MC Cable as Panel Feeders

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I need to run 4 200 Amp 120/240 Panels in a building that requires either the SER to be completely covered by Sheetrock or use metallic cable.

Question is, Is 2/0 CU MC Cable acceptable for Feeders?? My concern is that the Grounding conductor is only a #6, don't I need a #4 or is the combination of sheathing and grounding conductor make up for the #4 or is #6 sufficient?

Thank You,

Kris Quinn QEC
 
Re: MC Cable as Panel Feeders

That is because 2/0 cu is to small for a 200 amp feeder unless you are able to use Table 310.15(B)(6).

If you want to use an MC feeder for a 200 amp panel you will have to run 3/0 MC in order to get the 4 AWG ground.

You would have the same problem with SE cable.
 
Re: MC Cable as Panel Feeders

Originally posted by websparky:
6AWG is OK for eg for 200A
Click to expand...
DOH! :eek:

Your correct I did not even look at the table. :eek:

I am used to running 225 amp panels with 4/0 MC which require a 4 AWG EGC.
 
Re: MC Cable as Panel Feeders

I will be using Table 310-15(b)(6) and fusing the panels at the service entrance at 200 AMPS and running 2/0 MC Am I missing something and assuming that I am OK
 
Re: MC Cable as Panel Feeders

Kris, if you meet the criteria of 310.15(B)(6) the article section, you can use the table.

Roger
 
Re: MC Cable as Panel Feeders

George, You nailed it! It is a 4 unit apartment building with electric furnaces (Dont ask, he has gas on the premises, typical cheap land lord).

I could run SER but it would involve a lot of framing around some chases to get to the basement.
 
Re: MC Cable as Panel Feeders

:)

Pre-made cable is made with code in mind, at least everytime I second-guess SER and the like it's on the money.

Describe your problem a bit more? It has to be that protected the whole way? That's kinda weird.
:confused:

The most stringent fire code I've come across yet allows me to pull SER if sleeved at firewall penetrations with RMC with SER volume of the sleeve no greater than 55% and the other 65% filled with fire-caulk. Other than penetrations, it seems that you'd be firewalling for your SER itself? Sounds a little (lot) extreme.

Knowing what it's like pulling SER, I can't imagine how much fun it would be to drag x/0 MC cable through a unit. Jeez!

[ December 17, 2004, 08:22 AM: Message edited by: georgestolz ]
 
Re: MC Cable as Panel Feeders

By the way Thank you all for your interest.I stumbled upon this site accidentally and I am amazed by the wealth of info.

The AHJ informed me that the building is rated 3e or 3r and therefore I could use SER but it would have to be enclosed by 3 HR rated all the way through. This is not a problem for the 4 individual units above but getting through the stores on the 1st level to get to the basement involves some drop ceiling and open chases. It makes more sense to run armored and call it a day.

We ran all the branch circuits in AC If I dont respond again til later My Day Grabbed a hold of me and I will return.

Thanks again
 
Re: MC Cable as Panel Feeders

I have a question for you bigger cable pro's. I see this come up from time to time. Ryan, not long ago, called someone (I wont say) on an undersized EGC in MC for a range.

What's the deal with cable not having a EGC big enough to handle an application? Are these situations unusual or can I expect that the EGC is often too small to be legal in a cable?
 
Re: MC Cable as Panel Feeders

No most times the equipment ground in a cable is the correct size, as long as you are working from 310.16.

Once you use Table 310.15(B)(2) you must be careful.

If you increase the size of a cable for voltage drop you may run into problems with the EGC size and 250.122(B) which calls for the EGC to increase in proportion to the circuit conductors.

Also if you want to run cables in parallel say two 3/0 cables for 400 amps the EGC will be to small unless protected by a GFP breaker.
 
Re: MC Cable as Panel Feeders

So you're saying most cable is made with an EGC to satisfy 250.122 Ta. based on the ampacities of
of 310.16 Ta.?

Would that be the 90? column or are there further issues there?

Just using an arbitrary example. If I was going to run a 105 amp circuit using the 90? column from table 310.16 I can use #3 CU. and table 250.122 requires a #6 EGC. Is that what I would typically find in a cable?
 
Re: MC Cable as Panel Feeders

Originally posted by physis:
If I was going to run a 105 amp circuit using the 90? column from table 310.16 I can use #3 CU. and table 250.122 requires a #6 EGC. Is that what I would typically find in a cable?
Click to expand...
Yes 3 AWG cable has a 6 AWG EGC.

Cable sizes 14, 12 & 10 AWG all have full size grounds.

8 AWG cables have a 10 AWG EGC

6 & 4 AWG cables have a 8 AWG EGC.

3 AWG to 2/0 cables have a 6 AWG EGC.

3/0 & 4/0 cables have a 4 AWG EGC.

I have not worked with larger than 4/0 MC.
 
Re: MC Cable as Panel Feeders

Originally posted by physis:
Just using an arbitrary example. If I was going to run a 105 amp circuit using the 90? column from table 310.16 I can use #3 CU
Click to expand...
By the way you can not run a 105 amp circuit with 3 AWG.

It is unlikely you will find 90 C rated terminals to permit you to use that column except for derating purposes.

3 AWG CU maxs out at 100 amps for most uses.

[ December 18, 2004, 06:48 PM: Message edited by: iwire ]
 
Re: MC Cable as Panel Feeders

You can do that by just tightening the terminal screws a little extra can't you? :D :D
 
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