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1. You need to know the actual rating of any sub-section buss that
you will be backfeeding with PV. Do not backfeed this buss with more
than 100% of it's ampacity.<br>
<br>
2. Evaluate 120% of the 4000A buss against the 3500A main and all PV
backfeed all of the subsections.<br>
<br>
Mark Frye<br>
<br>
<div class="moz-cite-prefix">On 2/17/2015 7:37 AM, Allen Frishman
wrote:<br>
</div>
<blockquote
cite="mid:F8EF7397-A945-4D3A-923A-6C9EDA382F66@aeonsolar.com"
type="cite">Mark,
<div>Thank you, your response is very helpful! How does the
120% rule get applied to the 1000A sections in my example?
When grid connecting downstream on the load side of the switches
on the 1000A sections do we ignore the rating of the 1000A bus
bar being protected by a 3500 Amp Fuse? If yes what section
in the code allows this?</div>
<div><br>
</div>
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<p class="MsoNormal"><i><span style="font-size: 10.5pt;
color: black; ">Al Frishman</span></i><span
style="font-size: 13.5pt; color: black; "><br>
</span><span style="font-size: 13.5pt; color: rgb(3, 1,
0); ">Aeon</span><span style="font-size: 13.5pt;
color: rgb(255, 151, 0); ">Solar</span><span
style="font-size: 13.5pt; color: black; "></span></p>
<p class="MsoNormal"><i><span style="font-size: 10.5pt;
color: black; "><a moz-do-not-send="true"
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699-6641</a> - cell</span></i><span
style="font-size: 10.5pt; color: black; "><br>
</span><i><span style="font-size: 10.5pt; color: black;
"><a moz-do-not-send="true"
href="tel:%28888%29%20460-2867"
value="+18884602867" target="_blank">(888)
460-2867</a></span></i><span style="font-size:
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<div>On Feb 17, 2015, at 10:23 AM, Mark Frye wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
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<div bgcolor="#FFFFFF" text="#000000"> NEC 2008, 240.21
(B)(1)(1) a.<br>
<br>
Each of the smaller buss sections are feeders which are
sized according to the tap rules. I believe the answer to
your question is that the larger fuse can't protect the
smaller buss. <b>But</b>, the likelihood of a short
developing in that section of the circuit is very small
and if one did, damage to the equipment would be limited
that area. This is the essence of allowing taps.<br>
<br>
Mark Frye<br>
<br>
<div class="moz-cite-prefix">On 2/17/2015 6:17 AM, Allen
Frishman wrote:Wrenchers,</div>
<blockquote
cite="mid:BE91068C-B519-4CBB-AA32-6C4372622C1C@aeonsolar.com"
type="cite">
<div>I run into lots of Service Equipment that has a
Large Service Switch which feeds multiple Sections
with the Bus bar on each section rated significantly
less than the main bus. A specific example that I
am currently looking at has a 4000Amp Switch with a
3500 Amp Fuse which feeds 3 (1000 Amp) switchgear
sections. How is it possible that the 3500 Amp
Fuse protects the (3) 1000 Amp Sections? In this
particular case each of the 1000 Amp Sections has
between 3 and 6 fused switches on them. The sum of
those switch/fuse ratings exceeds 1000 Amps in each
case. For reference - This service gear is over 40
years old. </div>
<div><br>
</div>
<div>All thoughts are appreciated.<br>
<div> <span class="Apple-style-span"
style="border-collapse: separate; font-family:
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<p class="MsoNormal"><i><span style="font-size:
10.5pt; color: black; ">Al Frishman</span></i><span
style="font-size: 13.5pt; color: black; "><br>
</span><span style="font-size: 13.5pt; color:
rgb(3, 1, 0); ">Aeon</span><span
style="font-size: 13.5pt; color: rgb(255,
151, 0); ">Solar</span><span
style="font-size: 13.5pt; color: black; "></span></p>
<p class="MsoNormal"><i><span style="font-size:
10.5pt; color: black; "><a
moz-do-not-send="true"
href="tel:%28917%29%20699-6641"
value="+19176996641" target="_blank">(917)
699-6641</a> - cell</span></i><span
style="font-size: 10.5pt; color: black; "><br>
</span><i><span style="font-size: 10.5pt;
color: black; "><a moz-do-not-send="true"
href="tel:%28888%29%20460-2867"
value="+18884602867" target="_blank">(888)
460-2867</a></span></i><span
style="font-size: 10.5pt; color: black; "><br>
</span><i><span style="font-size: 10.5pt;
color: black; "><a moz-do-not-send="true"
href="http://www.aeonsolar.com/"
target="_blank">www.aeonsolar.com</a></span></i></p>
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