[RE-wrenches] DC voltage drop
Greg Egan
greg at remotepowerinc.com
Sat Feb 20 21:00:06 PST 2010
I use this one at http://www.southwire.com/ProductCatalog/voltdrop.jsp
I check the single phase box for DC circuits.
Best,
Greg
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> Today's Topics:
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> 1. Re: calculating DC voltage line loss (Windy Dankoff)
> 2. Re: calculating DC voltage line loss (William Miller)
> 3. Re: calculating DC voltage line loss (Hugh)
>
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 20 Feb 2010 14:05:33 -0700
> From: Windy Dankoff <windydankoff at mac.com>
> To: re-wrenches at lists.re-wrenches.org
> Subject: Re: [RE-wrenches] calculating DC voltage line loss
> Message-ID: <F0FED95D-D30C-4595-AEDA-3E551C634177 at mac.com>
> Content-Type: text/plain; charset="us-ascii"; Format="flowed";
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> Marco,
>
> Here's another method that you can print to a sheet of paper. I
> published this in Home Power in 1989 and it's been widely used ever
> since. So it's an unusual approach, but proven to be consistent with
> published charts regardless of voltage. It applies to DC and "simple"
> AC as you'll see.
>
> http://www.conergy.us/PortalData/3/Resources/products/solar_pumps/pdf/wire_sizing_chart.pdf
>
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> ------------------------------
>
> Message: 2
> Date: Sat, 20 Feb 2010 13:50:14 -0800
> From: William Miller <william at millersolar.com>
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] calculating DC voltage line loss
> Message-ID: <6.0.1.1.2.20100220134923.03b4dec0 at millersolar.com>
> Content-Type: text/plain; charset="us-ascii"; Format="flowed"
>
> Marco:
>
> Installers world wide have commented favorably on the tool we
> developed. It can be found
> at: http://millersolar.com/resources/resources.html
>
> William Miller
>
>
>
>
>
> At 11:48 AM 2/20/2010, you wrote:
>
>> Content-Type: multipart/related;
>> boundary="----=_NextPart_000_009E_01CAB211.DC8DF740"
>> Content-Language: en-us
>>
>> xmlns:ns0="urn:schemas-microsoft-com:office:smarttags">
>> Can anyone pass on a good website address that provides the means to
>> calculate DC line loss over distance?
>>
>> The ones that I've come across don't allow for entering in whatever you
>> want as far as specified DC voltage.
>>
>> Thanks,
>> marco
>>
>> f11587.jpg
>>
>> Marco Mangelsdorf, President
>> 69 Railroad Avenue, A-7
>> Hilo, Hawai'i 96720
>> (808) 969-3281, 934-7462 facsimile
>> <http://www.provisiontechnologies.com>www.provision-solar.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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> ------------------------------
>
> Message: 3
> Date: Sat, 20 Feb 2010 23:09:51 +0000
> From: Hugh <hugh at scoraigwind.co.uk>
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] calculating DC voltage line loss
> Message-ID: <p062309acc7a616496639@[192.168.1.3]>
> Content-Type: text/plain; charset="us-ascii" ; format="flowed"
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>
>> Can anyone pass on a good website address that provides the means to
>> calculate DC line loss over distance?
>>
>>
>
> I normally just use the resistivity of copper and make an estimate of
> the operating temperature. Most of the standard tables that you find
> in books assume that the temperature of the copper wire is at the
> limit for PVC insulation (around 70 degrees C) but in reality you
> will be working much lower (for energy efficiency) and thus have
> lower resistance.
>
> As usual it's a lot easier for us with metric units of measure (wires
> are sold according to their cross section in square mm) but you can
> also do this with AWG. Remember that increasing wire gauge by 3
> halves the area, so #6 has half the sectional area, and hence twice
> the resistance of #3.
>
> Here are some resistances I worked out for an article in HP magazine
> 134 (back page basics) using "English" units. But here I am giving
> you the figures at 3 different temperatures to emphasise the effects
> of temperature:
>
> FEET PER OHM OF TWIN CABLE
> === === === ===
> #AWG 0 35 70 degrees C
> === === === ===
> 0 5,541 4,639 3,989
> 1 4,394 3,679 3,164
> 2 3,484 2,917 2,509
> 3 2,763 2,313 1,989
> 4 2,191 1,835 1,578
> 5 1,738 1,455 1,251
> 6 1,378 1,154 992
> 7 1,093 915 787
> 8 867 726 624
> 9 687 575 495
> 10 545 456 392
> 12 343 287 247
> === === === ===
>
> The figures are FEET ONE WAY to make one ohm for a 2-core cable. For
> example if you use #8 at an operating temperature of 35C then you get
> 726 feet of wire run (actually using 1452 feet of actual wire) to
> make one ohm.
>
> It's easy to use. Say your current is I and the wire run is L.
> Volt-drop will therefore be
>
> V = I x L / 726 (in this case).
>
> Say 10 amps and 100 feet then you will lose 1000/726 = 1.4 volts.
>
> No sense in calculating a string of decimals, since the temperature
> is only estimated anyway.
>
> Using this stuff you can build your own spreadsheet or even do the
> calcs quickly in your head to a useful level of accuracy once you
> have a bit of experience. As I say its a lot easier with metric
> units where the wires sizes are multiples of 1 sqmm, and about 28
> metres of that stuff is one ohm.
>
--
Greg Egan
Remote Power Inc.
981 Gold Mine Trail
Fairbanks, AK 99712
P. 907.457.4299
U.S.Distributor for Outback Power Systems and other premium power equipment.
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