L5wolvesf
Well-known member
Hopefully this is a simple question. How many Romex cables is 1/2inch EMT designed or allowed to contain? It looks like adding a third cable might be too tight of a squeeze.
Thank you
Thank you
Romex in EMT
- Thread starter L5wolvesf
- Start date
Ray-CA
Well-known member
I'm not an electrician, but I don't believe that Romex is designed or intended to be installed in emt. You can run individual wires and there are web sites that can tell you how many wires a 1/2-inch, 3/4-inch etc. emt will safely hold.
Ray
PS: https://www.google.com/search?q=emt...9j69i57j0l4.8796j0j7&sourceid=chrome&ie=UTF-8
Ray
PS: https://www.google.com/search?q=emt...9j69i57j0l4.8796j0j7&sourceid=chrome&ie=UTF-8
bczygan
Well-known member
342.22 Number of Conductors
The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9.
Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.
334.2 Definitions
Nonmetallic-Sheathed Cable. A factory assembly of two or more insulated conductors enclosed within an overall nonmetallic jacket.
NM-B is not approved for wet locatiions, even in conduit.
The number of conductors shall not exceed that permitted by the percentage fill specified in Table 1, Chapter 9.
Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.
334.2 Definitions
Nonmetallic-Sheathed Cable. A factory assembly of two or more insulated conductors enclosed within an overall nonmetallic jacket.
NM-B is not approved for wet locatiions, even in conduit.
Zeke
Well-known member
Simple answer: none.
You are better off bringing the NM-B to a box and stranded or solid wires from there into your conduit.
There are a number of reasons not to run Romex in a conduit although technically it is allowed in dry locations (inside). But to run more than one cable is just not a sound practice.
This is inside my garage, all the drops from the ceiling of my garage (block construction) to the switches/outlets are in EMT (metal conduit).
I am looking to add an outlet where there is a 2 gang box with 2 Romex cables to both switches there. I will change out the box to a 3 gang.
I'm not an electrician so are you saying my existing setup - Romex cables (in some places 2 cables) in EMT on block walls - is not recommended?
If not I'm curious as to why?
Thank you
bczygan
Well-known member
Follow the code I referenced above for conduit sizes. Romex in conduit is fine.
I have the same situation.
Bill
lakeroadster
Well-known member
L5wolvesf,
I found these helpful...
https://www.garagejournal.com/forum/showthread.php?t=53919
http://forums.mikeholt.com/showthread.php?t=86048
I found these helpful...
https://www.garagejournal.com/forum/showthread.php?t=53919
http://forums.mikeholt.com/showthread.php?t=86048
Last edited:
aandpdan
Well-known member
Romex is often installed in conduit for mechanical protection, just like you have in your garage.
It is permitted by Code.
It is permitted by Code.
Stuart in MN
Well-known member
It's permitted by code to run Romex in conduit, the conduit just has to be sized appropriately. You go by the largest cross section dimension of the Romex, then use that number along with one of the many conduit sizing programs available online to determine what diameter conduit is required.
rlitman
Well-known member
All correct. Just one addition to this. Romex is not round. For conduit fill calculations, the major diameter (the widest part) must be used in the calculations, not the minor diameter (the narrowest part).
Knowing this, and assuming that Romex is 1/2" wide, the Romex works out to a cross sectional area of 0.196" (again, because code considers the circular cross sectional area of a cable, and not the actual cross sectional area). A 1/2" trade sized EMT conduit has a cross sectional area of 0.30 sq-in. A single cable is allowed to fill 53% of the conduit area (the fill percentage DROPS when more than one cable is considered), which is 0.16 sq-in, so the number of Romex cables allowed in a 1/2" conduit is ZERO.
Considering a 3/4" EMT conduit, it works out to ONE Romex per 3/4" conduit is perfectly allowed, but two or more would exceed the fill table requirements. For 1" EMT, two Romex cables would meet the 31% fill requirements for two cables, but three would exceed the 40% fill for three or more cables, so the answer is that TWO would be allowed in 1" EMT.
mrramsey
Well-known member
Do yourself a favor and just buy THHN wire. Unless you have a really short run Romex is a ***** to pull through conduit. Just my experience.... I just pulled 30' with bends of THHN in 1/2" conduit for my heater today. Easy peasy.
I think most people are missing the fact that this is not a complete conduit system and simply a sleeve for the wire were it comes down the cement wall. OP please correct me if this is not the case.
This is extremely common with any exposed concrete wall with wood framing above and perfectly acceptable.
I would absolutely not splice the romex and run thhn just a few feet down to the switch/outlet.
In regard to the original question, 3 12/2 cables physically will not fit in a 1/2 conduit.
I'm not sure of the exact rule for this since I think it differs from the standard conduit fill calculations. I was under the impression that only 1 12/2 was allowed in 1/2 but I have nothing to back that up. I have many times ran 2 12/2's through 1/2 conduit though...
This is extremely common with any exposed concrete wall with wood framing above and perfectly acceptable.
I would absolutely not splice the romex and run thhn just a few feet down to the switch/outlet.
In regard to the original question, 3 12/2 cables physically will not fit in a 1/2 conduit.
I'm not sure of the exact rule for this since I think it differs from the standard conduit fill calculations. I was under the impression that only 1 12/2 was allowed in 1/2 but I have nothing to back that up. I have many times ran 2 12/2's through 1/2 conduit though...
Last edited:
See chapter 9 table note# 2. Fill restrictions for cable only apply to complete conduit systems. Not intended to apply to sections of conduit used to protect exposed wiring from physical damage.
1/2" can be used. See chapt 9, table note# 2. Physically fitting the cables in is a limiting factor and the time it takes makes larger obviously the smarter choice.
Turns out this is an understatement. Kinda like when I was learning to surf even the “little waves” would wipe me out.
When I first asked the question it was just about the Romex physically fitting – maybe it still does. I thought there might be a simple answer. Now I know the EMT in this situation is “for mechanical protection” and that it might have to be sized according to the Code too.
This is an add on to existing wiring and will be a short pull on a drop down. I also have a load of Romex from the prior owner. Wouldn’t want to pull what you described.
Thank you for this. The Romex I have is 3/8inch wide and the marking on it (hard to read) looks like it says 14, it has 1 black, 1 white, and 1 copper conductor.
Every drop in my garage is 1/2inch and most have one Romex cable.
QUOTE=Bert_;6814168]I think most people are missing the fact that this is not a complete conduit system and simply a sleeve for the wire were it comes down the cement wall. OP please correct me if this is not the case.
This is extremely common with any exposed concrete wall with wood framing above and perfectly acceptable.
I would absolutely not splice the romex and run thhn just a few feet down to the switch/outlet.
In regard to the original question, 3 12/2 cables physically will not fit in a 1/2 conduit.
I'm not sure of the exact rule for this since I think it differs from the standard conduit fill calculations. I was under the impression that only 1 12/2 was allowed in 1/2 but I have nothing to back that up. I have many times ran 2 12/2's through 1/2 conduit though...[/QUOTE]
You are correct on what I am trying to do. It looked iffy now I know it won’t go. Thank you.
Since the right way to do it is in larger conduit I could step it up to 3/4inch – correct? Also, is the grey PVC acceptable in my situation and is grey PVC allowed to be connected to metal 3 gang switch boxes?
This is extremely common with any exposed concrete wall with wood framing above and perfectly acceptable.
I would absolutely not splice the romex and run thhn just a few feet down to the switch/outlet.
In regard to the original question, 3 12/2 cables physically will not fit in a 1/2 conduit.
I'm not sure of the exact rule for this since I think it differs from the standard conduit fill calculations. I was under the impression that only 1 12/2 was allowed in 1/2 but I have nothing to back that up. I have many times ran 2 12/2's through 1/2 conduit though...[/QUOTE]
You are correct on what I am trying to do. It looked iffy now I know it won’t go. Thank you.
Since the right way to do it is in larger conduit I could step it up to 3/4inch – correct? Also, is the grey PVC acceptable in my situation and is grey PVC allowed to be connected to metal 3 gang switch boxes?
Thank you, they are but they raise another question.
This pic is the conduit that comes into my garage and the Romex goes from here to the various switches and outlets. It has at least 10 cables, in 1 1/4inch EMT, it physically protects the Romex cables. It seems o be tightly packed’ It is about 6 ft tall from the top (in the pic) to where it goes out through the block wall into the meter/circuit breaker box.
Attachments
lakeroadster
Well-known member
But common sense dictates there is a limit to how much romex / wire you should cram into a conduit... right?
Which leads us to this......
Well, you have already had a great explanation by rlitman above about the NEC rules for EMT fill volumes with Romex.
Furthermore we know the NEC has rules about bundling, unless the cable is derated.
So logically the code has a problem with wires being together as such. (possibly due to over heating due to the crowded condition?). That same logic would also seem to apply what you are showing.
But.. it depends on when the installation was done, and what was in the NEC at that snapshot in time, and if any updates have been done to your installation.
If you are updating, my understanding is whatever you update has to meet the current code.
Attachments
Last edited:
Falcon67
Well-known member
Just running things in conduit once in a while to project wires close to machines, I'd not run any "romex" in 1/2" because it's too small unless it's like one cable going 2 or 3 feet straight. Any bends, fergetit. 3/4 min and that's for one. Maybe two if you flatten them out and tape together for the run. And I'd not count on getting anything else in there later even with a pull string.
sberry
Banned
I also wouldn't lose sleep over a piece for protection. All this is different for heavily loaded equipment etc.
sberry
Banned
The rules are in place for good reason. Let me get that out of the way first. I have a couple full conduits, they are legal but just for theory,,,, there are a couple general circuits, an equipment one and a couple lights. While bundled wire is a concern none of them really have the potential to be loaded significantly. Got a couple lights wired to a couple,, the recepts are 12 on 20 but light load and a hoist is 15a on a 10 and occasionally 20 on it for minor welding and very little of this could be fully loaded if one tried.
bczygan
Well-known member
If it were me, I would try to come close to the rules for an end to end conduit, even though this is just a case of protecting exposed Romex. It would make easy installation too.
Bill
Bill
Yeah, I want to be as close to within the rules as possible.
So I looked at what I have and came up with this . . . is it OK to run 2 protective conduits into one 3 gang box? The 2 existing cables will remain as is. The additional conduit will protect the Romex for the outlet I put in that box. Later I will run an additional outlet about 5 feet further across the work bench off the new outlet. Does this sound right?
Another simple question – ha ha ha
arkieguide
Well-known member
- Joined
- Aug 10, 2017
- Messages
- 50
You have 14/2 wg - If you have the wire why not buy some 3/4" emt run it then put one 14/2 wg into it. When you put to many wires into a pipe you run a chance of to much heat causing a fire.Yes I have seen the damage it can do.be save, in electricity safety is very important.
sberry
Banned
If you are not trying to run 2 electric heaters at max from the outlet with the light wire loaded at 15A all this doesn't mean squat. Protecting the wire from damage does. While its true that the wire has a 20 or 15 breakers it doesn't mean that's the load on them. I was eluding to that in some of my other ramble.
I got a pipe with 9 wires, 2 circuits carry 2A when all are active, 2 5A if the lights are on and one 30A wire with 15 on it for 45 seconds, one circuit could see an additional 4 1/2 grinder for few seconds, none of this makes for heat.
I got a pipe with 9 wires, 2 circuits carry 2A when all are active, 2 5A if the lights are on and one 30A wire with 15 on it for 45 seconds, one circuit could see an additional 4 1/2 grinder for few seconds, none of this makes for heat.
sberry
Banned
None of this is like continuous process machinery, not like a commercial kitchen and even then not all those circuits are continuous or fully loaded to wire capacity and if they are there is already factor in place for derating if needed.
I put a piece of 12 in a basement convenience outlet the other day, 3 ft long down the wall, no one has used it yet and while it does technically violate fill its never going to result in a problem.
Look at the combed romex thread, only a shade from being bundled but not all these circuits will run at once, couldn't if they tried.
I put a piece of 12 in a basement convenience outlet the other day, 3 ft long down the wall, no one has used it yet and while it does technically violate fill its never going to result in a problem.
Look at the combed romex thread, only a shade from being bundled but not all these circuits will run at once, couldn't if they tried.