedule (at specific
times of the day, programmed by the user), by external
trigger (a user-initiated signal such as a switch or button),
or by manual command (initiated on the E2 front panel by
the user).
11.3.2.1 Defrost States
The defrost cycle for a Standard Circuit application
consists of three steps.
1. Pump Down (Elec & Hot Gas only) - The defrost
cycle begins with this step immediately after the
refrigeration solenoid is turned OFF. During the
Pump Down phase, the application waits for a
user-specific amount of time to elapse before
turning on the defrost heat. This allows refriger
-
ant in the evaporator to be evacuated before
defrost heat is activated. The compressor(s)
remain ON during Pump Down.
2. Defrost - During the defrost phase, refrigeration
is disabled. If using electric defrost heaters will
be ON. If using hot gas, heated refrigerant will be
pumped through the coil. This phase will con
-
tinue until the defrost is terminated (see Section
11.3.2.3 for information on how defrost is termi-
nated).
3. Run-Off (Elec & Hot Gas only)- After defrost
heat is deactivated, the application waits for the
Run-Off time to pass before re-entering refrigera
-
tion mode. This allows melted frost on the evapo-
rator to drain from the coil so that it will not re-
freeze when refrigeration begins again. After the
user-specified Run-Off time has passed, the
defrost cycle has ended.
11.3.2.2 Defrost Types
There are many different ways used to defrost a refrig-
erated case. A Standard Circuit application is capable of
employing five different strategies to accommodate five
different types of defrost.
Timed and Reverse Air
Timed defrost and Reverse Air defrost are two differ-
ent defrost strategies, but both are alike in the way they are
controlled by a Standard Circuit application. In both
defrost types, no heat is applied to the evaporator. The
application simply turns the refrigeration solenoid OFF for
the duration of the defrost cycle.
When these defrost types are used, Pump Down and
Run-Off times are not necessary; therefore, they will not
be part of the defrost cycle.
Hot Gas and Reversed Cycle Hot Gas
Hot Gas and Reversed Cycle Hot Gas require the use
of hot gas from the refrigeration lines. During these types
of defrost, the application will open the circuit’s liquid line
solenoid AND will send a command to the refrigeration
rack to open the Master Liquid Line Solenoid. As a result,
heated refrigerant will be pumped through the evaporator
coil.