KMC Controls XEE-6311 - Manual (Page 4)

KMC Controls
AN0604D Revision B
Tips for connecting 24-volt power
Connecting to controllers
1–18
.
– –
–
24 VAC 120 VAC
Grounded secondary connections
KMC recommends that secondaries of transformers powering network devices
be floating!
Some conditions exist, however, that require that the secondary of a
transformer be connected to earth ground. In the United States, for example:
◆ The National Electrical Code® requires (section 250.20) grounding
transformers for AC systems of less than 50 volts if the primary voltage
exceeds 150 volts to ground or if the main transformer supplying power to
the building is ungrounded.
◆ Some municipal electrical codes more restrictive than the NEC may require
that the secondaries of all transformers that supply 24 VAC be grounded.
IF a grounded secondary is mandated, ground the common (–) wire from the
transformer to an equipment grounding screw in the equipment enclosure. If
more than one controller is powered from the transformer, ground both at the
same ground screw.
– – 24 VAC 120 VAC
Illustration 4 Powering two controllers from one transformer
Illustration 5 Grounding the secondary of a transformer (when required)