SB304- SB50 limits [RE-wrenches]

[Pat Kiernan, Eco Electric, Inc.]

I prefer using larger conduit, but in a pinch you can use conduit fill of
60% in short nipples.

NEC Chapter 9 Notes to Tables
4. Where conduit or tubing nipples having a maximum length not to exceed 24
in. (610 mm) are installed between boxes, cabinets, and similar enclosures,
the nipples shall be permitted to be filled to 60 percent of their total
cross-sectional area, and Section 310-15(b)(2)(a) adjustment factors need
not apply to this condition.

Pat Kiernan

Eco Electric, Inc.
PO Box 550
Carbondale, CO 81623
tel/fax (970) 963-3132
e-mail: ecoelec at rof.net
----- Original Message -----
From: Phil Undercuffler <phil at positiveenergysolar.com>
To: <RE-wrenches at topica.com>
Sent: Tuesday, November 13, 2001 9:17 AM
Subject: Re: SB304- SB50 limits [RE-wrenches]


> ----- Original Message -----
> From: <sunwise at cheqnet.net>
>
> <snip> I've used 3/4 inch liquid tight and bushings on
> > the RV end on the last couple SB50's I installed.
>
> 3/4" liquid tight?  How in God's green earth do you fit adequate wires
into
> 3/4"?  Much less if you use 90s, which seem to be even harder to cram
wires
> through!
>
> Figure that's two wires in, two wires out, plus ground, plus temp comp,
plus
> shunt sense.  When I do the math, figuring 40% fill area for more than 2
> wires and 18 gauge for the sense wires, that works out to #10 wire max!
> Unless you are only using a 3048 AND using it to downcut 48 volt arrays to
a
> 24 volt battery bank that really seems to be choking the performance you
> paid for.
>
> I usually  use minimum #6 to utilize the 50 amp output capacity (with a 60
> amp breaker).  That gets hard to  cram through even a 1" offset.  My wish
> list would be 1 1/4" KOs, not 3/4".  I've only found the 1/2" handy if I'm
> routing the temp sense directly to the batteries and not through the main
DC
> feed conduit.
>
> FYI, in many instances I use a 1" offset out the right hand side of a DC
> Disconnect into a QO 2-4 70 box and another 1" offset going up into the
SB,
> and use a two pole breaker to handle both sides of the controller.  Frees
up
> a little space in the DC disconnect for ease of access or DC loads and the
> trio nestles up nicely.  In addition an oversized array input conduit and
> wire can easily be terminated at the QO.  The box and breaker is about the
> same cost as two Heinemanns.  John Wiles questions using QO breakers on
24v
> array inputs, but I have no reservations.
>
> Enjoy the Sun!
>
> Phil Undercuffler
> Positive Energy
>
> "The most beautiful experience we can have is the mysterious....
> the fundamental emotion which stands at the cradle of true art
> and true science"  --Albert Einstein
>
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>

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