Discharge Air Controller (DAC) Manual
Mounting and Powering • 3
2.2.1. Choosing Transformer Sizes
The transformer used to power the DAC should
have at least a 20VA rating. The DAC should not
share a transformer with any other devices.
2.2.2. The DAC Power Wiring
The DACs can be powered by one of the 50VA
non-center-tapped transformers listed in
shows how to wire the transformers to the
DAC boards.
Neither side of the secondary should be connected
to ground. Also, do not connect the center tap (if
provided on the transformer) to ground. The entire
secondary of the transformer should be isolated from
any ground
.
2.2.3. Wire Types and Maximum
Distances
For powering I/O boards, use only the listed wire
types in
. Two-conductor non-shielded
cables are the recommended wire for connecting the
transformer to the DAC. Shielded cable should not be
used for power wiring. The center tap should be left
disconnected, if present on the transformer.
The wire length from the transformer determines
the type wire gauge used. In most cases, the distance
between the DAC and the transformer that supplies
power to it is not enough to be of concern;
however, it
is very important NOT to exceed this maximum wire
length or the controller will not operate correctly.
Use these formulas to determine if the wire gauge
you are using fits within specification:
Sensors requiring 24VAC should not be powered
from the same transformer powering the input board.
Any devices that will be connected to the DAC’s
inputs or outputs must be powered with a separate
24VAC transformer.
Transformer
P/N
VA Rating Primary Voltage
640-0041
50 VA
110 VAC
640-0042
50 VA
220 VAC
Table 2-2
- Transformers Compatible with DAC
Figure 2-2
- Non-Center-Tapped Transformer Wiring
Power Wiring Types
14 AWG
Belden 9495
18 AWG
Belden 9495
Table 2-3
- Power Wiring Types
14 AWG:
Feet = 1920/VA
18 AWG:
Feet = 739/VA
(VA is the total VA rating of the controller)
For example, if you had an 80 VA load:
14 AWG: 24 ft.
18 AWG: 9 ft. (rounded down)
Table 2-4
- Power Wire Lengths
