Honeywell AUTOMATIC CONTROL SI Edition, Engineering Manual

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INDIVIDUAL ROOM CONTROL APPLICATIONS
ENGINEERING MANUAL OF AUTOMATIC CONTROL
397
INTRODUCTION
This section describes applications for air terminal units and
unitar y equipment used in indi vidual r oom contr ol. The air
ter minal units co vered inc lude var iable- and constant-v olume
units connected to single- and dual-duct air handling systems.
The unitar y equipment descr ibed inc ludes na tur al convection
units, radiant panels, unit hea ter s, unit v entila tor s, fan coil units,
and heat pumps.
In indi vidual r oom contr ol, the contr ol of a r oom or space is
maintained b y a r oom sensor and a contr olled device such as a
valve or damper actua tor, a bur ner unit, or a compr essor. The
method of control may be pneumatic, thermal, electric, electronic,
or dig ital. As environmental and standar d code r equir ements
change, the control system can be upgraded to enhance the
operating capabilities of the system and the terminal units, resulting
in comple x contr ol str ategies for eac h type of ter minal unit.
Applications presented in this section are based upon DDC
and a BMS . If a BMS is not a vaila ble, contr ol r emains
unchanged and the BMS displayed data points should still be
available for oper ator s and tec hnicians via a por table ter minal.
Simple systems suc h as unit hea ter s ar e also shown in Electr ic
Control Fundamentals section.
Lar ge air handling units and c hiller plants typicall y use
general purpose digital controllers, while rooms typically use
contr oller s designed f or r oom contr ol. Thus, a VAV box
contr oller ma y be configur ed to contr ol a var iety of VAV boxes
in a variety of ways, but cannot be programmed to control a
multi-zone unit. Specifiers of room control strategies must
check with vendors to be sure the specified applications can be
performed within available products. Many room control
schemes ar e used toda y. This section pr esents onl y a few of the
more common ones. Room control strategies must be
coordinated with primary air and water systems to assure
compa tibility.
Control schemes are presented in a BMS graphic display
for ma t, including softw ar e and some eng ineer ing da ta.
Automation concepts are presented at the end of this section.
With most r oom units, sever al units ma y be combined on a
single displa y for oper ator simplicity . Although v alua ble in this
discussion, the level of technical data could overwhelm the
nontec hnical oper ator. In all cases the da ta displa ys should
consider the user’ s need to kno w and a bility to under stand .