Download - Engineered Air

Although a single earth ground connection to the common terminal of
UNT110/111, UNT120/121, and UNT140/141 series controllers is
allowed, you may not intend to have one. The procedures described in the
following directions may be used when no earth ground connections to
the UNT are intended or to ensure that there is only one earth ground
connection.
Isolation and
Grounding UNTs
without an Earth
Ground
Connection
This section will help you ensure proper isolation within your system.
These procedures are not required, but are recommended to reduce
installation errors. To ensure proper isolation, test the following:
•
field device wiring for proper isolation
•
transformer for isolation and correct polarity termination
•
connected field devices, transformer, and UNT for proper isolation
62 UNT Controller—Unitary Controller (UNT)