Viconics VBZS User Manual

Viconics BACnet Zoning System

Application Guide

VZ7260X5x00B and VZ7656X5000B Controllers

VBZS_Rel2_Application_Guide-E04

(R1 Issue Date: January 10th, 2012)

Table of Contents:

Please refer to the installation manuals of the zoning system controllers for all required information related to wiring, installation, commissioning and integration:

• For detailed information on the Viconics VZ72xx zone controller, please refer and read the VZ72xx product guide. Installation and commissioning information is available on document: LIT-VZ7260X-Exx

• For detailed information on the Viconics VZ76xx RTU controller, please refer and read the VZ76xx product guide. Installation and commissioning information is available on document: LIT-VZ7656X-Exx

• Information on 3

party BACnet integration, is available on document ITG-VZ7xxx-BAC-Rel2-Exx

1. System Overview and Architecture

A. Initial design criteria considerations B. Scalability and limitations C. Local Zone with Terminal Reheat or Without Terminal Reheat D. Atypical zone areas E. By-pass damper design rules F. Indoor Air Quality Control Standards

2. Zone controllers VZ7260X5x00B operation and strategy

A. Demand based heating and cooling system B. Overrides and user zone interface lockouts C. Zone set point limits D. Heating and cooling weight zone selection E. Minimum, maximum and max heat flow adjustments F. Terminal reheat lockout G. Passive infra red motion detector cover (PIR) H. AI4 CO2 / Other Sensor Input Operation I. Disable Minimum Position parameter J. Heating and Cooling Performances

3. RTU controllers VZ7656X1000B operation and strategy

A. Operation data exchanged B. Occupancy and overrides C. RTU interface lockouts D. RTU heating and cooling supply air temperature lockouts E. RTU heating and cooling outdoor air temperature lockouts F. Critical mid-season changeover G. By-pass damper / VFD control and operation

H. Minimum Supply Heat Temperature Control and Lockout I. Indoor Air Quality Control & Operation

4. BACnet Communication system overview

A. 3rd party BACnet integration B. Communication wiring and layout C. Communication status LED and troubleshooting

5. System commissioning

A. Proper commissioning zone controllers B. Proper commissioning RTU controllers C. Operational system checklist

6. Things you need to know

A. Single 24 VAC zone transformer vs. multi 24 VAC zone transformers B. Critical point checks C. Balancing and capacity

1) System Overview and Architecture

The Viconics Zoning System product is comprised of two controller types.

• The VZ7260X5x00B Zoning controller

• The VZ7656X1000B RTU / HP controller

When combined, they deliver a simple and efficient demand based system implementation which controls pressure dependent VAV zones with roof top units (RTU). The system is designed to work with small to medium sized RTU staged heating and cooling equipment (2 to 20 tons).

A local BACnet RS485 MS-TP communication bus between all devices insures proper communication and data exchange of all required information between the zones and the RTUs. They can be seamlessly integrated into any 3

party BACnet supervision system.

The Viconics VZ7260X5x00B BACnet zone controller family is specifically designed for local pressure dependent VAV zone control within Viconics zoning system product family. The primary damper output uses a common 0 to 10 VDC VAV actuator for control.

The product features a backlit LCD display with dedicated function menu buttons for simple user operation. Accurate temperature control is achieved due to the product’s PI proportional control algorithm, which virtually eliminates temperature offset associated with traditional, differential-based controllers.

The zone controllers also feature a 0-10VDC sensor input that can be used for CO2 level monitoring and/or control via the VZ7656E1000B RTU controller, or with any other 0-10VDC sensor.

The Zone controllers are also compatible with the new Viconics PIR cover accessories. Controller is equipped with a PIR cover which provides advanced active occupancy logic. The system will automatically switch occupancy levels from occupied to stand-by and unoccupied as required when activity is detected or not detected by the unit. This advanced occupancy functionality provides valuable energy savings during occupied hours without sacrificing occupant comfort. All zone controllers can be ordered with or without a factory installed PIR cover.

The following hardware is required for operation of the zone controllers but not included:

• 24 VAC power supply. Dedicated to a single zone or many zones

• An analog 0 to 10 VDC pressure dependent actuator

• Terminal reheat if required by the design

• Proper wiring of all components as per the installation manual

• Proper network wires pulled through all devices communication connections

The Viconics VZ7656X1000B BACnet Roof Top Unit (RTU) controller has been specifically designed for equipment control based on the zone demands..

The product also features a backlit LCD display with dedicated function menu buttons for simple operation. Accurate temperature control is achieved through to the product’s PI proportional control algorithm, which virtually eliminates temperature offset associated with traditional, differential-based controllers.

These controllers also contain extra digital inputs, which can be set by the user to monitor filter status or can be used as a general purpose service indicator. Some models contain a SPST auxiliary switch, which can be used to control lighting or disable the RTU economizer function during unoccupied periods. They also features a discharge air sensor input. Particularly, the VZ7656E1000B features a 0-10VDC fresh air damper output that can be used to for free cooling (economizer function) and/or for CO2 level control. Proportional static pressure logic (input and output) has been integrated onto the controller to provide a complete single packaged unit for most small to medium size jobs.

The following hardware is required for operation of the RTU controllers, but not included:

• 24 VAC power supply. Typically taken directly from the RTU power supply (C & RC)

• An outdoor air sensor (Viconics S2020E1000)

• A supply air duct sensor (Viconics S2000D1000)

• A return air duct sensor (Viconics S2000D1000)

• A 0 to 5 VDC static pressure sensor and transducer

• An analog 0 to 10 VDC by-pass damper actuator (spring-return or not)

• Proper wiring of all components as per the installation manual

• Proper network wires pulled through all devices communication connections

Zone Controllers Available Models & Features:

iconics Part

Number

Control

Outputs

PIR Cover

VZ7260F5000B VZ7260F5500B VZ7260C5000B VZ7260C5500B

2 x Analog 0 to 10 VDC

1 x Auxiliary reheat

contact

PIR cover ready. PIR cover factory installed PIR cover ready PIR cover factory installed

2 x Analog 0 to 10 VDC

1 x Auxiliary reheat

contact

2 x Tri-state floating

1 x Auxiliary reheat

contact

2 x Tri-state floating

1 x Auxiliary reheat contact

Master Controllers Available Models & Features:

iconics Part

Number Controlled Equipment Main Control Outputs

Unique Features

VZ7656R1000B VZ7656H1000B VZ7656F1000B VZ7656E1000B

Rooftop Unit Heat Pump Unit Rooftop Unit Rooftop Unit

2H / 2C 3H / 2C 0-10VDC Analog Heat / 2C 2H / 2C

- Reversing Valve Output

- 0-10VDC Analog Heat Output

- Minimum Supply Air Temperature Control

- 0-10VDC Fresh Air Damper Output

- 0-5VDC Airflow Sensor Input

- CO2 Level Control Sequence

- Free Cooling Economizer Sequence

BACnet System Overview

Viconics VZ72605x00B Zone controllers are used in conjunction with the VZ7656X1000B roof top controller controllers. When combined, they are designed for operate typical single or multistage RTUs and their associated local zones.

Typical BACnet zoning system installation

Please refer to the following Viconics documents for detailed information and design guidelines on the BACnet zoning system version:

The following documents are available at: www.viconics.com

• For detailed information on the Viconics VZ72xx Zone controller, please refer and read the VZ72xx Product Guide. Installation and commissioning information is available on document: LIT-VZ7260X_B-Exx

• For detailed information on the Viconics VZ76xx RTU controller, please refer and read the VZ76 Product Guide. Installation and commissioning information is available on document: LIT-VZ7656X_B-Exx

• PIR cover installation information is available on document: PIR Cover Installation-Exx

• Information on 3

party BACnet integration, is available on document ITG-VZ7xxx-BAC-Exx

As an example, a typical job layout system may feature 3 RTU controllers with 31 zones total. This would bring to total number of nodes (individual Com addresses) to 34. RTU 1 would have 10 zones under its command, RTU 2 would have 10 zones under its command and RTU 3 would have 11 zones under its command.

1A) Initial Design Considerations

The scope of this document is not intended to be a resource or white paper on VAV zoning system design. There are many good resources available on the subject of VAV zoning systems and their associated advantages and disadvantages. Please consult these resources for further information on this subject.

It is the responsibility of the designer and installer to ensure the following considerations are met:

• Size the installed equipment for properly calculated heating and or cooling peak loads. There are no advantages to over sizing the system’s capacity to more than what is required as this simply leads to short cycling of the equipment during small load periods.

• Properly size and layout all ductworks including the by-pass damper according to local codes and standards in effect.

• Properly size the capacity of the zones according to the actual requirements of the room. Using square footage calculations only can create situations where the installed total deliverable load may be insufficient for the actual intended use of an area. Conference rooms, computer rooms, cafeterias or other rooms where large gatherings occur would be a prime example of this scenario.

It is not the mandate of the zoning control system to correct for wrong initial mechanical layout and or load calculations

of the mechanical equipment. The control system will attempt to deliver the loads required by master demanding zones

by distributing the total available capacity of the installed equipment to the required demanding areas. If the equipment

is undersized for the required peak loads, the control system will distribute the available capacity according to the

priorities requested hence making most of the areas comfortable.

Proper planning and design will ensure that a job site will be up and running faster with less service calls during the initial occupancy period.

1B) Scalability and Limitations

The system is fully scalable in terms of number of zone controllers and RTU controllers used on the same network layer (BACnet MS-TP or Wireless models).

BACnet controller system overview:

A BACnet MS-TP network segment is a single 22 gauge shielded network wire loop run between all devices communication connections that is no longer than 1200 meters (4000 feet). It is possible to install up a maximum of 64 nodes on a single network segment.

To install more than 64 nodes or if the network wire loop is longer than 1200 meters (4000 feet), repeaters will be needed for proper communication. Please refer to the BACnet integration guide if repeaters are required. With the proper use of repeaters, the maximum number of nodes on a single BACnet MS-TP trunk can be extended to 128 nodes.

Smallest System Supported Largest System Supported

Single Segment of 64 nodes maximum

32 zone reporting to 32 RTU Maximum

Single Network trunk of 128 nodes maximum

63 zone reporting to 63 RTU Maximum

Number of Zones Number of RTUs Number of Zones Number of RTUs

1 zone reporting to 1 RTU Minimum 63 zone reporting to 1 RTU Minimum

1 zone reporting to 1 RTU Minimum 126 zone reporting

1 RTU Minimum

With BACnet supervision devices and multiple systems installed on a job site, there is no practical limit to the number of zone and RTU controllers which can be installed on a single job site.

1C) Local Zone with Terminal Reheat or without Terminal Reheat

Including or excluding use of terminal reheat is dictated by design criteria’s of the installer. The use of terminal reheat in a VAV system will always result in a more comfortable set-up for the occupants of the space. However this may not be practical from a cost standpoint or regional requirements. System designs will vary from Northern to Southern and Eastern to Western geographical locations because of the specific regions peak load requirements.

In colder climates, VAV system heating operation without the use of terminal reheat typically always results in colder outside walls. Although the zone dry-bulb temperature may be well maintained, it may be possible for occupants not to be comfortable simply because of the low outside wall temperate.

Also, in the perimeter zones, the delivery process of the heating capacity from the ceiling is not as efficient as when delivering the heating load directly where the losses occur such as in the case of a perimeter electric baseboard or perimeter hydronic baseboard.

In regions where the heating load is small and required for only a small portion of the year, a properly sized up zone VAV can deliverer the required heating demand and insure comfort without the use or terminal reheat. However it is important to design the zone ductwork and area diffusers to be the most efficient with air delivery close to the outside walls.

In certain problematic cases where air delivery may be an issue, the use of fan powered VAV units may reduce the occupant discomfort by providing constant airflow to the zone and maximizing the air delivery process.

1 D) Special Considerations

A typical office installation may require that a single unit service areas being used for different applications. These areas will commonly be a combination of external and internal zones.

It is always good to verify the intended use of all areas knowing their true peak loads before committing to its final design and sizing.

It may be necessary to oversize or undersize the design to meet their daily demands. The following are examples of when over sizing of a zone damper may be needed:

• Areas with oversized windows that are exposed to the sun longer

• Conference rooms

• Cafeterias

• Areas with vending machines

• Areas with extra lighting

• Areas with computers, photocopier, etc…..

Areas such as computer rooms, kitchens and certain types of conference rooms may warrant a totally separate system of their own and should not be part of the zones attached to an RTU. Certain critical areas may call for cooling all year long and based on system settings could only guarantee occupant comfort a portion of the year.

Knowing the critical areas of a building in advance and designing for them specifically will always result in a more comfortable occupant. And it can be as simple as adding terminal reheat, radiant floor heating, a fan powered VAV or even a separate small water source heat pump to critical area.

1E) By-Pass Damper Design Rules

A bypass damper is an airflow regulating device connected between the supply and return ducts. The bypass damper will automatically open and bypass supply air normally delivered to the zone directly from the supply to the return on a pressure rise when the VAV zone dampers are closing.

The by-pass damper should be sized to allow at least 70 to 80% of the nominal airflow of the RTU. A simple way to determine if it is sized properly, assume all VAV zones are closed to their minimum position. The by-pass should be large enough to re-circulate all the air from the RTU minus the amount set by the minimum positions at the zones. A properly sized damper will result in an efficient and quiet operation.

1F) Indoor Air Quality Control Standards

The IAQ control is achieved by the VZ7656E1000B controller through CO2 level and minimum fresh air control. The building CO2 level has to respect the local building codes. The recommended outdoor air flow per the ASHRAE standard for office buildings (Air class 1) is as follows:

Table from: ASHRAE Standard 62.

2) Zone Controllers VZ7260X5x00B Operation

The following information needs to be carefully read and properly understood if proper system commissioning is to be achieved.

Contrary to low end commercial and residential zoning controllers which use a two positions open-close actuator, Viconics VZ7260X5x00B uses proportional analog 0 to 10 VDC modulating damper actuator. This enables performances and control sequences to be much closer to what is normally found in DDC application specific control devices.

The operation of the ZONE controllers is intrinsically linked with the operation of their RTU controller. Although it will operate in a stand-alone mode if the communication network is down, normal operation of the system as a whole requires that communication with the RTU controller is functional.

Data exchanged from the ZONE controllers to the RTU controller:

• Current PI heating demand ( output value is based on PI heating weight configuration )

• Current PI cooling demand ( output value is based on PI cooling weight configuration )

• Transferred CO2 Level ( Value is based in the Occupancy status and AI4 Parameter setting )

Data exchanged from the RTU controller to the ZONE controllers:

• Current central system occupancy

• Current system mode active ( hot air or cold air being delivered )

• Outdoor air temperature

2A) Demand Based Heating and Cooling Systems

System operation as a whole consists of selecting which zone controllers will have heating and cooling weighted votes used by the RTU controller to which they are attached. The weighted heating and cooling demand values from the selected master zones are then used by the RTU controller to determine if heating or cooling action is required for the system as a whole.

Both internal and external zones are typically serviced by the same unit. This means that the system may be exposed to conflicting heating and cooling demands in mid-seasons. The conflicting demand conditions are addressed with the heating and cooling lockouts based on the outside air temperature value at the RTU.

The heating or cooling action at the zone is dependent on how the RTU controller treats and calculates what will be delivered point in time to the zones. Many factors can influence the delivery or availability of hot air or cold air to satisfy the current zone demand point in time.

The following is an example of a RTU system mode calculation based on highest, average of the three highest demands or the average of the five highest demands.

Example 1 with 3 voting master zones only

oting Zone 1 Voting Zone 2 Voting Zone 3 RTU Control Type

Current heat

demand

50% 0% 0%

Heat weight set Heat weight set Heat weight set

50% 100% 100% Resulting heat weight to RTU

25% 0% 0% 25% 8.3%

Current cool

demand

0% 100% 100%

Cool weight set Cool weight set Cool weight set

100% 100% 50% Resulting cool weight to RTU

0% 100% 50% 100% 50%

Current heat

demand

Resulting heat weight to RTU

Current cool

demand

Resulting cool weight to RTU

Current heat

demand

Resulting heat weight to RTU

Current cool

demand

Resulting cool weight to RTU

Highest Average of 3

highest

It can be seen here that the resulting demand used by the RTU controller for the three master voting zones are different and will result in different heating and cooling actions simply based on the RTU configuration.

Example 2 with 3 voting master zones only

oting Zone 1 Voting Zone 2 Voting Zone 3 RTU Control Type

Current heat

demand

100% 0% 0%

Heat weight set Heat weight set Heat weight set

100% 100% 100% Resulting heat weight to RTU

100% 0% 0% 100% 33.3%

Current cool

demand

0% 100% 100%

Cool weight set Cool weight set Cool weight set

100% 75% 75% Resulting cool weight to RTU

0% 75% 75% 75% 50%

Current heat

demand

Resulting heat weight to RTU

Current cool

demand

Resulting cool weight to RTU

Current heat

demand

Resulting heat weight to RTU

Current cool

demand

Resulting cool weight to RTU

Highest Average of 3

highest

It can be seen here that the resulting demand used by the RTU controller for the three master voting zones are different and will result in different heating and cooling action simply based on the RTU

configuration.

• If the RTU is set to Control Type = Highest demand, the current action delivered by the RTU

will be heating.

• If the RTU is set to Control Type = Average of 3 Highest demand, the current action

delivered by the RTU will be cooling.

Example 3 with 5 voting master zones only

oting

Zone 1

Current heat

demand

100% 0% 50%% 50% 0%

Heat weight

set

100% 100% 100% 50% 100%

Resulting

heat weight

to RTU

100% 0% 50% 25% 0% 100% 58.3% 35%

Current cool

demand

0% 100% 0% 0% 100% Cool weight

set

100% 50% 50% 50% 75%

Resulting

cool weight

to RTU

0% 50% 0% 0% 75% 75% 41.7.3% 25%

oting

Zone 2

Current heat

demand

Heat weight

set

Resulting

heat weight

to RTU

Current cool

demand

Cool weight

set

Resulting

cool weight

to RTU

oting

Zone 3

Current

heat

demand

Heat

weight set

Resulting

heat

weight to

RTU

Current

cool

demand

Cool

weight set

Resulting

cool

weight to

RTU

oting

Zone 4

Current

heat

demand

Heat

weight set

Resulting

heat

weight to

RTU

Current

cool

demand

Cool

weight set

Resulting

cool

weight to

RTU

oting

Zone 5

Current

heat

demand

Heat

weight set

Resulting

heat

weight to

RTU

Current

cool

demand

Cool

weight set

Resulting

cool

weight to

RTU

RTU Control Type

Highest Average

of 3

highest

Average

of 5

highest

It can be seen here that the resulting demand used by the RTU controller for the five master voting zones are different and will result in different heating action simply based on the RTU configuration.

Please note that the heating or cooling action delivered to the zones is also dependent on heating and cooling lockout functions based on the outdoor and supply air temperature. Please see the next section for more information.

2B) Overrides and User Zone Interface Lockouts

Each zone controller can have a function locked out for the local user. This can prevent unwanted inputs to the system as a whole when the zone controllers are installed in public areas or when certain local user interface functions of the zone controllers are to be prevented.

Lock level is access through the lockout configuration parameter. Please set the appropriate level for each individual zone in the system according to their requirements.

VZ72xx Controller Lockout Level Configuration Value 0 1 2 3

Local occupied set point access using the Up and Down arrow keys Yes Yes Yes No Pressing the local override key will command the local override function only,

Yes Yes No No However the local heating and cooling demands are not sent to the RTU controller and the central system will not restart.

Typically used only when perimeter reheat is used and re-started during an override period.

Pressing the override key allows an override for this zone controller only. Pressing the local override key will command the local override function and Yes No No No

allow the local heating and cooling demands to be sent to the RTU controller. This will have the effect of re-starting the central system and allowing delivery of hot or cold air based on the current local demand.

Pressing the override key allows an override for this zone controller only. All other zones although being delivered hot or cold air will still be in unoccupied mode and using their unoccupied set points.

Pressing local keys that have their function locked out will display a “keypad lock” message on the zone controller display.

If a global override is required for the whole system and all zones return to occupied mode, then the override needs to be enabled at the RTU controller itself. This can be accomplished by using the local user menu at the RTU controller or configuring the extra digital input as a remote override button if the location of the override button is required to be installed centrally.

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