MC cable used for power distribution?

[jsldesign]

Anybody ever seen MC cable used as a power distribution means from main switchgear (480V 3phz) to power distribution panels in an industrial facility?

I'm more of a controls / PLC / machinery kind of guy - don't deal with power distribution systems. I am doing some controls work at a client site and noticed the electricians pulling very large MC cable all over the building. I took a look at the electrical drawings - conduit and wire is detailed on the drawings, but the electricians say they use this large MC in place of conduit "all the time". These feeds are running from main switchgear to 800A distribution panels in some cases. Any thoughts on this?

 

[dpc]

It's permitted just about anywhere, exposed or concealed including hazardous locatons. Okonite makes their C-L-X up through 35 kV.

It is actually the preferred cabling method for EMI reduction in the feeders running from Adjustable Frequency Drive outputs to motors.

My experience with contractors is that they prefer conventional conduit and wire because they think it is less expensive, all things considered. But in Canada, it is much more popular. If you need to put a bunch of 90 deg bends in the circuit, it works much better than conduit, because you don't have to pull the wire.

 

[alehman]

As dpc said, MC is permitted by codes in many types of environments if installed correctly. Installation and supporting requirements are significantly different than conduit.

However, substitution of MC if cable in conduit is specified on the drawings should not be allowed unless approved by the engineer and owner. Some contractors will make this substitution without asking because it saves considerable labor. If they bid the job based on conduit as specified, the owner has good justification to make them remove it or provide a substantial credit. The owner may also want to verify that they are installing the specified conductor material (copper or aluminum).

 

[mc5w]

When I was wiring a factory back in the 1990s I really wished that I could get 200 amp MC cable but nobody in Akron, Ohio wanted to stock it. Pulling a 200 amp line is a bit like doing unmentionable things to an elephant. Fortunately, in this facility I was able to hook up a forklift truck to the pull line.

For some purposes MC cable has better grounding integrity because both the internal grounding conductor and the sheath are qualified grounding paths so that it can be sold to health care facilities. You have fewer joints that can come apart not not tightened by the installers.

 

[mc5w]

When I was wiring a factory back in the 1990s I really wished that I could get 200 amp MC cable but nobody in Akron, Ohio wanted to stock it. Pulling a 200 amp line is a bit like doing unmentionable things to an elephant. Fortunately, in this facility I was able to hook up a forklift truck to the pull line.

For some purposes MC cable has better grounding integrity because both the internal grounding conductor and the sheath are qualified grounding paths so that it can be sold to health care facilities. You have fewer joints that can come apart or not tightened by the installers.

 

[amazingmg]

CLX cable is used extensively in Phosphate Chemical plants and mining facilities in Florida.

I think the first use here was back in the late 70's. I always heard it was originally from Canada. "Black Anaconda" was the brand back then (haven't seen that one in a while). It is great stuff. Very durable. Even when the PVC jacket gets cut the metal armor (Aluminum) is continuous (no interlocking) so it remains impervious to acid, chemicals, weather, etc.
Note that there is a big difference between CLX and "Interlocked" armor cable. Interlocked armor is more like seal-tite in construction (spiral wrap of interlocked metal, although it still has the PVC jacket). A lower spec. cable. Contractors like to substitute it sometimes in place of CLX because of price or delivery.
The PVC jackets are color coded btw. Black is 600V. Yellow is 5KV. Red (sometimes looks pink) is 15KV.
Nothing new here. Actually very old school in industrial installations IMO.

 

[amazingmg]

Oh, I used a piece of CLX once to put in a feeder for a hot tub for a friend (a left over tail). The inspector questioned what the heck it was, but didn't red tag the installation.

 

[EEJaime]

Aside from the contractual implications of not installing the specified material and risking an engineer like myself walking in and telling them to "remove all of this and install it as specified" - there are certain environments where code specifically prohibits it's use. See NEC Article 334-Metal Clad Cable, 334-4 "Uses not permitted". Among those listed are: "...where exposed to destructive corrosive conditions such as direct burial..., in concrete, where exposed to cinder fills, strong chlorides, caustic alkalis, or vapors of chlorine or of hydrochloric acids, unless the sheath is suitible...etc....

I caution you to also be aware that 334(B)-10(Installation), there are several references to the need to support cables at not more than 6'-0" intervals, and that if they are installing this on a system designed for conduit, I doubt that the additional supports were added.

Good luck, but I definetely would get this cleared by the Engineer of Record and the Owner's representative.

 

[resqcapt19]

mc5w,

For some purposes MC cable has better grounding integrity because both the internal grounding conductor and the sheath are qualified grounding paths so that it can be sold to health care facilities.

The metal outer jacket of the commonly available MC, that with the interlocking armor jacket, is not suitable for use in areas of healthcare facilities covered by 517.13 in the NEC. The code section requires the use of a outer metallic jacket that is suitable for use as an equipment grounding conductor. The outer jacket of the interlocking armor is only suitable for use as an equipment grounding conductor when combined with the internal equipment grounding conductor. See 250.118(11). Type AC is suitable for this application, because its outer metal armor is suitable by itself as an EGC. Also MC cable with smooth or corrugated tube type of armor is also suitable for this application, but those types of MC and not anywhere near as common as the interlocking armor type.
Don

 

[amazingmg]

Good points, Jamie.

However you neglected to include the part in that NEC section that talks about the sheath or suitable protection.....

.....MC cable shall not be used where exposed to the following destructive corrosive conditions, unless the metallic sheath is suitable for the condtions or is protected by material suitable for the conditions

CLX comes with a PVC jacket. What else would you install in an environment that had some of the chemicals listed in the code or even just harsh chemicals? Short of using stainless steel conduit (which might not be adequate either), PVC coated GRS pipe would be the next best thing. But, now we are comparing PVC coated MC cable to PVC coated pipe?

It all depends on who you are working for and what the industry or situation is. Of course, I wouldn't suggest changing a spec. on the fly without some authorization from the customer/client.

MC cable is a very viable alternative to conduit and wire. Not only that, in some installations it would be short sighted not to use it.

From HW&C 2002 Catalog for applications of 15KV impervious continuously welded armor power cable:

"Application: For use in harsh enviroments where maximum conductor protection is required. Used for primary power and feeder circuits in a broad range of commercial and industrial power distribution systems. Approved for use in wet or dry locations at 105deg C, for installation indoors or outdoors, aerially, in conduits, ducts, cable trays or direct burial in circuits not exceeding 15000 volts.
Impervious continuously welded and corrugated aluminum armor cable is recommended as an economical alternative to wire in conduit systems."

 

[mc5w]

1. Interlocking armor cable for health care facilities has an aluminum grounding strip in contact with the armor as well as the insulated copper grounding wire.

2. According to buddies of mine who do million dollar industrial electrical jobs, any kind of stainless steel, bronze, brass, or schedule 40 copper pipe is NOT going to be UL listed. You would have to persuade the electrical inspector to allow National Sanitation Foundation listed pipe. However, the NSF listing for stainless steel pipe a tube is more stringent in regard to internal smoothness than Underwriters Laboratories because these pipes are also used for liquid foods and need to be cleanable on both the inside and outside.

 

[amazingmg]

. According to buddies of mine who do million dollar industrial electrical jobs, any kind of stainless steel, bronze, brass, or schedule 40 copper pipe is NOT going to be UL listed. You would have to persuade the electrical inspector to allow National Sanitation Foundation listed pipe. However, the NSF listing for stainless steel pipe a tube is more stringent in regard to internal smoothness than Underwriters Laboratories because these pipes are also used for liquid foods and need to be cleanable on both the inside and outside.

Was this comment in regards to my mention of stainless steel pipe? To clarify, I have only seen SS pipe used for conduit in Brewerys (as much for looks as anything). I was simply trying to think of anything that might come close to the durability and impervious characteristics of PVC jacketed MC cable to make a point......there isnt' much. If you find something that destroys CLX in a SS tray, then you are in trouble.

 

[resqcapt19]

mc5w,

1. Interlocking armor cable for health care facilities has an aluminum grounding strip in contact with the armor as well as the insulated copper grounding wire.

That is type AC, not type MC.
Don