The National Electrical Code (NEC) 2023 provides guidelines for determining the appropriate conduit size based on wire size, type, and number of conductors. Conduit sizes are typically measured in inches and are influenced by various factors, including the kind and quantity of installed wiring. For example, a 1″ schedule 80 PVC conduit will fit six 12 AWG THWN conductors, while a 2″ LB conduit is large.
Conduit sizes can be found in both flexible and rigid designs, with metal conduit using aluminum or steel, while plastic conduit could be made from plastic. For 6/3 wire, a 1″ schedule 40 PVC conduit is generally recommended, but it may vary depending on the conduit material and specific project requirements.
In order to ensure proper airflow, cable cooling, and prevent jams, it is essential to have an adequate amount of empty space within a conduit. An online voltage drop calculator can help determine conductor size based on the maximum load needed, and larger sizes can be ordered for specific commercial and industrial applications.
Conduits can be used in either rigid or flexible forms, protecting wires and being used in exposed locations or unfinished areas like basements. The most common diameters for conduits are 1/2 inch to 6 inches, and sizes are typically stated in inches. For specific commercial and industrial applications, conduit sizes can be ordered in millimeters based on the outer diameter.
In conclusion, any outdoor conduit should be suitable for modern electrical installations, with a suitable space factor for proper airflow, cable cooling, and heat dissipation.
📹 Electrical Conduit: Types and Uses
In today’s video we want to talk to you about a common component commonly used by most almost all electricians today.
What type of conduit fitting used for outside installation?
Compression fittings are of paramount importance in outdoor settings, as RMC, or rigid metallic conduit, boasts thicker walls than EMT, thereby conferring enhanced strength and resilience to harsh conditions.
Should outdoor wiring be in conduit?
Conduit is often necessary for outdoor wiring to protect wires from damage and moisture. There are two main types: rigid metal conduit (RMC) and electrical metallic tubing (EMT). RMC offers better protection and requires less digging, while EMT is typically used above ground or in protected areas. Conduit also simplifies future maintenance, allowing for easy replacement or addition of wires. Electrical wire can be outside, but it must be designed for outdoor use.
What conduit to use for outdoor?
PVC conduit is a lightweight, cost-effective, and resistant to moisture, corrosion, and UV radiation. It is suitable for various outdoor applications like landscape lighting, sprinkler systems, and electrical outlets. Rigid Metal Conduit (RMC), also known as galvanized steel conduit, is a heavy-duty option for outdoor electrical installations. It is made of steel and coated with zinc for superior corrosion protection.
RMC is commonly used in industrial settings, outdoor infrastructure projects, and areas where the conduit may be exposed to significant mechanical stress. However, it requires special tools and fittings for installation. The PAG13PVC Series is a flexible metal conduit water-proof option.
What is the NEC code for exterior outlets?
Outdoor receptacles must be protected by ground-fault circuit-interrupter (GFCI) systems, with exceptions for snow-melting or deicing equipment. These protections can be provided by GFCI receptacles or circuit breakers. Homes should have at least one outdoor receptacle at the front and rear of the house, accessible from the ground and no more than 6 1/2 feet above grade. Attached decks and balconies with interior access should have a receptacle no more than 6 1/2 feet above the deck or balcony walking surface.
Receptacles in damp locations must be weather-resistant and have a weatherproof cover, while those exposed to weather must be weather-resistant and have a weatherproof “in-use” cover. A permanent swimming pool must have an electrical receptacle no closer than 6 feet and no further than 20 feet from the closest edge of the pool, with GFCI protection. Receptacles used to power pump systems on pools and spas must be no closer than 10 feet from the inside walls of a permanent pool, spa, or hot tub if not-GFCI protected, and no closer than 6 feet from the inside walls if GFCI protected.
Rules for outdoor lighting are primarily about using fixtures rated for use in damp or wet locations. Light fixtures in wet/exposed areas must be listed for wet locations, while fixtures in damp areas must be listed for damp locations. Surface-mounted electrical boxes must be raintight/weatherproof, and low-voltage lighting systems must be listed by an approved testing agency. Switches controlling pool or spa lights or pumps must be located at least 5 feet from the outside walls of the pool or spa unless separated by a wall.
What are the requirements for outdoor electrical conduit?
Rigid metal conduit (RMC) requires a trench 6 inches below the surface, while underground feeder (UF) cable requires a minimum 24-inch deep trench. PVC conduit requires 18 inches of soil above it. The backfill material must be smooth and not contain stones or rocks. All underground electrical cables require a conduit to support and protect them for at least 18 inches underground to its connection at the LB conduit body or box.
Which conduit is not rated for outdoor use?
Despite the numerous benefits of PVC conduit, it is not recommended for use in areas with direct sunlight exposure due to the potential for accelerated aging.
Is flexible conduit suitable for outdoor use?
Flexible conduits are versatile electrical conduits used in various applications. The standard type is flexible metal conduit (FMC), which can be used in sealed and exposed conditions. It is not recommended for outdoor or wet conditions. Liquidtight flexible metal conduit (LFMC) is a watertight outdoor electrical conduit with plastic sealed coverage, suitable for outdoor applications and direct burial. Non-metallic flexible conduit (LFNC) is an inexpensive option for outdoor applications, such as backyards.
It can be placed indoors in walls and ceilings and is suitable for direct burial. Flexible conduits are commonly used in building construction, residential buildings, indoor wire runs, outdoor equipment, and connecting junction boxes to electric appliances. They are also suitable for connecting critical circuits and lighting fixtures. The conduit’s liquid-tight nature makes it suitable for direct burial.
How do you run electrical conduit through an exterior wall?
To install a conduit, turn off the power and turn off the circuit breaker at the service panel. Install cable connectors, mark the studs, drill a hole in the wall for the conduit, cut and bend it, insert it into the hole, install conduit supports, and pull the wire through the conduit. Use a non-contact voltage tester, stud finder, conduit bender, fish tape, drill, drill bit set, caulk gun, hacksaw, screws, utility knife, and Ell puller. Include cable, cable connectors, conduit hangers, drywall anchors (optional), wire nut, and silicone caulk. This DIY project can save time and improve lighting in outdoor spaces.
Can schedule 40 conduit be used outdoors?
Schedule 40 rigid PVC conduits are suitable for aboveground use in residential, commercial, and industrial settings, shielding wires from physical damage, moisture, and environmental factors. They are known for their corrosion resistance, ease of installation, and cost-effectiveness. The term “schedule” refers to the standard used to define the conduit’s wall thickness and strength, while “40” specifies the exact wall thickness and pressure rating for the conduit within this classification. These conduits are commonly used in residential, commercial, and industrial settings to protect wires from physical damage, moisture, and environmental factors.
Should I use schedule 40 or 80 conduit?
Schedule 80 PVC conduit is a type of pipe made from polyvinyl chloride (PVC) with a thicker wall than standard Schedule 40 PVC conduit. This increased wall thickness makes it more robust and suitable for applications requiring higher crush resistance and pressure rating. Schedule 80 PVC conduit is required for installations in high temperature environments and is suitable for applications where temperatures may be high.
What are the NEC requirements for outdoor connections?
Outdoor receptacles must be protected by ground-fault circuit-interrupter (GFCI) systems, with exceptions for snow-melting or deicing equipment. These protections can be provided by GFCI receptacles or circuit breakers. Homes should have at least one outdoor receptacle at the front and rear of the house, accessible from the ground and no more than 6 1/2 feet above grade. Attached decks and balconies with interior access should have a receptacle no more than 6 1/2 feet above the deck or balcony walking surface.
Receptacles in damp locations must be weather-resistant and have a weatherproof cover, while those exposed to weather must be weather-resistant and have a weatherproof “in-use” cover. A permanent swimming pool must have an electrical receptacle no closer than 6 feet and no further than 20 feet from the closest edge of the pool, with GFCI protection. Receptacles used to power pump systems on pools and spas must be no closer than 10 feet from the inside walls of a permanent pool, spa, or hot tub if not-GFCI protected, and no closer than 6 feet from the inside walls if GFCI protected.
Rules for outdoor lighting are primarily about using fixtures rated for use in damp or wet locations. Light fixtures in wet/exposed areas must be listed for wet locations, while fixtures in damp areas must be listed for damp locations. Surface-mounted electrical boxes must be raintight/weatherproof, and low-voltage lighting systems must be listed by an approved testing agency. Switches controlling pool or spa lights or pumps must be located at least 5 feet from the outside walls of the pool or spa unless separated by a wall.
📹 CONDUIT FILL EXAMPLES for the Modern Electrician – How Many Conductors Can I Put In…
This video is packed with useful information on how to calculate examples of conduit fill using the National Electrical Code as the …
Non-electrician here, but perusal the website to START my education because I plan to re-wire my house in a few years. Looking in my basement, I see a few tubes of 1/2′ NMT filled with Romex along the walls. Some have one, others have two. Is Romex, when still fully sheathed, considered one conductor or still considered multiple? In either case, I feel these conduits are overfilled.
A few points. 1) heat is a factor in raceway fill since mutual heating becomes an issue. There are Performance and Prescriptive Requirements and the prescriptive requirements that demand the maximum fill are to also help satisfy the performance requirements so as to not damage the thermal properties of the insulation. 2) Yes, another key factor is indeed reducing the potential for damage during the installation. Remember, that Informative Annex C is only for raceway fill as a short cut when ALL the conductors are the same size, it doesn’t reference heat simply because it is again simply giving users as a shortcut method to maximum fill if all the rules are adhered to. Back to heating, just because the values of 310.15(B)(a) and 310.15(B)(a) appear to have no relationship to raceway fill they do when ampacity is involved and the perfect world of 310.15(B), such as more than 3 current-carrying conductors are encountered. The annular space that is also maintained helps to allow heat dissipation, not removal. Just some thoughts to share. Now, if the heat was not involved AT ALL then why do you think nipples allow fill allowances to he up to 60%, it is due to the limited length and availability of enhanced heat dissipation. Clearly, the reduced nipple length is not an installation damage concern during the installation. Point is they all work together in a Performance and Prescriptive method by using all areas of the NEC.
I’ve watched a few of your articles & stumbled on this one. I don’t do a lot of electrical anymore but I’m building a large shed for my woodworking equipment. This conduit episode is perfect as I need to run about 100’ of 1/0 Thhn Thwn 2 for a sub panel.Also thanks for the ugly’s book have one on order. I also just subscribed as I believe you website is awesome.
Please check your code book. If you read the informational notes of Annex C in the NEC Handbook it leads you 300.17, which clearly reads… “the number and size of conductors in any raceway shall not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the conductors or their insulation”.
Hi, looking at this, something does not add up, for instance, table say only 8 THHN conductors/wires are allowed in a 1/2 ” PVC sch40 conduit, right ?, but you are supposed to be able to use 40% of the conduit cross section area, if you do the math, 8 wires is only about 16% of the cross section, so what is right ?? Well, my dimension were wrong, so 8 wires 12 gauge take 31.26 to 33.8 % (depending on sizes of both pipe and wire), so now makes sense, if sizes/dimensions are wrong the math won’t make sense. And actually I put only 6 scrap pieces of wires to see how they would look in the pipe, and it look crowded, so 8 is enough, and pulling them in curves etc, might not be easy, so the code makes sense. 😂😂
I think the other reasoning behind it is that conductors expand/contract depending on ambient temperature (especially in unconditioned spaces, or if buried). If conduit was crammed full during the winter for example, and all the conductors expand during the summer, it’s possible they could get damaged somehow. But yeah biggest one is probably just for sake of pulling conduit and the jacket not getting destroyed.
Honestly, the internet is scaring me. I’m looking toward relocating (or having it done) my main panel and meter and upgrading from the currently existing two panels (one in the main house and one in the semi-detached former two car garage/previous owner’s workshop) to those two plus three more panels: one in the “pool house”, one in the tool shed/workshop, and one in the “barn.” I was thinking about duct banks and what size conduit I’d need to run the feeds underground for all three panels (since the closest is about 100 feet, the next one at about 125 and the third at about 185 feet). I mean, I thought it, and whoa, here’s a article talking about it. scary.
Dustin, Very good article! A couple finer points. The conductor areas listed in the tables are information based on Southwire. Exception allows you to use manufacturers information for specific conductors. Also, somewhere in the back it says that at 40.5% you can round down. I’m sure you can guess how I found this out after designing electrical for 35 years. I needed both to be legal. Very respectfully, Kevin
Hey boss man i came across your articles a few weeks ago and im really excited about starting out in learning this trade . Im 32 married with three children, iv always done blue collar work my whole life, such a- yard care -tree care -a little bit of remodeling-alot of painting -and framing new construction, any way i never graduated or got a GED, but i feel like the electrician trade would be a good fit for me and my body, i was in a very bad vehicle wreck three years ago. I broke my back and neck, some ribs and my left collarbone, im back at well 85% i feal like your a strait shooter, id like to hear your thoughts on starting my apprenticeship for the electrician trade, and would anyone even look my way to train me, would love to hear from ya brother, no sugar coating on your opinion 👊.
Great job explaining thank you can you send one your cool t-shirt im Mari it’s my 3 year apprentice electrician and I always ask guys at work about wires how many wires can feed through EMT 2″ 3″ 4″ I think they don’t have no clue or they’re jealous cause I’m women. Thumbs up actually right now I’m read NEC 2021 book.
As a professional electrical engineer I found this article helpful. I’ve taken my fair share of academic courses and certifications and there is so much information to remember its insane. I have to do fill and bend radius calculations on a daily basis so i tend to forget some of the other useful pieces of code in the NEC.
This makes sense for new installations. What are some things that are done for existing installations?For example, suppose your conduit was behind a brick wall and adding one new conductor would exceed the 40% limit. Do you have no choice but to tear into the wall and disconnect all the wires to install a larger conduit in order to pass inspection? My assumption was that the purpose of limiting the numbers is to insure that there was room for more if a modification is made.
Good article BUT the NEC will argue with you about derating of conductors and the AHJ may make you change them if not factored correctly. Derating the size has to be applied when running more than 3 current carrying conductors in a conduit. This is why is makes more sense to run smaller conduits like 3/4″ with less conductors because it’s not economical to upsize the wire when you fill a larger conduit with more conductors & the wire size needs to be increased due to derating. This is one subject that is always argued upon in the field. Wish the NEC would clear it up better. Other factors to consider are ambient temps say in a boiler room that has temps above 86 deg F. Also the termination lug rating of equipment can dictate what rating of wire amp table you can apply. Say your breaker lug has a rating of 75 c you can’t use the 90c amperage table for wire size. I advise Apprentices to dig a bit deeper & check several opinions from Youtube & Google for you answers. On another thought the factories I’ve worked in over the years have plenty conduits overfilled with general purpose branch circuits, not that it’s right but they operate fine. You really need to be careful when running heavy amperage circuits like motor loads ect in the same conduit. I don’t claim to be an expert but have 40+ years experience.
This is great info and have had to use this plenty of times but is only good for maybe control wire. I don’t get this chart because of the derating factor chart. See if your inspector passes you with 16 #12 in a 3/4″ emt for branch circuits. Also i think the derating chart should be for continuous loads . Or at least some type of residential exemption.
I would like input on a conduit question. People putting NM in conduit. My first reaction is no you can’t put NM in conduit but.. I have also heard there is nothing in the NEC code that says you can’t. The thermal characteristics are different between single vs a bundle of wires so you do have to oversize the conduit compared to a bundle of single wires. If you feel like commenting please tell me where in the NEC book it’s covered. Great article thanks
I asked ChatGPT 4o “So I have a 4-aug wire, a black one. I have a red 4-aug wire and a green 8-aug wire. According to the National Electric Code of 2020, in terms of conduit fill, am I under code if I use a Schedule 40 1-inch conduit?” It answered me: “To determine if your wire setup is within the code for conduit fill according to the 2020 National Electrical Code (NEC), we need to refer to NEC Chapter 9, Table 5 for the wire dimensions and Table 4 for the conduit fill capacities. Here’s the step-by-step process: 1. *Determine the cross-sectional areas of the wires:* – For 4 AWG wire (both black and red): – THHN/THWN insulation has an approximate area of 0.0837 square inches each. – For 8 AWG wire (green): – THHN/THWN insulation has an approximate area of 0.0366 square inches. 2. *Sum the areas of the wires:* \\( \\text{Total Area} = (2 \\times 0.0837) + 0.0366 = 0.204 \\text{ square inches} \\) 3. *Check the fill capacity for Schedule 40 1-inch conduit:* – According to NEC Chapter 9, Table 4, the maximum fill for a 1-inch Schedule 40 PVC conduit is 0.346 square inches (40% fill for three or more conductors). Since the total area of your wires (0.204 square inches) is less than the allowable fill capacity (0.346 square inches), you are within the code for conduit fill using a 1-inch Schedule 40 conduit. Therefore, using a Schedule 40 1-inch conduit for your specified wires is compliant with the 2020 NEC code.” What a genius!
I came looking for big wire porn….. got math instead….. haha. But really, this is good stuff, things that often get overlooked. Most electricians I’ve worked along side go with the (how much is too much to pull) measurement style. Or the, “I’m not going to add more conduit so get the damn thing in there” style of measurement.
300.17\tNumber\tand\tSize\tof\tConductors\tin\tRaceway. The number\tand\tsize\tof\tconductors\tin\tany\t raceway\tshall\tnot\tbe more\tthan\twill\tpermit\tdissipation\tof\tthe\theat\tand\tready\tinstallation or\twithdrawal\tof\tthe\tconductors\twithout\tdamage\tto\tthe conductors\tor\tto\ttheir\tinsulation.
Kind of in the weeds a bit more, but when filling conduit with multiple branch circuits, do you try to even out which line (120/240 split phase) the branch circuits are supplied by, if running hot and neutrals in separate conduits? Ex: 8 conductors, 4 branch circuits, if all on line 1 supply, would increase mutual inductance in both the conductors and any EMT/Liquidtight metallic. This would increase your eddy currents, reducing your ampacity margin, right? Or is this just not a big enough impact to consider?
Great vid….with helpful info. Liking these quick short vids touching on the “main” points of each subject etc…..& then on some you delve a little deeper👍🏻 Any new apprentice or helper I get, I tell them about your website, & that you have some great vids etc….that they can watch & enjoy. Very useful for anyone at any stage in their carrier. Have enjoyed the “podcast” type vids w/ the different ppl you’ve “interviewed/talked with” recently. Like that can put vid on & listen while I work👍🏻 Loved the stories & life experience from the last one a lot😊 (hope keep up w/ normal vids & throw those in couple times a month). Cheers✌🏼
What is the difference between nipples and conduit? Is it just the length (9.0 seems to indicate 600mm (24in) is a qualification characteristic), or are there other different characteristics between nipples and conduits? Are you allowed to have bends in a nipple (like, a jog to connect misaligned holes on two electrical boxes), or once you put a bend in a nipple does it become a conduit?
I have to say I disagree on the conduit fill doesn’t apply to heat argument. While the damaging of the insulation while pulling is probably more pertinent to the conduit fill, it is still relevant to think about heat. The more conductors in a a conduit the more heat (wattage/resistance) per length and therefore the more likely insulation may breakdown. Either way we are worried about the insulation breaking down and potential shorts between conductors.
i am completing the design for the full electrical remodeling of the warehouse. i’ve devised the calculator for the conduit fill check. dustin, if yopu are interested, let me know. the program is fast and accurate, and the data is taken from the “uglly’s”. thanks for the article and for your website. toly
This made a lot more sense seeing the highlighted sections and tabs in both your codebook and your ugly’s. Im soon to be a fourth year and haven’t had a full on immersion into the way to effectively tab a code book let alone an ugly’s. If you have time, could you either link a previous article or potentially create something informative, using examples like the brilliant ones in this article, to illustrate where and what to highlight. The stuff we use all the time, maybe a penultimate “the final test” article, or just something to help us highlight and label our books. Did I see that you have the tables tabbed on the top edge as opposed to clumped in and lost among the other articles. That’s BRILLIANT! Super helpful to see something like that, as many code tabs instruct us to put them all on the one mail edge. I love the outside the box creativity. It’s inspiring.
Someone please explain to me why you would want to put more than one romex wire through a single tube of conduit. Obviously this section of the code is there because people do it but I can’t understand what circumstance that would be necessary. Why not just run more conduit or split it off with a junction box?
Hey Justin, great article. I a question regarding running ethernet cabling for cameras. I’m running Cat6 and thinking about using Emt can I this table or the section for low voltage. I’m looking to run Cat6 line from the basement to the second floor for residential on the outside no way to fish up in the wall. What you suggest, Thanks
Dustin, Great article I have a question for you. I’m replacing 1×50 wire degraded cable with 5 x CAT 6 cables through an existing already buried 3/4″ conduit. What are your recommendations? Based on all your NEC warnings requirements with no more than 40% fill, I’m I screwed from the start? I’m routing CCX lines. I prefer 1 cable, 1 line for simplicity. I can reduce down to 3 cables, but I don’t really want to use wire for different purpose than it’s intention and don’t want to replace a hack with a hack.
I don’t know why YouTube is so interested in showing me old conduit fill articles this is the third this week, but f it here’s a copy pasta of my post from one of those other articles. This is a section of code that really irritates me at least for branch circuits. Don’t get me wrong it’s necessary for calculating the size pipe you need for large conductors and special cases like isolated grounds. However, after you have applied corrections for ampacity the actual practical limit is 9 current carrying conductors (#10’s on a 20A circuits) anything more and the step up in wire size becomes impractical, who’s going to pull #8 (THHN) for a 20A circuit? Plus you then have to upsize the conduit from 3/4 min. to 1-1/4 for up to 16 or 1-1/2 to 20 the pipe can handle 22 correction step up is at 20. I can’t say you’ll never do any of this, but seriously this section is mostly navel-gazing at best and leads to bad installs that could end up in dangerous situations and worst.
Haven’t been in industrial much? The codes generally above and beyond sure but it’s the same principle as ty-wraping. In our local, no more then 6 MC under one wrap to allow for heat disipation. You’d agree in the MC case it’s got nothing to do with insulation damage. Although that’s definitely part of pipe fill
The volume of a conduit is reduced to 40% because of heat not because you might nick the wires. Any Ferris material in an electric field will have eddy currents causing a magnetic field. The AC electricity is 60 cps causing the electrical field to change and reverse 60 times in a second. The continuing reversal of the electric field causes heat. The chart that you referred to as the volume of the circular mil area of a wire. A wire is not a square it’s a circle. Thank you for your effort.
Is it normal for a first year to go back and fix a journeyman’s mistakes? Is it normal to fix a second year’s mistakes? I know I’m a first year so I’m basically the bitch of the whole ordeal, but I’m often getting sidetracked from my own work to go fix or assist someone else. If this is not a normal thing, what should I say to my foreman? I haven’t gotten in any hot water yet for being slow but he’s seen some of my work which when alone he says looks good, but when I’m assisting the other co-workers throughout the day I noticed I tend to slip a bit more trying to remember what I was doing and he’ll notice it in the quality of my work. Does anyone have any helpful advice? Thank you in advance I just really want to do well.
This is a really good article. I’m a 2nd year apprentice. My supervisor and I were just talking about conduit fill these last two weeks in the field. Today in my apprenticeship class we talked about conduit fill and today you uploaded this article. Always nice hearing it from multiple perspectives. I always feel it helps to ask while in the field and then do my own research on the question when I get home. It helps me retain the information and be able to apply it on the job. Thanks for another great article.
Dustin, I have to disagree with your claim that heat is not a factor in Conduit fill. Starting with the basics, NEC 300.17 says: ” The number and size of conductors in any raceway shall not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the conductors or to their insulation. ” That’s a pretty clear statement, Yeah, Chapter 9 and Annex C don’t mention heat, but they aren’t the only applicable parts of the code. If you went solely by Annex C, you could put 16 #12 THHN conductors in 3/4″ EMT. That’s all well and good from the standpoint of physical damage while pulling the wire, but NEC 310.15 (C) would also require you to derate the ampacity of those conductors to 50%. The full ampacity of #12 THHN would be 30 amps per Table 310.16, so 50% of that would be 15 amps. If you go by only chapter 9 and Annex C, it would seem like you could run 8, 20 amp circuits in 3/4″ EMT, but if you consider all applicable parts of the NEC, you can only run 4, 20 amp circuits in 3/4″ EMT. As far as your comment that you don’t think the conductors are at max value, as a practical matter, you’re right, the circuits probably won’t all be running at max current at the same time, so it probably won’t create issues. But codes are designed around assuming the worst case scenario will happen, not assuming that it probably won’t.