Neutral To Safety Ground Bonding; Figure 2-22, Neutral-To-Ground Connection (Inverter Mode); Figure 2-23, Neutral-To-Ground Connection (Standby Mode) - Sensata Magnum Energy MS Series Owner's Manual

2.6.5

Neutral to Safety Ground Bonding

The standards for safely wiring residential, commercial, RV/truck, and marine installations in the
United States require the neutral and safety ground to be connected at the AC source; whether
it is the utility feed in your home, an inverter, or a generator. This is to establish a specifi cation
that maximizes the possibility that a circuit breaker will activate if a hot wire-to-ground fault
occurs. These standards also require that the AC neutral be connected to safety ground (often
called a "bond") in one, and only one, place at any time. The single bond is established in order
to make the electrical panel's neutral line safe, by connecting it to ground. Without this bond,
the neutral can have up to 60 VAC with respect to ground. On the other hand, if more than one
bond is established, currents can circulate between neutral and ground and cause "ground-loop"
currents. These ground-loops can trip GFCIs, cause an electric shock hazard, and may be the
reason for other annoying side eff ects.
In applications where you are using an inverter as one of your AC sources along with another
AC source (i.e., utility power or generator), there is the potential of having multiple connections
(bonds) between neutral and ground. Therefore, you must ensure that the inverter does not also
connect the neutral-to-ground while the other AC source is actively powering the inverter loads.
This can be prevented if your inverter is equipped with automatic neutral-to-ground switching.
WARNING: In most electrical systems, the neutral-to-ground bond is located in the
main utility service entrance panel. Remove any bond downstream from the inverter to
prevent multiple bonds. If there is an inverter sub-panel—separate from a main electrical
panel—it should have a removable wire that allows the neutral bus to be unbonded from
the ground busbar.
All MS Series inverter/chargers have automatic neutral-to-ground switching to specifi cally work
in multiple source or mobile (i.e., truck/RV/boat) applications. The MS Series inverters use an
internal relay that automatically connects the AC neutral output terminal to the vehicle/boat's
ground while inverting (Inverter mode) to provide the neutral-to-ground bond; as shown in Figure
2-22. However, when an external AC source (i.e., shorepower or a generator) is connected, another
neutral-to-ground connection is introduced in the system. When the MS Series is connected to
this external AC source and goes into Standby mode, the internal relay automatically opens the
neutral-to-ground connection as shown in Figure 2-23. This design keeps two neutral-to-ground
connections from occurring at the same time, thereby preventing an electrical shock hazard
between the vehicle/boat's neutral and the external AC source's neutral.
Inside MS Series Inverter /Charger
(Inverter Mode)
Neu-Gnd Relay (K1)
NEUT IN
GROUND
Neutral -to-Ground Connection
(inside AC compartment)*
Figure 2-22, Neutral-to-Ground
Connection (Inverter Mode)
* – Normally located in the AC compartment; however, on MS2000 models the neutral-to-ground is
located internally on the AC board.
© 2016 Sensata Technologies
Inside MS Series Inverter /Charger
NEUT IN
NEUT OUT
GROUND
Figure 2-23, Neutral-to-Ground
Connection (Standby Mode)
Installation
(Standby Mode)
Neu-Gnd Relay (K1)
Neutral -to-Ground Connection
(inside AC compartment)*
NEUT OUT
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