Auto-Zone Control Systems Zoning Design User Manual

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Zoning
ZoningZoning
Design GuideDesign Guide
Design Guide
Design GuideDesign Guide
Zone
Zone
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Table Of Contents
How Auto-Zone Works ..........................................................................................................5
Why Should I Use Auto-Zone?..............................................................................................6
What Is Unique About Auto-Zone? ....................................................................................6-8
Zoning Systems Versus True VAV Systems .......................................................................... 9
Basics Of Designing A Zoning System................................................................................ 10
Design Considerations ................................................................................................... 11-12
Zoning Design Procedures.............................................................................................13-21
System Installation .........................................................................................................22-26
Application Notes ................................................................................................................27
Table Of Figures & Tables
Figure 1-1: Auto-Zone Plus System Overview .................................................................... 5
Figure 1-2: Zones Affected By Outdoor Load...................................................................13
Figure 1-3: Zone Layout With External Zones Only ......................................................... .14
Figure 1-4: Zones With North And South Exposures ....................................................... .14
Figure 1-5: Zoning And Constant Volume Units ................................................................14
Figure 1-6: Round Bypass Damper.................................................................................. .16
Figure 1-7: Rectangular Bypass Damper & Kit ................................................................ .16
Figure 1-8 Preferred Sensor Location ..............................................................................1 7
Figure 1-9: Acceptable Sensor Location ........................................................................... 17
Figure 1-10: Least Desirable Sensor Location .................................................................... 17
Figure 1-11: Pressure Dependent Damper .........................................................................1 8
Figure 1-12: Pressure Independent Damper.......................................................................1 8
Figure 1-13: WattMaster Communications Wire ................................................................. 23
Figure 1-14: Auto-Zone Basic System Communications Loop Wiring ................................2 4
Figure 1-15: Auto-Zone Plus System Communications Loop Wiring .................................. 24
Figure 1-16: Transformer & Wire Sizing Considerations.....................................................26
Table 1-1: Round Damper Selection Data.......................................................................... 19
Table 1-2: Rectangular Damper Selection Data .................................................................2 0
How Auto-Zone Works
Zoning Design Guide
The Auto-Zone control system converts single-zone constant volume rooftop packaged or split system HVAC units into variable air volume/variable tempera­ture multiple zone systems. The microprocessor based Zone Manager calculates the heating and cooling re­quirements for each zone based on real time informa­tion received from each Zone Controller/Damper. The Zone Manager then directs the HVAC unit to provide the appropriate amount of heating, cooling, and venti­lation to satisfy each zone’s requirements. A bypass damper controlled, by a static air pressure sensor, modu­lates a bypass damper to maintain constant duct pres­sure.
The Auto-Zone system uses a unique 3 tier approach to controlling the system:
Voting Zones
System Demand
Priority
This 3 tier system works in an integrated fashion to maintain proper control of the equipment and effective control of comfort in the zone.
First the zone must initiate a vote to the HVAC unit. This occurs when a zone becomes more than 1 degree off setpoint. At this time a vote is placed for heating or cooling. Next the controller evaluates the total cooling demand or heating demand within the entire building to see which requirement is more critical. Finally, the system looks for any priority conditions, which would take precedence over other zones. All three of these elements working together provide accurate and stable control of comfort.
Additional control features are taken into account to provide a very effective control of the system. Some of these include priority override, supply air temperature limits, outside air temperature lockouts, and min./max. control over damper position.
Substantial savings can be realized using the Auto-Zone Zoning system instead of having to install multiple roof­top units to accommodate multiple zone requirements. The Auto-Zone Zoning system is versatile and can be used with any packaged roof top unit or split system. It controls a variety of terminal unit functions including single duct pressure dependent, pressure independent, series fan and parallel fan terminals.
CONNECT TO OTHER ZONE MANAGERS
120/9 VAC
TRANSFORMER
AVOID
DIRECT
SUNLIGHT
NETWORK COMM LOOP
AC LINE VOLTAGE
COMPUTER (OPTIONAL)
RemoteLink
CONTROLS
REMOTE LINK
(OPTIONAL MODEM)
2 CONDUCTOR
24 GA.
OUTSIDE AIR SENSOR
24 VAC
GROUND
COMMLINKII
CONTROLS
COMM LINK II
INTERFACE
( OPTIONAL )
CONTROL CABLE
SUPPLY AIR
TEMPERATURE
SENSOR
2 CONDUCTOR
ZONE MANAGER
LOCAL COMM LOOP
120/24 VAC
TRANSFORMER
24 GA.
SYSTEM MANAGER
FAN
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EXHAUST AIR
RETURN AIR
MODULATING
3 CONDUCTOR
24 GA.
LO
BYPASS DAMPER
STATIC PRESSURE SENSOR & PICKUP TUBE
HI
2 CONDUCTOR
24 GA.
RETURN AIR SENSOR
CONNECT TO OTHER ZONE CONTROLLERS OR CV UNITS
SUPPLY AIR DUCT
MODULATING
DAMPER
ZONE
CONTROLLER
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ZONE 1
TEMPERATURE SENSOR
MODULATING
DAMPER
ZONE
CONTROLLER
WARMER
NORMAL
COOLER
OVR
ZONE 2
TEMPERATURE SENSOR
W/OVERRIDE AND SETPOINT ADJUST
UP TO 16 ZONES
Figure 1-1: Auto-Zone Plus System Overview
Auto-Zone Systems 5
Zoning Design Guide
Why Should I Use Auto-Zone?
Auto-Zone is a proven system with a long history of successful installations. Our systems have been refined over the years with the help of feedback from people in the field who work and live with these systems on a daily basis. Our success is greatly due to the fact that we have implemented changes and enhancements based
on real world experience not from tinkering with equip­ment in an isolated lab environment. This real world approach provides engineers, contractors, and end us­ers with a zone control system that is efficient, reliable, and most importantly, keeps the customers comfortable!
What Is Unique About Auto-Zone?
Auto-Zone is unique because it has many features not found on other systems. These features include
Non-Proprietary Design
Auto-Zone will work on any manufacturers HVAC equipment that will accept a standard thermostat con­nection. This protects the end user from being locked in to one source for service and support. In addition, Auto­Zone Systems include very comprehensive documenta­tion, which was written in a format specifically for a “non-controls technician”. Because the manuals are so user friendly, it prevents the end user from being “locked-in” to one contractor for service. Any new con­tractor needs only a copy of the system manual to have as much technical information as any previous contrac­tor.
Pre-Engineered Software
System design, software, and documentation has already been done for you. This eliminates the costly expense usually associated with conventional DDC systems, making the Auto-Zone system more competitive and easier to install and operate.
One System for Zoned or Single Zone Systems
Not only does Auto-Zone provide a networked zone control system for one or multiple zoned HVAC units, you can also connect individual single zone units to the system eliminating the need to use programmable ther­mostats.
Easy to Configure
Since Auto-Zone components are grouped into pack­ages, configuring a system has been simplified. This reduces the chance of ordering errors and makes sys­tem layout effortless!
User Friendly Set Up
Since the Auto-Zone comes with menu driven, fill in the blank programming, system setup is simple. The system manual takes you step by step through the set up process. Default parameter values are programmed into permanent memory so the system can be opera­tional at start-up. Specialized training is not required.
6 Auto-Zone Systems
Zoning Design Guide
True Network Communications
The Auto-Zone uses a three wire, RS-485 loop for com­munication between all controllers in the system. This provides a very reliable form of communication with flexibility of installation. The loop can be wired in a “daisy chain” or “star” configuration. Many other zon­ing systems utilize “home run” wiring that requires all communication cables to be brought back to a central point adding additional cost to the project and compli­cating wiring.
High Integrity Communications
Many communicating control systems are susceptible to electrical interference. One major manufacturer of zoning systems recommends that their communication cable should not be strapped to conduit because of po­tential interference. The Auto-Zone Systems have a communication bus that is almost immune to any noise problems that may be found in most commercial facili­ties.
Microprocessor Controllers
All controllers in the Auto-Zone have an on board microprocessor. This is what gives the Auto-Zone its powerful features and capabilities not found in other systems.
Stand Alone Systems
All Auto-Zone Systems are true stand-alone and do not require a computer to operate. Unit controllers main­tain their own 7 day time clock, 365 day holiday sched­uling, and setpoints within each controller.
Menu Driven Operators’ Interface
All Auto-Zone systems have an operators’ keypad and display terminal. This gives you access to system sta­tus and parameter values without the need for a com­puter. The 4 line by 20 character display is backlighted making it easy to read even in low light environments. Menu driven programming makes the system extremely user friendly. In addition, the interface panel is pass­word protected to keep unauthorized users from access­ing the system.
Communications Via Optional Modem
The Remote Link is used for achieving remote commu­nications with the Auto-Zone system. It connects to the
CommLink II communications interface and a local phone line. With the Remote Link, the Auto-Zone sys­tem can be monitored and controlled from a remote lo­cation, using a computer and the ZoneView AZ or Plus software packages.
Memory Backup
Instead of batteries, which have to be replaced, Auto­Zone utilizes super capacitors to provide power for memory backup during power outages. The major ad­vantages to this approach is that super capacitors are more reliable than batteries and they recharge in a mat­ter of seconds instead of hours. T ypical memory backup is good for a minimum of 10 days.
Modulating, Heavy Duty Actuators with Real Time Feedback
All Auto-Zone actuators utilize true modulating con­trol unlike many systems, which are two position. This gives the system-improved control, which translates, to better comfort levels. Our actuators are also rated for 2-½ million cycles, making our actuators some of the most reliable in the industry. One other critical feature is the real time feedback. Many other systems have no feedback at all. They blindly estimate the travel time of their actuator, which, in the real world, is not a very repeatable estimate. To help correct the problems in­herent with this approach, they recycle all the actuators in the system once or twice a day . They may save a few dollars by not including feedback but they sacrifice sys­tem performance. Not so with Auto-Zone.
Commercial Grade – Insulated Round Zone Dampers
Auto-Zone only uses commercial grade zone dampers, not cheap, flimsy, “light commercial” or “residential” style dampers like many other manufacturers. Our round damper is ARI certified and comes from the factory fully insulated. Why? When many zone dampers are installed they are improperly insulated or not insulated at all. This can cause problems with the damper “sweat­ing” from condensation. With factory insulated zone dampers, we eliminate a common problem for the con­tractor while insuring the end user will not have prob­lems with condensation dripping down onto the ceil­ing.
Auto-Zone Systems 7
Zoning Design Guide
What Is Unique About Auto-Zone?
Rectangular Dampers
Auto-Zone uses only top of the line, aluminum air foil rectangular control dampers. No other zone system on the market today utilizes a damper of this quality and performance!
Patented Flush Mount Room Sensors
Our flush mount room sensors are so unique, they are patented (U.S. Patent No. 4,659,236). Even though part of the sensor is recessed into the wall to provide an attractive yet tamper proof flush mounting, internal wall temperatures do not influence the sensor. A special plate on the face of the sensor accurately senses space tem­perature. Even though the attractive off white plastic housing is a preferred color, the sensor housing can be painted or wallpapered to blend with room decor with­out affecting sensor performance. The sensors are of­fered in four different configurations:
Sensor
Sensor w/override
hundreds. ZoneView is not copy protected so it can be installed on multiple PC’s’ without additional expense. Just some of its many features include but are not lim­ited to:
Pre-designed status screens for all controllers
Alarm dial out capability
Programming of all system parameters
Trend logging to Excel™ spreadsheets
Alarm Handling
Custom graphics capability
Sensor w/setpoint adjustment
Sensor w/setpoint adjustment & override
Modular Connections
Many Auto-Zone auxiliary devices are connected to the controllers via modular plugs like the ones used on tele­phones. This simplifies installation and eliminates the possibility of wiring errors. The devices, which utilize this method, are damper actuators for zone and bypass control, auxiliary relay boards, and static pressure/air flow sensors. There is one interesting side note about the auxiliary relay board and airflow sensors. These devices are typically used on the zone controllers in the Auto-Zone Basic & Plus systems. When the system is powered up, it automatically looks to see if these de­vices are connected to the controller. If they are, the controller automatically reconfigures itself to utilize these devices and activates the appropriate set up screens back at the operators interface. Pretty neat don’t you think!
FREE! Windows™ Graphics Software
Each Auto-Zone system can be monitored on site or remotely using a PC and our ZoneView Plus™ Win­dows 98 software. This full-featured package is very user friendly and can be used to monitor one system or
Open Protocol System
Auto-Zone is an open protocol based system allowing other manufacturers to develop direct interfaces to the communications loop. This gives you the ability to in­tegrate the Auto-Zone system into products from other vendors. Our engineering staff will be glad to assist any vendor in this process.
8 Auto-Zone Systems
Zoning Design Guide
Zoning Systems Versus True VAV Systems
General
Even though there are some similarities between zone control systems and Variable Air Volume (VAV) sys­tems, there are some major differences. In many cases systems will be called VAV when in fact they are really a zoning system or are referred to as a zoning system when they are really a VAV system. Always make sure that you do not try to adapt a zoning system to a VAV design system. Understanding the differences will help you to prevent misapplication of the Auto-Zone zoning system. In the paragraphs that follow we will try to ex­plain the differences, advantages and disadvantages of each and explain their operation.
V AV Systems
These systems consist of an HVAC unit that is gener­ally a cooling only unit and VAV terminal units located in the downstream ductwork that are used to control the amount of constant temperature air delivered to the various building zones. Sometimes the HV AC unit may have gas or electric heat, but it is typically sized and applied for morning warm-up purposes. The HV AC unit is designed to vary the volume of air that is supplied to the duct system by using either inlet vanes or an elec­tronic variable frequency drive. These devices modu­late to control the air flow through the supply fan in response to the static pressure in the duct system. VAV systems typically use high velocity VAV terminal units to distribute the air to the zones. As the various VAV terminal units in the different zones open and close to supply the constant temperature air to the spaces, the HVAC unit varies the volume of constant temperature air based on the static pressure in the ductwork. The HV AC unit is designed to maintain a constant cold sup­ply air temperature regardless of the air flow volume in the system. The HVAC unit cycles it’s cooling stages to maintain a constant predetermined supply air tem­perature. It typically runs continuously based on a sched­ule. For perimeter zones requiring heat, reheat coils (electric or hot water) located in the terminal units are used to supply heated air to the space. Many times fan powered terminal boxes are used and in many cases also incorporate electric or hot water heating coils to provide perimeter zone heating. In summary a true V AV system uses a variable volume fan supplying constant temperature air to the system with variable volume ter­minal units used to control the volume of constant tem­perature air delivered to the space. Generally these sys­tems use pressure independent damper control.
Auto Zone Systems
The Auto-Zone zoning system is completely different in operation and design from the VAV system previ­ously discussed. One of the major differences between the zoning system and a true VAV system is that the HVAC unit used on a zoning system utilizes a constant volume fan. Air volume control of the zoning system is achieved by bypassing air from the HVAC unit supply duct back into the HVAC unit return air duct on the unit inlet. This bypass air is controlled based on a static pres­sure sensor located in the supply air duct downstream of the unit supply air discharge. The bypass damper modulates open and closed based on the static pressure in the duct. The temperature at the HV AC unit dischar ge varies in relation to the demand from the zones. Typi­cally the HVAC units used for the zoning system will have both heating and cooling capabilities. The fan sup­plies a constant volume of cold or hot air to the duct system and which is fed to the individual zones by modu­lating zone dampers. Each zone controller relays its heat­ing or cooling demand to the HVAC unit controller. The HVAC unit controller determines its mode of operation (heating, cooling or vent mode) depending on the de­mand from the zone controllers. The unit controller uti­lizes a voting system to determine the correct mode of operation. Each zone controller determines (based on its heating and cooling setpoints) whether or not to use the air being supplied by the HVAC unit. For example, one of the zones is calling for cooling when the tem­perature in the duct is above the zones cooling setpoint. This zone will move to its minimum cooling position to prevent warm air being introduced into the space. With the zoning system the zone dampers are generally pressure dependent. Pressure independent operation is available but is not very common. Reheat and/or fan powered terminal units can be used but aren’t commonly part of the typical zoning system.
Conclusion
In many cases VAV systems go over budget because of the increased cost of a VAV, HVAC unit and the expen­sive VAV controls associated with the system. Many times the system can be redesigned to a zoning system using Auto-Zone controls with a significant cost sav­ings and equal or better performance and comfort than the VAV system would provide. Be sure to follow the instructions in this design guide for your zoning sys­tem.
Auto-Zone Systems 9
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