Trace Engineering DR Series Owner’s Manual - Version 3.2 - 9/7/98 - Page 23
Grounding Electrodes / Ground Rods
The purpose of the grounding electrode (often called a ground rod) is to “bleed” off any electrical
charge that may accumulate in the electrical system and to provide a path for “induced
electromagnetic energy” or lightning to be dissipated. The size for the conductor to the grounding
electrode or grounding system is usually based on the size of the largest conductor in the system.
Most systems use a 5/8” (16 mm) copper plated rod 6 feet (2 meters) long driven into the earth as
a grounding electrode. It is also common to use copper wire placed in the concrete foundation of
the building as a grounding system. Either method may be acceptable, but the local code will
prevail. Connection to the ground electrode should be done with special clamps located above
ground where they can be periodically inspected.
It is often desirable to use multiple ground rods in a larger system or systems. The most common
example is providing a direct path from the solar array to earth near the location of the solar array.
Most electrical codes want to see the multiple ground rods connected by a separate wire with its
own set of clamps. If this is done, it is a good idea to make the connection with a bare wire
located outside of the conduit (if used) in a trench - the run of buried wire may be a better
grounding electrode than the ground rods!
Well casings and water pipes can also be used as grounding electrodes. Under no circumstance
should a gas pipe or line be used. Consult local codes and the NEC for more information.
Bonding the Grounding System to the Neutral and Negative Conductors
This is the most confusing part of grounding. The idea is to connect one of the current carrying
conductors (usually the AC neutral and DC negative) to the grounding system. This connection is
why we call one of the wires “neutral” in the North American type electrical systems. You can
touch this wire and the grounding system and not be shocked. When the other ungrounded
conductor (the hot or positive) touches the grounding system, current will flow through it to the
point of connection to the grounded conductor and back to the source. This will cause the
overcurrent protection to stop the flow of current, protecting the system. The point of connection
between the grounding system and the current carrying conductor is often called a “bond”. It is
usually located in the overcurrent protection devices enclosure. Although it can be done at the
inverter, codes do not generally allow it since the inverter is considered a “serviceable” item which
may be removed from the system. In residential systems it is located at the service entrance
panel, after the power has gone through the kilowatt-hour meter of the utility.
In some countries, the neutral is not bonded to the grounding system. This means you may not
know when a fault has occurred since the overcurrent device will not trip unless a “double” fault
occurs. In some marine electrical codes this type of system is used.
Bonding must be done at only one point in an electrical system. Our systems inherently have two
separate electric systems - a DC system and a AC system. This means that two bonding points
will occur in all inverter applications. The bonding point will also be connected to the chassis
ground conductors. It is common to have two separate conductors connect the ground electrode
and the two bonding points. Each conductor should use a separate clamp.
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