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.

Electrical Conduit Installation Tips for Homeowners & DIY Repairs

Watch 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 2019-07-04 by (mod) - AC Condenser unit electrical whip too tight or too short

Too tight, no slack = failure likely and also there's shock risk.

Movement and vibration combine with a tightly-stretched electrical conduit to risk breakage of the electrical connections, water leaks into wiring, shock hazards, equipment failure.

On 2019-07-04 by Dan

Does the a/c whip that’s for the outside condenser in this condo set up seem OK? It seems that it violates UL 360 or UL 1660, which I read to require the conduit be protected from damage.

Damage seems certain since the left, inner unit can’t very well be worked on without straining that stretched whip and possibly loosening the terminations and causing an electrocution hazard for someone somewhere along the line.

On 2018-11-26 by (mod) -

Vincent said:
What a great and helpful post, I really learned a lot from this.

On 2018-08-30 by (mod) - find previous copies of locally-adopted electrical code

Ed

Because few building departments have posted as public record the history of their adoption of previous versions of the model building code, it will be best for you or your paralegal to contact the DuPage County Illinois building department, then ask to see a history of when various electrical codes were adopted by the county.

Then you'll find when EMT (Electrical Metallic Tubing) was first cited.

Look for Article 358. Electrical Metallic Tubing (Type EMT)
Or in some older documents Article or Chapter E 348 Electrical Metallic Tubing
eg: http://docs.legis.wisconsin.gov/code/register/1968/145b/remove/e348.pdf (1964)

DuPage County Building Department
Jack T. Knuepfer Admin Bldg.
421 N. County Farm Road
Wheaton, IL 60187 USA
630-407-6700
www.dupageco.org/buildingzoning/

On 2018-08-29 1 by Ed Barbeau

What year did DuPage county put EMT piping into the housing code?

On 2018-07-28 0 by Old Framer / questions about sub panel wiring and FMC.

I have several questions about sub panel wiring and FMC.

I am replacing a Federal Pacific sub panel that is currently wired with 3 wire range 3/6. My plan includes isolated neutral from ground at sub panel and 4 red black white and green @ 6 gauge stranded. Which I planned to run through 1" FMC. The current sub panel is below the existing GE twin loadcenter.

The feed from the panel comes out the middle of the bottom and goes down and curves past the sub panel and then curves 180 degrees to go up through the bottom of the sub panel. So maybe a 225 degrees of bend in the way it is without any conduit. And here is the problem I cannot possibly follow that path with conduit as it cannot bend in such a tight turn.

Something I was once told for the good bad or ugly of it by an older gentleman was that when mounting two electrical boxes nearby each other with FMC there was a desire to create some type of bend down in the FMC to lessen the ability of fire to transfer from one box to the other.

This may make sense on some ship without any fire suppression system but I am really not sure where this idea came from. I haven't found anything in any code or past reference materials to suggest this style is either necessary or was code. Not sure where it comes from.

Though the 1" conduit will not bend that much in a stud bay I could either mount it upside down to which is not what I would normally want to do. Or as I have found the conduit will hit the new box on a proper sized hole on the right side should I would assume this would be acceptable. I have seen many photos of sub panels next to panels on the net and not anything really much about code and conduit in between.

I could go through the top directly from the panel. My impression was you did not want to do this as fire could spread from one box up easier. However there is a 15 am circuit that enters the existing sub panel through the right top corner and another wire in the way too in between.

I will need at least 4" of space or so to put a box there to continue that old 15 amp circuit to make all the way to the sub panel through its knockout design.

Questions:

1) Can a sub panel be connected directly to a panel. I'm not planning to do this but I got the impression its allowed from looking for the answer.

2) Can these 4@6 gauge wire come through the right side of the sub panel from the panel above in FMC.

3) Is there any minimum bend requirement at all for FMC other than not to be more than 360 or something?


3) Is there any code that truly states one must have bend in FMC between boxes mounted nearby each other or is that just some old concept?

I can add some photos later if necessary.

Please elaborate what is correct.
Thank You my Sparky friends in advance!

On 2018-06-07 by (mod) -

I'll look further. Out would be surprising if such connectors don't exist. Have you tried calling the manufacturers directly?

On 2018-06-06 by Joe

Yes, I've used the connector shown below to connect liquid tight to EMT, but I haven't been able to find anything that connects two liquid tight flexible metal conduits to form a splice. My local big box stores don't have anything, and my local electrical part suppliers couldn't find anything.

If you (or anyone) knows of a coupler to do this, I'd like to know what it is and where I can get them for 1/2" and 3/4" liquid tight flexible metal conduit. Otherwise, The only way I know to do this is to make the coupling above ground through a junction box. Thanks!

On 2018-06-06 by (mod) - a way to splice together two sections of liquid-tight flexible metal conduit

Joe,

There are liquid tight connectors for joining sections of electrical conduit.

Below I will show typical liquid tight connectors used with Type B NM Liquid-Tight electrical conduit. There are similar products for other water tight flexible electrical conduit materials including metal conduit.

You'll find those at your electrical supplier or at building supply stores such as Home Depot or Lowes.

On 2018-06-06 by Joe

Is there a way to splice together two sections of liquid-tight flexible metal conduit other than bringing both ends to a junction box? I'm looking for some sort of coupling that can be buried if possible.

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

Anon

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., PREMISSIBLE CONSTRUCTION to USE NMC CABLE [PDF] Carlon Sales, Gross Automation Inc., 3680 N. 126th St., Brookfield, WI 53005 USA Email: sales@grossautomation.com Tel: (877) 268-3700, retrieved 2018/05/10, original source: www.carlonsales.com/techinfo/codesstandards/CS-NM_Cable_Construction.pdf

Copied at this website because 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?

Also see ELECTRICAL CONDUIT, NON-METALLIC

On 2018-05-10 by (mod) -

Anon

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 by Anonymous

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

On 2018-04-24 by (mod) -

Bob,

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 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 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 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 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 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 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 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 by (mod) -

Subber

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 https://inspectapedia.com/electric/Electrical_SEC_Sizes_Amps.php 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 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 by (mod) -

Bill,

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 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 by (mod) -

Amgie,

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

On 2017-12-30 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 by Jose

Are seal offs required on conduit under dental chairs

On 2017-12-17 by (mod) -

Mark

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 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 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 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

IMC INTERMEDIATE METAL CONDUIT, THREADED & NON-THREADED - https://inspectapedia.com/electric/Electrical_Conduit_Wiring.php#IMC

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

Thanks again

Daniel

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

WHAT ABOUT IMC CONDUIT

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

WHAT ABOUT IMC CONDUIT

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

Gino

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.

Reply:

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?

Reply:

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 www.bradfordinsulation.com.au/Regulations/BCAFire/Class1a.aspx

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 www.capetown.gov.za/en/Planningportal/Documents/Boundary% 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.

Question:

(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

Reply:

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

Reply:

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

...

Continue reading  at ELECTRICAL CONDUIT, METALLIC - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Electrical Conduit Types, Applications, Codes, Standards, Sources

• ELECTRICAL CONDUIT, METALLIC
• ELECTRICAL CONDUIT, NON-METALLIC
• ELECTRICAL CONDUIT PULL BOXES
• ELECTRICAL CODE BASICS
• ELECTRICAL CONDUIT BEND CONNECT TOOLS
• ELECTRICAL CONDUIT DEFECTS & DAMAGE
• ELECTRICAL WIRING BOOKS & GUIDES
• NATIONAL ELECTRIC SURFACE CONDUIT CATALOG 1950 [PDF]
• SAFETY for ELECTRICAL INSPECTORS.

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