ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
by Docholiday. 01/22/18 10:52 AM
AreMetal Ladders Ever OK For Electrical Work?
by gfretwell. 01/22/18 01:15 AM
VDE 0100 to introduce AFCIs
by sparky. 01/20/18 05:09 PM
MRI LED lights dimmer control replacement - wow!
by Potseal. 01/19/18 08:52 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
1 registered members (brsele), 29 guests, and 14 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Voltage Drop Question #101758
02/26/03 04:40 PM
02/26/03 04:40 PM
RobbieD  Offline OP
Joined: Feb 2003
Posts: 231
I have a question about voltage drop. I know how to use D3 Table, I can figure out the voltage drop for a two wire circuit No-problem. I don't know how to figure out the voltage drop for a three phase circuit though. In the old code books it was easy because on Table D5 they used to give you the -CM Area- in the 2002 code book they don't. The old formula: CM=(K)(I)(L)(1.73)

Table D5 has taken away the CM Area.
So how do you find the voltage drop in a three phase circuit using the 2002 CEC?
For example three-phase (no neutral) going to a motor controller.
Sorry for all the questions but I thought that I would take advantage of all the expertise.

Tools for Electricians:
Re: Voltage Drop Question #101759
02/27/03 06:57 PM
02/27/03 06:57 PM
RobbieD  Offline OP
Joined: Feb 2003
Posts: 231
Hey is anybody out there? Hey Tony could you help me with my question?


All that I am looking for is if I was to use the 2002 CEC only would I be able to find the voltage drop in the three phase circuit. I don't think I can. I think that I would require some other book most likely a manufacturers pamplet with info on the specific wire. I'm not sure though maybe I'm not looking in the right place in the code book that's why I asking the question. I am positive that people have calculated voltage drops in three phase circuits before. I am just curious on how they do it with just the code book.

Re: Voltage Drop Question #101760
02/27/03 07:33 PM
02/27/03 07:33 PM
Tony Moscioni  Offline
Joined: May 2001
Posts: 144

Here is the formula in calculating Voltage Drops in Three Phase Circuits:

Three Phase Formulas as Follows:

%VD,3PH= KFactorxAmpsxLength of CCT in Metres
Phase to Phase Supply Voltage-volts

Single Phase Formulas as Follows:

%VD,1PH= KFactorx1.15xAmpsxLength in Metres
Phase to Neutral Supply Voltage

If you are using the OESC 2002'look under Table D3.

For other nominal voltages, multiply the distances in metres by the other nominal voltage (in volts) and divide by 120.

Example on use of Table:

Consider a two conductor circuit of No. 12 AWG copper NMD90 carrying 16 A at nominal 240 V under maximum ambient of 30°C. The maximum run distance from the centre of distribution to the load without exceeding a 3% voltage drop is:

Maximum run length for No. 12 AWG, 16 A, 1% voltage drop at nominal 120 V from Table is: 6.1 m

Distance Correction Factor to be used is:

From Table 2, allowable ampacity for 2
conductor No. 12 AWG NMD90 (90°C rating per Table 19) is 20 A. The given current is 16 A or 80% of the allowable ampacity.

The Distance Correction Factor to be used, from Note (3), 90°C row, 80% column, is 1.00.

The maximum run length is:

6.1 m x 3% x 1.00 x 240v = 37m

Beyond this distance a larger size of conductor is required, ie, No. 10 AWG (30 A allowable ampacity) beyond 37 m up to and including 62 m.

9.7 ,m x 3% x 1.06 x 240v = 62m

Tony Moscioni
Electrical Inspector
Electrical Safety Authority

Re: Voltage Drop Question #101761
02/27/03 07:40 PM
02/27/03 07:40 PM
RobbieD  Offline OP
Joined: Feb 2003
Posts: 231
Thanks Tony, Is it possible to calculate the voltage drop of a three phase circuit using only the 2002 CEC?


2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Nicholson Ga
Posts: 34
Joined: June 2006
Show All Member Profiles 
Top Posters(30 Days)
Admin 21
Potseal 15
sparky 15
Popular Topics(Views)
243,595 Are you busy
180,393 Re: Forum
170,862 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.027s Queries: 14 (0.005s) Memory: 0.9590 MB (Peak: 1.0893 MB) Zlib enabled. Server Time: 2018-01-22 18:22:52 UTC