MC Cable

[rich000]

Can MC cable (14-2) be used to wire a residential garage?

Article 330 says it can be used as open runs of cable not subject to physical damage.

Rather than fish wires through walls, the MC cable would be run exposed to supply electrical outlets.

Also, there is no seperate ground wire, just the bonding wire. Is this considered ground along with the outer sheath and would you connect the bond wire to the receptacle's ground point?

Thanks.

 

[chris white]

Re: MC Cable

Type MC cable has a full sized insulated (green) grounding wire. Type AC uses the armor plus a bonding wire for the equipment ground. If that's what you're using, you cut off the wire, bend it back over the armor before you put on the connector. Use a separate jumper(green or bare) the same size as your circuit conductors to connect from your receptacle's green screw to the outlet box.

 

[physis]

Re: MC Cable

Where I'm at we're not allowed to use MC in the garage if it's exposed. We have to use EMT.

As far a grounding, 330.40 (listed connectors) acheives sheathing bonding. The green wire is treated as any other grounding conductor.

The sheath must be grounded but can not be used as a grounding conductor.

 

[ryan_618]

Re: MC Cable

250.118 in the '99 NEC item (11) says that the sheath can be used as an egc.

 

[don_resqcapt19]

Re: MC Cable

ryan,

250.118 in the '99 NEC item (11) says that the sheath can be used as an egc.

You must read all of the details in the section. The armor for MC can be used as an EGC, only if listed and identified for use as an EGC. Look at 250.118(11)(a). For the interlocking armor(most common) type of MC cable the armor is used in combination with an internal EGC. This type of armor is never suitable by itself as an EGC. The smooth or corrugated tube (rare) types of MC cable the outer armor in itself may be suitable for use as an EGC if so listed.
Don

 

[don_resqcapt19]

Re: MC Cable

Ryan,
I'm sorry. Your post did specify the '99 code and I missed that. I am looking at the 2002 code. The wording was changed to reflect the fact that the armor of the interlocking tube type of MC cable is not listed for use as an EGC.

(11) Type MC cable where listed and identified for grounding in accordance with the following:
a. The combined metallic sheath and grounding conductor of interlocked metal tape?type MC cable
b. The metallic sheath or the combined metallic sheath and grounding conductors of the smooth or corrugated tube type MC cable

From the UL Guide for MC PJAZ

... The equipment grounding conductor required within a cable with interlocked metal tape sheath may be insulated or bare and may be sectioned. Any additional grounding conductors have green insulation. ...

Don