Grounding; System Grounding; Equipment Or Chassis Grounds; Ground Electrodes / Ground Rods - Apollo Solar 3224 User Manual

4.2 Grounding

4.2.1 System Grounding

System grounding is often the most misunderstood wiring concept. The subject is more easily
discussed if it is divided into three separate subjects. The grounding requirements vary widely by
locale and application. Consult local codes and the NEC (ANSI/NFPA 70) for specific requirements.

4.2.2 Equipment or Chassis Grounds

This is the simplest part of grounding. This involves connecting the metallic chassis of the various
enclosures to have them at the same voltage level. This reduces the potential for electric shock. It
also provides a path for fault currents to flow resulting in blown fuses or tripped circuit breakers. The
size of the connecting conductors should be coordinated with the size of the over current devices
involved. Under some circumstances the conduit and enclosures themselves will provide the current
paths.

4.2.3 Ground Electrodes / Ground Rods

There are two purposes of the grounding electrode, also known as a ground rod. The first is to
"bleed" off any electrical charge that may accumulate in the electrical system. The second is to
provide a path for 'induced electromagnetic energy' or lightning to be dissipated. The size of 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' (16mm) copper plated rod 6 feet (2meters) long
driven in to 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. While either method may be acceptable,
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.
Well casings and water pipes may be used as grounding electrodes. Under no circumstance should
a gas pipe or line be used. Consult local codes and the NEC (ANSI/NFPA 70) for more information.

4.2.4 Bonding the Grounding System to the Neutral and Negative Conductors

This is the most confusing part of grounding. The purpose 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 North American electrical systems. You can touch this wire
and the grounding system and not receive a shock. 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 over current protection to shop 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 over current
protection devices' enclosure. Although the point of connection 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 the point of connection is located at the service entrance panel.
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 over current device will not trip unless a "double" fault occurs.
This type of system is used in some marine electrical codes.
Bonding must be done at only one point in an electrical system. Our systems inherently have two
separate electric systems- a DC system and an 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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