Emerson E2 How Zones Work, Applications That May Be Connected To Zones, MultiFlex RTU Board, AHUs

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.

11.7.3Applications 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.

11.7.3.1MultiFlex 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.

11.7.3.2MultiFlex 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.

11.7.3.3AHUs

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-

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