EMT versus Flex versus grey conduit

[green.bubbly]

Getting ready to wire the inside of my 24x24 Mueller steel garage. Can anyone give me the pros and cons of using either the grey PVC conduit, EMT conduit and the flex cable conduit?

I am leaning towards the grey PVC since it seems to be the easiest to work with with my skill level. The flex tubing looks like it would be a ***** to cut and attach clamps to and I do not have a tubing bender for the EMT. This will be a simple wiring job, some 120 receptacles, a few lights and a garage door opener. I may run two 220 circuits for future use.

I plan on running the conduit behind OSB walls. I was planning on having four receptacle circuits, one for each wall with about 7 receptacles on each circuit. I have plenty of 14-2 and 12-2 wire already purchased. Any other thoughts or concerns would be greatly appreciated.

 

[Charles (in GA)]

When you say you have already purchased 14-2 and 12-2 I guess you mean you have purchased Romex house wire. This is a horrible choice if you intend to run wire in conduit. Romex cable is a real bear to pull in conduit, and you will be cussing all the way thru the first pull, and will probably quit after that. It just isn't worth the effort. In conduit you need to be pulling loose THHN wire from spools with a fish tape.

As far as conduit type, with PVC you either need a special (expensive) heater type bender to form the PVC with, or you end up gluing pipe, sweeps, ells, and such together. End result may not be a very neat job and may not be very easy to pull wire in either. (all of those joints don't help at at all inside the conduit)

With PVC you have to pull a ground, while with EMT you have the option not to, even though I recommend it for a couple of reasons. EMT is not difficult to bend after you waste a section or two learning, and the bender is quite inexpensive. You get less joints for a smoother, easier pull.

This is the best info I've found for how to on bending EMT.

http://www.mikeholt.com/documents/freestuff/BendingRoundRaceways.pdf

You could use MC or BX metal jacketed flexible cable. Not real nice looking, but it works.

Charles

 

[green.bubbly]

Correct, it is Romex that I have but it is no big deal if I have to purchase THHN as I will be using the Romex on my house anyway. I have never had to deal with conduit and I did not even think about it being a pain to pull Romex through conduit.

Thanks for the link on bending EMT, definitely saved that pdf.

 

[Qckrun]

Get a licensed electrician, enough said.

 

[green.bubbly]

Get a licensed electrician, enough said.

Qckrun
Junior Member

Join Date: Apr 2011
Posts: 1


You were holding up on your first post to tell me this?


Care to chip in a few bucks to pay him?

 

[HoseB]

Care to chip in a few bucks to pay him?

If you're thinking it's OK to pull romex through conduit, I can only imagine the other "shortcuts" you'll be taking.

Pay a licensed electrician for an hour of his time to inspect your plans before you start. This will save you the expense/aggrevation of doing everything over again (or save your shop from fire).

 

[green.bubbly]

If you're thinking it's OK to pull romex through conduit, I can only imagine the other "shortcuts" you'll be taking.

Pay a licensed electrician for an hour of his time to inspect your plans before you start. This will save you the expense/aggrevation of doing everything over again (or save your shop from fire).

I took two years of electrical in high school and am very capable of doing wiring but have never used conduit. I am not claiming to be a code expert but I am confident in my knowledge and experience enough to not worry about fires.

 

[HoseB]

Two years of electrical in high school?!? Aww heck, why didn't you say that in the first place? Go for it!

 

[Delta74]

Use the PVC, make drops into the wall, and use a 90 at the top hooked up to a 4x4 box, use the romex in the attic and tie into the loose wires, there ya go, easy to access any wires, can pull new feeds as you need them and keep expanding and not need the PVC everywhere, bit of both worlds, and forget the expensive PVC bender, use a propane torch with a fan head, or better yet fire up the BBQ, keep rolling the pipe and heat the pipe till its soft and form your weird angles, if ya get it wrong, re heat the pipe, and try again, when done the BBQ is hot put the steaks on, grab a beer.

oops forgot, you could use the ENT thats the corrigated pvc pipe, its easy to work with, connectors and couplings just Push on ( with elbow grease ) but there a bear to remove, but the stuff is really flexible.

 

[green.bubbly]

Two years of electrical in high school?!? Aww heck, why didn't you say that in the first place? Go for it!

My point was that I do have some electrical training and years of experience. This is a simple straight forward electrical project on a detached garage. I am not trying to take a job away from a licensed electrician. Am I to assume you hire out professionals for every job you do around your house in a field you are not certified?





Is there a specific code that forbids using Romex in conduit?

 

[mrb]

Pay a licensed electrician for an hour of his time to inspect your plans before you start. This will save you the expense/aggrevation of doing everything over again (or save your shop from fire).

i always see people making suggestions like this. Has anyone successfully hired an electrician for an hour to look over their DIY work? I cant imagine any electrical contractor putting his livelyhood on the line in this fashion (as a professional, he can be liable for things the diy did based on his instruction)

 

[mrb]

Is there a specific code that forbids using Romex in conduit?

no but fill has to be taken into consideration based on the total area of the cable, not the 2 or 3 wires inside it. and its just a bad idea.

 

[HoseB]

Am I to assume you hire out professionals for every job you do around your house in a field you are not certified?

Hell no. I do all my own work, to include plumbing & electrical. I'm certified in neither. But I do know not to put romex in conduit.

 

[HoseB]

i always see people making suggestions like this. Has anyone successfully hired an electrician for an hour to look over their DIY work? I cant imagine any electrical contractor putting his livelyhood on the line in this fashion (as a professional, he can be liable for things the diy did based on his instruction)

I did a complete service upgrade on my shop (60a to 100a) and had an electrician friend check it out. He gave it the and didn't charge me. I offered to pay, but he declined. (And he couldn't believe that a booger-eater like me was able to do such a nice job inside the panel).

 

[Delta74]

Some home owners do a hell of a nicer job then the pro's, anyway other bad reason for Romex inside conduit other then fill, if your inspector has a bur up his *** that day, he could give you grief that its not secured properly to the box,( no connector ) not straped down and want it de rated ( hey I got some right dicks around here for inspectors) cause its in the conduit and cant radiate heat when under load.

 

[green.bubbly]

Use the PVC, make drops into the wall, and use a 90 at the top hooked up to a 4x4 box, use the romex in the attic and tie into the loose wires, there ya go, easy to access any wires, can pull new feeds as you need them and keep expanding and not need the PVC everywhere, bit of both worlds, and forget the expensive PVC bender, use a propane torch with a fan head, or better yet fire up the BBQ, keep rolling the pipe and heat the pipe till its soft and form your weird angles, if ya get it wrong, re heat the pipe, and try again, when done the BBQ is hot put the steaks on, grab a beer.

oops forgot, you could use the ENT thats the corrigated pvc pipe, its easy to work with, connectors and couplings just Push on ( with elbow grease ) but there a bear to remove, but the stuff is really flexible.

Thanks for this information. Now I am more informed and hungry.

no but fill has to be taken into consideration based on the total area of the cable, not the 2 or 3 wires inside it. and its just a bad idea.

Thanks. It will only be one run per conduit but being that the runs will be fairly short and not much wire will be needed, I will purchase some THHN and make it easier to pull. The fact that I had rolls and rolls of Romex, I just never considered buying THHN.

 

[gatchel]

Some home owners do a hell of a nicer job then the pro's...

If you hang out here and pay attention to some of the posts here, you'll end up knowing more than some "pro's" and some "inspectors".

 

[Underdog]

If you're thinking it's OK to pull romex through conduit, I can only imagine the other "shortcuts" you'll be taking.

Pay a licensed electrician for an hour of his time to inspect your plans before you start. This will save you the expense/aggrevation of doing everything over again (or save your shop from fire).

Unless you have an electrician as a Friend, I doubt any electrician is going to offer advice then worry about how you carry out that advice. Before the flames I took a class for My master electrical license exam from Mike Holt himself back in the 80's.

Electric wiring is pretty straight forward with common sense. With a little help from this board and other places the OP should do just fine.

 

[Falcon67]

The "secret" to Romex in conduit is to use larger conduit. LOL. Actually, the way I use it is to do standard runs in the attic, then use a busing in the top of a conduit stub that drops down into the wall area below the ceiling. Note - I've only done stick built stuff. But they are also right - if you have more than one cable in that run you'll be 10x better off pulling individual wires.

STRIKE->> You can also strip long runs of Romex if you have that much extra time. If it's a full conduit install, sell the Romex and go get 500' spools.

See answer by MRB - not allowed.

 

[Zeke]

Well, he said he could use the Romex in his house, so he won't have to sell it.

Stripping long runs is not all that hard with the correct tool. I don't think anyone pointed out specifically that he can use romex in a steel building behind walls with the proper hardware. I'm not sure where to find the code and I don't have a very new NEC, but it was last I knew OK to use romex above 8' properly supported. Might want to look into that.

Lastly, green.bubbly, you really don't need to defend or justify yourself when the dogmatic contingent is barking. Like the poster said, the GJ bbs can help with most all questions and procedures. Like you, I have some training in electrical and at least passed the electrical part of the GC test in CA which ain't no joke. But I don't pretend to know all what a journeyman sparky knows.

PS, if you actually bend PVC with heat for any reason, put about 5lbs of air inside to keep the walls from collapsing. You can make an adapter for that low of pressure out of almost anything.

 

[mrb]

you cannot strip the jacket off romex to use the wire that was inside. The wires in romex are not marked and may not be used by themselves.

 

[Aceman]

I'm constantly amazed at how many people want to pull Romex into conduit or even try and strip the sheath off to just use the wires inside.

Does anyone value their time?

Since it sounds like most of the OP's electrical is behind OSB, I'd suggest MC cable. Leave the stubouts long enough that it'll stick through the OSB and be able to make up in the box. Make sure you holesaw your holes through the OSB in the correct locations to line up with the KO's in the boxes you'll be using.

 

[green.bubbly]

I'm constantly amazed at how many people want to pull Romex into conduit or even try and strip the sheath off to just use the wires inside.

Does anyone value their time?

Since it sounds like most of the OP's electrical is behind OSB, I'd suggest MC cable. Leave the stubouts long enough that it'll stick through the OSB and be able to make up in the box. Make sure you holesaw your holes through the OSB in the correct locations to line up with the KO's in the boxes you'll be using.

Initially, the hardship of pulling Romex through a conduit never dawned on me since I have never had to deal with conduit before.

Now with that said, IF I could use the stripped Romex, I would. Why? Because I have more time than money and so do many other people. I am trying to build a new garage/shop and a new home so if I could save a few bucks here and there why not? If sitting outside drinking a beer and stripping Romex for an hour could save me $200.00, why not do it? Heck, crackheads do this all the time.

Now if money were no object, then yes, I would not waste my time.

 

[green.bubbly]

Did some price shopping today at HD and it seems that by far, the pvc pipe is the cheapest route. No far behind is the metal EM conduit and for a lot more, the plastic flex tubing comes in third.

I think I will go with the pvc conduit for cost and ease of use. I will not need a pipe bender, the fittings are cheaper and I am comfortable cutting and gluing pvc.

I will get the grill heating up...

And yes, I will purchase some THHN.

Now for my stupid question of the day, do I need green ground wire or can I use bare copper in the conduit for grounds?

 

[Falcon67]

>Heck, crackheads do this all the time.
Yes they do. Had a rent house once, cleaned over 200 lbs of rubber shreds out of the living room after some renters bailed on us.

I pull Romex in short conduit runs because it is what I have. I cannot justify the expense of having individual 250' rolls of THHN sitting around. It's a pain yes, but its workable.

I would pull green, but that's just because I like colors. I noticed at HD the other day that 250' of 12-2 MC cable was only $30 more than a roll of Romex. Not bad, but that's still $100. Don't discount the MC cable as it's very easy to run with the proper fittings. I used some on my mill hookups and really liked it. Look to a supply house for the THHN - my neighbor works for a big supply house and says they can beat the **** out of the box stores on anything BUT Romex. HD, Lowes, etc buy Romex by the box car so they really have the best prices on that. Everything else you may well be getting hosed on. Don't walk away from the metal conduit until you price some stuff at a supply house. Might be worth the effort.

 

[Charles (in GA)]

Electrical supply houses around here are way high on everything. I try not to buy anything from them.

Charles

 

[Thruxton]

I really like MC, the only thing I would add to above comments, is buy the tool! Even on a tight budget you will be very glad you did.

 

[Charles (in GA)]

Like this...............

http://www.idealindustries.com/prodDetail.do?prodId=35-782&div=3&l1=cable_cutters&l2=sir_nickless

http://www.licensedelectrician.com/Store/ID/BX_MC_Flex_Cutter.htm

Charles

 

[Gooch]

Grounds are permitted to be Bare, Insulated, or Covered.

I really like MC, the only thing I would add to above comments, is buy the tool! Even on a tight budget you will be very glad you did.

I find it's pretty easy to strip MC with a tin snips.

 

[smike]

Of the 3 choices, go with the pvc. Emt can be a challange if you never bent conduit before. Ent the plastic fexable stuff just looks like **** unless it is hidden behind a wall. You can glue pvc fittings to it.
You can buy all the pvc fittings including 90 and 45 degree bends. Where it is exsposed strap it every 3' to keep it straight. It likes to droop over time with hot summers with the weight of wire. For custom bends or offsets you can use a heat gun, just keep it moveing. Use single condutor wire and make sure their stranded. They are a lot easier to pull and easier if you ever want to and more later.

I will be useing pvc in my new 30x50 garage. I will be installing most of the electric under the concrete.

 

[harvero]

You can always use one of these to heat the grey conduit.

Years ago I worked for a Industrial Electrician. He use to have me pull romex through EMT. We use a little silicone lube to ease the insertion. An example of a typical application would be a wall mount outlet in a warehouse, where romex was ran in a wire chase then over to EMT for the down run down the wall. The romex would enter the top of the EMT and there either was a internal bushing installed on the top of the EMT or a EMT box connector.

I've read elsewhere that the 2005 NEC states:

342.22 Number of Conductors
The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9.
Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.

and

334.2 Definitions
Nonmetallic-Sheathed Cable. A factory assembly of two or more insulated conductors enclosed within an overall nonmetallic jacket.

 

[Charles (in GA)]

342.22 pertains to Intermediate Metallic Conduit.

The correct cite for the discussion here would be 358.22 which pertains to EMT, but the text is exact same wording.

Problem with fill is Chapt 9 says that an elliptical shaped cable, which Romex basically is, has to have the area calculated using the MAJOR DIAMETER of it to calculate the area as if it were ROUND. (circle diameter)

In addition, a multiconductor cord or cable is treated as a SINGLE CONDUCTOR when determining fill. Max fill varies with the number of conductors, (one conductor is 53% max fill, while two conductors is 31% max fill and over two conductors is 40% max fill.

Charles

 

[Aceman]

You have to remember Charles that the conduit fill requirements only apply to complete conduit systems only, not those conduits only used for sleeves to protect from physical damage. Since there isn't a box on both ends of that conduit in the picture, it's only a sleeve.

Ch. 9
Table 1
Notes to Tables(2)

 

[mrb]

You have to remember Charles that the conduit fill requirements only apply to complete conduit systems only, not those conduits only used for sleeves to protect from physical damage. Since there isn't a box on both ends of that conduit in the picture, it's only a sleeve.

Ch. 9
Table 1
Notes to Tables(2)

i thought for it to be a sleeve the conduit has to be disconnected at both ends. If the conduit lands in a box at one end it needs a EMT->romex clamp at the other end....

 

[green.bubbly]

Am I wrong or do the NEC codes seem more confusing and complicated than our federal tax code?

 

[green.bubbly]

Ok, spent over two hours in Home Depot going back and forth between pvc and the MC cable. Ended up going with the MC cable. I think at the end of the day, it will be less bending and fewer damn connectors needed.

I probably would have gone with the pvc and the THHN wire but at $77.00 per 500 feet for the hot, neutral and ground, plus all the PVC connectors and sweeps, I went with the MC cable.

I read a few places about a MC cable cutter sold at HD but I can not find such a tool there. Of course I had no idea what I was looking for and the employees only offered me a black stare. Can anyone point me in the right direction on this tool? And do I need the anti-short bushings?



Damn this conduit!





Is this the tool?

 

[premierplayer]

that's the tool
YES, use the plastic cones

 

[green.bubbly]

that's the tool
YES, use the plastic cones

Thanks. Any idea if Lowes of HD sells this tool? I can not find it on their website.

 

[Charles (in GA)]

If you are only doing a few pieces, you can easily get by with dykes, but if you are doing a whole building, it will speed up the job alot.

Charles

 

[Norcal]

that's the tool
YES, use the plastic cones

BTW, redheads are NOT required on MC cable, but are cheap insurance IMO, plus the manufacturer supplies them w/ the cable. I do not leave them out.