ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by gfretwell - 03/28/24 12:43 AM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
0 members (), 255 guests, and 16 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
#127800 01/04/02 09:44 AM
Joined: Dec 2000
Posts: 84
C
cinkerf Offline OP
Member
In today's code question of day http://www.ecmag.com/cqd/index.cfm?ID=20020104 two methods for performing voltage drop calculations were given for an A.C. circuit. Is one method better than other? Is one method more popular than the other?

Stay up to Code with the Latest NEC:


>> 2023 NEC & Related Reference & Exam Prep
2023 NEC & Related Reference & Study Guides

Pass Your Exam the FIRST TIME with the Latest NEC & Exam Prep

>> 2020 NEC & Related Reference & Study Guides
 

Joined: Oct 2000
Posts: 4,116
Likes: 4
Member
Frank,

I've always tried to use formulas that are simple (for me) to remember. In this case Ohm's Law; (I = E/R)

E = I x R where E is the Voltage

Bill


Bill
Joined: Jul 2001
Posts: 311
F
Member
Thanks Bill. By the way, Happy New Year....

Joined: Jul 2001
Posts: 599
J
JBD Offline
Member
For short distances (less than 150 ft), I use simple formulas. I like the Square D Motor Data Calculator voltage drop feature.

For longer distances I like to consider the impedance of the system rather than only the resistance. This means worrying about the raceway, Power Factor, and phase configuration. I use the tables in the Ferraz-Shawmut Book of Electrical Information.

Joined: Nov 2000
Posts: 2,148
R
Member
I just found this site with some downloadable elecrical software. It has a series voltage drop calculator for multiple loads on long runs. It is free and I downloaded it this morning. Looks like it will work nice, but I haven't really played with it yet. http://www.edreference.com/default.asp
Don(resqcapt19)


Don(resqcapt19)
Joined: Jul 2001
Posts: 311
F
Member
Over the years I've take several certification examinations. Only small calculators were permitted to be used. I've had luck using the following calculation for voltage drop for single phase circuits: VD=2KLI/CM. x.866 if three phase circuit. For these particular exam questions power factor, raceway etc were not a factor. I was thankful for that...

For those of you who took exams, what formula did you use?

[This message has been edited by Frank Cinker (edited 01-06-2002).]

Joined: May 2001
Posts: 717
G
Member
Guys,
Ugly's has always been the standard around here. Don, Uglys was issued to me by the IBEW in my apprenticeship, since we came through about the same time didn't you use it ? If they quit publishing Uglys I've always said I'm leaving the trade. It is also the standard used locally for most every test.

Single phase, 2 wire = 2K X L X I / Cm

3 phase, 3 wire = 1.73K X L X I/ Cm

K = 12.9 for copper, 21.2 for aluminum
L = length, I = amps, and Cm = Circular mil area from Chap 9, Table 8

The only thing you have to check occasionally is the "K" rating, that has moved around since I came in the trade because the cma table was revised.

I've been around long enough that #10 wire was 10,000 cm, it has been revised to 10,380, but the formula has pretty much remained the same. [Linked Image]

Joined: Nov 2000
Posts: 2,148
R
Member
George,
They didn't give us "Ulglys", but those are the formulas that we were taught.
Don


Don(resqcapt19)
Joined: Dec 2001
Posts: 270
E
Member
The K factor has changed through the years because the Ohms per 1000ft figure in Table 8 of Ch 9 depends on the assumed temperature. In the '87 code they stopped assuming 25C and started assuming 75C.
K is just shorthand for: (dc resistance value) X (circular mil area) divided by 1000.
You have to watch out for the assumed temperature if you are going to use the formula with a K factor...not to be confused with K factors of transformers!

[This message has been edited by Elzappr (edited 01-11-2002).]

Joined: Nov 2000
Posts: 2,236
Likes: 1
Member
I would not have passed my journeyman's without an UGLY's... Is the 2002 out yet?


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
Page 1 of 2 1 2

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5