Paralleling Wire

[Alwayslearningelec]

What does that mean when you run parallel sets?

 

[ohmhead]

What does that mean when you run parallel sets?

Well its what it says parallel two or more conductors that share the current flow or amps in circuit .

Two or three or more together is able to handle that current better then one as the size of the wire alone of one wire .

 

[Smart $]

What does that mean when you run parallel sets?

One set is the minimum number of current-carrying conductors required for a circuit to operate as designed, whether it be service, feeder, branch, motor, etc.

Parallel sets simply indicates multiple sets, with the purpose of serving as a larger-sized-conductors single set.

 

[iwire]

What does that mean when you run parallel sets?

Once you get to about 300 amps you can choose to run multiple conductors of the same phase to make terminating them easier. For 300 amps I could run a single set of 350 Kcmil copper or two sets of 1/0 copper.

Another example if I had a 600 amp feeder to run here are just some of the combinations I could use.

• One set of 1500 Kcmil copper (625 amps x 1)
  
• Or two sets of 350 kcmil copper (310 amps x 2)
  
• Or three sets of 3/0 copper (200 amps x 3)
  
• Or four sets of 1/0 copper (150 amps x 4)

Often it costs less to use more wire of smaller sizes, it is worth running the figures for each job.

 

[jumper]

Once you get to about 300 amps you can choose to run multiple conductors of the same phase to make terminating them easier. For 300 amps I could run a single set of 350 Kcmil copper or two sets of 1/0 copper.

Another example if I had a 600 amp feeder to run here are just some of the combinations I could use.

• One set of 1500 Kcmil copper (625 amps x 1)
  
• Or two sets of 350 kcmil copper (310 amps x 2)
  
• Or three sets of 3/0 copper (200 amps x 3)
  
• Or four sets of 1/0 copper (150 amps x 4)

Often it costs less to use more wire of smaller sizes, it is worth running the figures for each job.

Bob, good example, but the code on parallel wires is not based on amperage. 310.4 says 1/0 or bigger. Yes this is approximately 300 amps with 2 1/0 cu per phase.

I am only writing this for OPs benefit, I understand that you know this. I am not trying to be a smart aleck.

 

[Rockyd]

Don't forget to consider the labor factor(s) involved for each method(s) in number of men to manage the pull(s). Hate to see a money slip away over labor just because the wire was cheaper, but the sum total didn't balance to your favor!

 

[iwire]

Don't forget to consider the labor factor(s) involved for each method(s) in number of men to manage the pull(s).

I agree, that is why I say run the numbers, if it is PVC going a trench labor for an additional conduit is minimal.

OTH running an additional PVC coated RMC in a tight location could be very expensive.

 

[Alwayslearningelec]

Got it, thanks very much. As far as terminating I guess they still get terminated under the same lug, if its additional wires?

 

[don_resqcapt19]

Got it, thanks very much. As far as terminating I guess they still get terminated under the same lug, if its additional wires?

Only if the lug is listed for use with more than one conductor. Many are not.

 

[Volta]

But you would need to use the same type of lug, so as to terminate the conductors comprising each phase as identically as possible.

 

[growler]

Got it, thanks very much. As far as terminating I guess they still get terminated under the same lug, if its additional wires?

It also depend on where you are terminating these conductors. There may be a bus with serveral lugs per phase. With a very large service there can be many parallel runs to terminate both at the transformer and the switch grear. For a smaller service there can be a multi-tap type lug on the main breaker, you will see lots of double lugs but I'm thinking they got to around 6 termination for a lug ( different spaces, same lug ). These need to be purchased for the breaker used.

 

[Alwayslearningelec]

Growler I was just goging to ask that. I would think that the standard breaker etc would only have enough for one set. Where would the other set get terminated?

 

[iwire]

Growler I was just goging to ask that. I would think that the standard breaker etc would only have enough for one set. Where would the other set get terminated?

Any breakers above 200 amp frame size are going to come with options as far as the terminals go.

For example an 800 amp breaker might have 3 different lug kits available.

You might have the following options.

• Two barrel lug for two - 750 kcmils or less
  
• Three barrel lug for three - 500 kcmils or less
  
• Four barrel lugs for four - 350 kcmils or less.

This is why planing is important, you need to make sure to coordinate the breaker terminals with the number and size of the conductors you plan to run,

 

[jzadroga]

Once you get to about 300 amps you can choose to run multiple conductors of the same phase to make terminating them easier. For 300 amps I could run a single set of 350 Kcmil copper or two sets of 1/0 copper.

Another example if I had a 600 amp feeder to run here are just some of the combinations I could use.

• One set of 1500 Kcmil copper (625 amps x 1)
  
• Or two sets of 350 kcmil copper (310 amps x 2)
  
• Or three sets of 3/0 copper (200 amps x 3)
  
• Or four sets of 1/0 copper (150 amps x 4)

Often it costs less to use more wire of smaller sizes, it is worth running the figures for each job.

These numbers are based on running 1 set per conduit right? If they were in the same conduit there would be derating.

 

[growler]

This is why planing is important, you need to make sure to coordinate the breaker terminals with the number and size of the conductors you plan to run,

Very good point, there really is a lot of planning that needs to go into a job. Little things like not having the right lugs ( cost of lugs ) don't mean much as far as the bid but it sure can cause some delays on the job and any delay is lost labor cost.

Years ago I noticed something that really bothered me. On a normal commercial job lots of 1900 boxes are used and some of the screws are missing. Guys would go and take screws out of new boxes to use on the boxes missing screws becuse no one thought to purchase extra 8-32 screws and now you have even more boxes with missing screws. How much labor does it take to pay for a couple boxes of extra screws?

This stupidity may only happen in the South ( and maybe on just some jobs I have been on ) I really don't know. It's a little thing but guys running around looking fors screws to attach a plaster ring or cover plate?