The MultiFlex CUB-II
Overview of the MultiFlex CUB-II and CUB-TD • 1
1
Overview of the Multi-
Flex CUB-II and CUB-TD
The MultiFlex CUB-II and CUB-TD boards
are “smart” input/output boards designed to con-
trol single condensing units. A single condens-
ing unit is a self-contained compressor and
condenser bearing unit which controls refrigera-
tion in a single case line-up or walk-in cooler.
The MultiFlex CUB-II controllers are capable of
commanding compressors, condensers, refriger-
ation, and defrost for a single condensing unit
using on-board I/O and control algorithms. The
CUB-TD controller is a more limited board that
controls only condensers, using a temperature
differential control strategy.
The MultiFlex’s I/O Points
The compact size of the MultiFlex allows
technicians to easily field-mount the MultiFlex
CUB-II and CUB-TD in a panel or enclosure
close to the single condensing unit, allowing for
easy local connection of sensors and transducers.
The board has 16 analog inputs (for connection
to vital input sources, such as suction pressure
transducers and case temperature sensors) and
eight relay outputs, rated 2.0 amps max, for acti-
vating and deactivating compressors, defrost,
and condenser fans.
Independent System Control
The MultiFlex CUB-II and CUB-TD con-
trollers are equipped with software and an
enhanced processor, which gives them the capa-
bility of controlling independently without the
need of a central controller (such as CPC’s E2 or
Einstein RX Refrigeration Controller). However,
the CUB-II and CUB-TD are designed to inter-
face with an E2 or Einstein for purposes of dis-
playing status on status screens, reporting
alarms, and recording logs. The CUB-II and
CUB-TD may be configured either with a CPC
Hand-Held Terminal (HHT) or through the E2 or
Einstein front panel.
1.1. The MultiFlex CUB-II
The MultiFlex CUB-II controllers are capa-
ble of handling all aspects of single condensing
unit control, including compressors, condensers,
refrigeration, and defrost, using on-board I/O
and control algorithms. The CUB-II is capable
of controlling one single-stage compressor,
refrigeration and scheduled/terminated defrost in
a case circuit with up to six temperature inputs,
and condenser control using either a control by
pressure strategy (activates up to two fans to
maintain a set discharge pressure) or temperature
differential strategy (activates up to four fans to
maintain a set difference between the ambient
temperature and the drop leg refrigerant temper-
ature).
1.2. The MultiFlex CUB-TD
The MultiFlex CUB-TD is a “stripped” ver-
sion of the MultiFlex CUB-II that includes only
an algorithm for temperature differential (TD)
condenser fan control. Up to four condensing
unit fans are cycled on and off as required to
meet compressor unit heat of rejection load. The
TD algorithm subtracts plenum air temperature
from the drop leg temperature and uses the dif-
ference between the two temperatures as a con-
trol value. If the difference is higher than the
setpoint, the fans are staged on. If the difference
is lower than the setpoint, the fans are staged off.
The temperature differential control capabili-
ties of the CUB-TD are identical to those of a
CUB-II operating in temperature differential
mode, except the CUB-TD controls condensers
only. The CUB-TD only has inputs for reading
temperatures and outputs for controlling up to
four fans. For control of any other single con-
densing unit subsystem, a CUB-II will neces-
sary.
