NM versus MC versus steel MC

[winnie]

This verges on a DIY question, and I will not be offended if a moderator closes the thread. In this case I am acting as a homeowner specifying work to be done. I am not asking for instructions on how to do this work.

I hold an 'aesthetic' opinion that metal armor cable is 'better' than NM. I am trying to figure out if this is illusory or if there is real benefit.

In my new (old) home, the earliest wiring uses AC cable, without a bonding strip. The armor itself is much more substantial than modern aluminum armor MC cable.

In a single family residence, where NM may be used, what (if any) would the benefits be to specifying MC cable? Would it make any sort of real difference in the performance or safety of the installation, or would it just add $$$ to any work done, without real benefit.

Does the thin aluminium 'armor' on 'MC-lite' provide any better protection for the conductors than the plastic on NM?

Is modern steel armor MC any tougher than the aluminium armor, or have they learned to make the steel very thin?

As best I can determine, the 'code' benefits are that MC cable could be used between a normal breaker and an AFCI receptacle (where AFCI is required), and that MC cable could be run across joists in an exposed basement without a running board.

Specifically asking the professionals: what do you do in your own home? Do you run EMT even though you are not in Chicago?

Thanks
Jon

 

[kwired]

There is no doubt it takes more force to cause damage to even light aluminum sheath then to the thin plastic sheath of NM cable.

Then you must also consider just how much is exposed to any potential damage and whether the higher cost MC is worth the expense when NM is acceptable code wise and has little risk when run in covered locations.

If you have a location where severe physical damage is likely - neither is acceptable.

 

[junkhound]

what do you do in your own home?

betcha I'll catch flak for the cross joist EMT usage:

In own home all the runs across basement joists are in EMT.

Why? because the EMT is a nice support for lumber, conduit, pipe, and moulding stored between joists, and wife likes to hang clothes on all those EMT 'clothes rods' as she takes clothes out of the dryer. Do know NEC prohibits conduit from supporting boxes, but there is a lot of non-electrical stuff it can support also (grin).

oH, yeah, to be PC, I take clothes out of the dryer also , to dispel any notions of sexism in jobs, eh?

We built our entire home 100% DIY: where there are 2 or more 20A NM runs to similar locations, most are run in EMT, then branch out, actually saved a few buck in material. Far end of house is 70 ft from service. Have 6 subpanels, all served by EMT - 1.5" and 1" EMT.

All 30A or larger circuits are in EMT with a few MC terminations such as water heater, heat pumps, AC, etc.

One caveat: We had access to surplus THHN and THWN wire spools ends at $1.00 pound, and EMT and fittings for 25 cents a pound, sure made sense to maximize EMT with NM at the time being $50/250' or so to use EMT.

PS: also understand if moderator wants to delete.

 

[growler]

In my new (old) home, the earliest wiring uses AC cable, without a bonding strip. The armor itself is much more substantial than modern aluminum armor MC cable.

In a single family residence, where NM may be used, what (if any) would the benefits be to specifying MC cable? Would it make any sort of real difference in the performance or safety of the installation, or would it just add $$$ to any work done, without real benefit.

Well MC cable with metal boxes and fitting resist rodents much better than NM.

Will you even see any benefit to wiring with MC? I doubt it.

Call your insurance carrier and see if they would give a better deal for a home with MC cable. Remember that insurance normally will not cover rodent damage.

 

[petersonra]

There are a lot of installations wired in NM that never have any issues at all.

But, if it is exposed or otherwise potentially subject to damage you might gain some protection by going with MC or EMT. My suspicion is that MC is not a whole lot better then NM as far as being protected other than rodent damage, and that is generally not all that much of a problem, although I am sure it has been for some people now and then. But, it is relatively rare.

EMT provides more protection.

I am not a huge fan of MC where it can get caught on something. I am not saying it is a bad idea, but the cost of running it is not much less than EMT and I suspect EMT is a more robust installation.

Now if you are running it through metal framing or joists MC might well be a lot easier to install than EMT and might be cost effective.

Personally, for most residences, any of these wiring methods seems acceptable to me.

 

[ActionDave]

I wired my house in NM. If I were going to spend the money for any kind of upgrade, and that is a big if, I would use AC, its tougher than MC and you don't have to mess with EGC.