spade terminal as shown in Figure 7. See Table 6 for
more information.
Figure 7: 24 VAC Supply Power Spade Terminal
Wiring
Important:
• The supply power terminal block on the
VMA18 is a two-position spade lug (Figure
7). Exercise caution while rewiring the power
plug when replacing an existing controller.
Stray wire strands may make contact and
cause a short circuit across the 24 VAC power
supply.
• To maintain proper phasing when replacing
the existing VMA14xx controller with the
VMA18 controller, connect the power wire
from 24 VAC: 1 terminal on the existing
controller to the HOT power terminal on
the VMA18. Also connect the power wire
from the 24 VAC: 2 terminal on the existing
controller to the COM power terminal on the
VMA18 controller.
The supply power wire colors may be different on
transformers from other manufacturers. Refer to
the transformer manufacturer’s instructions and
the project installation drawings for wiring details.
Important:
Connect 24 VAC supply power to
the VMA and all other network devices so that
transformer phasing is uniform across the
network devices. Powering network devices
with uniform 24 VAC supply power phasing
reduces noise, interference, and ground loop
problems. The VMA does not require an earth
ground connection. However, when grounding
the secondary of the 24 VAC transformer
is required, only one connection to ground
should be made near the transformer.
Figure 8: Transformer Grounding
CAUTION
Risk of Personal Injury and Property Damage
Improper wiring of this terminal may cause a short cir-
cuit across the 24 VAC power supply on -1 models.
ATTENTION
Risque de blessure et dégâts matériels
Improper wiring of this terminal may cause a short cir-
cuit across the 24 VAC power supply on -1 models.
To wire the VMA18 Series controller, complete the
following steps:
1. Terminate wiring per engineering drawings.
2. Wire network sensors and other devices to the
VMA's SA Bus.
3. Wire the N2/FC Bus in a daisy chain (see Table
4. Ensure that the VMA’s device address DIP
switches are set to the appropriate device
.)
5. Connect the VMA controller to 24 VAC, Class 2
power.
Refer to the
N2 VMA Application Note (LIT-12011829)
for more information about replacing an existing
controller with an VMA18 controller.
VMA1826/1832 VAV Controller Installation Guide
7
