Emt Conduit Installation Guide

Electrical metallic tubing, or EMT, is the most common type of conduit for exposed interior installations, such as in a basement or an unfinished garage or workshop. It is the lightest and thinnest of the rigid metal conduit types and comes in a few different diameters; 1/2-inch is the most standard size for household circuits. Flexible Conduit Adapter Kit Installation Guide (Continued) 2 Installing the Flexible Conduit Cable on a PS 124 Install the flexible conduit cable assembly to the PS 124 as follows: 1. Unplug the IEC power cord from the PS 124. Remove and retain the two Phillips head screws that secure the IEC plate to the PS 124 rear panel. OUTPUTS RED-OVERLOAD. Examples are electrical metallic tubing (EMT), which is lightweight and easy to install; intermediate metallic conduit (IMC), which has a thicker, galvanized wall, making it suitable for outdoor applications; and galvanized rigid conduit (GRC), which is thickest and offers the most protection.

POST a QUESTION or READ FAQs about how to buy, bend, wire, & install electrical conduit in buildings

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Metallic Electrical Conduit:

Here we describe the various types & applications of metallic electrical conduit, flexible and rigid, or conduit made of aluminum, galvanized steel, PVC-coated steel, and stainless steel. We include ips for installing & inspecting electrical conduit in homes and electrical conduit cutting, bending, installing suggestions

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

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.

Even when a hot line switch is off, one terminal on the switch is still connected to the power source.

Before doing any work on the switch, the power source must be turned off by setting a circuit breaker to OFF or removing a fuse.

See SAFETY for ELECTRICAL INSPECTORS and ELECTRICAL WIRING BOOKS & GUIDES

Electrical conduit for wiring has some advantages in protecting wires and also in running multiple wires to a location.

The proper selection of electrical conduit materials, fittings, and installation are important for safe electrical wiring.

Our photo (above left, courtesy of Tim Hemm), shows an electrical conduit snafu along with an unsafe FPE Stab-Lok electrical sub panel. Both flexible electrical conduit and rigid conduit were used. Our arrow points to an improper 'bend' made in the rigid metal electrical conduit. [3]

Electrical Conduit Types, Applications, Codes, Standards, Sources

EMT ELECTRICAL METALLIC CONDUIT - THIN WALLED METAL CONDUIT - rigid
FMC FLEXIBLE METAL ELECTRICAL CONDUIT - flexible
IMC INTERMEDIATE METAL CONDUIT, THREADED & NON-THREADED - rigid
LFMC LIQUID-TIGHT FLEXIBLE METAL CONDUIT & WHIPS - flexible, liquid tight, with wire
RMC RIGID METAL CONDUIT - rigid

ENT ELECTRICAL NONMETALLIC TUBING - rigid plastic conduit
ENT & LFNC NON-METALLIC ELECTRICAL CONDUIT- flexible plastic & liquid-tight flexible plastic conduit
FLEXIBLE LFNC PRE-WIRED WHIPS - flexible, liquid-tight, with wire

Photo above: EMT, thin walled electric metal conduit. [Click to enlarge any image]

Steel electrical conduit and tubing (EMT) have been used for many decades to protect electrical wiring from mechanical damage and to provide electromagnetic field or electromagnetic interference shielding for circuits and wiring of various types.

Vendors of EMT point to both its high re-cycled content (63%) and its recyclability at the end of its life. EMT is produced either in a basic oxygen furnace (BOF) or an electric arc furnace (ARF). - (NEMA 2017)

The range of electrical conduit materials and properties is large and is designed both for special applications such as corrosion or moisture resistance.

The inside diameters of conduit vary from the nominal diameter sizes, and include 23/32', 21 32', 5/8', 39/64', 37 64', and 2 1/16' inside actual dimensions.
The wall thickness of electrical conduit materials ranges among 1/8', 7/64', 3/32', 5/64', 1/16' and 3/64'
Rigid conduit is sold mostly in 10 ft. lengths with 5 ft. lengths available usually for the larger-diameter sizes.

EMT, Electrical Metallic Tubing, Thin-wall metal conduit

The most common type of electrical conduit for house wiring is the thin-wall type. Thin-wall conduit is too thin for threaded joints. It is joined to other lengths of conduit and to boxes by pressure-type fittings.

EMT Conduit is sold in two metallic types:

304 Stainless Steel EMT, in sizes 1/2' to 2' in diameter in 10 foot lengths (Calbrite Brand) environments.
Stainless steel EMT conduit and fittings combine strength with ductility, resulting in an affordable, lightweight and easy-to-handle conduit assembly. EMT can be installed indoors and outdoors in accordance with UL and NEC® requirements. - (Calbrite 2017)
Galvanized Steel EMT, in sizes 1/2' to 4' in diameter in 5 ft. lengths (some sizes) and 10 ft. lengths (most diameters) (GAV, Allied and other brands)
EMT Compression Fitting conduit, sold in 1 1/4' to 2 1/2' diameter, 10 ft. lengths, easy installation, no need to stock couplings (Allied & other brands)
EMT Green Conduit, in steel, 1/2' & 3/4' diameter, 10 ft. lengths, hot-galvanized, used to identify emergency circuits and critical circuits in hospitals, healthcare areas etc.
EMT with Integrated Setscrew Couplings, 1 1/4' to 3' diameter, 10 ft. lengths, simplified installations, smooth interior raceways.
EMT Red Conduit, in steel, 1/2' & 3/4' diameter, 10 ft. lengths, used to identify fire alarm & security system wiring, hot dipped galvanized, easy-bending (Allied & other brands)
PVC-Coated Steel Conduit such as CalPipe's Calbond™, used in hazardous locations, oil and gas, and mining industries.
PVC-coated steel conduit is produced in North America by Calpipe Industries, Robroy Industries, and by Thomas & Betts (ABB Group).

Thin-wall conduit is sold in ten-foot lengths in either one-half inch or three-quarter inch (outside) diameter.

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.

These wire capacities are for individual wires, not pairs. The wires used are the same as the individual conductors found in steel armor cable and plastic sheathed cable. Wires in conduit must follow standard coding. In a two-wire electrical circuit you need one black wire, one white wire, and one ground wire.

The general procedure for using thin wall conduit is similar to the use of steel armor cable. The big difference is that conduit cannot be 'snaked' through openings in ceilings and walls.

You must have full access to joists and studs to install electrical conduit. So you probably won't want to use it unless your local code requires it.

In the U.S. manufacturers of EMT or Electrical Metallic Tubing include Allied, Calbrite, and Granger-Approved brands.

Reader Comment: more wires allowed in thin wall metal conduit: NEC Table C.1

2016/08/22 Alan said:

The conduit fill listed under thin-wall metal conduit [above] is wrong. Granted, under normal conditions, you generally cannot go over 9 current carrying conductors in a conduit without needing to reduce its current carrying capacity below the size circuit for which it is generally used (e.g., #14 = 15A; #12 = 20A). A

NEC Table C.1 (for electrical metallic tubing, EMT) allows for 12 #14 and 9 #12 in 1/2' conduit, and 22 #14 and 16 #12 in 3/4' conduit.

lso, good luck pulling nine #12 wires in a 1/2' conduit, but just wanted to point out that NEC allows for more conductors than indicated above.

Also, I should note that is for THHN - other types may allow for more or less.

Spacing & Support for Rigid Metal Electrical Conduit

See NEC Table 344.30 (B)(2)

Rigid metal electrical conduit to 1/2-3/4' or 12.7-9.1 mm: 10 feet or 3.05 meters between supports
Rigid metal electrical conduit 1' or 24.5mm in diameter: 12 ft / 3.66 m
Rigid metal electrical conduit 1 1/4 - 1 1/2' in diameter: 14 ft / 4.27m
Rigid metal electrical conduit 2 - 2 1/2' in diameter: 16 ft / 4.88 m
Rigid metal conduit 3' in diameter or larger: 20 ft or 6.1 m

EMT Resources, Sources, Standards

Calbrite™ Corporation, 6451 Northwind Pkwy., Hobart, IN 46342 USA, Tel: 219-844-6800 Website: www.calbrite.com
Calbrite™, Stainless Steel Conduit Systems, Stainless Steel EMT, retrieved 2017/08/08, original source: http://www.calbrite.com/submittal-sheets/Conduit/SS-EMT-Conduit.pdf
NATIONAL ELECTRIC SURFACE CONDUIT CATALOG 1950 [PDF]
Standard: UL / cUL 797A
Standard: ANSI C80.3 for installation in accordance with Article 358 of ANSI/NFPA 70,'National Electrical Code' (NEC).
Wheatland Tube, 'CONDUIT TUBING, EMT, IMC, RMC' [PDF], Wheatland Tube, JMC Steel, includes 2011 National Electrical Code References. Wheatland Tube, 700 South Dock Street, Sharon, PA 16146 USA, Tel: 800.257.8182 Email: info@wheatland.com Website: wheatland.com

FMC, Flexible metal electrical conduit

Flexible metal conduit or FMC, is a helically-wound flexible metal electrical wiring conduit, often made using aluminum such as the ALFlex™ conduit shown here.

Flexible metallic electrical conduit is used principally in commercial and industrial construction world wide. In residential applications you may find FMC used to connect an electric oven or electric cooktop.

This conduit is also sold as LFMC or liquid-tight flexible metal conduit.

LFMC is described in the U.S. National Electrical Code NEC® Article 350 and must comply with UL 360 in the U.S. or CSA C22.2 No. 56 in Canada.

Flexible metal conduit is sold in rolls and cut to the necessary length, joined with appropriate fittings.

Shown is Alflex™ 3/4' diameter metallic flexible conduit produced by Titan.

[Click to enlarge any image]

Pre-Wired Flexible Electrical Conduit Whips

What's the Difference between Flexible Metal Electrical Conduit and Armored Cable or 'BX' Wiring?

Flexible metal conduit sold for electrical wiring (previous photo above) is sold empty, and is larger in diameter than pre-wired armored cable such as the 12/3 Armorlite® armored cable shown here.

This electrical cable is pre-wired with THHN/THWN conductors and is intended for use in cable trays and includes a green-insulated ground wire.

Watch out. Do not use set-screw type connectors with this cabling.

Electrical Conduit Installation

Doing so risks pinching the cable end and cutting into the wires, causing a short circuit.

FMC and LFMC Standards, Codes, Installation Guidelines

The following Standards govern FMC and LFMC

UL 1, Flexible Metal Conduit, Abstract: These requirements cover flexible aluminum and steel conduit designed for use as metal raceway for wires and cables in accordance with the National Electrical Code, NFPA 70.
UL 360, Liquidtight Flexible Metal Conduit
Abstract:

1.2 This conduit is for applications in which flexibility of the conduit is necessary during installation, operation, or maintenance and the contained conductors need protection from vapors, liquids or solids.
1.3 This conduit is circular in cross section, having an outer liquid-tight, nonmetallic, sunlight-resistant jacket over an inner flexible metal core, and is for use in wet, dry, or oily locations in which the conduit is exposed but is not subject to physical damage.
Conduit that is not marked with a temperature designation or is marked '60 C' is for use at temperatures not in excess of 60°C (140°F).
Conduit that is for use in dry or oily locations at a temperature higher than 60°C (140°F) is marked '____C dry, 60 C wet, 70 C oil res' or '____C dry, 60 C wet, 70 C oil resistant' with '80 C' or '105 C' inserted as the dry-locations temperature.
1.4 Conduit that is marked '80 C dry, 60 C wet, 60 C oil res' or '80 C dry, 60 C wet, 60 C oil resistant' is for use at 80°C (176°F) and lower temperatures in air, and 60 °C (140°F) and lower temperatures where exposed to water, oil or coolants – that is, to cutting oils and the like in machine-tool and other industrial applications.
1.5 Conduit marked in accordance with 24.4(g) is limited to use in oil free environments.
1.6 Fittings for conduit are covered in the Standard for Conduit, Tubing, and Cable Fittings, UL 514B.
1.7 These requirements do not cover liquid-tight flexible nonmetallic conduit. Flexible nonmetallic conduit is covered in the Standard for Liquid-Tight Flexible Nonmetallic Conduit, UL 1660, and the fittings for this conduit are covered in the Standard for Conduit, Tubing, and Cable Fittings, UL 514B.
1.8 These requirements do not cover flexible metallic tubing.
1.9 These requirements do not cover electrical nonmetallic tubing (ENT).

Photo above: rigid and flexible metallic electrical conduit in an older home.

UL 467 on Grounding and Bonding
Abstract:
This Standard applies to grounding and bonding equipment for use in accordance with the Canadian Electrical Code, Part I, CSA C22.1, in Canada, the National Electrical Code, NFPA 70, in the United States, or the Standard for Electrical Installations, NOM-001-SEDE, in Mexico.
1.2 This Standard applies to the following grounding and bonding equipment:
a) ground clamps, bonding devices, grounding bushings, water-meter shunts, grounding electrodes, and the like used in a grounding system;
b) equipment for making electrical connections between
i) the grounding conductors used in electrical power systems, non-current-carrying metal parts of electrical equipment, armored grounding wires, metal raceways, and the like; and
ii) grounding electrodes;
c) equipment for making electrical connections between
i) the grounding conductors used in telecommunications systems such as telephone, radio, CATV, network power broadband, and the like; and
ii) grounding electrodes;
d) hospital grounding jacks and mating grounding cord assemblies (for Mexico and the United States, see Annex a);
e) bonding devices for making electrical connections between
i) the hex head of a brass fitting used in a piping system in accordance with 250.104 of NFPA 70; and
ii) the grounding electrodes; and
f) intersystem bonding terminations for connecting intersystem bonding and grounding conductors for other systems in accordance with NFPA 70.
UL 514A/CSA C22.2 No. 18.1/NMX-J-023/1-ANCE on Metallic Outlet Boxes
UL 514B/CSA C22.2 No. 18.3/NMX-J-017-ANCE pertaining to Conduit, Tubing and Cable Fittings
UL 514C Nonmetallic Outlet Boxes

In addition, NEMA, the National Association of Electrical Equipment and Medical Imaging Manufacturers has produced a number of standards and installation procedures, bulletins and guides for FMC and LFMC including

NEMA RV 3-2014, Application and Installation Guidelines for Flexible Metal and Liquidtight Flexible Metal and Nonmetallic Conduits
NEMA FB 1-2014, Fittings, Cast Metal Boxes, and Conduit Bodies for Conduit, Electrical Metallic Tubing, and Cable
NEMA FB 2.20-2014, Selection and Installation Guidelines For Fittings for Use With Flexible Electrical Conduit and Cable

Contact NEMA at

NEMA, 300 North 17th Street, Suite 900, Arlington, Virginia 22209 USA, Tel: 703 841-3200, Website: http://www.nema.org/
Website Excerpt:

The National Electrical Manufacturers Association (NEMA) is the association of electrical equipment and medical imaging manufacturers, founded in 1926 and headquartered in Rosslyn, Virginia.
Nearly 350 members strong, its companies manufacture a diverse set of products including power transmission and distribution equipment, lighting systems, factory automation and control systems, and medical diagnostic imaging systems.
NEMA list of FMC & LFMC standards & NEMA publications, retrieved 2017/08/08, original source https://www.nema.org/Products/Pages/Flexible-Metal-Conduit.aspx

IMC Intermediate Metal Conduit

Intermediate Metallic Conduit or IMC is lighter weight, metallic conduit and is rated as stronger than other rigid conduit. IMC was first produced by Allied Tube & Conduit.

IMC, provided in both threaded IMC and non-threaded IMC forms, is a rigid metallic conduit tubing, typically hot-dipped galvanized steel or stainless steel. The interior of galvanized steel IMC is usually coated with an anti-corrosion layer.

Threaded IMC is joined by threaded couplings, C condulets, sweeps and bends. The tubing is cut with a pipe cutter or tubing cutter, and then threads cut using a thread cutting tool. When cutting IMC, take care to remove burrs on the tubing interior that would otherwise damage electrical wires being pulled through the conduit.

IMC is typically used in hazardous locations, and in its stainless steel formulation, IMC is widely used in the food and beverage industry, in chemical plants, in cosmetic and pharmaceutcial industries, in refineries, in pulp and paper mills, in marine and coastal sites, in other corrosive environments.

An advantage of IMC is its larger interior diameter compared with RMC of the same nominal sizes, making it easire to pull wires.

IMC is sold in these forms

304 Stainless Steel IMC in 1/2' to 2' diameter, 10 ft. lengths (Calbrite & other brands)
304 Stainless Steel IMC , non-threaded IMC, 1/2' to 2' diameter, joined using compression fittings, for improved impact resistance & corrosive environments where the conduit is exposed to 'washdowns'
316 Stainless Stee IMC l in 1/2' to 2' diameter, 10 ft. lengths (Calbrite & others)
316 Stainless Steel IMC , non-threaded IMC, 1/2' to 2' diameter, joined using compression fittings, for the same non-threaded IMC applications as described above.
Galvanized steel IMC in 1/2' to 4' diameter, 10 ft. lengths (Grainger Approved GAV, Allied, other brands)
1/4' ID IMC is also available.

IMC Standards, Certifications, Suppliers, Product Resources

Non-threaded IMC is joined by compression fit type couplings like the stainless steel Calbrite™ IMC coupling shown here.

Calbrite™ Corporation, 6451 Northwind Pkwy., Hobart, IN 46342 USA, Tel: 219-844-6800 Website: www.calbrite.com
UL / cUL 1242
Articles 342 & 344 of ANSI/NFPA 70, U.S. 'National Electrical Code' (NEC)
ANSI C80.6
Thiele, Timothy, 'What is Intermediate Metal (IMC) Conduit? Strong but Lighter Rigid Conduit', (2017), retrieved 2017/08/08, original source: https://www.thespruce.com/what-is-intermediate-metal-conduit-1152710
Wheatland Tube, 'CONDUIT TUBING, EMT, IMC, RMC' [PDF], Wheatland Tube, JMC Steel, includes 2011 National Electrical Code References. Wheatland Tube, 700 South Dock Street, Sharon, PA 16146 USA, Tel: 800.257.8182 Email: info@wheatland.com Website: wheatland.com

LFMC: Liquid Tight Flexible Metallic Conduit Whips, Pre-Wired

In nearly all new installations the electrician uses a pre-wired liquid tight electrical conduit whip (photo above) to connect outdoor electrical equipment exposed to the weather, such as an air conditioner or heat pump compressor/condenser unit.

Shown is a six-foot 3-wire Carlton Carflex™ whip assembly produced by Thomas & Betts. [5]

[Click to enlarge any image]

For special applications such as shown in our sketch (below), flexible conduit is often used for convenience or to avoid vibration problems, but steps must be taken to prevent water from entering the conduit and/or special water-resistant wiring and fittings are required.

Pre-wired whips in residential applications (photo above right) are found connecting air conditioner & heat pump compressor units to their outside power source. There the flexible whip avoids problems with vibration-loosened connections in the conduit.

Electrical whips are also used for connecting spas and swimming pool equipment.

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Watch out: Flexible conduit and whips are 'flexible' but not to degrees that exceed the laws of physics and the properties of the materials.

If you force flexible conduit or a pre-wired conduit whip to bend too acutely over too short a radius such as at its connection to a rigid surface the conduit will eventually break, as Tim Hemm's photograph (left) illustrates.

LFMC Resources

Carlton Carflex™ whip
Liquid-Tuff™ Liquid Tight FLex Metallic Conduit, Steel, PVC-jacketed Conduit, 3/8 in Through 1 1/4 in Trade Sizes are Square Lock Formed; Include an Integral Bonding Strip of Copper that is Enclosed Within the Convolutions Throughout their Entire Length, WEEE Compliant; UL-360; ANSI; CSA LL18858; UL E29278
Product Description:
For corrosive environments involving water or other liquids, choose liquid-tight flexible conduit (LFMC). When paired with the appropriate fittings (sold separately), this jacketed conduit provides a liquid-tight seal even as it bends and curves and can be used in direct burial, concrete, and lighting applications.
When environments where liquids, temperature, gas, and combustion are a concern, this harsh environment liquid-tight flexible metallic conduit is the solution. It has a PVC jacket for protection in interior and exterior locations, including direct burial and concrete. - retrieved 2017/08/08 from Grainger

RMC Rigid Metal Electrical Conduit - threaded metal electrical conduit

Rigid metal conduit is a heavier gauge steel electrical conduit using threaded couplings and fittings and is the thickest, or stiffest of the conduit materials used for electrical wiring.

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A typical RMC and often the only RMC residential application is to enclose the electrical service entry wiring from the electrical company's overhead wires at the mast-head down to the electrical panel mounted on the building wall.

Our photo shows a damaged, bent-over RMC masthead over a private home in New York. This sort of damage can happen when a tree falls on the electrical wires between pole and masthead.

[Click to enlarge any image]

RMC is sold in both straight lengths and into pre-formed sweeps and bends at 90° and 45° angles.

Rigid metal conduit and its necessary couplings, bends, sweeps, and Condulets that permit wiring insertion & splicing are sold in the following forms and metals:

304 Stainless Steel EMT, in sizes 1/2' to 2' in diameter in 10 foot lengths (Calbrite™ Brand) used in industries including chemical, food & beverage, petrochemicals, transportation, wastewater treatment, and in hazardous or explosion-risk environments.
316 Stainless Steel EMT, in sizes 1/2' to 2' in diameter in 10 foot lengths used as described above, to meet UL and cUL 1242A / ANSI listing standards.
Aluminum RMC in sizes 1/2' to 4' in diameter, 10 ft. lengths, (Gav, Allied and others)
Galvanized Steel RMC, in sizes 1/2' to 4' in diameter, 5 & 10 ft. lengths, (Gav, Allied, Power4 First, other brands)
Galvanized Steel RMC with threaded couplings, in 2 1/2' to 4' diameter, 10 ft. lengths, simplified installation

[Photos needed - use the page top or bottom CONTACT link]

Grainger (https://www.grainger.com) lists a full inventory of types of metal and non-metallic conduit products as you may also find at your local electrical contractor-supplier and at some building supply stores such as Lowes & Home Depot.

RMC Rigid Metal Conduit Resources

The stainless steel C Condulet shown here and used for snaking or connecting electrical wires inside of RMC is a Calbrite™ product - contact information is given below. Stainless steel RMC is used where corrosive environments will exceed the limitations of aluminum, fiberglass, rigid steel, PVC, & PVC Coated conduit. (Calbrite 2017).

Galvanized RMC meets these standards in the U.S. & Canada

American National Standard for Rigid Steel Tubing (ANSI® C80.1)
Calbrite Corporation, 6451 Northwind Pkwy., Hobart, IN 46342 USA, Tel: 219-844-6800 Website: www.calbrite.com
CSA C22.1, Canadian Electrical Code, Part 1, NOM-001-SEDE, Standard for Electrical Installations
Underwriters Laboratories Standard for Rigid Steel Tubing (UL6)
National Electric Code® 2002 Article 344 (1999 NEC Article 346)
Federal Specification WW-C __581 (cancelled by the U.S. federal government that has adopted the UL6 and ANSI C80.1 standard, this specification can still be referenced) (Calconduit 2017)
UL / cUL 6A Listed RMC

RMC Suppliers, North America

Calconduit™, Galvanized Rigid Conduit Specifications, Galvanized Rigid Couplings, Galvanized Rigid Elbows, Galvanized Rigid Special Radius Sweeps, EMT ELbows, Aluminum Rigid Elbows, Aluminum Rigid Sweeps, retrieved 2017/08/08, original source: http://www.calconduit.com/products/galvanized-rigid-conduit.html
Wheatland Tube, 'CONDUIT TUBING, EMT, IMC, RMC' [PDF], Wheatland Tube, JMC Steel, includes 2011 National Electrical Code References. Wheatland Tube, 700 South Dock Street, Sharon, PA 16146 USA, Tel: 800.257.8182 Email: info@wheatland.com Website: wheatland.com

Tools you and procedures for bending, cutting, installing, electrical conduit

This discussion has moved to a separate aritcle at ELECTRICAL CONDUIT BEND CONNECT TOOLS

Electrical Wiring Conduit Defects Found by Visual Inspection

This discussion has moved to a separate aritcle at ELECTRICAL CONDUIT DEFECTS & DAMAGE

Emt Conduit Specifications

This website provides information about a variety of electrical hazards in buildings, with articles focused on the inspection, detection, and reporting of electrical hazards and on proper electrical repair methods for unsafe electrical conditions.

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

Or see ELECTRICAL CONTUIT, METALLIC FAQs - questions & answers posted originally at this page.

Or see NATIONAL ELECTRIC SURFACE CONDUIT CATALOG 1950 [PDF]

SAFETY for ELECTRICAL INSPECTORS.

SEWER SEPTIC GAS CONDUIT LEAKS - odors carried into a home through its electrical conduit

Or see these

Conduit

Electrical Conduit Types, Applications, Codes, Standards, Sources

EMT ELECTRICAL METALLIC CONDUIT - THIN WALLED METAL CONDUIT - rigid
FMC FLEXIBLE METAL ELECTRICAL CONDUIT - flexible
IMC INTERMEDIATE METAL CONDUIT, THREADED & NON-THREADED - rigid
LFMC LIQUID-TIGHT FLEXIBLE METAL CONDUIT & WHIPS - flexible, liquid tight, with wire
RMC RIGID METAL CONDUIT - rigid

ENT ELECTRICAL NONMETALLIC TUBING - rigid plastic conduit
ENT & LFNC NON-METALLIC ELECTRICAL CONDUIT- flexible plastic & liquid-tight flexible plastic conduit
FLEXIBLE LFNC PRE-WIRED WHIPS - flexible, liquid-tight, with wire

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Technical Reviewers & References

[1] Elizabeth Sluder, Montross, VA, the original author of this article, is a public school teacher who writes basic educational articles about a variety of building, construction, and other topics. Her husband, a licensed electrician, consults for her writing on electrical topics. Her articles appearing at the InspectAPedia ^TM Website have been edited, illustrated, and on occasion content has been added by the website author. These articles are © 2010 InspectAPedia copyright-protected, all rights reserved.
[2] Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted a Home Inspection Home Study Course, and publications such as the Home Reference Book, the Home Reference eBook, and report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
[3] Timothy Hemm has provided photographs of various electrical defects used at the InspectAPedia ^TM Website. Mr. Hemm is a professional electrical inspector in Yucala, CA.
[4] NFPA - the National Fire Protection Association can be found online at www.nfpa.org
[5] The 2008 NEC National Electrical Code (ISBN 978-0877657903) Online Access LINK (you'll need to sign in as a professional or as a visitor)
[6] Thomas & Betts Corporation, Memphis TN, website: www.tnb.com.
[7] Eric Galow, Galow Homes, Lagrangeville, NY. Mr. Galow can be reached by email: ericgalow@gmail.com or by telephone: 914-474-6613. Mr. Galow specializes in residential construction including both new homes and repairs, renovations, and additions.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Recommended books on electrical inspection, electrical wiring, electrical problem diagnosis, and electrical repair can be found in the Electrical Books section of the InspectAPedia Bookstore. (courtesy of Amazon.com)
'Electrical System Inspection Basics,' Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
'Simplified Electrical Wiring,' Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
'How to plan and install electric wiring for homes, farms, garages, shops,' Montgomery Ward Co., 83-850.
'Simplified Electrical Wiring,' Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
'Home Wiring Inspection,' Roswell W. Ard, Rodale's New Shelter, July/August, 1985 p. 35-40.
'Evaluating Wiring in Older Minnesota Homes,' Agricultural Extension Service, University of Minnesota, St. Paul, Minnesota 55108.
'Electrical Systems,' A Training Manual for Home Inspectors, Alfred L. Alk, American Society of Home Inspectors (ASHI), 1987, available from ASHI. [DF NOTE: I do NOT recommend this obsolete publication, though it was cited in the original Journal article as it contains unsafe inaccuracies]
'Basic Housing Inspection,' US DHEW, S352.75 U48, p.144, out of print, but is available in most state libraries.
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Installing Thinwall Metal Conduit
Installing Flexible Metal Conduit
Installing Rigid Nonmetallic Conduit

Making sure that electrical wires are safely secured and protected will keep your home safe.

Thinwall metal conduit can be curved to take corners or, for large sizes, can be fitted with elbows.

Most local codes require that exposed wires be contained within conduit, and for good reason. Electrical wiring can pose a serious fire risk if the wires are damaged or cut. Loose wires also run the risk of being tugged or pulled from their connectors or outlet box.

There are three common kinds of conduit, each requiring a different installation technique: thinwall metal conduit (type EMT), flexible conduit (also called just “flex,” or Greenfield), and nonmetallic conduit (PVC).

Before beginning the actual wiring, you must install the entire conduit system. Planning ahead is a must because you want as direct and straight a route as you can achieve.

Choosing the right kind of electrical conduit for a particular job is key to a successful installation. It will not only minimize the likelihood of future repairs but also reduce the difficulty of the repair should problems arise. Following is a closer look at the three main types of conduit and how to install them.

Installing Thinwall Metal Conduit

In any room where aesthetics are not an issue, such as an unfinished basement or garage, EMT is a good choice to enclose exposed wiring. You will need to determine the correct size conduit based on the number of wires you will be pulling through (see the chart in Electrical Conduit for guidelines). At the same time, keep in mind that pulling wires through a larger conduit than may be necessary will make the job easier.

When creating a conduit system, you will be cutting, coupling, and bending conduit to follow the route you have planned. EMT can be bent with a conduit bender, though you might opt to buy conduit and fittings that are pre-bent, which will cut down on your labor.

EMT requires metal housing boxes, which can be attached to walls or ceilings. Use panhead wood screws for wood framing; however, use masonry screws or expanding anchors for concrete, brick, or block.

Cutting & reaming conduit. EMT can be cut using a tubing cutter or a simple hacksaw. After cutting, be sure to “ream,” or smooth, the edges with a round metal file. If you don’t, burrs or ragged edges could damage the conductors.

Conduit routing logistics. If the simplest route you can plan still contains more than a total of 360 degrees in bends, installing a pull box in a central location (and definitely at a T intersection where a conduit splits in two) will help ease the wires through the route. After the wires are pulled, add a faceplate to conceal the exposed wires. If you don’t have the need for a pull box, simply use corner elbows.

Conduit straps should be used to anchor EMT 3 feet from a pull box and no more than every 10 feet elsewhere in the run. Depending on the surface to which the conduit is being mounted, use the appropriate fastening devices.

Making conduit connections. Sections of EMT can be joined using threadless setscrew couplings. End pieces of conduit slip inside either end of the coupling and are tightened down with setscrews. Elbow fittings come with their own dedicated setscrews.

Joining conduit to boxes. With indoor applications, metal conduit runs to a square or octagonal metal box through a knockout. Choose a box that is large enough to easily accommodate the size of the conduit.

If you are mounting the housing box and conduit directly to a wall, connect them with offset fittings. Connect each fitting to the box with a locknut and each fitting to the conduit with its integral setscrew connector.

Installing Flexible Metal Conduit

Also called Greenfield, or simply “flex,” flexible metal conduit is a good choice for large appliances such as washing machines that might need to be moved for repairs as well as for tight spaces that would make bending EMT too difficult.

Flexible conduit provides a protective sleeve for electrical wires.

Cutting flexible conduit. Like EMT and PVC, you can cut flexible conduit easily with a hacksaw. If you are using connectors and couplings that screw in, there is no need to ream the ends of the conduit after cutting.

Bending & supporting flexible conduit. Even though flexible conduit lives up to its name, a single run between boxes and fittings should not bend more than a total of 360 degrees. Conduit straps should be installed no more than a foot from a box or fitting and no more than 4 1/2 feet apart in a run.

Grounding conduit. Local codes require that flexible conduit be grounded; most systems simply run a grounding wire alongside the circuit conductors.

Installing Rigid Nonmetallic Conduit

The most commonly used of all nonmetallic conduit for home applications is Schedule 40 PVC. Resistant to fire, heat, and sunlight, this plastic conduit is lighter weight, less expensive, and easier to work with than EMT. However, it is not permitted in certain regions, so check your local building codes before installing it. To make sure you purchase the right stuff, check that it is marked with an endorsement from a testing lab for electrical materials; PVC pipe that is used in irrigation applications is not an appropriate substitute.

Nonmetallic conduit also requires using PVC housing boxes. Since nonmetallic conduit systems are not grounded, a grounding wire must be run alongside the conductors.

Cutting & trimming conduit. As with EMT, PVC can be easily cut with a hacksaw. Be sure to file down rough edges after cutting to prevent the conductors from becoming damaged.

Emt Conduit Installation Cost Per Foot

Joining conduit. Straight Schedule 40 PVC comes in lengths that are 10 feet and have one coupling apiece. Use gray conduit cement to join conduit to fittings.

Bending nonmetallic conduit. PVC conduit can be bent using an infrared heater specially made for this purpose. Do not try any other heat source, such as a blowtorch, or you will simply ruin the conduit. Of course, the easiest method is simply to buy PVC that has already been bent. When designing your system, plan it so that no run of conduit between boxes or fittings makes more than the equivalent of a 360-degree turn.

Supporting conduit. To support nonmetallic conduit, place straps no more than 4 feet from each box or fitting as well as along the run.