Conduit Fittings Guide: Types, Uses and Selection Tips

What is a conduit fitting?

A conduit fitting connects, terminates, adapts, seals or provides access to a raceway system.The fitting must match the wiring method and perform its intended job without damagingconductors or weakening the raceway.

Conduit fittings include connectors, couplings, locknuts, bushings, hubs, nipples,reducers, adapters, conduit bodies and fittings for flexible raceways. Many common productsare covered by UL 514B, but the product markings and manufacturer instructions determinethe permitted uses of a particular fitting.

Straps and hangers are related support hardware. For support selection and spacing, seeRevco'sconduit clamps and straps installation guide.

Choose the fitting by the job it needs to do

Common conduit fitting types

Connectors

Connectors terminate conduit or tubing at a box, cabinet or enclosure. EMT connectors arecommonly available in set-screw and compression styles. Flexible raceways use connectorsdesigned for the specific raceway, such as FMC, LFMC or LFNC.

Do not assume a fitting is suitable outdoors because it uses a compression nut. For a wetlocation, the product must be specifically identified for that environment. Look formarkings such as “raintight” where required.

Couplings

Couplings join two sections of conduit or tubing. Standard couplings connect the same wiringmethod and trade size. Combination couplings join different wiring methods, such as EMT toflexible metal conduit or armored cable, when the product is listed for that transition.

Avoid improvised combinations of reducers, locknuts and unrelated connectors. Use onefitting identified for the complete transition.

Bushings, locknuts and hubs

Locknuts secure threaded fittings to an enclosure. Bushings provide a smooth surface thathelps protect conductor insulation. Insulated and grounding bushings serve differentpurposes and should not be treated as interchangeable.

The need for a bushing, bonding bushing or equivalent fitting depends on conductor size,raceway type, service conditions and the termination. Check the applicable NEC section andthe equipment design rather than applying one rule to every entry.

Hubs are used where a secure or environmentally rated connection is needed at an enclosure.Confirm that the hub matches the raceway threads, enclosure opening and requiredenvironmental rating.

Elbows, sweeps and pull elbows

Elbows and sweeps change the direction of a raceway. Long-radius sweeps can reduce pullingtension. Pull elbows provide access but must remain accessible after installation.

Many common raceway articles limit the total bends between pull points to 360 degrees.Check the article governing the actual wiring method before laying out the run.

Conduit bodies

Conduit bodies provide access for pulling conductors and changing direction. Commonconfigurations include LB, LL, LR, C and T.

Do not make splices in a conduit body unless it is marked with a usable volume and thecompleted installation satisfies the applicable fill requirements. Conductors 4 AWG andlarger may also trigger pull-space requirements.

For more detail, seeConduit Bodies 101.

PVC adapters, couplings and expansion fittings

PVC systems use fittings designed for rigid nonmetallic conduit and the approved joiningmethod. Clean, prime and cement the joint according to the product instructions.

Temperature changes can cause long aboveground PVC runs to expand and contract. Where thecalculated movement requires an expansion fitting, install the fitting, fixed points andsupports as one planned system.

SeeHow to Choose Conduit Cement and Primerfor PVC joining guidance.

Flexible-conduit fittings

FMC, LFMC and LFNC require connectors identified for the exact flexible raceway. Straightand angled fittings are available, but some angled flexible-raceway connectors are notpermitted where concealed. Check the applicable raceway article and product information.

Where movement or vibration is expected, confirm the permitted raceway length, support,bonding and environmental conditions. Flex should solve an actual movement or connectionproblem, not cover poor raceway layout.

How to choose the right conduit fitting

1. Identify the wiring method.Determine whether the raceway is EMT, IMC, RMC, rigid PVC, FMC, LFMC, LFNC or another system.
2. Confirm the trade size.Match the fitting to the conduit and enclosure opening. Do not size from appearance alone.
3. Define the fitting's job.Decide whether it must connect, couple, transition, seal, protect, reduce, expand or provide access.
4. Classify the environment.Determine whether the location is dry, damp, wet, corrosive, washdown, buried or classified.
5. Check conductor and pulling requirements.Consider conductor size, bend limits, pulling access, box dimensions and conduit-body volume.
6. Review bonding and grounding.Confirm whether the fitting is part of the equipment-grounding path or requires added bonding components.
7. Read the product markings.Verify the listing, material, environmental rating and permitted installation method.
8. Follow the installation instructions.Use the specified preparation, sealing method, wrenching surfaces and torque values where provided.

Four jobsite examples

Dry-location EMT entering a junction box

Use an EMT connector that matches the trade size and enclosure opening. Set-screw andcompression connectors may both be options in a dry location when properly listed andinstalled. Confirm whether an insulated throat, locknut or separate bushing is required.

EMT entering an exterior enclosure

Use an EMT connector specifically identified as raintight and install its gasket or sealingcomponents as directed. A standard compression fitting should not be assumed to provide araintight connection.

Conductors installed in a raceway in a wet location must also be suitable for wet locations.

Liquidtight flexible conduit serving a motor

Choose a connector listed for the exact liquidtight raceway and environment. Confirm thestraight or angled configuration, permitted flex length, support, bonding and equipmentmovement before ordering.

Long exterior PVC run

Use fittings identified for the PVC raceway and environment. Calculate expected thermalmovement before deciding whether an expansion fitting is required. Coordinate the expansionfitting, fixed point and straps so the system can move as intended.

Common fitting mistakes

• Using a fitting made for a different raceway or trade size.
• Assuming every compression fitting is raintight.
• Using a standard fitting where corrosion or washdown exposure requires something else.
• Improvising a transition instead of using a listed combination fitting.
• Failing to ream or deburr a cut raceway before installing the fitting.
• Splicing in a conduit body that has no marked volume.
• Ignoring pull-space requirements for larger conductors.
• Overtightening a fitting or wrenching it from the wrong surface.
• Blocking access to conduit-body or pull-elbow covers.
• Forgetting bonding or grounding requirements at the enclosure.
• Using dry-location conductors inside a raceway in a wet location.
• Skipping expansion planning on long PVC runs.

Before ordering, collect these details

• Raceway type and trade size.
• Enclosure opening or knockout size.
• Connector, coupling, transition or access requirement.
• Dry, damp, wet, buried, corrosive or classified location.
• Straight or angled configuration.
• Conductor size and quantity.
• Required enclosure or fitting environmental rating.
• Bonding or grounding requirement.
• Project specification and preferred manufacturer.
• Required date and pickup location.

Frequently asked questions

Are compression EMT fittings automatically raintight?

No. The fitting must be specifically identified as raintight. Verify the product marking,gasket arrangement and installation instructions.

What is the difference between a connector and a coupling?

A connector normally terminates a raceway at a box, cabinet or enclosure. A coupling joinstwo sections of raceway.

When is an insulated bushing required?

The answer depends on the conductor size, raceway, entry and equipment termination.Check the applicable NEC provisions and fitting or enclosure design.

Can conductors be spliced inside an LB?

Only when the conduit body is marked with a usable volume and the completed splice satisfiesthe applicable fill and conductor-space requirements. If the marking is missing or unclear,use the body as a pull point only.

Can different conduit materials be joined?

Yes, when a listed transition or combination fitting is identified for both wiring methods.Do not assemble unrelated fittings and assume the result is approved.