Does THHN Wire Have To Be In Conduit?

Electrical wiring isn’t a job that’s sometimes finished by householders and DIYers. Nevertheless, some folks do minor electrical repairs and additions to {the electrical} programs in properties. One of the crucial complicated elements of correctly putting in electrical wiring is knowing when to surround the wiring in a conduit. Many individuals marvel if THHN wires have to be run in conduit with a purpose to be correctly put in.

THNN, Excessive Temperature Thermoplastic Nylon, refers back to the properties and supplies used to insulate the wires. In accordance with the Nationwide Electrical Code (NEC) Artwork 300, particular person conductors have to be put in in a conduit, cable or enclosure. Most native constructing codes are primarily based on the NEC. Consequently, a THHN cable have to be put in in a conduit to fulfill electrical codes.

It’s uncommon for THHN cables to be put in in a residential electrical set up. The added expense and labor required to put in conduit makes Romex electrical cable rather more widespread for residential installations. THHN cables can be utilized anyplace Romex cables are put in offered the THHN is protected by conduit and the suitable housings and connectors.

Want electrical wiring or panel improve providers?

Obtain free, no-obligation quotes from skilled contractors close to you.


What’s THHN wire?

THHN stands for Thermoplastic Excessive Warmth Resistant Nylon Coated. This refers back to the properties of the insulating materials that protects the wire. Most often, THHN wire is rated for functions as much as 600 volts and in environments the place the temperature doesn’t exceed 194 levels Fahrenheit. THHN wire isn’t designed for moist areas.

Basically, THHN sire is appropriate to be used in all industrial and residential AC wiring functions the place it meets the voltage and temperature scores. Per the Nationwide Electrical Code, THHN wires utilized in an AC electrical system have to be put in in conduit. Most native constructing codes comply with the NEC code.

What sorts of conduit can I take advantage of with THHN wire?

THHN wire is appropriate to be used with all seven conduit sorts in residential and industrial AC electrical system installations. The nylon and PVC insulation of THHN stranded wire makes it a superb alternative for pulling by way of conduit.

Remember that some sorts of conduit should not appropriate for outside or underground installations. Your native constructing code is the very best supply for figuring out what sort of conduit materials is suitable to your set up.

What number of THHN cables can I run by way of a conduit?

Two components sometimes decide what number of particular person THHN wires will be run by way of a given line. The thickness of the wire being pulled by way of the road is an element. The inside diameter of the pipe is the opposite issue. The NEC units requirements for the variety of wires that may be pulled by way of conduit.

The next desk describes what number of THHN wires of a given diameter will be pulled by way of the most typical sizes of conduit utilized in america.

line measurement and kind 14AWG 12AWG 10AWG 8AWG 6AWG
½ inch EMT 12 9 5 3 2
½ inch IMC 14 10 6 3 2
½ inch GRC 13 9 6 3 2
¾ inch EMT 24 17 11 6 4
¾ inch IMC 24 17 11 6 4
¾ inch GRC 22 16 10 6 4
1 inch EMT 35 26 16 9 7
1 inch IMC 39 29 18 10 7
1 inch GRC 36 26 17 9 7

Can THHN wire be utilized in underground strains?

THHN can be utilized underground offered it’s routed by way of the suitable conduit. Not each sort of line is designed for underground use. If THHN cable is used, it have to be routed by way of a water-resistant conduit. THWN, a type of THHN wire, is designed to be used in moist areas and is often utilized in functions the place water is or could also be current.

You can not bury THHN or THWN immediately underground. The insulation isn’t designed or permitted for direct burial. PVC electrical conduit is the widespread sort of conduit for underground electrical installations. Some metallic pipes can be utilized underground however require watertight connections

Why does not Romex need to be within the conduit like THHN?

Romex is a model identify for electrical cords generally utilized in residential wiring. Romex is a bundled wire with a non-metallic sheath. The Nationwide Electrical Code considers the jacket of Romex cable to be conduit or conduit for {the electrical} wires within the bundle.

Romex’s sheathing must be non-conductive, flame retardant, and moisture resistant. This meets the NEX necessities for shielding {the electrical} wiring. The NEC additionally specifies the place Romex could also be used and the way the Romex must be hooked up, supported and secured to junction containers.

Some jurisdictions don’t enable using Romex in residential buildings. Armored cable is the widespread sort of wiring utilized in residential communities in these jurisdictions.

ROMEX vs. THHN wire

THHN and Romex wires can in lots of instances be used for a similar functions. Easy wire sort has its personal benefits and downsides. Understanding these professionals and cons is essential to creating the very best resolution to your cabling activity.

Execs and cons of Romex wire.

Romex is broadly utilized in residential PBX wiring in america. Its many benefits make Romex an affordable and economical methodology {of electrical} wiring. The principle benefits of Romex embody the next.

Some great benefits of Romex

  • Romex is obtainable in a wide range of sizes and bundle combos. Normal sizes vary from 14 to 2 AWG with one to 3 conductors within the bundle.
  • Romex NM-B is NEC compliant for residential functions for all department wiring providers. The PVC jackets are versatile and make set up simpler. ROMEX is appropriate for inside partitions, garages and above-ground surfaces.
  • Romex is coloration coded for simple identification. The colour of the PVC jacket shortly and simply identifies the dimensions of the cable.
  • Set up is fast and straightforward, and will be finished proper by way of partitions, attics, and basements with no conduit.

Nevertheless, Romex isn’t with out its drawbacks. Some installations might not be appropriate for Romex

The disadvantages of Romex

  • Romex isn’t designed for outside use. Publicity to direct daylight and the weather can shortly degrade, crack and fail the PVC sheathing. Most US constructing codes don’t enable Romex to be put in outdoor with any type of further safety resembling conduit.
  • If it’s important to function Romex in a cable duct, the cable duct have to be dimensioned accordingly. Making an attempt to tug Romex by way of a line that’s too small can stretch and injury the PVC jacket.
  • Romex is definitely broken or pinched when making exit and entry factors round the home. The entry and exit factors of the home have to be fitted with an appropriate connector or bushing to guard the PVC sheathing.
  • Romex operating by way of studs in inside partitions can simply be broken by nails or screws. Care must be taken to not use fasteners close to the Romex wire information.

Broadly utilized in residential development, Romex provides a cost-effective and secure method to run drop cables round your house.

Execs and cons of THHN wire

THHN is broadly utilized in industrial electrical installations for a lot of causes. Nevertheless, it’s not the reply to each wiring scenario. You have to take these benefits and downsides of THHN wire into consideration in your planning.

Some great benefits of THHN

  • THHN wire’s PVC and vinyl insulation makes it simple to tug by way of conduit. In functions the place conduit is required to fulfill constructing codes, the flexibility to tug giant bundles of wire by way of the put in conduit is essential.
  • THHN wiring is broadly accepted by constructing codes in america. This makes planning your mission a lot simpler in some instances.
  • THHN is appropriate to be used in excessive temperature areas. Most often, THHN can be utilized at temperatures under 90 levels Celsius.

THHN wire is the mainstay of {most electrical} installations. Romex is in style for residence wiring the place constructing and electrical codes enable.

The disadvantages of THHN

  • The principle drawback of THNN wiring is the NEC’s requirement that the THHN wiring be routed in an acceptable conduit or conduit. Putting in the road provides to the price of the set up. Particular abilities and instruments are required to correctly set up the road, which incurs further prices.

Virtually each constructing code in america requires electrical circuits inside a industrial constructing to be routed in conduit. THHN wire is the selection of most electricians when the wire must be enclosed in electrical conduit.

Is THHN Wire the identical as THWN?

THWN wire is identical as THHN. Nevertheless, THWN is rated waterproof. THWN is NEC permitted to be used in moist areas in underground functions that might not be watertight.

Most single strand THHN wire now offered in america is twin rated THHN and THWN. In case your cable is marked THHN and THWN, the cable can be utilized in functions the place moisture could in any other case be an issue.

Want electrical wiring or panel improve providers?

Obtain free, no-obligation quotes from skilled contractors close to you.


THHN wire and conduit functions

The Nationwide Electrical Code is specific in its necessities for THHN. In all functions the place AC energy is supplied with THHN wire. The wire have to be in a correctly put in conduit or conduit. Operating THHN wiring within the open or unprotected isn’t solely unsafe, it additionally doesn’t adjust to electrical codes.

Dennis Howard

Dennis is a retired firefighter with an intensive background in development, residence enchancment and transforming. He labored part-time within the trades whereas serving as an lively obligation firefighter. After his retirement he began a transforming and residential restore enterprise which he ran for a number of years.