Electrical question...conduit versus in-wall wiring

[Jason Morgan]

I am wondering about what is preferable? in-wall wiring or conduit. I assume its cheaper and easier to do in-wall, but it seems easier to do conduit after all the wall board is up. That way I can insulate, put of the wall board and then put in the electrical rather than the reverse. Any suggestions one way or another?

[Ken Fitzgerald]

Jason.....In my opinion, it's easier the other way. You just drill holes to run the wire through the studs. If you use fiberglass insulation, you cut the batts to the required length and split the batt to a height slightly higher than your wire runs and install it. I'm sure it's cheaper too. Conduit, o8utlet boxes, junctions boxes,connectors all are more expensive. Of course, you have to notch the wall board or plywood...but if you are using wallboard, a dremel tool can eliminate that notching problem.

Also, that leaves the surface of your walls smooth for placing cabinets wherever you desire.

That's what I did with my shop.

[Lewis Cobb]

I am wondering about what is preferable? in-wall wiring or conduit. I assume its cheaper and easier to do in-wall, but it seems easier to do conduit after all the wall board is up. That way I can insulate, put of the wall board and then put in the electrical rather than the reverse. Any suggestions one way or another?

Hi Jason - I have a combination in my shop - partly due to to the fact that the plan was always changing. When I built the shop I put in 120V receptacles in-wall on all the walls, 220V receptacle on one wall and in the middle of the floor where the tablesaw was going to go. Lo and behold, once I have the shop insulated, sheetrocked, painted and generally "finished" I decided I needed more 220V outlets, an electrical heater outlet, move a 3 way switch, fan on the ceiling, etc etc - so I now am installing conduit around the room as well. Mainly the conduit in my room is carrying the 220 feeds, but there's a few "rogue" 120 runs as well.

I think the moral of the story is to try and plan things before you finish the room but also plan for where you are going to place conduit after you finish the room ;)

[keith ouellette]

I did mine in wall but one thing I thought of while installing was how much big cable I could save by going with conduit. I used 8ga for some of my outlets and have one with 6ga. Instead of running up the inside of the wall over the cieling and back down I could have used individual wires in conduit and saved many feet. I didn't work out the cost difference of wire verses cable with shorter length and adding plastic conduit so it might be a minor issue. Just a thought you might look into. 12ga and under in the walls and 10ga and over outside.

[Sean Troy]

I did mine in wall but one thing I thought of while installing was how much big cable I could save by going with conduit. I used 8ga for some of my outlets and have one with 6ga. Instead of running up the inside of the wall over the cieling and back down I could have used individual wires in conduit and saved many feet. I didn't work out the cost difference of wire verses cable with shorter length and adding plastic conduit so it might be a minor issue. Just a thought you might look into. 12ga and under in the walls and 10ga and over outside.

8ga. and 6ga.? You running a power plant there? LOL

[keith ouellette]

8ga. and 6ga.? You running a power plant there? LOL
The 6ga for my ark welder (50amp breaker). The 8ga is for my 5hp planner(40amp breaker) 10ga to my 30amp breaker outlets. My power plant uses much larger cable than this. If you are going to build your own power plant you should look into it.

[Greg Peterson]

All of my 120v circuits are in the wall. Walls are insulated and wallboard will be going up soon. All the 120v circuits are for outlets and lighting, with only one circuit being dedicated to a single piece of equipment (air compressor).

If I already had the heavy equipment, I would run the 240v circuits in the wall also. But, with a very limiting budget, I have to kind take an educated guess as to what equipment I will end up having.

The service panel is in the shop(formerly known as the garage). For my 240v circuits, I'm going to set up a main lug load center and run all my 240v circuits via conduit as my needs require. This puts all the big shop equipment and its double pole breakers in its own box. If I added five 240v circuits, this would require 25% of the breaker capacity of the service panel. Better just to move those circuits over to a dedicated load center.

And, even though you don't mention it, I'll throw it out there anyway: You can never have enough outlets. It's not so much about quantity of outlets as it is the location of an outlet when you really need one. Being that the shop is a work space, things are moving in, around and out. Some outlets, usually the one you really need, are bound to hidden behind something leaning against the wall, even if you place the outlets well above 48".

So, when planning outlets, it's all about location, location, location.

[Jason Morgan]

Thanks for all the great advice. I guess I just didnt want to overlook something, but it sounds like in-wall is the obvious choice. I can put the conduit up later if I need to I guess.

Thanks!

[Terry Kelly]

I like the conduit route myself that way it is pretty easy to upgrade with in reason, 20a to a 30a circuit for example, or to add a seperate circuit if needed. Just don't over fill right off the bat and leave room for future growth. Plus if ya wanted to you could rough-in the boxes where you think you may need them in the future but not pull the wire to them til you need them.. Just a few thoughts...Na haven't done this before...

[Bruce Wrenn]

First, are you confusing the conduit, and the EMT? Conduit is threaded, and EMT assembles with mechanical fittings. With EMT, or conduit, you don't have to pull a ground wire. EMT also leaves you a passage way for future changes, without ripping off wall finish. Please don't install 1/2" stuff though. There isn't enough room to go back later and add another circuit. The 3/4 stuff will only cost a few bucks more. In my shop I have a nine foot ceiling. I have several runs of surface mounted EMT near ceiling. Behind the finished wall, I drop down with EMT also.

[Randall Davis]

First, are you confusing the conduit, and the EMT? Conduit is threaded, and EMT assembles with mechanical fittings. With EMT, or conduit, you don't have to pull a ground wire. EMT also leaves you a passage way for future changes, without ripping off wall finish. Please don't install 1/2" stuff though. There isn't enough room to go back later and add another circuit. The 3/4 stuff will only cost a few bucks more. In my shop I have a nine foot ceiling. I have several runs of surface mounted EMT near ceiling. Behind the finished wall, I drop down with EMT also.

EMT is conduit threaded (rigid)is also conduit.
If you have a one man hobby shop save time and money put some thought in to your layout and use 12/2 romex for the general duty outlets. Wire your dust collecter, table saw, compresor to manufacterers specs. If your planer, jointer, drill press and table saw are all 240 volt save $ on breakers and panel space, run one 30 amp circuit to feed all of them unless you have figured a way to run two of these machines at the same time.

[Rod Sheridan]

Since my shop is in the basement, and the walls are poured concrete, I used EMT for all my wiring except lighting.

I used 1/2" EMT with qty 3 12 gauge T90 conductors ( two lines, one neutral) plus a #14 ground.

This was used to feed one duplex 15A 240 V receptacle (6-15R) and one duplex 15A 120 V receptacle in a split configuration (5-15R) fed from a 15 A 2 Pole breaker.

The above receptacles were mounted in a 4 inch square box, which gave me a 15A 240 circuit for machinery, and two 15A 120 circuits for machinery. This is suitable for my 3HP saw, shaper and planer, as well as the 2HP Bandsaw, as well as the lathe and drill press.

I doubt if I'll ever have to upgrade it, however 1/2 inch EMT with T90 conductors, you can install qty 9 12 gauge, or qty 5 10 gauge conductors, not that I'd ever use fill values that high however.

The conduit route allows you to change the wiring configuration easilly, just pull in different conductors as your requirements change.

Regards, Rod.

[Greg Crawford]

Being in Wisconsin, I'm puzzled at why heating hasn't come into play. With every penetration through the walls and ceiling, heated air escapes (or cold air enters) the conditioned space. While this may seem minimal, it also means that cold air is passing through the insulation, reducing it's effectiveness. In my shop, the final plan is all conduit, with controlled ventilation passing through a heat exchanger to cool the incoming air and remove some of the moisture. Of course, my conditions are hot and humid, but the principles are the same.

[Cliff Rohrabacher]

Metal Conduit allows you to use Multi strand wire. Multi. Strand carries more current.

[Rob Russell]

FYI, "conduit" is a generic term used for round raceway. The typical round metal tubing used as raceway is EMT - Electrical Metallic Tubing and has not threads. The EMT connectors are all screw fittings, where a set screw clamps down on the EMT.

There are other types of raceway that are allowable - non-metallic/PVC is another type. It comes in varying wall thicknesses - Schedule 40, Schedule 80, etc. that's the stuff you glue together.

[Rod Sheridan]

FYI, "conduit" is a generic term used for round raceway. The typical round metal tubing used as raceway is EMT - Electrical Metallic Tubing and has not threads. The EMT connectors are all screw fittings, where a set screw clamps down on the EMT.

There are other types of raceway that are allowable - non-metallic/PVC is another type. It comes in varying wall thicknesses - Schedule 40, Schedule 80, etc. that's the stuff you glue together.


Hi Rob, normally PVC is not used inside a building due to flame spread issues. I'd check with your local authority before using it inside a shop.

Regards, Rod.

[Michael Lutz]

I would go the conduit route. It makes it easier to make changes later. You can use PVC conduit indoors, but I would avoid using it anywhere it could get hit by an impact. EMT would be a better choice.

Mike

[Roland Chung]

Consider using a combination of romex and emt. Run 12-3 romex everywhere that you know you will ever want an outlet. Use 2 gang boxes everywhere with 1 outlet wired on each circuit. Put romex in the walls to every location where you know what you will be running and that you know what the requirements are (20a, 30a, etc). Put your known lighting electrical in the ceiling if you can.

Add another dedicated run of romex for every large 120v machine that you know you will have and that you know what the electrical requirements will be.

Flex is conduit and it can be easily installed inside of the walls before insulation and drywall. It will give you the best of both worlds - hidden in the walls (or exposed) and expandable (you can pull extra wires if your needs change). Flex can look sloppy on long exposed runs as it can sag between clamps. It is great inside of a wall. Consider using larger flex where you might need additional runs of larger wires - instead of multiple runs of flex or romex. Electrical materials are expensive - you may as well use only what you are sure that you need for now and expand only as you need to.

Since some of these wiring techniques may be new to you, have everything inspected. The inspector will help you catch any glaring mistakes before you cover your walls. If the idea of having everything inspected is intimidating to you - then hire an electrician and tell him how you would like things done (in general - like locations and # of circuits). He will offer professional advice and make sure that everything is done to code. Make sure that he pulls permits and is licensed and insured.

RC

[Eric Gustafson]

Metal Conduit allows you to use Multi strand wire. Multi. Strand carries more current.

This is not something I have ever heard. From my understanding, multistrand wire is just more flexible. 12 gauge solid should have the same capacity as 12 gauge stranded. I am not an electrician, however.

[Greg Funk]

This is not something I have ever heard. From my understanding, multistrand wire is just more flexible. 12 gauge solid should have the same capacity as 12 gauge stranded. I am not an electrician, however.
Correct. The difference between stranded and solid wire is negligible: 5.21 vs 5.32 ohm/km for 12 AWG.

Greg

[Chris Friesen]

Being in Wisconsin, I'm puzzled at why heating hasn't come into play. With every penetration through the walls and ceiling, heated air escapes (or cold air enters) the conditioned space.

I'm in Saskatchewan, Canada. The insulation has vapour barrier, and every outlet has a vapour barrier box around it sealed to the insulation vapour barrier. This is standard building code practice. I also caulked the holes in the vapour barrier boxes where the wires penetrate. There's no heating impact.

Something that nobody has mentioned yet is the fact that you start having to derate the conductors once you have multiple circuits in conduit. Granted, you can start at the full ampacity of the wire, but still once you have more than 7 or so conductors then you need to up the wire guage to compensate. This starts increasing costs.

[Randall Davis]

The EMT connectors are all screw fittings, where a set screw clamps down on the EMT.



Not all, if EMT is used outdoors a set screw connection is not permitted. In that case compresion fittings are used.

[Jim Becker]

My answer is...."Yes". I have both. In-wall for all the original shop circuits and some conduit down the walls for later modifications. I also have two drops that I did in conduit from the beginning and that allowed me to change the ciruits easily later as my machinery evolved. I think that conduit/raceway can be really convenient in a shop environment, although there obviously is a cost involved.

[Rob Russell]

Hi Rob, normally PVC is not used within a building due to flame spread issues. I'd check with your local building authority before using it inside a shop.


RNC (Rigid Nonmetallic Conduit) is listed for inside use. HDPE conduit is not. Based on the "Uses Permitted", it sounds like HDPE is really for underground use.



Rob The EMT connectors are all screw fittings, where a set screw clamps down on the EMT.

Not all, if EMT is used outdoors a set screw connection is not permitted. In that case compresion fittings are used.

True, but in the interests of not confusing issues, I left that out. Most of our workshops are indoors.

[Bruce Wrenn]

EMT is conduit threaded (rigid)is also conduit.
If you have a one man hobby shop save time and money put some thought in to your layout and use 12/2 romex for the general duty outlets. Wire your dust collecter, table saw, compresor to manufacterers specs. If your planer, jointer, drill press and table saw are all 240 volt save $ on breakers and panel space, run one 30 amp circuit to feed all of them unless you have figured a way to run two of these machines at the same time.My copy of the NEC has them in two very seperate sections. Rigid is refered to as conduit, but EMT is refered to as strictlly EMT. Kinda like is it a concrete, or cement floor? Both are used interchangably, but only one is correct.

[Randall Davis]

My copy of the NEC has them in two very seperate sections. Rigid is refered to as conduit, but EMT is refered to as strictlly EMT. Kinda like is it a concrete, or cement floor? Both are used interchangably, but only one is correct.


They are very diffrent they are not necessarily used interchangably and they are both conduits. Conduit is also made of polyvinylchloride and other materials.

[Dan Clark]

EMT is conduit threaded (rigid)is also conduit.
If you have a one man hobby shop save time and money put some thought in to your layout and use 12/2 romex for the general duty outlets. Wire your dust collecter, table saw, compresor to manufacterers specs. If your planer, jointer, drill press and table saw are all 240 volt save $ on breakers and panel space, run one 30 amp circuit to feed all of them unless you have figured a way to run two of these machines at the same time.
Randall,

It turns out that I'm wrestling with the same issues in updating my garage/shop. For lights and other relatively permanent items, I agree with you. However...

While NEC 2005 allows you to go either way, for tools... I'm be concerned what happens when you change your mind. IF you have you workflow down pat (I don't) and IF you know the tools that you will be using for years to come (I don't), then fixed placement of Romex in walls is a great idea.

Right now, I use Festool tools a lot. They are portable and can be moved around easily. However, I expect to add more fixed tools like a bandsaw, drill press, maybe a small table saw, and jointer. OR, I might decide that Festool, Makita, Bosch, Hilti, or several of other good tool vendors has a better more flexible solution. And that's the problem - While some technology is fairly static, there are lots of new tools coming on the market that will displace current technology.

For example, there are multiple add-on rail systems for circular saws, routers, jig saws, and other tools. Festool is a big name in the built-in rail system market now. BUT, but Hilti and Makita have come out with some very nice tools to which they've added built-in rails.

For example, the new Makita SP6000K1 plunge saw is now available in Europe and the UK. It's a very nice looking saw and has built-in dust collection and attaches to a Makita guide rail. Add Makita quality and you've got a nice combo. This is brand new and a big change for Makita. But in a few years, I suspect that dust collection and built-in guide rails will be common-place in many great quality tools (this could give Festool fits ;)).

So what happens to your shop when you make a committment to one strategy now and then find better ways of doing things?

IMO, surface mounted electrical conduit is the way to go. The minimal extra expense in the short run will give you on-going benefits in terms flexibility and configurability. I'm going add extra circuits now (110 and 220) and stub them out to a surface-mount box. Then I can add or change the electrical configuration to suit my needs at any given time.

Regards,

Dan.

[Randall Davis]

Randall,

It turns out that I'm wrestling with the same issues in updating my garage/shop. For lights and other relatively permanent items, I agree with you. However...

While NEC 2005 allows you to go either way, for tools... I'm be concerned what happens when you change your mind. IF you have you workflow down pat (I don't) and IF you know the tools that you will be using for years to come (I don't), then fixed placement of Romex in walls is a great idea.

Right now, I use Festool tools a lot. They are portable and can be moved around easily. However, I expect to add more fixed tools like a bandsaw, drill press, maybe a small table saw, and jointer. OR, I might decide that Festool, Makita, Bosch, Hilti, or several of other good tool vendors has a better more flexible solution. And that's the problem - While some technology is fairly static, there are lots of new tools coming on the market that will displace current technology.

For example, there are multiple add-on rail systems for circular saws, routers, jig saws, and other tools. Festool is a big name in the built-in rail system market now. BUT, but Hilti and Makita have come out with some very nice tools to which they've added built-in rails.

For example, the new Makita SP6000K1 plunge saw is now available in Europe and the UK. It's a very nice looking saw and has built-in dust collection and attaches to a Makita guide rail. Add Makita quality and you've got a nice combo. This is brand new and a big change for Makita. But in a few years, I suspect that dust collection and built-in guide rails will be common-place in many great quality tools (this could give Festool fits ;)).

So what happens to your shop when you make a committment to one strategy now and then find better ways of doing things?

IMO, surface mounted electrical conduit is the way to go. The minimal extra expense in the short run will give you on-going benefits in terms flexibility and configurability. I'm going add extra circuits now (110 and 220) and stub them out to a surface-mount box. Then I can add or change the electrical configuration to suit my needs at any given time.

Regards,

Dan.

Dan, I understand your thought process, but isnt it true that you can add surface mounted conduit at any time in the future if needed?

[Charles Grosjean]

Another option is Wiremold 4000 series surface mount raceway. Looks much nicer than conduit/boxes, holds a lot of wire, derating rules are different (YMMV), extremely flexible and very easy to reconfigure. Wiremold makes plates/brackets for just about any device you might want. Fairly common in industrial applications.

http://www.wiremold.com/shared_content/pdf/ed531.pdf

[Rob Russell]

Another option is Wiremold 4000 series surface mount raceway ... derating rules are different (YMMV)

Why do you say that derating rules are different for Wiremold raceway? Is it classified as "Metal Wireway"?

[Dan Clark]

Dan, I understand your thought process, but isnt it true that you can add surface mounted conduit at any time in the future if needed?
Randall,

Not exactly...

For the new power tool circuits, my plan is to run new Romex from the main circuit breaker boxes through the ceiling to several ceiling, surface-mount boxes (one per new 110 and 220 circuit, maybe 3-4 total). Think of these as "main distribution points".

Each of these boxes will be fairly large (maybe a 42 cubic inch metal box) to easily meet code, allow useful working space for heavy gauge wires, and allow multiple conduit connection points. Surface mount conduit will run from the electrical distribution point boxes to where power is needed.

The key point is the surface-mount distribution points. With these points and surface-mount conduit, it's a relatively simple matter to add or subtract conduit runs.

With Romex only, once everything is closed up behind sheetrock, it's difficult to change. To add conduit runs, you'd have to rip off the sheet rock, run the new circuit, and then replace it.

Regarding metal versus PVC...

Metal boxes and conduit are a bit more hassle to work with initially, but I think they may be a bit safer, and provide more configurability and parts reusability than PVC. PVC is very tough, but the metal is tougher. I think it would be a bit safer. With metal conduit, you need a conduit bender. However, once bought, I think you have more flexibility - literally and metaphorically. Within limits, you can bend the pipe into odd shapes to get around obstacles. With PVC you'd have to add special fittings and pieces - lots of gluing. With PVC, the fittings can be used only once; once glued they are toast. With metal, they can be unscrewed and reused.

I don't think there's a clear black and white on whether metal is better than PVC. For me, the current balance is toward metal.

That's my thinking now, but I won't be installing all of this for 2-3 months. Show me a good argument for changing and I'll switch (pardon the pun). :D

Dan.

[Randall Davis]

Randall,

Not exactly...

For the new power tool circuits, my plan is to run new Romex from the main circuit breaker boxes through the ceiling to several ceiling, surface-mount boxes (one per new 110 and 220 circuit, maybe 3-4 total). Think of these as "main distribution points".

Each of these boxes will be fairly large (maybe a 42 cubic inch metal box) to easily meet code, allow useful working space for heavy gauge wires, and allow multiple conduit connection points. Surface mount conduit will run from the electrical distribution point boxes to where power is needed.

The key point is the surface-mount distribution points. With these points and surface-mount conduit, it's a relatively simple matter to add or subtract conduit runs.

With Romex only, once everything is closed up behind sheetrock, it's difficult to change. To add conduit runs, you'd have to rip off the sheet rock, run the new circuit, and then replace it.

Regarding metal versus PVC...

Metal boxes and conduit are a bit more hassle to work with initially, but I think they may be a bit safer, and provide more configurability and parts reusability than PVC. PVC is very tough, but the metal is tougher. I think it would be a bit safer. With metal conduit, you need a conduit bender. However, once bought, I think you have more flexibility - literally and metaphorically. Within limits, you can bend the pipe into odd shapes to get around obstacles. With PVC you'd have to add special fittings and pieces - lots of gluing. With PVC, the fittings can be used only once; once glued they are toast. With metal, they can be unscrewed and reused.

I don't think there's a clear black and white on whether metal is better than PVC. For me, the current balance is toward metal.

That's my thinking now, but I won't be installing all of this for 2-3 months. Show me a good argument for changing and I'll switch (pardon the pun). :D

Dan.

Sounds like a good plan! Stick with the metal (EMT) it will make for a much nicer job. good luck!

[Rob Russell]

Charles sent me a PM about the raceway. If the Wiremold is classifed as a "Surface Metal Raceway", then article 386 of the NEC has specific provisions for it. From that section,


The derating factors of 310.15(B)(2)(a) shall not apply to conductors installed in surface metal raceways where all of the following conditions are met:
(1) The cross-sectional area of the raceway exceeds 2500 mm-squared (4 in.-squared)
(2) The current-carrying conductors do not exceed 30 in number
(3) The sum of the cross-sectional areas of all contained conductors does not exceed 20 percent of the interior cross-sectional area of the surface metal raceway

Based on the above and the fill table at the back of the Wiremold document, you can get more circuits in this larger "surface metal raceway" Wiremold than normal (round) conduit.

Neat to know. Thanks.

[Dan Clark]

Charles sent me a PM about the raceway. If the Wiremold is classifed as a "Surface Metal Raceway", then article 386 of the NEC has specific provisions for it. From that section,


The derating factors of 310.15(B)(2)(a) shall not apply to conductors installed in surface metal raceways where all of the following conditions are met:

(1) The cross-sectional area of the raceway exceeds 2500 mm-squared

(4 in.-squared)

(2) The current-carrying conductors do not exceed 30 in number
(3) The sum of the cross-sectional areas of all contained conductors does not exceed 20 percent of the interior cross-sectional area of the surface metal raceway


Based on the above and the fill table at the back of the Wiremold document, you can get more circuits in this larger "surface metal raceway" Wiremold than normal (round) conduit.


Neat to know. Thanks.

Rob,

I looked at Wiremold or some other raceway a few months ago. I can't remember the name or many other details, but I got the impression that it was very expensive.

Do you have a sense of the cost to outfit something like a two-car garage/shop?

Thanks,

Dan.

[Rob Russell]

Dan,

Sorry - I don't. The pieces of Wiremold that Home Depot carries aren't cheap, though, and they are for the much smaller stuff.

Rob

[Dan Clark]

Rob,

Thanks. I'll check it out the next time I'm in HD. If it's within reason, I might use it for the flexibility.

Dan.