Xantrex Technology 120 VAC/60 - Manual (Page 35)

INSTALLATION
 2001 Xantrex Technology, Inc.
5916 - 195th Street N. E.
Arlington, WA 98223
Telephone: 360/435-8826
Fax: 360/435-2229
www.traceengineering.com
SW Series Inverter/Charger
Part No. 2031-5
Rev. C: February 2001
Page
27
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.
NEUTRAL-TO-GROUND BOND SWITCHING (RV AND MARINE APPLICATIONS)
As required by NEC code and UL specification 458, inverter/charger installations in the U.S. that are used
in RV or Marine applications employ ground-to-neutral switching. The purpose for this requirement is to
ensure that all the neutral conductors are connected (“bonded”) to a single ground point in a three-wire
(hot, neutral and ground) AC system. This prevents a voltage difference from developing between the
vehicle/boat’s AC neutral and the external AC source’s (generator or shore power) neutral, which may
cause an electric shock or cause nuisance tripping of GFI’s. The SW Series Inverter/Charger does not
include Neutral-to-Ground switching and must be provided in the AC installation.
When the unit is operating as an inverter, the AC output neutral should be connected or “bonded” to the
frame/hull (chassis ground). When an external AC source (AC shore cord) is provided, the inverter’s AC
output neutral should be disconnected from the frame/hull (chassis ground) and allow the “bond” to be
provided by the external AC source. The requirement to switch the neutral can be met by your inverter
internally or can be easily met by using an external relay to connect and disconnect the external AC
source’s neutral. If another AC source (on-board generator) is included in the RV or boat, this AC source
neutral is required to be connected to ground when it is being used, and to disconnect all other neutrals
from ground. An AC transfer switch can be used if it switches both the shore cords and generators neutral.
In some marine applications, neutral-to-ground switching is not required or acceptable. The potential for
galvanic corrosion caused by small leakage currents between boats with dissimilar metals is present. The
proper and safe ways to prevent this is by using galvanic isolators or include an isolation transformer for
the AC input. Disconnecting the common ground between the AC and DC system could contribute
to a hazardous and potentially fatal situation.
The figures below graphically describes the neutral-to-ground switching system for the two cases in
question: the unit operating as an inverter feeding the AC subpanel, and the unit connected to an external
AC source (generator, shore power, etc.).
Figure 12, Neutral-To-Ground Bond Switching: No External AC Source Connected
NEUTRAL-TO-GROUND SWITCHING
RELAY (provided in the AC installation):
Connects the output neutral to chassis or
vehicle ground when AC is not present at
inverter input. This assures all equipment in
the vehicle is referenced to the same
ground.
INVERTER
(AC Terminal Block)
NEUTRAL-TO-GROUND
“BOND” is provided by this relay
for the entire AC system
No external AC
source is present
AC NEUTRAL OUT
AC HOT OUT
CHASSIS GROUND
RY1
AC NEUTRAL IN
EARTH GROUND
AC HOT IN
GROUND
NE
UT
RA
L
AC PANEL
(RV/Marine)
HOT
The neutral conductor should
not be connected to the
equipment grounding
conductors or enclosures.