Does Electrical Code prevent me from placing ALL wires in steel conduit?

Factual Questions
1

Simple question - there’s a chance my house may need a major re-wiring (as part of a proper grounding). Forget about the practicalities and expense of running steel conduit to every single box. Academically speaking, I was told that it was a “code violation” by a know-it-all home improver to enclose wire in steel conduit all the way from the breaker box to the outlets. True, false, or 'depends"?

Seems to me like you would, in most circumstances, be adding safety. His judgment was that “if you have a break or short, it’s too hard to find it, and those steel pipes will heat up and set your whole wall on fire.” Bwah?

2

In my juristiction, exactly this is required for commercial buildings. It makes it easier to remove or add circuits, and offers more protection to the wire when remodeling. This is considered because commercial buildings are frequently passed from company to company, and remodled along the way.

NEC DOES forbid metallic conduit in some cases, mostly related to corrosion concerns. Underground burial, and farm buildings (barns for example) come to mind.

Your contractor is BSing you. Conduit, especially in the case of retrofit is a royal PITA, and he doesn’t want to deal with it. Retrofitting sucks at best, and conduit puts it over the edge, so I can’t blame him for not wanting to, but condem him for lying. I think metal studs were invented mainly to make running conduit easier, and are used in many commercial buildings for that reason. There are many other construction details used in residential building that are not conduit friendly.

3

The only problem that I have heard of that comes even remotely close to this is if you use conduit as a raceway for running Romex. If you do, then you have to derate based on the Romex jacket taking up space inside the conduit. This becomes an inspector’s decision since Romex isn’t listed in the derating tables. Don’t use Romex and you don’t have this problem.

4

Conduit is encouraged however maybe the OP means all wiring which would include low voltage wiring for telephones, intercoms, home entertainment etc.

The only code issue there (AFAIK) is that if it shares a raceway, the low voltage wiring must have an insulation rating that is equivalent to the power wiring which is generally 600V.

In my experience however, separation of such system wiring is encouraged so as to minimise induced currents, harmonics and ‘crosstalk’ into the LV wiring.

5

[QUOTE=MrFloppy]
Conduit is encouraged however maybe the OP means all wiring which would include low voltage wiring for telephones, intercoms, home entertainment etc.
[/QUOTE]

Nope, just electrical. My plan should I go ahead with a home improvement is to have the maximum possible fire protection, and to design for that in mind by enclosing all AC lines in steel conduit the entire way.

It looks like it’s just like when I asked about my driveway and getting it fixed. It seems many contractors have a cookie-cutter approach, and if you ever deviate from it they either lie to you and tell you it’s illegal, or dig in their heels and refuse to do it. Like when I talk about using steel structurally in the house, and they tell me “that’s against ‘code’! You can’t use steel anywhere in the structure, or else it’ll fail inspection and they’ll condemn your house!!!”

Want to hear some another good one? “GFCIs are more dangerous. They might protect you from being shocked, but they short out all the time and can burn your house down.”

6

[QUOTE=cornflakes]
The only problem that I have heard of that comes even remotely close to this is if you use conduit as a raceway for running Romex. If you do, then you have to derate based on the Romex jacket taking up space inside the conduit. This becomes an inspector’s decision since Romex isn’t listed in the derating tables. Don’t use Romex and you don’t have this problem.
[/QUOTE]

Can you get around it by using a larger diameter conduit?

Also, is there any real reason other than price that I wouldn’t want to install very heavy-gauge wire, such as 8-gauge copper? Would it be too hard to hook up to outlets and such? If so, what is the heaviest wire I should spec and have a reasonable chance that a contractor will agree to it?

7

I am a licensed electrician. That being said, my primary skill sets are really in HVAC, where I am a journeyman.

To add to the discussion, I can tell you that while the whole country it seems uses the NEC (NFPA Article 70 IIRC) as gospel, every jurisdiction has the right to modify the local code as they see fit. My brother (a journeyman electrician in Chicago) states that conduit is required in residential homes. He works for someone else, but even when he does side jobs he uses steel conduit. If it’s going to be inspected in Chicago, it will be in conduit; romex not allowed. So…I say check your local code.

If you want to run EMT, I wouldn’t run romex through it. It would be a PITA to pull. I’d buy spools of 12 gage THHN and pull it. As to conduit size, there are sizing charts in the NEC as to the free air space you must maintain in each conduit. It’s a little Greek if you haven’t used it before, but it is discernable. (or you can ask the local electrical supply house)

As to wire size, 14 gage (15 amp) seems to be the code for garden variety circuits here. In my home I put in a 200 amp panel and ran 12 gage (20 amp) circuits and dedicated a circuit to every room. (most homes double up rooms) Of course, stoves, A/C systems etc will be governed by the manufacturer. (and be dedicated) I have a dedicated cicuit for every room in the house (including bathrooms & kitchen) and a separate circuit for outside outlets, coach lights and security lights. I don’t know if I’d run a basic circuit larger than 20 gage. Rather, I’d run more [dedicated] circuits with 12 gage wire, with dedicated circuits for hot tubs, outside lighting etc.

8

[QUOTE=Una Persson]
Can you get around it by using a larger diameter conduit?

Also, is there any real reason other than price that I wouldn’t want to install very heavy-gauge wire, such as 8-gauge copper? Would it be too hard to hook up to outlets and such? If so, what is the heaviest wire I should spec and have a reasonable chance that a contractor will agree to it?
[/QUOTE]

I don’t think an electrician will have a problem with 12 gage circuits. At 10 gage, they’ll look at you funny and be resistant I believe. It will be hard to work with and impossible/difficult to hook up to recepticles.

And unneccessary, unless you have some heavy loads you’re not telling us about. Further, the weak link will become the recepticles which will be rated at 15 amps. (although you can buy them rated at 20 amps)

A better approach, IMO, is not larger wire, but more circuits. That will give you better protection. I don’t think you’d ever want to put in a breaker that was larger than the weakest rated component. 12 gage is rated at 20 amps. You can buy recepticles rated at 20 amps. That gives you a 20 amp circuit and breaker. )Most homes are wired at 14 gage) Why run 8 gage?

9

[QUOTE=Una Persson]
My plan should I go ahead with a home improvement is to have the maximum possible fire protection, and to design for that in mind by enclosing all AC lines in steel conduit the entire way.
[/QUOTE]

I’m curious about this. Do you really get that much better fire protection by having steel conduit rather than plastic, or even by having conduit at all? Is the worry that a breaker would get stuck, causing a short to catastrophically heat the wires?

10

[QUOTE=Sal Ammoniac]
I’m curious about this. Do you really get that much better fire protection by having steel conduit rather than plastic, or even by having conduit at all? Is the worry that a breaker would get stuck, causing a short to catastrophically heat the wires?
[/QUOTE]

I’m an Engineer, not an electrician. I have to assume that galvanized steel would be more resistant to fire from a short than plastic would. I guess the issue is, plastic would be less likely to conduct anything…

Here’s something I don’t know - if you use steel conduit, is the conduit itself grounded?

The place I would be running wires to would be in the loft, where the plan would be to utilize about 800-1000 ft^2 of space to make 2-3 nice rooms. I could definitely get with running more circuits as you guys suggest.

There is a quick and easy route down to the breaker box via a vertical space in the house through which the flue to the water heater and furnace runs. It would be easy to run a vertical piece of, say, 3-inch steel pipe down from the loft all the way to near the breaker box, by placing it in that same vertical space. I’m assuming there would be a minimum distance, however, that even a wire in a pipe would have to be from a hot furnace flue? I could get it at least a foot away…

11

The conduit is grounded by being mechanically connected at one end to the breaker box and at the outlet boxes which should all have a ground lug/screw.

Incidently, when I was working in the UK, ‘EMT’ wasn’t allowed, the reason being that the ground return circuit may be compromised by the simple set screw couplings (20 years ago - may be different now). All conduit was solid drawn steel with threaded couplings. Here in the US, I only ever specified rigid steel conduit for hazardous locations. EMT is the norm for commercial buildings.

12

[QUOTE=Kevbo]
I think metal studs were invented mainly to make running conduit easier, and are used in many commercial buildings for that reason. There are many other construction details used in residential building that are not conduit friendly.
[/QUOTE]

This is a big reason why conduit isn’t seen much in residential construction. Running conduit through wood studs is a big PITA. In addition, if you run conduit to every box, the boxes themselves must be commercial-style metal boxes, not the normal cheap plastic boxes normally used in houses.

Most electricians (including me) would consider wire in EMT conduit much safer than Romex.

13

[QUOTE=Una Persson]

There is a quick and easy route down to the breaker box via a vertical space in the house through which the flue to the water heater and furnace runs. It would be easy to run a vertical piece of, say, 3-inch steel pipe down from the loft all the way to near the breaker box, by placing it in that same vertical space. I’m assuming there would be a minimum distance, however, that even a wire in a pipe would have to be from a hot furnace flue? I could get it at least a foot away…
[/QUOTE]

If you are going to run all the wires in one big conduit, then you’ll need a junction box at the far end where smaller pipes branch off. You could even make this a small breaker panel. You could also switch from conduit to Romex at that point.

14

Conduit is fine for new construction, and as noted, is the default standard in some areas of the US. The allegation you heard was hooey. I’d like the party making the statement to explain how sufficient current to pyrolyze wood could flow without any overcurrent protective device activating to interrupt the fault current.

While the NEC is the most often cited source, there is also the International Residential Code. It is very close to the NEC, but there are differences. To muddy the waters further, just because a new edition of a model code has been published, it doesn’t automatically become the governing document until adopted by the citing political entity. Example: the 2008 NEC won’t be adopted by the Commonwealth of PA until some time in early 2010, and a member of our Inspector’s Association who lives on the PA/NY border reports that New York State is still using the 1999 NEC.

Back to your conduit issue- installing conduit as a retrofit is going to be expensive because it will be labor intensive. There are limitations to the size of conduit you can run through wood framing members: 40% of the depth of a bearing member, so a 2 x 4, which is really 3.5" can have a through bore of not more than 1.4" or 1 3/8", per IRC 602.6 and UBC 2320.11.9. Should you wish to face notch, the maximum depth is 25%, per the same two code references.

If you’d like metallic protection, and the ability to fish through existing openings, then type MC would be the ticket. While similar in appearance to type AC, which most folks call BX, MC has a full size insulated grounding conductor. That would strike me as being the best compromise.

15

[QUOTE=Una Persson]
I’m an Engineer, not an electrician. I have to assume that galvanized steel would be more resistant to fire from a short than plastic would. I guess the issue is, plastic would be less likely to conduct anything…

Here’s something I don’t know - if you use steel conduit, is the conduit itself grounded?
[/quote]
Yes.

Two things need to be considered, here. First, you’re bundling conductors together, and that reduces their ability to liberate heat, so their ampacity will have to be derated. Second, you’re placing conductors in close proximity to a heat source which places them in ambient atmosphere of higher temperature than ordinary, requiring further derating. The same thing has to be done for conductors in raceways supplying rooftop mounted appliances (air handlers, furnaces, A/C condensing units, fans, etc.) because the reflected heat from a black roof can elevate the operating temperature significantly.

16

Sorry I’m late with this…

[/quote]
I’m sure that you can. IIRC, sizing and/or derating involves the circuit’s amperage, wire gauge, and conduit size. All the same, it will be easier to run unjacketed wire.

(I’m just a DIY’er, so take this with a grain of salt, but) If you decide to run Romex to where the circuits drop to the service, you can run the Romex into a box, strip the rest of the jacket and run the drops inside conduit.

17

[QUOTE=Una Persson]
…I was told that it was a “code violation” by a know-it-all home improver to enclose wire in steel conduit all the way from the breaker box to the outlets. True, false, or 'depends"?

Seems to me like you would, in most circumstances, be adding safety. His judgment was that “if you have a break or short, it’s too hard to find it, and those steel pipes will heat up and set your whole wall on fire.” Bwah?
[/QUOTE]

I think Mr. Know-It-All took a steel pipe or two to the head. :smiley:

Code-wise, I grew up in Chicago, where at one point, even Class 2 stuff like telephone lines and doorbell wiring had to be in conduit, at least until it penetrated into a stud space - they weren’t allowing any visibly exposed wire of any kind back then. It took computers to get them to change their tune abour 25-30 years ago - businesses were leaving Chicago as it was otherwise too onerous to run the computer network cabling in conduit, and electricians knew nothing about network cables and damaged a whole lot of cable by manhandling it.

For retrofits, MC is great stuff. I’ve installed tons of it in spaces like garages where Romex is just too frail and susceptible to damage.

How many circuits are you planning to run? It may be more economical to install a sub-panel, rather than “home-run” a bunch of circuits to the main panel. You might also find that the existing main panel’s running low on both spaces to mount new breakers, and knockouts to accept new cables or conduits. A sub-panel just needs one two-pole breaker in the main panel (eg: 240 volt) to feed it, and one large knockout for its line.

You have the right idea about up-sizing wire, but 8 would be impossible to use with standard 15 or 20 amp receptacles. I don’t think you’d even be able to get #10 to work well, if at all. #12 will do well for either 15 or 20 amp circuits. As for the feed to the sub, I’m running #4 wire, and a 50-amp breaker. You can get away with #6 on 50 amps, but for the garage workshop, I’m running power tools with large start-up current draws.

18

Although rigid/EMT provide a functional ground,not all locales permit counting as such.Safer to size the run for a separate ground.

19

[QUOTE=Una Persson]
Nope, just electrical. My plan should I go ahead with a home improvement is to have the maximum possible fire protection, and to design for that in mind by enclosing all AC lines in steel conduit the entire way.

It looks like it’s just like when I asked about my driveway and getting it fixed. It seems many contractors have a cookie-cutter approach, and if you ever deviate from it they either lie to you and tell you it’s illegal, or dig in their heels and refuse to do it. Like when I talk about using steel structurally in the house, and they tell me “that’s against ‘code’! You can’t use steel anywhere in the structure, or else it’ll fail inspection and they’ll condemn your house!!!”

Want to hear some another good one? “GFCIs are more dangerous. They might protect you from being shocked, but they short out all the time and can burn your house down.”
[/QUOTE]

Sadly, I don’t think that it’s because you want to deviate from the “norm” that they try to BS you. Too many men these days still labor under the mistaken idea that women “can’t understand such things” and figure they can pull a fast one on you.

Since many of these neanderthals are difficult to identify until they open their mouths, I have two possible solutions to the problem: 1.) Have a copy of the code book handy (most bookstores carry them) and ask them to point it out to you. 2.) Have a display you can erect quickly for when they arrive, which prominantly displays your firearm collection and ample evidence that you know how to use them! :smiley: I had an uncle who used a similar tactic when he had problems getting his car repaired: He’d leave an ax handle visible on the seat and drag the shop boss out to look at the car. He never made threats or even mentioned the ax, just made his complaint. He claimed that it never failed to get the situation resolved.

20

I second everything Daneswithcats has said.