Danfoss VLT HVAC Operating Instructions Manual page 37

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VLT HVAC Drive Operating Instructions
4.1.19. Electrical Installation and Control Cables
Illustration 4.28: 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, break the screen or insert a 100 nF capacitor between screen and chassis.
Remove mains power from the frequency converter before changing motor wires.
NB!
Connect the common of digital and analog inputs and outputs to separate frequency
converter common terminals 20, 39, and 55. This will avoid ground current inter-
ference among groups. For example, it avoids switching on digital inputs disturbing
analog inputs.
NB!
Control cables must be screened/armoured.
MG.11.A4.02 - 09.10.06. VLT ® is a registered Danfoss trademark
4. Electrical installation
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