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Chapter Overview
This chapter describes the wireless
zone sensor system including system
layout, component functionality, and
specifications.
30
Wireless VAV
Systems
CHAPTER 7: WIRELESS VAV SYSTEMS
General Information
Spread Spectrum
Trane Wireless VAV Systems apply
spread spectrum technology to
accomplish wireless communication.
Spread spectrum technology is a
technique for spreading a data signal's
information over a frequency range that
is substantially larger than is required,
thus increasing the redundancy of the
communication. Upon reception, the
receiver "unspreads" the signal and
reads the information. Any receiver that
does not have a matching encoding
sequence can not unspread the signal
and sees the transmission as RF noise.
This spreading and unspreading
enhances the security of the system
and its ability to operate in the same
environment as other systems using
the same frequencies.
The sensor/transmitter simultaneously
broadcasts identical information over
two separate frequencies (911 and 918
MHz), making interference even less
likely.
Purpose of the Wireless System
The wireless system is a method for
eliminating the problems associated
with a wired sensor such as having to
run wire through solid or decorative
walls or having to move the sensor
after the occupant has redecorated the
space. The benefits are the flexibility in
system design and sensor location.
Zone sensor operation with wireless
offers some new capabilities. The first
feature is averaging. If more than one
sensor is assigned as an averaging
sensor to a UCM their temperature
readings are averaged. This gives the
ability to get a more accurate sample of
Figure 6. Wireless Zone Sensor and Receiver
a large space supplied by one VAV box.
It also provides better control when 1
VAV box serves multiple zones such as
small offices. Under the averaging
scheme, the local set point requests are
also averaged. The set point average
can be weighted by changing the set
point Vote value from 0 to 9. The
number assigned represents the
number of votes the sensor gets. A
Value of "0" removes this sensor from
the set point voting scheme.
For example:
Set Point
Set Point
Sensor
Value
Vote
T1
75
x
3
T2
65
x
1
Total
4
Calculation: 290/4 = 72.5°F Final Set Point Value
This allows someone who is more
affected by the temperature or in an
area that has a varying load such as
cold or hot outside walls to have more
impact on the set point.
An additional capability of the system is
the ability to use a sensor as a backup
to another sensor. If the primary sensor
stops communicating for some reason
the UCM automatically begins using
the backup sensor input.
Another added feature is the ability to
assign one sensor to multiple boxes.
This is a function of the way the sensor
transmits its information.
When the sensor broadcasts its
temperature it also sends the serial
number, the set point and the battery
Extended
Value
=
225
=
65
290
VAV-SVX01B-EN
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