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Thread: Doing surface mount wiring for my garage shop. What kind of wires in the conduit?

  1. #1
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    Doing surface mount wiring for my garage shop. What kind of wires in the conduit?

    Ok. I could really really use some help on what to use to put the new electrical circuits into my new shop in the 3rd bay of my garage.

    The garage is totally finished, all the way to texture and paint, so I thought I would go for surface-mounted circuits rather than cutting into and trying to make the new repairs when putting everything back look decent.

    So with the new panel up with plenty of new power and circuits I wanted to start running the lines to the outlet. With my shop arrangement and where the panel was put it pretty much means going up to the ceiling, across and then down the far wall to where I want the outlets.

    So off I went to Home Depot. In the course of 24 hours trying to figure everything out I talked to 4 different experts there at 2 HDs. I of course got four completely different and pretty much completely opposite answers. The somewhat abrasive older man who claimed to be a master electrician with 35 years of experience was helpful but not around for much time. His comment was 1 sentence: "Of course you can use Conduit to run your wire across". When I asked what kind he asked if I had ever used/bent the EMT before? I said no and his response was "Then use PVC as you are familiar with it." I have put in a number of sprinkler systems over the years. He then left for the day.

    He was followed by an even more abrasive but much younger woman who came on shift and basically told me that not just NO! but HECK NO! That running romex/cerrowire thru conduit was not only against code but lethally stupid as I would burn down my house in nothing flat. Her reasoning there was way way to much insulation on the wires. What on earth?!!? I had thought that would be what would keep the heat down! She cited an extensive knowledge of electrical code and promptly fled the scene. Her specific advice was to buy either completely seperate wires that were each individually shielded. Which is just pain to work with in comparison, or more specifically to buy some "Greenfield" armored cable that has the 12/3 that I needed already in it. But now instead of running one nice conduit line across and then distributing the multiple lines that were in it around I will have a rat's next approach of a 3+ seperate armored conduit lines going across.

    So off to the books at the front of the store. I looked at them an nothing was said either way. So back to home to look on the internet. A number of sites showed some examples of how to do this but with all of the pictures and explanations they had nothing about what type of wire.

    The saga continued with a couple of return trips looking for help to get different answers/suggestions on how to accomplish this feat.

    Well I trust the 18 year old kid I talked with last night a ton less than the experts I have run into here on the Creek. So here I am once again begged for the benefit of your experience and wisdom.

    The specifics of what I am trying to accomplish: I have a Powermatic 3250B, a 2hp HF dust collector, a chop saw, a small bandsaw, etc... I am planning to run a dedicated 110v line to the DC using 20amp and 12/2 wire. The Powermatic is a 20amp 12/3 220v dedicated line. The 3rd line is just a normal array of plugs to get power out to chargers the saw, etc... Then I was thinking about a dedicated 110v 20amp line for an A/C I have yet to buy but would really like to have.

    So I wanted to run 4 lines of the cerrowire thru 1 condition to a distribution box and go from there.

    Is this safe? Is it legal? I know codes differ from region to region in some ways but things that will burn the house down are pretty much against code everywhere. For the record I live in SLC, UT if that helps anyone...

    If you can't run wire down electrical conduit what on earth is the conduit for?

    Also should I buy the armored greenfield stuff. Can I bundle them in hangers on the walls/ceiling? to try and at least keep the mess down?

    Any advice, ideas, thoughts, comments, experiences would be great to have!

    Thanks a million,
    Joshua

  2. #2
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    Joshua, I am sure someone will chime in here with NEC specific articles. But until then, here's my experience.

    I move a lot and therefore wire my entire shop with surface mounted conduit. When I move I take it down and take it with me.

    If you have never bent conduit, be prepared for a bit of a challenge. The guys that do this day in and day out make it look easy. The little extra "S" bends (can't remember what they are called) that allow the main run to sit flat against the wall and then bump out to enter in the side of the box are a bear for me. However, it can be done with a little patience.

    As for what wire to use. You can run romex inside of conduit, it just isn't recommended because it's difficult. Everything I've read in the past indicates that there is no NEC code against it. But in my experience, it's cheaper and easier to buy spools of wire and then pull them individually through the conduit. I label the ends of all of them so I can easily identify a single line.

    I don't know if it's a rule, but I don't mix my 110 and 220 runs into the same conduit. I have two 110 conduits with two circuits each. Each of my 220 lines is a dedicated conduit (10 gauge wire is just to hard to pull multiples through and I know I'd be close to exceeding the max number of wires allowed inside the conduit).

    There is an NEC limit as to how many wires you can pull through a conduit. It depends on the size of conduit, size of wire, and wire type. I don't know the specifics though - again, I'm sure someone will chime in with the NEC code.

    Be well,

    Doc

  3. #3
    For metal or plastic conduit you need to run stranded wire, THHN.

    That's the spools of wire you see hanging on the racks. [Can be purchased by the foot]

    Sounds like you need to track down an electrician, or at least a friend that has some electrical experience to help you out.


  4. #4
    The idea is to run individual wires through the conduit, not Romex, but you can do that if you want (there is nothing inherently unsafe about it).

    Running individual strands is much easier, though - getting 3 wires wrapped in paper and insulation (aka Romex) to bend in conduit all in one pull is hard work.

    Really, the only thing to seriously worry about is sizing the breaker correctly for the gauge of wire you're using. Worrying about heat dissipation from the wires, conduit fill, etc, is unnecessary for a home shop.

  5. #5
    Joshua, Look up "multiwire branch circuits. What this does is allow for two 110's and a 220 from a double pole breaker. You run two hots, and a neutral to each location. Between each of the hots and the neutral, you put a 110 recpt. Between the two hots, you put a 220 recpt. Because you are most likely going to use GFCI recpts for the 110's, put your 220 recpt on first, and in another box below it, put the two 110's. If you use EMT, you don't have to pull a ground wire, but must use a bonding jumper on your recpts. The EMT furnishes your ground. You could run a loop of EMT, with boxes where recpts will fall around the ceiling. From boxes, just drop down to recpts. I use #12 THHN (solid) on my installation. Bruce

  6. #6

    Heat

    I believe the reason you were told not to run romex was due to heat build up. The same reason that 14 gage wire in free air will handle 20 amps (think knob and tube) and only 15 amps in romex. I had 3 romex wires that needed to leave the wall cavity for about 8 inches (to go around cement block). The inspector had to approve this (it was approved as a wire chase). Likewise if you bury your wire in a wall no more than six romex wires are permitted on a cable stacker, again because of heat build up.
    I would use emt and purchase a conduit bender. If your going to use the cheap switches and receptacles you should use solid thhn. The better ones have a clamp type connector that will permit you to use stranded wire, the screws by themselves will only hold solid wire.

  7. #7
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    Quote Originally Posted by Bruce Wrenn View Post
    Joshua, Look up "multiwire branch circuits.
    Bruce,

    That is awesome. That will actually solve a number of my problems. I looked it up and found the NEC 2008 document directly. Very cool. Small differences between NEC 2005 which I also found. For this type of circuit it appears the biggest difference is that in 2005 you could use seperate switches in the breaker and in 2008 it had to be a linked set of switches in the breaker.

    But this will definitely help me get the power I need over to the other side.

    To everyone: Thanks for the information. If anyone else had any other comments then please feel free to share!

    Thanks,
    Joshua

  8. #8
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    In terms of running NM-cable (aka "Romex") in conduit - it is allowed and in some cases is required. If the location of the installation is "subject to damage", then NM-cable must be protected and sleeving it in EMT or Schedule 80 PVC conduit accomplishes that.

    If you were to ever run NM-cable in conduit, there are some rules you need to understand about conduit fill. There are fill requirements for cable that basically specify how much free cross-section you must maintain within conduit. Chapter 9, Table 1 shows the fill percentages - 1 = 53%, 2 = 31%, over 2 = 40%. NM cable is ellipsoid in shape - you need to take the longest dimension and treat the cable as if it were round and that longest dimension was the diameter. Still, I wouldn't pull NM-cable through conduit unless I were sleeving it for protection - I'd go with individual conductors.

    THHN/THWN would be the conductors to use because a garage can be considered a damp location. You will also need to use GFCI-protected receptacles in your garage. Because of that, you can't do multiwire circuits unless you use a 2-pole GFCI breaker in the panelboard instead of having a GFCI receptacle protect other receptacles down-circuit from it. (You can't have a shared neutral with GFCI receptacles - the GFCI will trip).

    I've bent conduit and you will go through a stick or 2 of "practice" conduit before you get the hang of bending EMT. Schedule 80 PVC will certainly work although it's bulkier than EMT. Make sure that you have pull points at least every 360 degrees of bend - that's a code requirement.

  9. #9
    Quote Originally Posted by Rob Russell View Post


    THHN/THWN would be the conductors to use because a garage can be considered a damp location.
    I would disagree that a garage is a damp location, unless the roof leaks or leaky plumbing exists, it would be a dry location, a carport would be a damp location at certain times of the year.


    Most THHN is dual rated as THHN / THWN.
    Last edited by Rollie Meyers; 07-13-2009 at 7:49 PM.

  10. #10
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    If you don't want to learn to bend conduit, you can also use LR (or LL) conduit bodies and offset conduit nipples.

    I have no relation with the company linked to - they were just the first link that came up when I googled.

  11. #11
    Quote Originally Posted by Rob Russell View Post
    . Because of that, you can't do multiwire circuits unless you use a 2-pole GFCI breaker in the panelboard instead of having a GFCI receptacle protect other receptacles down-circuit from it. (You can't have a shared neutral with GFCI receptacles - the GFCI will trip).
    True, but with the low cost of GFCI recpt. (about $11) VS a GFCI breaker ($61), just put a pair of GFCI recpts at each location. Be sure and locate them after your 220 recpt. Plus if one trips, you don't have to go to panel to reset it. My grandsons (two of them) are serving in Iraq. Everything in the housing is 220. By doing this, our cheap government didn't have to go to the expense of installing GFCI recpts, or breakers. Several soldiers have been electrocuted, especially in the shower areas.

  12. #12
    Quote Originally Posted by Rollie Meyers View Post
    I would disagree that a garage is a damp location, unless the roof leaks or leaky plumbing exists, it would be a dry location, a carport would be a damp location at certain times of the year.
    The garage, like an unfinished basement, may or may not be a damp location, but for wiring purposes both are considered that they may be, thus the requirement that non-dedicated outlets in either one must be GFCI protected.

  13. #13
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    I bought the armored "Greenleaf", or is that "Greenlee", cables. So each cable instead of being paper and plastic wrapped like Romex is surrounded by a flexible metal sheath. I think it looks a fair sight uglier but hey I just need to get this going.

    I also bought a long fiberglass push/pull wire kit so that I can see what is actually in my walls. I might just try fishing them thru after all. You never know... If it works I am good, if not then I will just go "ugly" surface mount and be up and running again. Finally.

    Thanks for all of the help. IN my reading I found that romex is legal in conduit as long as you maintain the amount of open space that NEC requires. The problem is that it is so much more rigid than one wire seperate insulated wires that it is basically impossible to pull thru. You can help with sweeping corners that are long either by adding them on bending them into the wire itself. But in the end I got a decent deal and the individual armored cable was actually just a touch less than the romex. I will pay for in boxes and fittings but it seemed like a decent way to go as I test out what is inside of each of my walls. The one I have to go and the one I have to come down from.

    Joshua

  14. #14
    Where'd you buy the armored stuff? I just bought a 100' role, and it was almost $40 compared to $45 for 250' of romex.

    That stuff is pretty cool. I got the crank handle cutter for it too. I just ran all new wiring for our barn, and it was my first for EMT conduit, and also my first time using the armored cable.

    I was doing all the same reading and research. Came to the same conclusions too, so that's good to hear what you found out matched my research!

  15. #15
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    Quote Originally Posted by Dave Houseal View Post
    Where'd you buy the armored stuff? I just bought a 100' role, and it was almost $40 compared to $45 for 250' of romex.

    That stuff is pretty cool. I got the crank handle cutter for it too. I just ran all new wiring for our barn, and it was my first for EMT conduit, and also my first time using the armored cable.

    I was doing all the same reading and research. Came to the same conclusions too, so that's good to hear what you found out matched my research!
    I got it at the local Home Depot on Saturday morning. They did have a sale going on some stuff I don't know fi that was under the sale or not. I also didn't know it was normally more. I was buying the 12/3 armored wire I guess prices might differ for the different gauges.

    I will see if I can still find the receipt and will let you know if it indicates a sale/discount on the wire.

    Joshua

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