12/3 MC Vs 12 THHN in 1/2" EMT Cost Comparison

[dirtrunner0519]

I am about to start wiring my metal building, and everyone notes not to use Romex. I will be eventually furring all walls out with wood for the mezzanine going in. However, I am still pricing everything out Romex, 12/3 MC, 12 THHN in 1/2" EMT.

Metal Building- 30'x30'x24'. I will have 3 layers of circuits as in one row at 2', one row at 6', and one at 11.5'. This does not include misc. runs for garage door opener, lighting circuits at the ceiling. These are already installed with armor. Welding and heavy machinery circuits will be run with high rated cable.

Here are my numbers for some that are interested. I used all Home Depot pricing for Apples to Apples, that does not mean that a local wholesale supplier might not be cheaper. Although, I have found HD cheaper in emt and standard Romex etc then local wholesale, maybe due to buying power.

Here it is-
MC 12/3 for 500'- $272.00
12 THHN three conductor in 1/2" EMT 500'- $310.50
Romex 12/3 500'- $252.54

So to me it looks like MC cable is the cheapest option after Romex. Labor also is quite less due to Armor being a flex solution and there will be no bending required.

Please note the above pricing is just for wiring, this does not include boxes, hold downs, etc.

Opinions??

 

[mike93lx]

MC is not armor and does not protect wire anywhere near what EMT does. I think it is actually lumped in with romex from a protection requirement perspective.

If it is subject to damage, then conduit is the right answer

 

[alfredeneuman]

The same rule applies to MC cable as NM cable where protection against physical damage is involved. (It's supposed to be protected when surface mounted, unless it's out of reach)
You might just as well use Romex as MC.

 

[Bad Habit]

Keep in mind you can run multiple circuits in the EMT. Yes the wires would have to be de-rated, (While #12 can only be used with 20a overcurrent protection, it's still rated for 40a, THHN, for use when de-rating) but using a single home run conduit really simplifies getting multiple circuits across distances.

 

[aka Larry]

I did the same comparison when I did my metal building. I decided on EMT because it's easier to add components, and looks WAAAAAAAY better IMO. I'd never worked with EMT prior, but I found out it wasn't very difficult. Buy a bender, do some reading, practice on a couple of pieces, and have at it.

Here's a pic of my neighbor's shop done with MC. Could have done better for sure, but it just looks like **** IMO.

 

[alfredeneuman]

(While #12 can only be used with 20a overcurrent protection, it's still rated for 40a, THHN, for use when de-rating) but using a single home run conduit really simplifies getting multiple circuits across distances.

#12 THHN is rated for 30a (90 degree column) where derating is required, not 40a.
(You must be looking at the "in free air rating" instead of the "in conduit rating")

 

[dirtrunner0519]

I will look into getting some emt then and 12 THHN. Not my ideal option but from what everyone recommends it seems like it is the best.

 

[Bad Habit]

#12 THHN is rated for 30a (90 degree column) where derating is required, not 40a.
(You must be looking at the "in free air rating" instead of the "in conduit rating")

Yep, seemed strange to me, don't have to refer to ampacities as much as I use to and didn't pay attention to which table.

 

[wyliesdiesels]

I am about to start wiring my metal building, and everyone notes not to use Romex. I will be eventually furring all walls out with wood for the mezzanine going in. However, I am still pricing everything out Romex, 12/3 MC, 12 THHN in 1/2" EMT.

Metal Building- 30'x30'x24'. I will have 3 layers of circuits as in one row at 2', one row at 6', and one at 11.5'. This does not include misc. runs for garage door opener, lighting circuits at the ceiling. These are already installed with armor. Welding and heavy machinery circuits will be run with high rated cable.

Here are my numbers for some that are interested. I used all Home Depot pricing for Apples to Apples, that does not mean that a local wholesale supplier might not be cheaper. Although, I have found HD cheaper in emt and standard Romex etc then local wholesale, maybe due to buying power.

Here it is-
MC 12/3 for 500'- $272.00
12 THHN three conductor in 1/2" EMT 500'- $310.50
Romex 12/3 500'- $252.54

So to me it looks like MC cable is the cheapest option after Romex. Labor also is quite less due to Armor being a flex solution and there will be no bending required.

Please note the above pricing is just for wiring, this does not include boxes, hold downs, etc.

Opinions??

Everyone? Who is everyone?

And what is their reasoning?

As has been pointed out, youre no better off using MC if the reasoning is because of potential for damage.

Yep, seemed strange to me, don't have to refer to ampacities as much as I use to and didn't pay attention to which table.

What is strange?

 

[dirtrunner0519]

Everyone- AKA most of the threads I have found on GJ. Wire will not be in an area susceptible to damage at all. If it does get damaged then i have major issues beyond electrical.

 

[wyliesdiesels]

Everyone- AKA most of the threads I have found on GJ. Wire will not be in an area susceptible to damage at all. If it does get damaged then i have major issues beyond electrical.

Care to list the threads youre speaking of?

There is no prohibition on romex use in your application. So not sure what youre reading.

 

[dirtrunner0519]

Here are some examples- https://www.garagejournal.com/forum/showthread.php?t=226778
https://www.garagejournal.com/forum/showthread.php?t=357443
https://www.garagejournal.com/forum/showthread.php?t=23303

They all recommend the use of an EMT or armored cable. I would prefer to use romex, as i know it will not get damaged and will eventually be covered by shear walls.

 

[wyliesdiesels]

I only read the first link but no one in that thread said NOT to use Romex. Romex isnt prohibited in your applicarion.

And MC is not an armored cable.

If youre gonna use Romex make sure to use a grommet to protect the wire as it passes through the metal studs.

 

[Leaflessshadetree]

I'm using romex for all of the wiring done before insulating and finishing the walls.
I may use conduit for anything I add later.

 

[Leaflessshadetree]

I'm using romex for all of the wiring done before insulating and finishing the walls.
I may use conduit for anything I add later.

 

[wyliesdiesels]

Theres an echo in here.

 

[dirtrunner0519]

So i can use Romex then?

 

[mike93lx]

So i can use Romex then?

Sure, if it isn't subject to damage. Keep it in a wall. If it's exposed at working heights, use conduit

 

[teamextreme]

You don't list your location, (which you should) but the answer to this topic varies wildly depending on the local interpretation of the NEC's very vague rules of romex and MC not being exposed to physical damage. Some AHJ's interpret that to mean if you can see it, it's open to damage, others say as long as it's above a certain height you're ok, others say as long as it's inside a stud wall. You really need to find out what your local jurisdiction's rules are.

With a metal building though, if it were me, I'd be running EMT. One thing to consider, however, you say you'll be furring out wood walls "eventually". You definitely need to keep this in mind as to how will that will work with any wiring you install now?

 

[Aceman]

In metal buildings we use MC or 3/4" emt or a combination of both where it makes sense. I don't even use 1/2" emt, except for maybe the sleeves for T-stat wiring up to the hanging unit heaters.

3/4" holds a lot more wire and it's just as easy to bend as 1/2" in my opinion. It's also pretty easy to add a 50 amp welder circuit with 3/4" emt.

 

[sberry]

It is as easy, I understand Ace using 3/4 but I have never came back and wished I could add a welder circuit to someplace I had a 1/2 pipe. Main benifit of pipe is multiple circuits and can add switch wires.

 

[dirtrunner0519]

I am located in Socal. I will be using Romex, as all the walls will be covered with shear walls for the mezzanine once i get the design and permitting.

 

[dirtrunner0519]

Also 1/2" vs 3/4" EMT doubles at 3/4".

 

[dirtrunner0519]

Bringing back this thread, as I have still not decided which route to go. Can I use PVC conduit in lieu of the emt? My main issue here is that if i use Romex the walls will not be covered for a few months, and I do not want an accident to happen. MC cable just does not look neat when it is run, it will be buried eventually, via a shear wall.

Looking for recommendations

 

[tapered-pin]

Assuming you're not throwing anything sharp up against the cavities or installing the wall sheathing with a pneumatic nailer, there is nothing to worry about when using Romex wiring in a wall cavity that wont be "2 sided" for a few months.

You can use PVC, but it has it's own limitations for number of conductors allowed.
Metallic Clad cable is fine as well, but if you're going to end up covering up the wall anyway, it's silly to spend the money IMO.

NOTHING is gained by using something other than Romex.

 

[dirtrunner0519]

So my other question is then- Do I still use a metal box, the plastic ones do not seem to be built for exposed/surface mount?

 

[sberry]

Simply cover, even temp or rudimentary highly susceptible areas, this is not hi risk over short time. Use some Romex, it's not that big a deal. I have seen it get hit, wasn't a national disaster.

 

[sberry]

I saw it a while back, it was about 10 ft up on a switch loop and the handyman simply did a poor job of routing, would have been just as easy to move it a couple inches but the owner who was legally blind leaned a bunch of lumber up against it. Skinned the jacket. But there is lots of cable stapled in millions of garages against studs for decades, not saying it is right but if there isnt a scout troop or herd of maniacs tossing stuff against it till you get it sheated it can be fine, tack a fir strip in front of it etc.

 

[sberry]

Use plastic, once its covered it will be fine.

 

[tapered-pin]

So my other question is then- Do I still use a metal box, the plastic ones do not seem to be built for exposed/surface mount?

exposed is fine while waiting to cover them up..

to surface mount a plastic box after a wall is installed and "finished"? then you're right, steel boxes and EMT would be the way to go for that application.

 

[Crazyjake8493]

I would run Romex in the walls that will be finished later, and if you need to add something later on then surface mount in EMT. I've never been a fan of exposed PVC conduit indoors, looks like *** compared to EMT.

 

[sberry]

I will agree, usually looks like amateurs did it.

 

[finn]

Plastic requires that you run a separate green ground wire in the conduit.

Emt uses the conduit as the ground.

I used Romex along the ceiling for the lights, but emt for the outlets and switches when I enclosed and wired my shop lean to.

Emt looks better than Romex.