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Inverter Grounding Problems

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Jan 22, 2008
14
Beneteau Oceanis 48 Long Island, NY
I have a Xantrex Freedom SW 2000 inverter on the boat.
Recently, I discovered that the inverter does not have a ground wire.
The device can be grounded to the negative pole of the battery bank from the chassis of the inverter.
Is grounding an inverter necessary?
Should this have been done at the time of installation?
 

kenn

.
Apr 18, 2009
1,271
CL Sandpiper 565 Toronto
The negative terminal of the battery banks should not be considered as "ground" . Assuming you have a properly installed AC distribution panel, ground for the inverter is the ground bus of the AC panel.

This is all described very clearly in a number of books; I can highly recommend the Calder book.
 
Dec 19, 2006
5,727
Hunter 36 Punta Gorda
ground

My freedom 2000 does have a ground to the main ground bus at the panel.
Nick
 
Dec 25, 2008
1,577
catalina 310 Elk River
Be careful not to create a ground loop. I would not ground it to the AC ground.
 

kenn

.
Apr 18, 2009
1,271
CL Sandpiper 565 Toronto
Be careful not to create a ground loop. I would not ground it to the AC ground.
:cry:

Inverters generate AC, which is distributed by the AC panel. The Inverter shouldn't be grounded anywhere else.

paging Dr MaineSail...
 
Feb 26, 2004
21,892
Catalina 34 224 Maple Bay, BC, Canada
No, Don, you're not. I agree with your earlier suggestion. It's kinda the nature of the internet forums that sometimes RTFM gets overriden by well intentioned but incorrect advice.

Those of us who have this equipment on our boats have used the manuals to install them successfully. Having someone else do it has always seemed to me to be less safe, you know, for when, not if, something might go wrong. Unless you're a skipper who has the work done, but does understand it all.
 
Jan 22, 2008
14
Beneteau Oceanis 48 Long Island, NY
I accept the fact that I am a novice with electrical components and try to have skilled professionals guide me where I have questions. Well, not withstanding your comments, I still have questions.

I have quoted the installation manual on pages 17 and 19. This first paragraph suggests that the device auto-grounds and that a separate ground is not required for inverter function.


AC Output Neutral Bonding
The AC source must have its neutral conductor bonded to ground.
Bonding system
The Freedom SW provides a system that automatically
connects the neutral conductor of the inverter’s AC output circuit to safety
ground (“bonding” it) while the inverter/charger is inverting, and
disconnects it (“unbonding” it) when the inverter/charger is connected to
external AC power. This system is designed to conform to installation codes
that require AC sources such as inverters and generators to have their
neutral conductors tied to ground at the source of power in the same way
that the neutral conductor from the utility is tied to ground. These same
codes specify that the neutral can only be connected to ground in one place
at any one time.
Suitability
This automatic neutral-to-ground bonding system requires AC
input sources with bonded neutral. This will be the case in most situations:
in a utility feed, at an external AC hook-up, or a generator with a bonded
neutral. If not, have an electrician look into bonding the source’s neutral to
ground. See also “AC Input and Output Isolation” on page 26.
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
DC positive - the wire that provides DC current from the battery - a current carrying wire
DC ground - the wire that returns DC current to the battery - a current carrying wire
Chassis ground - the safety ground for the unit - a non current carrying wire

AC "hot" - the power wire for the AC circuit - a current carrying wire
AC "neutral" - the "ground" return wire for the AC circuit - a current carrying wire
AC ground - the wire that provides a safety ground for the AC current carrying wires - a non current carrying wire.

And then there is the RF ground for the radios, the bonding ground for the corrosion control, the lightning ground for the lightning protection system. These are all non current carrying wires BTW.

I think that about covers it.

Which wire did you think did not get connected?
 
Feb 26, 2004
21,892
Catalina 34 224 Maple Bay, BC, Canada
Bill's right. Please also be aware that many of those inverters are used in residential, not boating applications. That's why Don suggested reading the manual and being somewhat more specific with your question. IIRC, most of the manuals are pretty clear on the differences between residential and boats.
 
Feb 6, 1998
11,436
Canadian Sailcraft 36T Casco Bay, ME
I have a Xantrex Freedom SW 2000 inverter on the boat.
Recently, I discovered that the inverter does not have a ground wire.
The device can be grounded to the negative pole of the battery bank from the chassis of the inverter.
Is grounding an inverter necessary?
Should this have been done at the time of installation?
The AC input Green/Earth wire is, or should already be, grounded to the ships AC bus which is then tied to the ships DC bus.

These inverters are auto transfer "pass through" devices meaning you simply insert them into the incoming AC wire to the vessel. When they sense shore power they go out of invert mode and revert back to shore power. When shore is disconnected they can then be used for "inverting"..

The case or chassis ground on the unit is also there and needs to be connected. It should be no smaller than one size below the DC wire gauge and will be attached to the ships DC neg bus. So if your wires from the battery bank are 2/0 then you need at least a 1/0 green wire from case to the ships DC grounding bus or ships ground. This is an ABYC requirement for inverter, inverter charger or charger installations.

You have an Inverter/Charger and the case ground should definitely be attached.. Many installers cut this corner and shouldn't.

Also check your temp sensor and be sure it is connected to the banks negative terminal and not the positive. This is another very common "flub"...
 
Dec 25, 2008
1,577
catalina 310 Elk River
If this unit is stand alone, (which is the assumption I made) there is no correlation to the normal AC circuits and thus the ground should be kept separate. I did not understand this was a inverter/charger. Not sure I would install such a product, keep things simple and separate or you open yourself to failures that have unintended consequences.
 
Feb 6, 1998
11,436
Canadian Sailcraft 36T Casco Bay, ME
If this unit is stand alone, (which is the assumption I made) there is no correlation to the normal AC circuits and thus the ground should be kept separate. I did not understand this was a inverter/charger. Not sure I would install such a product, keep things simple and separate or you open yourself to failures that have unintended consequences.
Even with s stand alone inverter it still requires the chassis ground of not less than 1 size below the DC supply wire.
 
Feb 6, 1998
11,436
Canadian Sailcraft 36T Casco Bay, ME
To where the AC or DC ground?
DC ground bus. The AC ground bus is already tied to the DC bus but most often with smaller wire the same size as the AC input, such as 10GA for 30A service. Running to the AC bus would leave you with a jumper wire too small for the potential DC fault you are trying to protect against with the chassis ground.
 
Dec 25, 2008
1,577
catalina 310 Elk River
DC ground bus. The AC ground bus is already tied to the DC bus but most often with smaller wire the same size as the AC input, such as 10GA for 30A service. Running to the AC bus would leave you with a jumper wire too small for the potential DC fault you are trying to protect against with the chassis ground.
Good point!
 
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