KMC CONTROLS BAC-120063CW-ZEC Zoning Equipment Controller User Guide
- June 8, 2024
- KMC CONTROLS
Table of Contents
KMC CONTROLS BAC-120063CW-ZEC Zoning Equipment Controller
The Quest for Better Temperature Control
For years, inexpensive light-commercial systems typically consisted of an RTU
(Roof Top Unit) or HPU (Heat Pump Unit) packaged unit with a number of CAV
(Constant Air Volume) or pressure-dependent VAV (Variable Air Volume) zones.
Basic HPU or RTU—with Outside and Conditioned (Cooled) Airflows
CAV systems were made somewhat “variable volume” by dumping a portion of the air through a pressure-controlled bypass damper into the return air stream. This was to maintain a minimum flow across the coils as demands from the local zones varied.
CAV spaces were quite challenged by varying conditions. Varying occupancy or
outside conditions often led to spaces that became too hot or too cold and
then stayed that way for long periods of time.
CAV with Different Space Conditions
A better approach was a low-priced pressure-dependent VAV system. It
compensated for varying conditions, although consistent control was still a
challenge.
Pressure Dependent VAV with Different Space Conditions
The operation of one damper was affected by the actions of dampers in other
zones, and no minimum air flows into the spaces were maintained. If one zone
was satisfied, and the damper closed completely, other zones would suddenly
have more air flow. This would often overcool the other spaces before the
system would compensate. And without a minimum air flow, the first space could
soon get stuffy and too warm before the system finally responded. Setup of
these systems was always a challenge, especially when operating during spring
or fall seasonal changeover and when the spaces were subjected to variations
in occupancy and other common tenant conditions
Pressure Dependent VAV with Changing Duct Pressures
The Easy Pressure Independent VAV Solution
Now, however, there is a better and easier way. KMC has a notably improved
system for retrofitting older systems or installing new light-commercial
zoning systems. The ZEC (Zone Equipment Control) system consists of a BAC-
120063CWZEC (a special model of KMC’s award-winning FlexStat™ unitary
controller) along with KMC SimplyVAV™ controllers for pressure-independent VAV
control in their respective zones. A local pressure-dependent zone is
converted to pressure-independent operation with the insertion of a KMC SSS-
101x differential pressure flow pickup tube, and with the local zone operated
by the SimplyVAV terminal unit controller. Pressure-independent operation
compensates for the varying needs of the local zones while also compensating
for operations in other zones. Damper position is controlled for space
environmental conditions and differences in duct pressure.
Pressure Independent SimplyVAV with Different Space Conditions
Pressure Independent SimplyVAV with Different Duct Pressures
A connected STE-8000 series digital room sensor reads the varying
environmental conditions in that zone, and it is also the only tool needed to
configure and balance the SimplyVAV controller. Adding an STE-140x DAT
(Discharge Air Temperature) sensor adds changeover capability for heating and
cooling control.
Pressure Independent SimplyVAV with Changeover on a BACnet Network
For control of common commercial packaged unitary equipment, up to 16 zones,
with 16 SimplyVAV controllers, can work in conjunction with the BAC-
120063CWZEC model FlexStat. The ZEC FlexStat automatically switches between
heating and cooling control of the HPU or RTU based on local zone demands. The
ZEC FlexStat automatically discovers and communicates with the associated
SimplyVAV controllers via the integral BACnet MS/TP network. This provides
integration of the entire system.
HPU or RTU Controlled by a ZEC FlexStat
Additionally, the ZEC FlexStat controller can also provide a 2–10 VDC static
pressure setpoint signal to an optional KMC CSP-4702 pressure controller used
with a unitary system that has pressure bypass control.
ZEC FlexStat with CSP-4702 for Bypass Control
This model of FlexStat comes preconfigured, and if the defaults describe your
equipment, the occupancy schedule is the only required configuration needed
after mounting and wiring. The schedule is easily created via the FlexStat’s
onscreen menu. With no software required, the ZEC system is quick and user-
friendly to install and configure. Yet it also communicates with any Building
Automation System using a BACnet network for monitoring and additional control
options.
Scheduling on the BAC-120063CW-ZEC FlexStat
More Information
For more information about the powerful simplicity of this approach, visit the
KMC Controls web site (www.kmccontrols.com).
NOTE: For ZEC FlexStat specifications and accessories, see the
BAC120063CW-ZEC data sheet. For more information about applications, mounting,
wiring, configuration, and operation, see the installation guide.
NOTE: See also complete information about the digital SimplyVAV BAC-8000
series controller-actuators and the analog CSP-4702 bypass controller
actuator.
Important Notices
The material in this document is for information purposes only. The contents
and the product it describes are subject to change without notice. KMC
Controls, Inc. makes no representations or warranties with respect to this
document. In no event shall KMC Controls, Inc. be liable for any damages,
direct or incidental, arising out of or related to the use of this document.
KMC Controls® and the KMC logo are registered trademarks of KMC Controls. KMC
Commander™ and FlexStat™ are trademarks of KMC Controls. All other products or
name brands mentioned are trademarks of their respective companies or
organizations. All rights reserved. No part of this publication may be
reproduced, transmitted, transcribed, stored in a retrieval system, or
translated into any language in any form by any means without the written
permission of KMC Controls, Inc.
Support
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© 2022 KMC Controls, Inc. Specifications and design subject to change without notice
References
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