parallel feeds using MC

[nakulak]

I want to run some parallel feeds using MC. I've always done it in conduit before, but in this particular application MC is definitely the way to go (several 400A panels 208/y120 -hotel 2nd, 3rd 4th floor riser panels). Any issues with this installation that I'm overlooking ?

 

[tkb]

Undersized grounds

 

[infinity]

As Tim said you'll need an EGC in each parallel cable based on the size of the OCPD protecting the feeder. You might end up needing cables with a full size EGC in each one.

 

[RUWired]

Southwire lists there mc feeder cables on this chart. You would have to custom order the correct size ground.

http://www.southwire.com/flashapps/ElectricalCatalog/MCCatalogPage.html

 

[iwire]

If you have the pulling equipment maybe go single runs. Of course easy to say from here without seeing what kind of route you have to go.

 

[nakulak]

that's what I was worried about, thanks for the heads up

 

[mcclary's electrical]

Also, you have no way of proving each cable is equal distance, as you would in conduit

 

[LarryFine]

Also, you have no way of proving each cable is equal distance, as you would in conduit

Other than knowing how and making sure.

 

[Alwayslearningelec]

What is a parallel run?????? I heard of wire being ordered paralled before....

thanks.

 

[nakulak]

What is a parallel run?????? I heard of wire being ordered paralled before....

thanks.

sometimes its cheaper (for a variety of reasons) to install some sets of conductors in lieu of (whatever the correctly sized set of 1 set is). its called parallel sets. (310.4, 250.122 F)

 

[mcclary's electrical]

Other than knowing how and making sure.

I'm confident he could cut themthe same lenghth. I meant he would have no way of proving it to the inspector.

 

[LarryFine]

I meant he would have no way of proving it to the inspector.

Okay, just for fun, let's look at it from the other side: If you were an inspector, what would you accept as proof?

 

[shaw0486]

I ve done it and never had any problems with the ground

 

[iwire]

I ve done it and never had any problems with the ground

Regardless of you having 'no problems' it is still an NEC violation.

 

[iwire]

What is a parallel run??????

If you had a 3000 amp service what size conductor would you have to run if you did not run parallel sets on each phase?

 

[mcclary's electrical]

Okay, just for fun, let's look at it from the other side: If you were an inspector, what would you accept as proof?

If I could lay my eyes on it for it's entire run, and if it had the correct size ground, I would pass it. But if they disappeared for a long run through an attic or something, at that point, you cannot prove they are of equal length, as you could with conduits.

 

[iwire]

If I could lay my eyes on it for it's entire run, and if it had the correct size ground, I would pass it. But if they disappeared for a long run through an attic or something, at that point, you cannot prove they are of equal length, as you could with conduits.

When a conduit runs out of sight how would you know how it was run?

It's called a rough inspection here.

 

[don_resqcapt19]

If I could lay my eyes on it for it's entire run, and if it had the correct size ground, I would pass it. But if they disappeared for a long run through an attic or something, at that point, you cannot prove they are of equal length, as you could with conduits.

Sure you could...you could use a TDR or short two conductors of each set together at one end and use a micro-ohm meter at the other end and compare the resistance. In most cases, you can have a 5 to 10% difference in the conductor lengths without overloading the shortest set of conductors.

 

[wawireguy]

Is there a exception for grounds included in cable assemblies somewhere? I foggily recall something about neutrals or grounds that could be undersized if they were in a cable assembly. I could be way off on that one..

 

[petersonra]

Is there a exception for grounds included in cable assemblies somewhere? I foggily recall something about neutrals or grounds that could be undersized if they were in a cable assembly. I could be way off on that one..

A long time ago. but not now.