Manufactures on the list [RE-wrenches]

[Mark Frye]

Mark,

Thanks for the reply.

I guess I am still unclear about what is happening here.  I am sure a simple
line diagram, similar to the one presented by William Miller earlier in the
tread would be very helpful to me in understand this.

However, what I understand you saying is that under some rare conditions
Christopher could be correct on both counts, 1) fuse blows, clears fault,
and goes un-indicated, 2) controller continues to operate and generate power
from the array.

Questions of the efficacy of this design revolve around the issues of the
probability of the particular fault condition occurring and the relative
time constants acting on circuits based on system operating voltage.

Do I have this about right?

Thanks for your attention to this matter.
 
Mark Frye
Berkeley Solar Electric Systems
271 Vistamont Dr
Grass Valley CA 95945
(530) 401-8024
www.berkeleysolar.com
 
-----Original Message-----
From: Mark Edmunds [mailto:mark.edmunds at xantrex.com] 
Sent: Tuesday, March 04, 2008 8:59 AM
To: RE-wrenches at topica.com
Subject: RE: Manufactures on the list [RE-wrenches]


Blair, Todd, Mark, Wrenches -

I missed some of this dialog as I haven't had time to check the list for
a couple days, my apologies. As a manufacturer we are here to help
answer your questions about our products, but do get pushed to get a
little carried away by our friendly competitors once in a while. As a
general rule we will always avoid commenting on the products made by
others, and leave that to you all.

Back to Mark's original question on the XW charge controller.
Theoretically I suppose the answer could be yes. Anything is possible.
If there was a VERY LOW impedance bond from the PV negative line to the
controller chassis ground the GF fuse could blow, thereby breaking the
fault path, and the controller may not give an indication of this.  But,
you would be hard pressed to make this occur in the real world.  The
level of impedance found in array ground systems to earth or the fact a
fault is more likely to occur somewhere within the array itself would
ensure that the controller would detect a fault like this.  And as I
have already pointed out, this hasn't been an issue in the high volume
pure grid tie world.  And again...this approach is UL compliant.    

Now, if you don't accept this and want to plan for any eventuality no
matter how remote, feel free to add an external PVGFP to our charge
controller.  This would be the same as Outback's higher cost approach to
GF detection.  We allow for this for 2 reasons;

1) customers in Europe want this for floating arrays
2) customers in the US requested this to tie into existing PV systems
with external ground fault breakers already installed  

You can download the instructions to disable the internal ground fault
detection here...
http://www.xantrex.com/web/id/252/p/docs/pt/23/product.asp 

Hope this helps.

Cheers,

Mark


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