[RE-wrenches] Assembly Protects Conductors?

[Chris Mason]

Mark,
The term "recombiner" to me is an electrical panel used on the AC output of
multiple inverters to combine their electrical outputs.
That is different to a "combiner" which connects solar strings through
fuses to a busbar for connection to the inverter using one conductor pair.

In grid tied systems, you will probably not find breakers that can be used
in combiners as the 600V or 1,000v max DC voltage is above what most
breakers can operate at, hence the use of touch safe fuses.

I don't think the NEC recognizes recombiners panels as existing at all.
Standard rules require the breakers to be 125% rated as the output is
continuous.


On Fri, Aug 22, 2014 at 4:34 PM, <markf at berkeleysolar.com> wrote:

> Folks,
>
> In looking at a circuit breaker based re-combiner for the first time, I am
> now pondering the meaning of the Exception below:
>
> NEC 2014 690.8 (B) Conductor Ampacity. PV system currents shall be
> considered to be continuous. Circuit conductors shall be
> sized to carry not less than the larger of 690.8(B)(1) or (2).
>
> (1) One hundred and twenty-five percent of the maximum
> currents calculated in 690.8(A) before the application of
> adjustment and correction factors.
>
> Exception: Circuits containing an assembly, together with
> its overcurrent device(s), that is listed for continuous operation
> at 100 percent of its rating shall be permitted to be
> used at 100 percent of its rating.
>
> Just to be clear, it is only the assembly that can be used at 100 percent
> of its rating. (Isc*number of strings*1.25) The conductors in the circuit
> still have to be sized for continuous operation (Isc*number of
> strings*1.25*1.25).
>
> I ask because a vendor with a 100% circuit breaker re-combiner states in
> their cut sheet that use of the device "allow
> smaller home run cable sizes from the string combiner to the inverter". Is
> anyone aware of a means by which this claim can be substantiated?
>
> Thanks,
>
> Mark Frye
> Berkeley Solar Electric Systems
>
>
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-- 
Chris Mason
NABCEP Certified Solar PV Installer™
Solar Design Engineer
Generac Generators Industrial technician

www.cometsolar.com <http://www.cometenergysystems.com>
264.235.5670
869.662.5670
Skype: netconcepts
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