[RE-wrenches] Parallel Wire combining

[Daniel Young]

Essentially right.

 

The only thing you need to account for is the conduit run. If you run those 3x 1/0’s  for each leg in the same conduit, you then need to apply any applicable derates due to multiple current carrying conductors in a conduit, on top of any other conditions of use derates.

 

Or avoid that issue by having each parallel set of conductors in their own conduits. And, avoid having wires of different polarity/phase in separate conduits. I’ve heard of 3ph service entrances where all L1’s were in one metal conduit, then L2’s in a second metal conduit, L3’s in another, etc. The resulting electro-magnetic resonance between the conduits heated them to the point you could not lay your hand on the conduits. The separation of the wires by a metallic conduit acted like the iron core of a transformer (a crappy iron core) and heated up by the constant changes in the EMF. With DC, I would suspect that you would just essentially be building a full time electromagnet, not a heat issue, but might cause your clients to get a knock on the door by some boy scouts on an orienteering trip when their compasses all point to their house ;)

 

With Regards,

 

Daniel Young, 

NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90

NABCEP Certified Solar Heating InstallerTM: Cert #SH031409-13

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Bill Turberville
Sent: Tuesday, December 02, 2014 1:15 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Parallel Wire combining

 

I am sorry.  Bad fingers.  Three times the ampacity under the same conditions.

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Larry
Sent: Tuesday, December 02, 2014 12:09 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Parallel Wire combining

 

OK, let's use 1/0 for the example. 108,350 x 3 = 325,050. Do I now have a cable between 300 and 350 AWG?

Thank you,
 
Larry

On 12/2/14 10:51 AM, Bill Turberville wrote:

The minimum conductor size that can be paralleled, according to the NEC is 1/0.

 

William C. Turberville P.E.

President

Electrical Contracting Enterprises LLC

3080 Stage Post Dr ste 107

Bartlett, TN 38133

901-348-9230 ext 101 phone

901-289-6346 cell

901-348-2192 FAX

 

 

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jerry Shafer
Sent: Tuesday, December 02, 2014 11:45 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Parallel Wire combining

 

We have installed multible mcm 500 to meet this and there were three on each leg but that was because of the required size and bending room
Jerry

On Dec 2, 2014 7:43 AM, "Larry" <larry at starlightsolar.com> wrote:

Wrenches,

If I combine 3 conductors of equal length in parallel, is the resulting size equal to 3 times the Circular Mil area? For example, #4 is 42,080cm so are three #4's close to 2/0 (134,200cm) in size? Is it as simple as this? Assuming the conductors can not be removed individually, does this mean the current capacity is equal to the resulting wire size?

Thanks, Larry

 

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