Johnson Controls VMA1200 Series Technical Bulletin

Brand: Johnson Controls

Model: VMA1200 Series

Type: Technical Bulletin

This manual is also suitable for

ORKS

Systems Manual 1162

VMA1200 Section

Issue Date 0501

Code No. LIT-1162350

ECHNICAL

ULLETIN

Variable Air Volume Modular Assembly (VMA) 1200 Series

Overview and Engineering Guidelines

VMA1200 Series Overview and Engineering Guide......................... *3

Introduction........................................................................................................*3

Key Concepts.....................................................................................................*4

VMA1200 Series Models...............................................................................................*4

Definition of Terms........................................................................................................*6

Theory of Operation.......................................................................................................*9

Establish Zones.............................................................................................................12

Room Sensor Placement...............................................................................................12

Pressure Independent VMA...........................................................................................13

VMA Airflow Rate........................................................................................................ *13

Power Source..............................................................................................................*14

ORKS

Network Topology..................................................................................... *17

Inputs and Outputs......................................................................................................*19

CablePRO................................................................................................................... *21

CVTPRO..................................................................................................................... *21

Software Tools ............................................................................................................ *21

Related Documentation............................................................................................... *22

Procedure Overview......................................................................................... 23

Detailed Procedures........................................................................................*24

Determining VAV Box Requirements...........................................................................*24

Establishing the Room Schedule...................................................................................25

Developing Bills of Material and Placing Orders............................................................26

Configuring the VMA .....................................................................................................27

*Indicates those sections where changes have occurred since the last printing.

VMA1200

Appendix A: Reference Information ............................................... *28

Introduction....................................................................................................... 28

VMA Wiring List........................................................................................................... *29

VMA Wiring Interface Diagram.................................................................................... *31

VMA Parts List............................................................................................................. *32

FCC Part 15 Label.........................................................................................................33

VMA Specifications .....................................................................................................*34

Fabricating Your Own Interconnection Cable............................................................... *38

Sensor Interface.......................................................................................................... *39

Appendix B: Application Example.................................................. *42

Single Duct Application Example................................................................................. *42

*Indicates those sections where changes have occurred since the last printing.

VMA1200

Series Overview and Engineering Guidelines

VMA1200 Series Overview and

Engineering Guide

Introduction

The Variable Air Volume Modular Assembly (VMA) 1200 Series is a

configurable, integrated module that includes a Variable Air Volume

(VAV) controller, actuator, and differential pressure sensor. The VMA

is offered as two models: cooling only and cooling with reheat. The

models, which use the LonTalk protocol, are designed for pressure

independent, single duct systems. The reheat model can be used with

parallel or series fan powered boxes.

This manual is a reference tool for engineering VMA1200 installations

and applications. It is also a training tool to learn about the

VMA1200 Series controllers. It is task oriented for easy reference to

specific tasks. Refer to the appendixes at the end of this document for

wiring tables and diagrams, a parts list, specifications, and an

application example.

This document describes how to:

• determine VAV box requirements

• establish the room schedule

• develop bills of material and place orders

• configure the VMA

VMA1200

Key Concepts

VMA1200 Series Models

Table 1 lists VMA1200 Series features. Table 2 shows available

VMA1200 models.

Table 1: Feature Checklist

VMA Features Comments

Applications

Pattern Recognition Adaptive Control (PRAC)

on Zone Proportional Plus Integral (PI)

Temperature Loops

Eliminates manual tuning and seasonal retuning.

Adaptive Flow Control Loops No manual tuning, improved control and energy savings

Single Duct, Pressure Independent VAV Meets most VAV applications.

Side Loops without Interlocking Single Analog Input (AI) to Analog Output (AO)/Binary

Output (BO)

Fan Powered Boxes Series or parallel

Incremental, Proportional, and Three Stages

of Box Heat

Up to three stages or normally open/closed valves

Incremental, Proportional Two Position, or

One Stage Supplemental Heat

Normally open or closed valves

Damper Actuator

Clockwise (CW)/Counterclockwise (CCW)

Rotation Selection

Set via M-Pro software, VMA1200 Balancing Tool (VBT)

software, or network management tool for either direction

to close.

Software/Tools

Ability to Download Code Firmware Firmware code is upgradeable without removing the VMA.

Diagnostics

Moving Average Flow/Temperature

Diagnostic

Provides standard measure of control loop performance

over time.

Actuator Duty Cycle Diagnostic Indicates shaft slippage.

Commissioning

Balancing Tool with Automatic K-factor

Calculation

Palm compatible handheld device (Version 2.0 or later

operating system) on Zone Bus

Hardware

24 VAC Isolation Eliminates 24 to 24 VAC transformer and polarity concerns.

Multiple VMAs Powered by a 100 VA

Transformer

Up to 14 cooling only. Number of reheat/fan units depends

on power consumption of valve/fan relays.

Isolated Communication, Binary Outputs, and

24 VAC

Saves installed cost and improved electrical noise

rejection.

Ability to Drive Low Current Relays Down to

25 mA

Eliminates relay chatter.

13-Bit Analog Input/8-Bit Analog Output

Resolution

High accuracy and good device control

Analog Input Jumpers Eliminated All analog inputs are preset reducing labor.

Continued on next page . . .

VMA1200

Series Overview and Engineering Guidelines

VMA Features (Cont.) Comments

Differential Pressure Transducer

Dead Ended Transducer No filters or maintenance required.

Capacitive Technology Improved stability

Industry Accepted Flow Measurement

Accuracy

Even for flows below 250 fpm (1.25 m/s) typical

Temperature Sensors

Variety of Sensors Nickel, 1K platinum, 2.25K NTC

Temporary Occupied Button On TMZ1600, TE-6700, TE-7000 (Europe only) Series

room sensors

Temporary Occupied Light-Emitting Diode

(LED)

On TMZ1600, TE-6700, TE-7000 (Europe only) Series

room sensors for Occupied and Unoccupied modes

LED Indicator for Operation

Power/Communication

Verifies operation and power connections.

Physical

Small, One Piece Assembly

102 x 153 x 102 mm (4 x 6 x 4 in.)

Prewired to reduce installed cost.

Plenum Plastic Housing Rating UL 94-5VB plenum flammability may eliminate metal box

(check local codes).

Removable Input/Output (I/O) Screw

Terminals

Two or three position accessory kits

Node Installation

Service Pin Message Local pushbutton and remote access from Palm compatible

handheld device

Wink Function

Initiate via Palm compatible handheld device or network

management tool.

Bar Code Label

Two removable bar code labels printed with Neuron ID

VMA1200

Table 2: VMA1200 Series Models

Inputs/Outputs Points Rating VMA1210

(Cooling

Only)

VMA1220

(Cooling

w/Reheat)

Analog Inputs:

Zone Temperature

Zone Setpoint

Humidity, Dewpoint, or Sideloop

Supply Air Temperature or

Supplemental Heat Temperature

Velocity Pressure

AI-1

AI-2

AI-3

AI-4

Internal

1K Ni or Pt or 2.25K NTC

1.6K ohm Potentiometer (Pot.)

0-10 VDC

1K Ni or Pt or 2.25K NTC

0-1.75 inch W.C. (0-436 pa)

✔

Binary Inputs:

Temporary Occupied/

Standby/Room Sensor LED

Occupied

Off or Window or Shutdown

BI-1

BI-2

BI-3

Dry contact

✔

Analog Outputs:

Proportional Heat AO-1 0-10 VDC @ 10 mA

✔

Binary Outputs:

Fan

Box Heat--Incremental Valve or

1-3-stage Electric

Supplemental Heat--Incremental

Valve or 1-3-stage Electric

BO-1 to

BO-5

24 VAC triac @ 0.5A

✔

Actuator Motor

Internal

✔✔

Definition of Terms

Auto Calibration

The VMA has an Auto Calibration mode that runs periodically to

adjust the pressure sensor calibration due to offset tolerance and

mounting position.

Binding

A process performed by a network management tool that connects

Network Variable Outputs (NVOs) and Network Variable Inputs

(NVIs). These connections provide for peer-to-peer data transfers.

Commissioning

Verification of controller inputs and outputs and modification of the

controller configuration properties to meet installation specifications.

Configuration Properties

Data stored in non-volatile memory (Flash) in the controller that is

accessible from a network management tool.

VMA1200

Series Overview and Engineering Guidelines

Configuring

Building an application within the controller to establish the required

control sequence, setting the functionality of the controller.

Downloading

Writing the Heating, Ventilating, and Air Conditioning (HVAC)

application data and configuration properties to the controller. This is

accomplished using a software tool with a Personal Computer (PC).

ORKS







Network Services (LNS







) Protocol

Network management system protocol for L

ORKS

devices.

LONWORKS FTT-10A Transceiver

The Free Topology Transceiver (FTT) interface between the

VMA1200 and the physical network.

M-Pro

A software tool used to configure and download controllers.

M-Pro software is part of the System Tools in M-Tool.

Neuron

The microprocessor used in the VMA. Each neuron has a unique

48-bit ID for node identification.

NVI/NVO

ARK

 term for Network Variable Inputs/Outputs. These

variables may be read/written by network management tools. They

may be bound to other network variables in a system.

Palm Compatible Handheld Device

A handheld computer that uses software to configure and balance the

VMA1200. The PalmPilot unit is an example of this device.

SCPT/UCPT

ARK

terms for Standard Configuration Property Type and User

Configuration Property Type.

SNVT/UNVT

ARK

term for

Standard/User Network Variable Types.

A SNVT/UNVT defines the units, structure, and resolution of the

configuration properties, NVIs and NVOs.

VMA1200

Test and Balance (TAB)

Test and Balance (TAB) is a function performed to ensure the installed

system operates to design specifications. Balancing of the VMA zone

indicates whether the VAV terminal box achieves minimum/maximum

airflow settings. TAB must also be performed for the air handler and

the air duct distribution to the VAV box.

Variable Air Volume (VAV) Controller

An Application Specific Controller (ASC) used for digital control of

single duct, dual duct, fan powered, and supply/exhaust VAV box

applications.

Variable Air Volume Modular Assembly (VMA)

Includes a digital controller with integrated pressure transducer and

actuator.

Zone Bus

A local interface between the controller and the room sensor. By

connecting a Palm compatible handheld device with the proper

software to the CablePRO or CVTPROx00-0 and room sensor, the

Zone Bus allows you to monitor and commission directly through the

room sensor.

VMA1200

Series Overview and Engineering Guidelines

Theory of Operation

VAV systems are most easily understood by considering them as

cooling applications. As the zone temperature increases due to heat

produced by people, computers, or other heat sources, the VMA opens

the VAV box damper and lets cooler air in. The size of the space and

the internal and external heat loads dictate the volume of air required

to maintain a zone temperature setpoint. In addition, since the size of

the VAV box dictates its maximum cooling capacity, VAV box

performance is dependent upon the design engineer sizing the box for

each zone. If the installed unit is too small, insufficient cooling results,

and excessive flow rates cause audible noise. If the installed unit is too

large, proper control is difficult to maintain, since a small change in

damper position causes excessive airflow change. Boxes are

sometimes oversized to ensure quiet operation or to reserve cooling

capacity as zone usage changes.

A cooling only VAV system maintains a constant zone temperature

while varying the flow of air to the space. This is unlike a constant

volume system that maintains a constant volume of airflow to the

space but varies the temperature of the air stream in response to space

temperature changes. VAV systems are predominantly single duct, but

some are dual duct designs. The VMA can be configured for most

single duct pressure independent VAV applications. The M-Pro

software (part of M-Tool Release 2.0) is used to configure and

download VMA1200 applications.

The actuator drives the damper from full open to full closed in

90 seconds. The VMA incorporates flow feedback to accurately

position the damper and to minimize position hunting and motor

runtime. Control performance metrics are recorded and are available

via network variables to the Metasys Operator Workstation (OWS).

Figure 1 shows the VMA1200 in the Metasys Network. Figure 2 is a

functional block diagram of the VMA1200.

VMA1200

Operator Workstation

(with OWS, M-Pro,

and LNS Software)

Network Control Module (NCM)

N1 LAN

Room

Sensor

VMA1200

Zone

Bus

FTT-10

Palm Compatible

Handheld Device

MNET

Network

Bus

ON ORKS

CablePRO

Converter

Compatible

Devices

ON ORKS

Room

Sensor

Zone

Bus

Palm Compatible

Handheld Device

CVTPRO

Converter

VMA1200

Figure 1: VMA1200 Controllers in Metasys Network Diagram

VMA1200

Series Overview and Engineering Guidelines

Neuron

Application

Processor

FTT-10

Interface

COP8

IO Processor

Fblock2

Digital

Inputs

Analog

Inputs

Phone

Jack

Zone

Bus

Analog

Output

Triac

Outputs

Window Open

Occupancy Sensor

Temp Occ Button

Low

Space Temperature

Space Setpoint

Auxiliary Temperature

Auxiliary 0-10V

TE-6700, TMZ1600, or

Palm Compatible

Handheld Device

Heating Valve

Five 24 VAC Outputs for

Fan, Staged Heating, etc.

L W Network

ON ORKS

Isolated

CW CCW

Differential

Pressure

(DP) Sensor

Actuator

Motor

Figure 2: VMA1200 Functional Block Diagram

VMA1200

Establish Zones

When designing VMA systems, establishing zones correctly is critical

to take maximum advantage of the VMA’s exceptional accuracy and

rapid response capabilities.

The designer strives for the most uniform indoor environmental

conditions possible. A single thermostatic device (room sensor)

controls each area. A zone could also be thought of as an area where

the load is considered the same for every square foot of floor space.

HVAC system zones fall into two major categories: exterior zones and

interior zones. Exterior zones are spaces directly affected by outdoor

weather conditions. Heat losses or outdoor air conditions do not

influence interior zones. Interior zones usually have cooling or

ventilation requirements only.

Further divisions of interior/exterior zones may be required to

accommodate different occupancy schedules and/or solar loads.

Variations in internal loading dictate the selection of separate zones.

For example, in a restaurant, the kitchen has vastly different heating

and cooling requirements from the seating area.

Room Sensor Placement

Consider room sensor placement for each zone, making sure to:

• Verify that the room sensor is the correct one for the application.

• Review architectural requirements such as furniture height and

location, aesthetics, and type of mounting. Wall plates are required

if mounting on a conduit handibox.

• Review room sensor location. The best room sensor location is on

an interior wall, about five feet above the floor, out of direct

sunlight, out of the direct path of supply air from the diffuser, away

from heat sources, such as equipment, machines, and perimeter

radiation, and away from doors and other draft sources. Mounting

height may be affected by local codes or the accessibility needs of

persons with disabilities.

• Do not locate a sensor near zone boundaries where primary

influence is from an adjacent zone.

VMA1200

Series Overview and Engineering Guidelines

Pressure Independent VMA

The pressure independent VMA employs patented self-tuning,

cascaded proportional/integral control loops. The zone temperature

loop samples space temperature and resets the airflow setpoint

between the minimum and maximum flow settings. Since inlet duct

static pressure influences the amount of air passing through the

VAV box, the VMA airflow loop samples airflow via a flow pickup in

the box inlet. It modulates the damper to control the flow. Thus, the

VAV box flow is independent of duct static pressure.

The engineering basis for this method of control is that the temperature

of a space with a constant load is linearly proportional to the flow of

conditioned air into the space. The engineer must accurately determine

the required maximum and minimum flow for each space based on

heating, cooling, and ventilation loads.

VMA Airflow Rate

The VMA determines airflow rate by dynamic pressure measurement.

The VMA contains a Differential Pressure Transmitter (DPT) to sense

differential pressure in pressure independent VAV applications.

The DPT is connected to the VAV box airflow pickups. It measures

differential pressure and generates a proportional voltage signal. The

voltage signal from the DPT is read by the VMA and converted to

airflow in cubic feet per minute (cfm) or liters per second.

The DPT provides maintenance-free performance within the control

range of 1.25 to 18 m/s (250 to 3500 feet per minute [fpm]) when used

as recommended.

The minimum 1.25 m/s (250 fpm) velocity and the gain of the airflow

pickup produce an accurately measured pressure difference.

The VMA Auto Calibration function helps reduce the temperature

effect error by zeroing offset errors. As the ambient temperature

swings relative to the temperature at which the Auto Calibration

occurred, an offset error may occur (typically ±0.179 Pa/°C

[±0.0004 inch

W.C./°F]). When calibration occurs, this error becomes

zero.

The error envelope becomes smaller with increased airflow pickup

gain and with smaller ambient temperature deviations at the

transmitter location.

VMA1200

Power Source

You can use one 24 VAC power trunk to power multiple VMAs. In

this case, transformers of up to 100 VA are centrally located, and the

secondary run is without conduit and without concern about polarity.

Notes: The 24V power transformer must be UL/CSA listed as

NEC Class 2 Power Limited.

See NEC Article 725/Class 2 (30 VRMS maximum) and

(100 VA maximum).

The VMA1210 draws 7 VA including the internal damper actuator.

Therefore, 14 VMAs can be powered from one 100 VA transformer

without conduit. The number of VMA1220s is dependent on the

binary output loads and reheat actuators. The reheat actuators must be

added to the 7 VA of the controller, then divided into the 100 VA

transformer power. For example, the VMA1220 draws 7 VA without

loads. If there were only a single VA-8020 reheat valve per VMA, its

4 VA must be added to the VMA for a total of 11 VA. Then

nine VMA/VA8020s can be powered from one 100 VA transformer.

Table 3 shows the power rating for several cooling/heating coil valve

actuators. The valve power plus the VMA power must not exceed

100 VA. If a device is not listed in the following table, refer to the

product literature for that device.

Table 3: Actuator VA Power Rating

Actuator Type Power Rating

VA-8020

Incremental 4 VA

VA-8050

Incremental 6 VA

VA-7200

Incremental 6.7 VA

J Series Electric Zone Valve

On Off 7 VA

VA-8022

Voltage (0 to 10 VDC) 4 VA

VA-8052

Voltage (0 to 10 VDC) 6 VA

VA-7202

Voltage (0 to 10 VDC) 6.7 VA

VA-7450

Incremental 2.5 VA

VA-7452

Voltage (0 to 10 VDC) 2.5 VA

VA-7050

Thermal (DAO) 3 VA

VA-7310

Incremental 2 VA

VA-7312

Voltage (0 to 10 VDC) 2 VA

VA-7010

On/Off 7 VA

VA-7150

Incremental 2.7 VA

VA-7152

Voltage (0 to 10 VDC) 4.7 VA

VMA1200

Series Overview and Engineering Guidelines

When using a single transformer and running 24 VAC to multiple

VMAs, use a wire gauge large enough for the load. The voltage drop

on the 24 VAC cabling is much higher than for line voltage wiring for

the same power draw. For a 100 VA (equivalent to 100 watt) load at

120 VAC, only 0.8 ampere is required. However, at 24 VAC, over

four amperes are needed. Current draw determines the wire size.

Two connection methods are available. In the first method, individual

spade lugs accept a single 10 to 22 American Wire Gauge

(AWG)/4 mm

to 0.8 mm wire and still fit on 6 mm (1/4 inch) tabs. In

the second method, optional screw terminals are assembled over the

spade lugs. The screw terminals accept up to a single 12 AWG

(4 mm

) wire or two 14 AWG (2.5 mm

) wires. When two wires are

crimped into one spade lug, a larger spade lug barrel is needed.

Alternately, a wire nut can connect two heavy wires to a short 152 mm

(6 inch) thinner wire.

24 VAC

100 VA

< 88 ft of 14 AWG >

Example 1:

All VMAs are at one end.

VMA

24 VAC

< 176 ft of 14 AWG >

Example 2:

Transformer is centered.

VMA

100 VA

< 176 ft of 14 AWG >

Cablelength

Figure 3: Power Cable Lengths

A standard 14 AWG (2.5 mm

) wire (top example in Figure 3) is

limited to 27m (88 feet) with 14 cooling only VMAs when the VMAs

are all located at one end of the cable. If the transformer is centered

(bottom example in above figure) with seven VMAs on the left and

seven VMAs on the right, the distance in each direction can be

increased. This is because the current (and voltage drop) are halved in

each direction. In this example, both the left and the right legs can be

increased to 54m (176 feet) from the transformer, creating a 108m

(352 foot) total length.

VMA1200

Table 4 and Table 5 indicate the relationship between wire length and

power at the end of wires.

Table 4: Maximum Wire Length for Given Power/Gauge (U.S. Measurements)

Wire Size

8 Gauge 10 Gauge 12 Gauge 14 Gauge 16 Gauge 18 Gauge

Power (VA) at

End of Wire

Wire Length (Feet)

3520 2200 1400 880 550 350

1760 1110 700 440 275 175

1173 740 467 293 183 117

880 555 350 220 138 88

704 444 280 176 110 70

587 370 233 147 92 58

503 317 200 126 79 50

440 278 175 110 69 44

391 247 156 98 61 39

100

352 222 140 88 55 35

Table 5: Maximum Wire Length for Given Power/

Wire Gauge (Metric Measurements)

Wire Size

4 mm

2.5 mm

1.5 mm

Power (VA) at

End of Wire

Wire Length (Meters)

427

268

168

213

134

142

107

100

VMA1200

Series Overview and Engineering Guidelines

ORKS

Network Topology

The L

ORKS

FTT-10A used by the VMA1200 supports free

network topologies. Table 6 describes free topologies, and Figures 4

and 5 show supported topologies. For more information, see the

ORKS

Network Layout Technical Bulletin (LIT-1162150).

Table 6: Free Topologies

Category Free Topology

Architecture

Bus, star, ring, or mixed

Termination

Single termination for star, ring, or mixed

Double termination for bus

Connection

Connected by stub/multi-drop

Free Topology (Tree or Star)

L W Compatible Device

(Including NCM350/361)

ON ORKS

Legend:

Free_Top

Free Topology Terminator

Figure 4: Free Topology

VMA1200

L W Compatible Device

(Including NCM350/361)

ON ORKS

Bus End-of-Line (EOL) Terminator

Daisy-chained TopologyBus

Stub-wired TopologyBus

Legend:

Bus_Top

Figure 5: Bus Topology

Table 7 contains a specification example for the FTT-10A Transceiver.

This is just one example of the many available wiring styles. For more

complete information, refer to Echelon Corporation

ORKS

FTT-10A Transceiver User’s Guide.

Table 7: FTT-10A Transceiver Specification Example

Transceiver

FTT-10/FTT-10A

Topology

Free

Bit Rate

78 kbps

Maximum Node to Node Distance

500m (1640 ft)*

Maximum Total Wire Length

500m (1640 ft)*

Maximum Nodes

Node Application Current

* Belden 85102, 8471 Cable

VMA1200

Series Overview and Engineering Guidelines

Inputs and Outputs

For specific input/output range, wire length, wire size issues, refer to

the VMA Wiring List in Appendix A: Reference Information at the back

of this document.

Note: All terminals are spade lug type except the L

ORKS

Network Bus terminals, which are removable screw terminals.

Optional two or three position kits can be ordered to convert

the spade lugs to removable screw terminals. See Table 12.

Binary Inputs

There are three dry contact binary inputs on the VMA1200. A manual

override button on the room sensor initiates a Temporary Occupancy

mode of operation. The TE-6700 room sensor includes an LED in

series with the button to show the occupancy mode. The switch can be

pushed for as little as 0.2 seconds to detect a change.

The binary inputs on the VMA are inactive when open. They are

active when a contact closure to binary input common (COM) is

applied.

Binary Outputs

The VMA has zero (VMA1210) or five (VMA1220) user accessible

binary outputs. The damper actuator is wired internal to the VMA.

Each load is connected between the BO terminal and BCOM common

terminal. When required to meet codes, the 24 VAC terminal of the

VMA/transformer can be earth grounded. In this situation, the binary

outputs switch the transformer’s low side to the relays and actuators.

Analog Outputs

There is one analog output on the VMA1220. The VMA1210 has no

analog outputs. The load is connected between the analog output and

analog output common (COM) terminals. The output is controlled to

generate a proportional voltage output of 0 to 10 VDC. The maximum

load for each output is 10 mA with a minimum load resistance of

1000 ohms.

VMA1200

Analog Inputs

There are two external and one internal analog inputs on the

VMA1210 and four external and one internal analog inputs on the

VMA1220. They are preset for either temperature, setpoint, or voltage.

There are no jumpers to set. Shielding is not required, but if used, earth

ground the shield only at the VMA. You may use 24 AWG (0.6 mm)

twisted pair wire; however, this reduces the allowable wire length due

to the resistance. To minimize sensor error caused by field wiring, the

total resistance of the nickel or platinum resistive sensor wiring should

be less than 3 ohms. The NTC sensor accepts a larger wire resistance.

This wiring error effect is corrected through configuration properties

using a commissioning tool.

Do not share the temperature or setpoint common wire with voltage or

current transmitters on the Zone Bus. The maximum voltage drop on

the common wire must be less than 1 mV.

Zone Bus

The Zone Bus is a 2-wire local communications bus that allows a

Palm compatible handheld device with Johnson Controls VMA1200

Balancing Tool (VBT) software to commission and balance the VMA.

The Zone Bus connector also provides 15 VDC power to the

CablePRO or CVTPRO. The bus sustains no damage in the presence

of fault voltages of 15 VDC or 24 VAC.

Table 8: Zone Bus Specifications

Type

Multi-drop serial communications bus

Speed

1200 baud (bits per second)

Recommended Cable Type

1.5 mm

(18 AWG) with or without shield

(Belden 8760) or

0.6 mm (24 AWG) without shield (unshielded

telephone cable)

Maximum Bus Length

150 meters (500 feet) with 1.5 mm

(18 AWG)

cable or

15 meters (50 feet) with 0.6 mm (24 AWG)

cable

Voltages

Logic High Voltage

Logic Low Voltage

4 VDC minimum (approximately)

1 VDC maximum (approximately)

Data Transmission

1 Start Bit (low level)

8 Data Bits (least significant bit first)

1 Stop Bit (high level)

Isolation

Isolated from 24 VAC, Binary Outputs (BO),

and L

ORKS

Network Bus

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