Parallel conductor ampacity
- Thread starter laketime
- Start date
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Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
Yes, if there is no derating required.
- Location
- Logan, Utah
You are correct.
Chris
Chris
Volta
Senior Member
- Location
- Columbus, Ohio
Yes, allowed that way by Code.
Personally, I don't like to use every bit of the allowable ampacity of parallel wires. Clamp an ammeter on them sometime and you'll likely see that they are not carrying precisely the same current. That means the one with better connections carries more than its share, not a big difference, but I like to allow a few extra percentage points for that reason.
A circuit of two 3/0s carrying 400 amps would almost always force one wire to carry more than its rated 200 amps @ 75 degrees.
In your example, you'll not likely load and protect the wires at 460 amps, so it would be a fine design, in my opinion.
Personally, I don't like to use every bit of the allowable ampacity of parallel wires. Clamp an ammeter on them sometime and you'll likely see that they are not carrying precisely the same current. That means the one with better connections carries more than its share, not a big difference, but I like to allow a few extra percentage points for that reason.
A circuit of two 3/0s carrying 400 amps would almost always force one wire to carry more than its rated 200 amps @ 75 degrees.
In your example, you'll not likely load and protect the wires at 460 amps, so it would be a fine design, in my opinion.
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