Graphic Operator Terminal /
INSTALLATION TIPS
WARNING!
The graphic operator terminal does not have insulation that meets safety
requirements in the event of a potential short circuit between 230 V AC and 24 V DC. It is
assumed that the 24 V feed is secure. For example, SELV according to EN 60950 (protection
against electric shock) and UL 950.
Example:
This example explains why a secure 24 V DC feed can be ruined by mixing 24 V relay
contacts with 230 V AC relay contacts in a smaller controller. Check that the clearances and
creep age distances between 24 V DC and 230 V AC fulfill EN 60950 or UL 950. If not, input a
separate 24 V unit into the graphic operator terminal.
If there is a substantial distance between the relay contacts for 24 V DC and 230 V AC, it is
safe to use the same 24 V devices for all feeds.
Connect 0 V on the 24 V feed to the ground. This offers three advantages:
–
Safety is increased. The 24 V feed will not be live in the event of a faulty connection or
short circuit between 0 V (24 V) and 230 V phase.
–
Transients on the 24 V feed are connected to the ground.
–
No risk that the 24 V feed is at a high level in relationship to the ground. This is not
unusual since there is high static electricity.
6.6 Galvanic
Isolation
The graphic operator terminal has galvanic isolation against the 24 V DC feed but no galvanic
isolation between the communication ports for RS232, RS422/485 and USB. Only the Ethernet
connection isolation has galvanic isolation.
When a PC is connected to the terminal, the terminal’s internal 0 V (GND) is connected to the
protective ground via the PC.
A number of USB devices can have the shield connected together with the protective ground.
Here, the terminal’s 0 V (GND) is connected to the protective ground. For example, a USB
memory stick, keyboard or similar device is plugged in.
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