Emerson MultiFlex Series User Manual

Powering the MultiFlex Mounting and Powering • 7
2.3.1. Choosing Transformer Sizes
In most site installations, a single trans-
former will power multiple devices. Choose a
transformer with a VA rating large enough to
power all devices that will be attached to it.
Table 2-2 gives the VA ratings of the MultiFlex
board products. Refer to your site controller’s
manual for VA ratings of the other I/O boards
that may be powered by one of these transform-
ers.
2.3.2. MultiFlex 16 Power Wiring
The MultiFlex 16 requires connection to a
transformer with a center tap such as the 56VA
(640-0056) and 80VA (640-0080) transformers
listed in Table 2-1. The 56VA and 80VA trans-
formers have quick-connects on the primary and
secondary sides for connection to line voltage
and the MultiFlex 16 board. Figure 2-4 shows
how to make those connections. Note the center
tap connection on the secondary side (CT) must
be wired to the 0V terminal on the MultiFlex 16.
2.3.3. MultiFlex Combination Input/
Output Board Power Wiring
The MultiFlex 88, 88AO, 168, 168AO, and
168DO boards do not use a center tap. Instead,
the 0V terminal on the board should be con-
nected to a separate Earth ground.
Important! The rules that must be fol-
lowed when connecting a MultiFlex Combi-
nation I/O board to a transformer are
different depending on whether you have a
"new style" MultiFlex board with an isolated
power supply (all MultiFlex boards shipped
after November 1, 2002) or an "old style"
MultiFlex board (all MultiFlex boards
shipped before November 1, 2002).
A new-style MultiFlex Combination I/O
board has a green power LED located next to the
24VAC connection terminal in the upper right
corner of the circuit board (see Figure 2-5 for
reference).
Unit VA VAC Center
tapped?
MultiFlex 16 624Yes
MultiFlex 88,
88AO, 168,
168AO and
168DO
15 24 NO
Table 2-2 - Device Power Requirements
Figure 2-4 - 640-0056 and 640-0080 Transformer Wiring
Figure 2-5 - New-Style vs. Old-Style MultiFlex Board
POWER LED
New Style
MultiFlex Board
(Top Left Corner)
NO POWER LED
Old Style
MultiFlex Board
(Top Left Corner)
24 VAC
24 VAC

Emerson MultiFlex Series Specifications

General

Brand	Emerson
Model	MultiFlex Series
Category	I/O Systems
Language	English