Emerson E2 - Manual (Page 65)

IMC/Prodigy Rooftop Unit Controllers The RS485 Network and Hardware Setup • 6 - 5
To select a power transformer for a board or a series of
boards:
1. Determine what the total VA is for the boards
that will be powered by the transformer (see
Table 6-3).
Example: Two MultiFlex 168AOs (15 VA
each), and one 8DO (18 VA) boards are to
be powered by one transformer. The total
VA is:
2. Use a transformer that has a power rating
higher than the total calculated VA (see Table
6-2).
Example: For boards totalling 48VA, a 56VA trans-
former is sufficient, since 56VA is greater than 48VA.
I/O Board Transformers should be located within 10
feet of the board it is powering, preferably within the
board enclosure.
6.1.9.1 Wiring Types
For powering I/O boards, use only the listed wire types
from Table 6-4. Three-conductor non-shielded cables are
the recommended wire for connecting between the center
tapped transformer and the I/O boards. The third conduc-
tor should be connected to earth ground. If boards use a
center-tapped transformer, also connect the center tap to
the earth grounded third conductor.
The wire length from the transformer and the number
of boards connected to the same wire determines the type
wire gauge used. In most cases, the distance between the I/
O boards and the transformer that supplies power to them
is not enough to be concerned with. But it is very impor-
tant not exceed this maximum wire length or the boards
will malfunction.
Use these formulas to determine if the wire gauge you
are using fits within specification:
Sensors requiring 24VAC can be powered from the
same transformer powering the input board as long as the
resulting total load of both the input board(s) and the sen-
sor(s) connected to the transformer does not exceed the
transformer’s VA rating. Consult Section 6.1.9, Powering
the I/O Boards, and Section 8.6.1, Powering Echelon
Devices for more information.
6.1.10 Board Installation
The following pages give step-by-step graphical
instructions on all steps necessary to install each I/O Net-
work device so that it is powered up and able to communi-
cate with E2. If these devices have not yet been mounted,
refer to Section 3.2, Mounting I/O Boards for mounting
instructions for these devices.
6.2 IMC/Prodigy Rooftop
Unit Controllers
All E2 Building Controller (BX) versions 2.21F01 and
Unit Amps VA VAC Center-
tapped?
16AI 0.25 5.0 24 Yes
8RO/SMT 0.75 15.0 24 Yes
4AO 0.5 10.0 24 Yes
8DO 1.5 18 24 Yes
8IO/ARTC 0.75 18 24 No
IRLDS N/A N/A 120/240 N/A
RLDS N/A N/A 120/240 N/A
MultiFlex
ESR
3.3 80 24 Yes
MultiFlex
16
0.25 6 24 Yes
MultiFlex
88, 88AO,
168, and
168AO
0.75 15 24 No
MultiFlex
1616L,
1616LAO,
1616LDO
1.0 20 24 No
Table 6-3 - Device Power Requirements
2

15VA

1

18VA
 
+

48VA =
Power Wiring Types
14 AWG Belden 9495
18 AWG Belden 9493
Table 6-4 - Power Wiring Types
14 AWG:
Feet = 1920/VA
18 AWG:
Feet = 739/VA
(VA is the total VA rating of the I/O boards)
For example, if you had an 80 VA load:
14 AWG: 24 ft
18 AWG: 9 ft (rounded down)
Figure 6-3 - Power Wire Lengths