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11-26 • E2 RX/BX/CX I&O Manual 026-1610 Rev 13 14-SEP-2011
11.7.2 How Zones Work
A Zone is built by first creating a Zone application in
the E2 BX. Then, all HVAC unit applications that will be a
part of the Zone must be connected with the Zone applica-
tion. This connection process is known as association.
When a rooftop unit or AHU is associated with a Zone,
the E2 automatically makes a series of I/O connections
between the Zone application and the individual MultiFlex
RTU or AHU application. From that point on, the Zone is
responsible for passing along the following information to
the individual unit:
• The heating and cooling setpoints it will use
during occupied and unoccupied building
times.
• A command to operate in either occupied or
unoccupied mode (based on the Zone appli-
cation’s own time schedule input).
• Outdoor air and outdoor relative humidity
values.
• A signal to enable or disable economization
(based on the Zone application’s own econo-
mization checking method).
• A signal to begin or end dehumidification
(based on the Zone application’s own humid-
ity reading and dehumidification setpoint).
• A signal indicating the current season is
either SUMMER or WINTER.
• The combined Zone Temperature and Zone
humidity (based on a combination of each
HVAC unit’s space temperature and space
humidity).
• The fallback temperature and humidity set-
points to use in case the unit loses contact
with its Zone application.
11.7.3 Applications That May Be
Connected To Zones
There are three different HVAC applications that may
be associated with a Zone application: a MultiFlex RTU
application, a MultiFlex RCB application, and an AHU
application. The MultiFlex RTU and RCB applications
interface with the MultiFlex RTU and RCB I/O Network
boards that control rooftop units. AHU applications use
input and output points on the I/O Network to control air
handling units.
11.7.3.1 MultiFlex RTU Board
The MultiFlex RTU is a control board on the E2’s I/O
Network that controls the operation of a single rooftop
HVAC unit. This board has an on-board processor with
numerous inputs, relay outputs, and 0-10VDC analog out-
puts, and is designed for controlling advanced rooftop
units with a large number of heat/cool stages, variable-
position economizers, variable-speed fans, etc.
The E2’s MultiFlex RTU applications serve only two
purposes: to act as an interface between the user and the
MultiFlex RTU processor, and to allow communications
between the MultiFlex RTU board and the Zone applica-
tion. The MultiFlex RTU depends on the Zone application
to provide temperature setpoints, dehumidification and
economization enabling, and other information.
The MultiFlex RTU board also has the ability to act in
stand-alone mode without help from the Zone application.
The MultiFlex RTU has its own fallback temperature con-
trol strategy, and even has a seven-day fallback occupancy
schedule that may be substituted when communications
with the Zone is lost.
11.7.3.2 MultiFlex RCB Board
The MultiFlex Rooftop Control Board (RCB) (P/N
810-3062) is a rooftop HVAC control board for use either
as a stand-alone controller or in zone control applications
using a Retail Solutions E2 BX building control system.
The MultiFlex RCB is capable of controlling heat and cool
stages, fans, humidification and dehumidification devices,
economizers using on-board I/O and control algorithms, as
well as monitor and interact with other building control
systems and peripherals (such as smoke alarms and CO2
sensors).
Differences Between the MultiFlex RCB and the Mul-
tiflex RTU:
The RCB is an improved version of the MultiFlex
RTU. The RCB has sixteen fully configurable analog and
digital input points, whereas the RTU has only eight
inputs, two of which are configurable. The RCB has four
analog outputs for use in controlling variable speed fans,
economizers or modulating heating and/or cooling valves,
whereas the RTU has only two analog outputs for use only
with VS fans and economizers. The RCB also features a
more sophisticated HHT interface and updated algorithms
for controlling heating, cooling, dehumidification, and air
quality.
11.7.3.3 AHUs
An AHU controls all aspects of an air handling unit,
including up to eight stages of auxiliary or reclaim heat,
six cooling stages, dehumidification, analog or digital
economization, and support for single-, two-, or variable-
speed fans.
Normally, since AHUs are designed to cover a wide
area of space, AHU Control applications operate on their
own and are not associated with Zone applications (they
are large enough to be “zones” within themselves). How-