[RE-wrenches] Odd Outback FNDC/Mate issue

[Howie Michaelson]

Hi Dick,

I used the twisted pair that comes with the FNDC.  I believe it is rated
for 600 v.  I did, early on, pull the wires through the conduit for the
aforementioned reason, but this is the only installation that I had
trouble with in this fashion - perhaps it was because all the others were
48 vDC battery banks.  More recently I've shifted over to going straight
to the Buss bars in the FW box.  The Outback engineers couldn't come up
with a simple answer to why the battery cable fields caused the Mate or
hub to entirely shut off given the topology of the system.  At this point
they are not going to look into it further...

Thanks,
Howie
-- 
Howie Michaelson
NABCEP Certified Solar PV Installer™

Sun Catcher, LLC
Renewable Energy Systems Sales and Service
VT Solar & Wind Incentive Program Partner
http://www.SunCatcherVT.com
(cell) 802-272-0004
(home) 802-439-6096


On Fri, March 27, 2009 9:28 am, Richard.L.Ratico at VALLEY.NET (Richard L
Ratico) wrote:
> Howie,
>
> Very high, rapidly fluctuating, DC currents are carried by battery cables.
> These
> produce powerful, local magnetic fields. Many sources recommend twisting
> the
> cables together to reduce RFI. I have found this twisting hard to do well.
> Steel
> conduit accomplishes the same thing, more effectively. Resist the
> temptation to
> put any other wiring in that conduit. This would most likely be a code
> violation
> in any case; wires of different voltage ratings in the same conduit are
> generally prohibited.
>
> Dick
>
> Dick Ratico
> Solarwind Electric
>
> --- You wrote:
> Outback has now determined that somehow this induced current from the
> battery cables into the voltage sensing wires for the FNDC can cause the
> communication system to get overwhelmed, but they are not quite sure how.
> None-the-less, as of this week, they are recommending to run the FNDC
> voltage sensing wires (plus and minus) *not* along side the inverter
> cables.
>
> Hopefully, this is the end of this story...
>
> Has anyone experienced any similar symptoms?  This seems a first for OB,
> but I thought I'd ask here.
> --- end of quote ---
>
>