Siemens SINUMERIK 840D

OCTOBER 2005 PRE-INSTALLATION PROCEDURES 35
SIEMENS MAINTENANCE MANUAL
2.5 ELECTRICAL
GROUNDING
WARNING!
The importance of proper grounding CANNOT be over-emphasized! Improper
grounding will result in a wide range of hard-to-diagnose problems in communica-
tions, positioning, spindle motion, etc.
2.5.1 PRIMARY
GROUNDING
1. The grounding conductor shall be of copper. The material selected shall be
resistant to any corrosive condition existing at the installation or shall be suitably
protected against corrosion.
2. The grounding conductor shall be a No. 8 AWG (10 mm
2
) or larger equipment
ground conductor, and must be:
• solid or stranded
• insulated, covered, or bare
• installed in one continuous length without a splice or joint.
3. Individually covered or insulated grounding conductors shall have a continuous
outer finish that is either green, or green with one or more yellow stripes.
4. A No. 8 AWG (10 mm
2
) or larger equipment ground conductor and 3 phase
conductors must be contained within one of the following:
• rigid metal conduit
• intermediate metal conduit
• electrical metallic tubing
5. The ground conductor shall be connected between the VMC’s ground bus and the
approved ground bus contained within the voltage supply panel board or enclosure.
6. The VMC branch supply conduit, phase conductors and ground conductors must
be dedicated to a single VMC. They cannot be used to supply any other loads.
2.5.2 SUPPLEMENTAL
GROUNDING
1. Supplementary grounding electrodes shall be permitted to augment the equipment
grounding conductor; however, the earth shall not be used as the sole equipment
grounding conductor.
2. The supplemental grounding conductor shall be a No. 6 (16 mm
2
) or larger copper
conductor in the form of a wire, and must be:
• solid or stranded
• insulated, covered or bare
• installed in one continuous length without splice or joint
3. A No. 6 (16 mm
2
) or larger grounding conductor shall be run in one of the following:
• rigid metal conduit