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<p>When doing the volt drop calculation, be sure to correct for
temperature, per the note after table 8, chapter 9 of the NEC.
The table values default at 167 deg F (75 C). An underground
cable will be operating closer to earth temperature. When I run
volt drop for a 4/0 copper cable at 60 deg F, I'm seeing that you
could go over 60 amps and maintain a volt drop of 3%. <br>
</p>
<p>Not sure what the requirements for the building are, but that
exceeds most of my off grid systems. 60+ amps at a final voltage
of 232 v is almost 14kW. Is there air conditioning? What are the
calculated loads for this building? Is the inspector actually
calling this a problem? <br>
</p>
<p>I would do a proof of concept: turn every light on in the place,
along with some typical appliances (hair dryer, microwave) hit a
circular saw to really make the point, with a DMM plugged in. I
found long ago that actual measured volt drop was not as bad as
Chapter 9 first predicts.<br>
</p>
<p><br>
</p>
<pre class="moz-signature" cols="72">Ray Walters
Remote Solar
303 505-8760</pre>
<div class="moz-cite-prefix">On 4/18/20 3:41 PM, Darryl Thayer
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAHsrUiT6=c5nOV9cb2TQapCXOOyQ4jc3S6raqRLDCPS-iO660Q@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">
<div class="gmail_default" style="font-family:times new
roman,serif;font-size:large">Hi Mac, There are a few questions
like is it Al or Cu wire, What makes it unusable? </div>
<div class="gmail_default" style="font-family:times new
roman,serif;font-size:large">for Voltage drop, I use
Vd=2KIL/CMA for your case the unknown is the current. The
installation of an inverter with grid support. Many inverters
have this, you want a multimode inverter such as a Schneider,
Outback, SolArk and I could name at least 4 more. A normal
house will run on 30 amps. So assume 30 amps,
Vd=2x21.6x30x1100/211600 =6.7 volts</div>
<div class="gmail_default" style="font-family:times new
roman,serif;font-size:large">So if the main house is at 240
Volts the remote house is at 233 Volts. The multimode
inverter could be set at grid support beyond 30 Amps. For
higher house loads the inverter can support up to 30 to 50
amps additional. (SolArk is 50 amp) I would add a balancing
transformer at the end of the line to make the 120 loads
balance. (an Autotransformer) such that 120 volts loads are
balanced and the load is shared between 240-Volt conductors.
Based on my customers' experiences I would use AGM LA
batteries, as I expect low usage of the battery and quick
recharge, but that is the customer's choice. I had one
customer that had 10 years on the float-AGM battery set. </div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, Apr 17, 2020 at 8:15
AM Mac Lewis <<a href="mailto:maclewis1@gmail.com"
moz-do-not-send="true">maclewis1@gmail.com</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hi wrenches,
<div><br>
</div>
<div>I've got a architect client with a sub-optimal power
situation on one of the projects he is working on. I'm
running through a couple of scenarios that may work. Its
a ADU (accessory dwelling unit) that is about 1100' from
power. The farmer had taken it upon himself to bury some
4/0 a few years ago to run power out there. Voltage drop
is the big issue and its not going to pass the AHJ
inspection. We could just ditch the grid and go off-grid,
but it seems like a shame to not tap into the grid
resource. Instead of dealing with the voltage drop, I was
thinking it may make sense to rectify that low AC voltage
input and parallel a smallish battery bank (size is yet to
be determined), then use an off-grid inverter to serve the
loads at good voltage.</div>
<div><br>
</div>
<div>I am looking for feedback on this concept. What do you
think?</div>
<div><br>
</div>
<div>Also, are there any recommendations for good quality
rectifiers with wide input voltage window? </div>
<div><br>
</div>
<div>Thanks in advance for your help</div>
<div>
<div><br>
</div>
-- <br>
<div dir="ltr">
<div><br>
</div>
<div><font face="'times new roman', serif"
color="#305A78"><br>
</font></div>
<div><br>
</div>
Mac Lewis<br>
<br>
<span style="font-family:"Times New
Roman";font-size:medium;color:rgb(255,153,0)"><b><font
size="3" face="Arial, Helvetica, sans-serif">
<p align="left"><font face="Verdana, Arial,
Helvetica, sans-serif" color="#000000"><span
style="font-size:small"><span
style="font-family:arial;font-weight:normal;color:rgb(48,90,120)"><font
face="'times new roman', serif">"Yo solo
sé que no sé nada." </font><span
style="font-weight:700;color:rgb(104,104,104)"><font
face="'times new roman', serif">-Sócrates</font></span></span></span></font></p>
</font></b></span></div>
</div>
</div>
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