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grounding neutral

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Posted by Q on July 8, 2003, 8:49 pm
 
I have a 1000 watt Xantrex inverter that I would like to use as a backup to
my 3000 watt Vector. The Vector works fine in my house with standard wiring
which includes a grounded neutral. The Xantrex on the other hand says the
neutral cannot be grounded. I let the smoke out of a smaller inverter when I
plugged it into the house wiring with a grounded neutral.

My question is:

Is it safe to disconnect the neutral from ground?

Q



Posted by Dale Farmer on July 8, 2003, 9:48 pm
 


Q wrote:


    The answer is, it depends.  The manufacturers data with the thing should
have
some sort of diagram telling you how to connect it up to make a safe and
legal system.  Get and follow their directions.  The telling you that the
neutral
cannot be grounded makes me deeply suspicious about the quality and safety
of the unit, and I'd have someone who knows their way around inverters better
than I take a look at it.

    --Dale


Posted by Mark or Sue on July 8, 2003, 10:00 pm
 
I don't know if we have enough information to tell. Does this unit have a
grounding pin on its AC power outlets and if so how do they connect
internally to the inverter?. If the output is totally isolated from earth
ground, it is shock safe from ground faults but could be susceptable to
lightning strikes if connected to long wire runs. Since house distribution
systems are grounded (or more correctly must have their neutral and ground
wires bonded together), you will have limited use of this inverter if you
can't determine a way to ground the thing. I don't know why there would be a
difference between ground and neutral in an inverter...just where does
ground go that neutral can't?

--
Mark
Kent, WA




Posted by Bill Kaszeta / Photovoltaic Re on July 9, 2003, 3:48 am
 

I know that the Xantrex Portawattz line can not have the neutral grounded.  I
smoked one last week.  There is a hard to notice warning in the user
manual that the inverter is not to be connected to a wiring system with
a grounded neutral (grounded neutral is required by the USA National
Electrical Code).  I thought that they were trying to avoid a situation with
dual neutral-ground bonds.  Turns out that the AC is not isolated from the
DC input and that grounding the neutral when the dc is grounded causes
internal non-warranty damage.  Send the unit in with $US 65 and they will
replace it.  This is also the reason the Portawattz line is not UL listed.
Non-listed components should not be used in systems where the NEC
applies.

After calling/e-mailing all the smaller inverter manufacturers I found that
except for the Coleman Powermate (PMP800), all other small inverters
have this problem.  Even the Coleman is not UL listed.

I checked inside the non-functioning unit and there are no obvious burnt
components.  The basic dc/dc up converter (to 145 vdc) does not work
and the integrated circuit associated with this conversion is totally
unmarked.  Unit is made in China.

Therefore, I do not think you can use a low cost inverter as backup, but
investigate the Coleman.  Outpost.com has the 800W for about $US 70,
but the first unit I bought was dead on arrival.


Bill Kaszeta
Photovoltaic Resources Int'l
Tempe  Arizona  USA
bill@kaszeta.org

Posted by beachcooler on July 9, 2003, 11:12 am
 Q wrote:


If you have a grounded neutral, disconnecting it from ground will create an open
circuit. You must have a neutral coming in from the utility or make a neutral by
grounding. You can hook up your inverter just to your home without the utility
by doing away with the grounded neutral and the utility power, but double
insulated appliances will NOT be protected nor will you.



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