×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Calculate Voltage Drop

## Calculate Voltage Drop

(OP)
I need to connect Distribution Panel (UL891) with Remote Panel supplied by 24VDC from Distribution Panel to Remote Panel with a 300ft long 2 run per polarity (+,-). The load is approximately is 6Amps. I want to calculate voltage on the cables.

1. How to calculate voltage drop for 300feet long 2 parallel cable of 24VDC ?
2. What is best cable size I can use for less voltage drop ?
Replies continue below

### RE: Calculate Voltage Drop

From the information given:
Voltage drop; Less than 24 volts.
Less voltage drop; Bigger cable.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

### RE: Calculate Voltage Drop

No ampacity problem with 6 A per any conductor [from 14 awg copper and 12 awg aluminum]
according to NEC art.310.
Using a single conductor per + and a single per - for 3% voltage drop of 24 V [=0.72 V]
[Voltage drop in d.c. system it is V= Resistance*I[current]. So, you need a conductor of a resistance of 0.72V/6A=0.12 ohm for 2*300 ft. That means 1000/600*0.12=0.2 ohm/1000ft.
Let's say 60oC [maximum conductor temperature the temperature factor is 1.16 ]
kT=(230+60)/(230+20)=1.16
We chose 2 awg copper conductor 0.156 ohm/1000 ft at 20oC and 0.156*1.16=0.18 ohm/1000 ft or 1/0 aluminum 0.160 /0.185 ohm/1000 ft.

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!