UNT Controller—Unitary (UNT) Controller
93
+15VDC
24VAC
+15VDC
24VAC
AREF
N2-
N2+
ZBUS
24VAC
24VAC
24VAC
24VAC
24VAC
24VAC
visoxfmr
UNT100 / 101
L1
L2
To
Load
Isolation
Transformer
Isolation
Relay
ZBUS
AREF
N2-
N2+
Power
Transformer
120/24
Contactor
24/24
Figure 42: Transformer and Relay Isolation Wiring Diagram
for Series 100/101 UNT Controllers
All UNT100/101 connections must be isolated from earth ground to
protect the CBLPRO, laptop PC, or other system components from
damage. Due to OEM system designs and/or electrical codes, the
UNT100/101 may become earth grounded unless you take isolation
measures.
!
CAUTION: Potential equipment damage and improper
functioning. Do not earth ground the 24 VAC high
side of the UNT transformer or any of the UNT “BO”
terminals. If you do, the UNT N2 Bus
communications will cycle online and offline. You
will also damage all of the interface components that
are connected, including the CBLPRO, laptop PC,
Companion PC, and MM-CVT101.
Depending on the primary voltage of the power transformer and the
prevailing electrical code, the 24 VAC secondary might be earth grounded.
Earth ground on the 24 VAC side of the secondary destroys hardware by
creating a short circuit path through the CBLPRO and laptop PC serial
card during a download. Earth ground on either side of the secondary can
disrupt the isolation required for N2 communication integrity.
Grounding and
Isolation
UNT100/101
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