Electrical conduit at a service panel (C) D Friedman T HemmMetallic Electrical Conduit FAQs

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Metallic Electrical Conduit Q&A:

Frequently-asked questions about buying & installing metal conduit electrical wiring.

This article series describes both metallic electrical conduit and plastic or non-metallic electrical conduit products, and answers basic questions about installing electrical conduit. Electrical conduit is metal or plastic rigid or flexible tubing used to route electrical wires in a building.

The page top photo showing rigid conduit used to bring wires up to an electrical sub-panel was provided courtesy of Tim Hemm.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Electrical Conduit Installation Tips for Homeowners & DIY Repairs

Electrical conduit mistakes (C) D Friedman T HemmWatch Out: Do not attempt to work on your electrical wiring, switches, or outlets unless you are properly trained and equipped to do so. Electrical components in a building can easily cause an electrical shock, burn, or even death.

These questions & answers about electrical wiring in non-metallic conduit were posted originally at ELECTRICAL CONDUIT, METALLIC - be sure to review that a\rticle.

On 2018-05-10 by (mod) - where can non-metallic conduit be used in construction vs requirements for conduit in tall buildings?


The 2002 National Electrical Code (NEC) is permitting the use of Nonmetallic Sheathed. (NM) cables to be installed in buildings (structures) with heights higher than three stories. - Source: Kendall, David H., PERMISSIBLE CONSTRUCTION to USE NMC CABLE [PDF] Carlon Sales, Gross Automation Inc., 3680 N. 126th St., Brookfield, WI 53005 USA Email: Tel: (877) 268-3700, retrieved 2018/05/10, original source:

Find this article also at as we found the original article at Carlon Sales sometimes refusing to load.

If there is such a requirement where you live - as may be common in some cities - it's local to our country, city, state or province. What does your local electrical inspector say?


On 2018-05-10 20:28:12.497192 by (mod) -


If there is such a requirement where you live - as may be common in some cities - it's local to our country, city, state or province. What does your local electrical inspector say?

On 2018-05-10 18:44:20.710972 by Anonymous

Is it required by code to use metal conduit above three stories in a residential home/condo

On 2018-04-24 23:55:38.824246 by (mod) -


If I understand the question correctly, you don't want the screw to penetrate the flexible metal conduit at all. Instead the screw combined with a clamp is acting to pinch and mechanically hold or clamp the end of a flexible metal conduit. It doesn't actually screw into it.

On 2018-04-24 22:41:39.345985 by Bob

How do you get the ends to screw into flex metal conduit the ones that push into you’re box
I have the cutter but can not get it to screw in, I have been an hour trying to get it in

On 2018-02-27 15:41:19.319485 by (mod) -

OK Rick, keep me posted; use the picture frame icon next to the Comment button if you want to send along photos of the job.

On 2018-02-27 15:38:30.095140 by Subber

Ok friend, thanks again for your quick response. Heard that on some other site that I searched. I don't think our town is that strict, but I'll check. The person who built this house in 1961 ran romex (old style) along side with armored; I think he used what he had on-hand (which was apparent in how the rest of the house was built). Thanks again, Rick

On 2018-02-25 19:01:08.822918 by (mod) -

I suppose that could be a local code requirement - the local code official is always the final legal authority.

On 2018-02-25 17:57:48.490789 by Subber

It's not a commercial install; just some small projects in or near my garage. Seems that I read somewhere that wiring running perpendicular to or along joists had to be in conduit.

On 2018-02-22 04:07:38.734676 by (mod) -

If this is a commercial installation than different local regulations probably apply to your electrical wiring as well. the requirement to use armored cable or BX, versus plastic or Romex Wire, is also often regulated locally. For example in New York City residential wiring uses of armored cable where is in other counties of the state nonmetallic wire is permitted. Whether or not you need to run metallic sheathed cable or kind of it also depends on the exposure of the wire to damage. You probably don't need to do that but I really don't know since I don't know anything about your site.

On 2018-02-22 03:41:48.842430 by Subber

thanks for that. the other part of my query that I forgot to mention was whether I would need to run the wire in conduit if installing perpendicular to or along the joists? If so which type: EMT, Greenfield, PVC? Thanks again, Rick

On 2018-02-20 23:31:33.611407 by (mod) -


Start by noting the amps rating of your welder or the minimum circuit amps specified in its instructions.
While there can be higher amp uses in some circumstances, generally

#10 wire is going to run 30A
#8 wire is going to run 40A

See details at SE CABLE SIZES vs AMPS -

there we also discuss when to go to a larger wire size for longer wire runs.

On 2018-02-20 16:57:42.490863 by subbernh

I need to use conduit to run 60 to 70ft of cable from my entrance panel across the floor joists in my basement, then across the floor joists of our attached breezeway, and ending in my attached garage into a 220v welder outlet? I plan to use #8 or 10 awg copper? Thanks, Rick

On 2018-02-14 00:17:31.576518 by (mod) -


Yes, you could not properly secure BX / metallic cable at a plastic junction box, nor ground it.

2. Thst sounds reasonable.

In most jurisdictions even if your local codes permit or non licensed electrician to do wiring you still need to get a permit and inspections. Don't skip those as they increase your own safety and the quality of your job.

On 2018-02-14 00:04:40.055359 by Bill marcus

I assume running 110 and 240 Mc cable requires using all metal outlet boxes, and plastic non rubbing red protection plugs at the wire exit points.
Secondly, how do I safely run Mc cable near an existing gas pipeline in a finished dry walled basement ceiling....just move down a few hoist sections???

On 2018-01-02 17:50:59.829684 by (mod) -


You'd need to be sure the metal conduit is properly grounded

On 2017-12-30 19:25:17.025614 by Angie

Question: I'm planning to run some rigid conduit in my basement. Does the conduit have to be connected directly to the load center, or can the wires be run along a floor joist across the room and then drop down into conduit?

On 2017-12-28 01:38:40.061029 by Jose

Are seal offs required on conduit under dental chairs

On 2017-12-17 19:07:06.882397 by (mod) -


I generally trust licensed electricians to know the electrical code including local provisions where they work. However the local electrical inspector is the final legal authority to whom you have to address this question.

Flexible metal conduit is permitted by the model U.S. NEC 348.10 (2011 NEC) stating that flexible metal conduit (FMC) is permitted in exposed or concealed locations.

I'd add that flexible metal electrical conduit is permitted in *dry indoor*locations except for specific restrictions such as these situations where it would be hazardous:

In wet locations.
In hoistways, other than as permitted in 620.21(A)(1).
In storage battery rooms.
In any hazardous location, except as permitted by 501.10(B).
Exposed to material having a deteriorating effect on the installed conductors.
Underground or embedded in poured concrete.
If subject to physical damage.

OPINION If your electrician is of the view, as I might be, that a metal shop is an environment where wiring might be damaged and thus could kill someone, that would support use of rigid metal conduit.

On 2017-12-17 18:02:30.880859 by Mark

I live in Tn and I have a 30x40 metal shop which is residential. Can I use the flex conduit to wire my shop. I had a electrician to tell me I had to have regid conduit which he says cost more. Is this fact or just away to get more money. I'm on a budget. Thanks

On 2017-09-12 18:38:38.912834 by Jim

My house is cement block but I have to fir out inside walls for electric outlets. Second time my house has been flooded n I just want to plaster cement blocks inside n surface mount receptacles . That way I don't have to remove Sheetrock after every flood. Key west

On 2017-08-09 13:49:36.278196 by (mod) -

Thank you Saleem, you're quite right and we appreciate that you took time to comment about not finding IMC conduit information on the page above.

We've updated this article series, separating discussion of metallic and non-metallic conduit materials and work.

IMC is discussed at


I would much welcome further comments, critique, content suggestions.

Thanks again


On 2017-08-08 07:46:51.776443 by SALEEM


On 2017-08-08 by (mod) IMC CONDUIT

Thank you Saleem, you're quite right, I need to add information about IMC - Intermediate Metal Conduit, particularly as IMC has popularly replaced the heavier RMC - rigid metallic conduit - in some applications.

I'm working on it now.

On 2017-08-08 by SALEEM


On 2017-05-06 by (mod) the bx cable size i need


20A uses #12 copper electrical wire unless the run length is so long that you need to go to #10. Sounds as if you need a licensed electrician.

On 2017-05-05 by Gino

Wbat is the bx cable size i need to add a 220 breaker on a 12x12 General electric 110 volt 20 amp breamer, can it be done

On 2017-03-24 by (mod) Can I use sheathed cable in conduit?

Can and should and code = bottom line it's physically possible but not something I'd do: you're perhaps changing the heat properties and rating of the wiring as well as overcrowding the conduit.

On 2017-03-24 00:05:10.177993 by dave

Can I use sheathed cable in conduit?

On 2017-01-25 1 by Dong

I am working in a huge refinery project and I saw electrical conduit installed in parallel below the water drainage. But I couldn't make any violation due to the absence of a standard reference from NEC or any standard electrical book. Needing some other expert to help me on this issue. Thanks danjoe.

Is there any standard reference showing the conduit shall not be installed below the drainage pipe or water pipe on exposed or concealed pipe?


Reader comment:

(Mar 6, 2012) rich lindsay ----peterborough nh said:

Wiring through a metal fence! That jerk must have used a guidebook from a Nazi prisoner of war camp. His local town newspaper should put the picture and story on page one and indicate to the people such a hazard. He should be fined by the code agent and the amount also posted with the story. Talk about the south end of a horse.


Yep, we agree Rich.

Reader comments: numnber of wires in conduit

(Aug 22, 2012) Anonymous said:

"The one-half inch conduit can contain four No. 14 wires or three No. 12 wires. Three-quarter inch conduit accommodates four No. 10 or five No. 12 wires.

Aug 22, 2012) Anonymous said:

You write "The one-half inch conduit can contain four No. 14 wires or three No. 12 wires. Three-quarter inch conduit accommodates four No. 10 or five No. 12 wires."

I am not sure what type wire you are using, but with THHN or THWN code says one can put up to 9 #12 wires in 1/2" inch, and 16 #12 in 3/4" EMT. I realize that would be hard to pull, but I think your estimate is low.

(Nov 12, 2012) Wendell Mac Cormack said:

An insector cited me for an exposed wire caused by mt conduit slipped main power to house wgat do I do?

(Apr 3, 2014) Anonymous said:

all conduit caps can be exceeded as per, req #3561NEC variance, as long as the faever is 3 feet from the johnson rod.

Question: electrical conduit on the property boundary

Mary Ellen said:

A neighbour has run wiring in an electrical conduit within their boundary but on my side of the fence, under the fence rails. Is this legal?


Mary Ellen, this is an interesting question and not one of electrical code or even safe wiring practices, but rather one for your local building department about property line setback requirements.

Those requirements vary by country as well as local jurisdiction, and vary further by types of construction involved. For example where property lines are *very* close between neighbors, attached townhouses, electrical wiring and other building features must respect fire safety codes.

Quoting from an Australian building code example:

To minimise the spread of fire, fire growth as well as safety of occupants in the event of a fire a building must be constructed so as to satisfy the requirements of:

Part 3.7 of the Building Code of Australia - Housing Provisions (Volume 2) AS4072.1 and AS1530.4 with regard to fire stopping service penetrations. Manufacturer’s Specification to ensure that the product performs as tested. - retrieved 5/12/14 original source

In other jurisdictions, the authority may specify that even fences must be kept a specified distance back from the exact property boundary. - retrieved 5/12/14 0Walls%20%20Fences%20Policy_Final.pdf)

This sort of wiring constraint does not sound as if it applies to your case as I think you're describing outdoor property.

You don't state your country, city, state, so we don't have an idea what your local rules may require.

I suggest taking the question and your concern to your local building or zoning department for a specific answer.

Reader Commen on Number of Wires in Electrical Conduit

(4 days ago) Frank CArone said:

"The one-half inch conduit can contain four No. 14 wires or three No. 12 wires. Three-quarter inch conduit accommodates four No. 10 or five No. 12 wires."

[Reader says this is incorrect]

Check the "conduit and tubing fill tables for conductors and fixture wires of the same size"

Comment: Thanks, useful.

(June 11, 2015) (mod) said:
eliteelc01 said:
Many brave homeowners take on electrical work in the course of everyday household maintenance, but it is all too easy to make a mistake that could bring on both minor and major problems. Thanks for sharing useful tips.


(June 22, 2015) jim said:
can more than one circuit be run in a single conduit pipe

(Sept 24, 2015) can you run condit on a wooden fence. said:
Can you run conduit on a wood fence


Provided it is secured against mechanical damage including separation of connectors - which may be difficult to achieve.

Comment: hire an electrician

Re-posting without advertising link

KayEhm said:
"Do not attempt to work on your electrical wiring, switches, or outlets unless you are properly trained and equipped to do so."
Basically, unless you ARE a professional electrician, don't try this at home. Or, at the very least, consult with a professional electrical installation company. I'd suggest a small business like [deleted - a licensed electrical contractor or repair company] which is comprised of a handful of electricians with over 20 years in the electrical industry. They offer free quotes, and handle everything from inspection, design, installation, any future maintenance, and inspections. I'd rather be safe than sorry and investing some time to create a relationship with some professionals seems much more cost effective both financially and physically.

Question: advantages of conduit wiring over surface wiring

(Mar 5, 2016) Idakwo Emmanuel said:
Give three advantages of conduit wiring over surface wiring


Sorry, id. Yours sounds a bit too much like a test question or homework assignment.


Continue reading at ELECTRICAL CONDUIT, METALLIC or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.




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Electrical Conduit Types, Applications, Codes, Standards, Sources

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