For detailed information on configuring and wiring
an N2 Bus, refer to the
N2 Communications Bus
Technical Bulletin (LIT-636018)
.
VMA terminals and bus ports
See Figure 1 for input and output terminal and bus
port locations on the VMA18 Series controllers.
Observe the following guidelines when wiring a
VMA18 controller.
Input and Output terminals
The input spade terminals are located on the side
of the VMA near the N2/FC Bus terminal block. The
output spade terminals are located on the opposite
side of the controller near the power supply spade
terminals. See Table 4 for more information.
N2/FC bus terminal block
The N2/FC Bus terminal block is a blue, removable,
4-terminal plug that fits into a board-mounted jack.
Wire the removable N2/FC Bus terminal block plugs
on the VMA and other field controllers in a daisy-
chain configuration using 3-wire twisted, shielded
cable as shown in Figure 4. See Table 5 and Table 6
for more information.
Figure 4: N2/FC bus terminal block wiring
Note:
The Shield terminal (SHLD) on the N2/FC
Bus terminal block is isolated and can be used
to connect the cable shields on the bus (Figure
SA bus spade lugs
Wire the SA Bus spade lugs on the VMA and other
SA Bus devices in a daisy-chain configuration using
4-wire twisted, shielded cable as shown in Figure 5.
See Table 6 for more information.
Figure 5: SA bus spade lug wiring
Note:
Connecting an IOM to the VMA by using
the SA Bus connection is not supported.
Modular port
The modular (TSTAT) port on the face of the VMA
(Figure 1) is an RJ-45, 8-position modular jack used
to connect your new or existing sensor to the VMA
using one of the two included adapters. Refer to
the Sensor Replacement section in the
N2 VMA
Application Note (LIT-12011829)
.
Figure 6: Pin number assignments for the
modular port on VMA18 Controllers
Supply power spade terminals
Wire the 24 VAC supply power wires from the
transformer to the HOT and COM terminals on the
VMA1826/1832 VAV Controller Installation Guide
6
