NOTE
Please ensure that the temperature will not exceed the maximum ambient operating
temperature in the enclosure. This can be influenced by other heat generating
devices.
7.5. Safety
4
1
2
4
3
4
Power supply
230 V AC to 24 V DC
Power supply
230 V AC to 24 V DC
Power supply
230 V AC to 24 V DC
Operator panel
Operator panel
Operator panel
Distance?
Small controller with expansion unit
+24 V
+24 V
+24 V
0 V
0 V
0 V
230 V AC
COM1
COM100
Ch0
Ch1
Ch100
Ch101
5355
If a power supply that meets safety standards is used and only powers the HMI panel, there is no
problem. See 1 in drawing above.
However, if a 24 V unit that also powers other units is used, there is reason to be cautious, see 2 in
drawing above. The HMI panel 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 power supply is
secure, for example, SELV according to EN 60950 (protection against electric shock) and UL 950.
NOTE
Here is an example that explains why a secure 24 V DC power supply can be ruined
by mixing 24 V relay contacts with 230 V AC relay contacts in a smaller controller.
Check that the clearances and creepage 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 HMI panel.
If there is a substantial distance between the relay contacts for 24 V DC and 230 V AC, it is OK to use
the same 24 V devices for all feeds. See 3 in drawing above.
Connect 0 V on the 24 V power supply to the ground, see 4 in drawing above. This offers three
advantages:
• Safety is increased. The 24 V power supply is not 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.
Additional Installation Tips
2023-09 26 Beijer Electronics, MAEN330
To Next Page
Loading...
Need help?
General
