3. Set a unique and sequential device address for each
of the field controllers connected on the N2 bus,
starting with device address 1.
To ensure the best bus performance (if the protocol
is changed to BACnet MS/TP), set sequential device
addresses with no gaps in the device address range
(4, 5, 6, 7, 8, 9, and so on). The field controllers do
not need to be physically connected on the bus in
their numerical device address order.
4. Write each field controller’s device address on the
white label below the DIP switch block on the
controller’s cover.
Refer to the
N2 Communications Bus Technical Bulletin
(LIT-636018)
for more information on field controller
device addresses and how to set them on N2 buses.
Setting the EOL Switch
Each field controller has an EOL (End of Line) switch,
which, when set to ON (up), sets the field controller as a
terminating device on the bus. See
Figure 3
for the
end-of-line (EOL) switch location on the field controller.
The default EOL switch position is OFF (down).
Figure 15: EOL Switch Positions
To set the EOL switch on a field controller:
1. Determine the physical location of the field controller
on the N2 or FC Bus.
2. Determine if the field controller must be set as a
terminating device on the bus.
Note:
Refer to the
N2 Communications Bus
Technical Bulletin (LIT-636018)
for the N2 bus
EOL termination rules. Refer to the
MS/TP Communications Bus Technical
Bulletin (LIT-12011034
) for the FC bus EOL
termination rules.
3. If the field controller is a terminating device on the N2
or FC Bus, set the EOL switch to ON. If the field
controller is not a terminating device on the bus, set
the EOL switch to OFF.
Note:
When the EOL switch is set to ON, the LED
light on the face of the controller is illuminated.
Commissioning
Use the following procedure to commission the VMA18
controller:
1. Download the control application to the VMA controller
using the Controller Configuration Tool (CCT) .Refer
to the Controller Tool
Help (LIT-12011147)
for details.
2. Commission the VAV Box. Refer to the
Controller
Tool Help (LIT-12011147)
for details.
3. Perform airflow balancing on the VAV box. Refer to
the
VAV Balancing Tool Technical Bulletin
(LIT-12011087)
for details.
4. Perform commissioning checkout procedures. Refer
to the
Controller Tool Help (LIT-12011147)
for details.
CCT connects to the VMA using any one of the following
connection options: the MAP Gateway, BTCVT, the
Wireless ZigBee USB Dongle, or the wired BACnet
®
Ethernet to MS/TP Router. These connection options
require additional hardware listed in
Table 9
.
For more detailed N2 VMA controller commissioning
information, refer to the
N2 VMA Application Note
(LIT-12011829).
Note:
The MAP Gateway serves as a replacement for
the BTCVT, which is no longer available for
purchase, but continues to be supported.
Repair Information
If the VMA18 Series controller fails to operate within its
specifications, replace the unit. For a replacement unit,
contact the nearest Johnson Controls representative.
Troubleshooting
Table 8
provides LED status indicator information for
troubleshooting the VMA18 controller.
Note:
If you experience short circuits in the 24 VAC
power supply causing protective devices such as
breakers or fuses to trip, make sure that the power
connections on the VMA are not reversed. The
most common cause of this problem is when the
24 VAC power supply on the VMA is reversed but
not reversed on a connected secondary device.
Improper wiring of this power terminal may cause
a short circuit across the 24 VAC power supply
on -1 models.
22
VMA1826/1832 VAV Controller Installation Instructions
