Danfoss VLT HVAC Drive FC 100 Series Design Manual page 102

5. How to Install
5.2.25. Electrical Installation, Control Cables
5
Illustration 5.36: Diagram showing all electrical terminals. (Terminal 37 present for units with Safe Stop Function only.)
Very long control cables and analog signals may in rare cases and depending on installation result in 50/60 Hz earth loops due to noise from mains supply
cables.
If this occurs, you may have to break the screen or insert a 100 nF capacitor between screen and chassis.
The digital and analog in- and outputs must be connected separately to the frequency converter common inputs (terminal 20, 55, 39) to avoid ground
currents from both groups to affect other groups. For example, switching on the digital input may disturb the analog input signal.
NB!
Control cables must be screened/armoured.
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MG.11.B7.02 - VLT ® is a registered Danfoss trademark
®
VLT HVAC Drive Design Guide