[RE-wrenches] Head Spinning..(Con) fused.

[William Miller]

Eric:

The best resource I have found on this subject is the white paper that John 
Berdner wrote.  I have a copy on my web site: millersolar.com under Resources.

The general rule is no system with two strings combined needs fuses.  Run 
the calcs as presented in the white paper for verification.

Just because circuits share a J-box or conduit is not a reason to 
fuse.  Actual connection into an inverter is required before the number of 
strings is tabulated.

William Miller




At 08:40 PM 11/13/2010, you wrote:
>Wrenches,
>
>Can anyone shed guidance on the following for me? Should these strings be 
>fused:
>
>Total Modules: 44
>Total Strings: 4 strings of 11
>Total Inverters: 2
>
>Modules: Silicon Energy 195 Watt @ 8A
>Each string feeding an independent MPPT input on an Aurora PVI 4.2kW 
>Inverter (there are 2 / Aurora)
>Inverter is transformerless (READ 690.35 (B))
>
>Each strings passes through a shared SolaDeck jbox, no combining, and head 
>directly to their own dedicated GE THN2261RDC DC Disconnect before 
>entering a dedicated MPPT input on the inverter.
>
>My big question is 690.9 (A) exception (b) which states I don't need ocpd 
>as long as "The short circuit currents from all sources do not exceed the 
>ampacity of the conductors."
>
>Because all four strings pass through the same jboxs and conduit before 
>reaching their disconnect and could potentially short together, should I 
>fuse each string?
>
>Or am I just up too late reading code....?
>
>Thanks for being a resource.
>
>--
>Eric Thomas
>Solar Epiphany LLC
>(206) 919-3014
><http://www.solarepiphany.com>www.solarepiphany.com
>
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Please note new e-mail address and domain:

William Miller
Miller Solar
Voice :805-438-5600
email: william at millersolar.com
http://millersolar.com
License No. C-10-773985
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