Installation – Magnum Energy MS-PE Series User Manual

Page 34

2013 Magnum Energy, Inc.

Page 27

Installation

2.6.5

Neutral to Safety Ground Bonding

The recommended standards for safely wiring residential, commercial, and mobile installations

(e.g., caravans and boats) require that the neutral and safety ground 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

230 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 residential current devices (RCDs), cause an electric shock

hazard, and may be the reason for other annoying side effects.
In applications where you are using an inverter as one of your AC sources along with another

AC source (e.g., 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-PE Series inverter/chargers have automatic neutral-to-ground switching to specifi cally work

in multiple source applications. The MS-PE 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 2-14. However, when an external

AC source (e.g., shorepower or a generator) is qualifi ed, another neutral-to-ground connection

is introduced in the system. When the MS-PE 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 2-15. 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.

Figure 2-14, Neutral-to-Ground

Connection (Inverter Mode)

Figure 2-15, Neutral-to-Ground

Connection (Standby Mode)

Neutral

-to-Ground connection

(inside AC compartment)

GROUND

Neu-Gnd Relay (K1)

HOT IN

Inside MS-PE Series

Inverter

/Charger

(Inverter Mode)

NEUT OUT

NEUT IN

HOT OUT