ZEFNET Pro User Manual
12
CAUTION
: The two phases used must each measure 120V
to Neutral. Earth Ground must be connected to Neutral at
only one point, usually at the service entry breaker panel.
CAUTION
: If a 240V 3-phase feed is from a Delta-connected
secondary, the leg used must have a center-tap. That tap must
be Grounded. Only the two phases on either side of the center-
tapped leg can be used. See
Figure 5.
CAUTION: Warranty is void if this unit is not wired properly.
WARNING:
Only a qualified electrician should perform the
installation. The installation must be performed in accordance
with all local electrical codes and ordinances.
Only 3 wires are connected, but care must be taken that the service
transformer secondary connection is definitely known, and the 3 wires from
the main circuit breaker panel are connected and labeled correctly. Figures
3, 4, and 5 show the most common service transformer secondary wiring
formats.
Notice that L1, L2, & Ground are labeled on each diagram. Those
transformer outputs correspond to the same inputs on the ZEFNET Pro.
Also, each of the two 3-phase diagrams shows an L3 output, which is not
used. Do not connect all three phases of a 3-phase secondary to the
ZEFNET Pro. This is a single-phase device.
The Neutral at the service panel
must
be connected to Earth Ground
somewhere
in the system on
any
of the three connection arrangements.
Ground-fault protection is not possible unless the Neutral (center-tap on the
service transformer) is connected to an Earth Ground. If no Ground is
provided by the electrical service, a grounding stake must be driven into the
Ground nearby, following local electrical codes. The grounding stake must
