Off-grid update... [RE-wrenches]

[Christopher Freitas --- OutBack Power]

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Welcome back to the off-grid world Jim,  

There really isn't any difference in the installation requirements for a
12, 24 or 48 vdc system these days other than the ampacity of the
conductors.  Most wire, breakers, etc have maximum voltage ratings that
are well above the voltages encountered in a 12, 24 of 48 vdc system.
The 50 vdc limitation is rarely utilized by anyone to their benefit
these days - and when it was previously it was probably being done
incorrectly.  

One change to be aware of is that using multiple different voltages on
the same system is now pretty common - for example wiring the PV array
for a higher nominal voltage (such as 48, 60 or even 72 vdc) but the
battery staying at 24 vdc.  This improves the performance and lower the
total cost in many situations.  It also means you don't need to wrestle
with such large wires from the PV array.  

The "non-load break disconnects" I think is a reference to bolted
connections or Anderson type connectors for servicing the battery or
system. Not a big deal - you still need a real load break rated DC
disconnect for the battery in residential/commercial installations (but
not RVs or boats ?!?)

The other issue is that ground fault protection (GFP) is now readily
available and must be included on roof-top mounted PV arrays on houses.
This was always required but was not often enforced previously as there
was not listed hardware available to meet this requirement. Now days its
easy to include and is worth doing.    

Christopher Freitas
OutBack Power Systems
cfreitas at outbackpower.com
19009 62nd Ave NE 
Arlington WA 98223 USA 
Tel 360 435 6030
Fax 360 435 6019
www.outbackpower.com 


>> -----Original Message-----
>> From: Jim Duncan [mailto:ntrei at earthlink.net] 
>> Sent: Thursday, February 24, 2005 2:08 PM
>> To: RE-wrenches at topica.com
>> Subject: Off-grid update... [RE-wrenches]
>> 
>> 
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>> 
>> Wrenches, 
>> I'm planning my first off-grid install since the late '90s 
>> and I know a 
>> lot has changed both equipment wise and with the NEC. 
>> I thought that since a 48V system was considered being able 
>> to operate 
>> at above 50V so was considered not low voltage. Now the NEC 
>> refers to 
>> (24) 2V cells the same as a 12 or 24 V system. Is there no 
>> difference in 
>> the equipment, disconnect rating, ampacities, sizing etc?
>> Also what are some examples of 690.71 "Non-load break bolted 
>> or plug in 
>> disconnects..." in the battery container? 
>> Thanks as always
>> Jim Duncan
>> North Texas Renewable Energy Inc
>> Fort Worth, Texas
>> ntrei at earthlink.net
>> 817.917.0527
>> **************
>> There is one thing stronger than all the armies in the 
>> world, and that is an idea whose time has come. Victor Hugo
>> 
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