Electrical questions on using conduit

In theory, correct. In practice, it is just too easy to make mistakes. A mistake that is easy to avoid would be to use a 14-gauge neutral conductor (for a lighting circuit with a 15A breaker) for the

20A outlet circuit (which needs 12 gauge). Another mistake is if you have several circuits in the same conduit and you scramble the neutrals, so in the end most of the outlets from several circuits use just one neutral wire (which is overloaded now), while the other neutral wires are heavily underutilized. If you have multiple white conductors of the same gauge in a box, this can happen easily.

-- The address in the header is invalid for obvious reasons. Please reconstruct the address from the information below (look for _). Ralph Becker-Szendy _firstname_@lr_dot_los-gatos_dot_ca.us

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_firstname_
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The Japan Woodworker, 1731 Clement Ave, Alameda. Specializes in Japanese hand tools (I'm beginning to salivite just thinking about them), but also has a good selection of big machines.

Through 15 feet of straight conduit: trivial. Even if there are other conductors already in place. Probably don't even need a fish tape, just push the wire through (maybe get a piece of solid wire to use as a fish, then use it to pull stranded wire through). If you had said "50 feet of 1/2" conduit, with 3 ninety-degree bends, already stuffed", I would have said: Hard but doable (you'll have skinned knuckles afterwards).

Our worst experience with this was pulling three 2/0 conductors (about

1/2" of copper each, for a 200A service) through about 70 feet of 1 1/2" conduit, with a few bends. We ended up with one person pushing like mad, and filling the conduit with wire pulling lubricant, and the second person using their full 200 lbs weight as a gravity operated human winch. Took all afternoon, and afterwards all our hands were a big mess. It is very hard to hold on to wire that has been smeared with lubricant, so you keep sliding off, and hitting the sharp metal edges. Much fun. Should have used 2 inch conduit instead.

Good luck!

Reply to
_firstname_

Tell me more about that. If that's really true, I'll have to redo a lot of boxes before the building inspector shows up. I'll check into it.

Inside conduit, in practice, never. The only single-conductor wire that is commonly sold is THHN. And the wire inside NM-B is also de-facto THHN (even though it is not labeled such, it has to be rated to 90 degrees). Clearly, extension cords, outdoor underground feeders, and machine tools are a different story.

Looks like more work to me: You have to build all the furring or soffit to hide then NM-B in, then you have to cut and connect all the conduit stubs, and you still have to worry about getting the NM-B in and out of the conduit (easiest way is to put a small handy-box there). You would end up with way more pieces, and need more wire.

By the way, several posters mentioned Tapcon screws. I've used them for things like hanging shelving. But when I pulled my permit, the chief inspector (Santa Cruz county) said that even though the Tapcons are rated for structural use, and have ICBO evaluation reports, the building inspectors hate seeing them, because the tend to wiggle loose if you hit them a few times, or if something connected to them vibrates. So I have avoided them where it matters - just to avoid trouble with the inspector, and switched to plastic anchors (for non-structural things, like electrical boxes and plumbing) and steel anchors (for all structural stuff). This might be a general statement, or it might just be one inspectors pet peeve, don't know.

Reply to
_firstname_

IIRC, the OP mentioned he would only be running 2 outlets, with one or perhaps two neutrals.

Reply to
PrecisionMachinisT

On Tue, 21 Sep 2004 18:03:18 -0700, Wayne Whitney wrote (in article ):

Wayne,

If NM is allowed as a wiring method in your jurisdiction, then it can generally be used for exposed work in an unfinished residential basement, but not where it could be subject to damage. You can protect it with running boards, or sleeve it in conduit as necessary. However, for a workshop, IMHO, you're wise to consider another wiring method. It will make for a safer and more workman-like installation. In answer to your questions

1) In addition to EMT, the common raceway types are Rigid, Intermediate Metal Conduit (IMC), Rigid Non-Metallic Conduit (NMC), Flexible Metal Conduit (FMC or Flex), Armored Cable (AC) and Metal-Clad Cable (MC).

Rigid and IMC are heavywall aluminum or steel pipe used in various hazardous locations or where subject to extreme damage. They are difficult to bend and install and are over-kill for your proposed application.

NMC is a gray PVC pipe available in Schedule 40 or Schedule 80 wall thickness. It is joined by solvent cement and is relatively easy to install. It must be fastened within 3' of each box and every 10' otherwise. There is an assorment of boxes and fittings available in PVC which solvent weld to the pipe, or you can use conventional metal boxes and attach the pipe with a male threaded adaptor and lockring. NMC obviously does not provide a grounding path.

Flex is made of an interlocking spiral of aluminum or steel strip. It is relatively easy to install but difficult to fish. It must be fastened within

12" of each box and every 4 1/2' feet, but for a neat installation it is usually supported at much closer intervals. It provides a grounding path if the conduit and fittings are listed for grounding, otherwise it may only be used as the EGC where the ground return path does not exceed 6'.

AC and MC look like flex but come as an assembly with conductors installed. They are available with different conductor combinations: 14-2, 14-3, 12-2,

12-3 are commonly available. AC does not include a grounding conductor, instead it has an internal bonding strip which is folded back and clamped in each fitting to assure the ground path. MC includes an insulated grounding conductor. Both types provide a grounding path. AC must be supported like Flex but MC may be supported at 6' intervals. AC must have plastic "anti-short" bushings installed in the cut ends where they attach to a clamp or fitting.

I personally like using EMT, but installing it can be tedious. Bending becomes easy after 10 years of practice, but initially there's a lot of wasted pipe. You probably should consider NMC or MC as your wiring method.

For two circuits of #12 THHN conductors, 1/2" NMC, EMT, or Flex will be comfortably adequate.

2) Yes, EMT is acceptable as the EGC, but it provides a better ground return path to include a bare or insulated grounding conductor. And yes, every box must be bonded, generally by looping one of the EGC's around the grounding screw before nutting the EGC's together. If you don't run an EGC, then any receptacle's ground terminal must be pigtailed to the box, unless the receptacle is identified as suitable for grounding through the box-mounting screws. Even then it's good practice to pigtail them - it guarantees the ground path even if the mounting screws are loosened or removed.

3) To anchor to concrete, you'll need a percussion (hammer) drill and a suitable bit. You can use a regulary rotary drill and masonry bit, but the drilling will be tedious. You can use metal anchors and screws or masonry screws alone (Tapcons). I prefer the Tapcons. They're expensive, but save time and make a very firm connection. I buy them in bulk, but I've seen them in boxes of 100 with the appropriate bit included. 3/16" x 1 1/4" would be the right size for box and conduit straps. They have combination hex and phillips heads. Use a hex drive for installation - it takes a bit of torque.

4) For a home workshop, two 20 Amp receptacle circuits for plug and cord tools sounds like a good plan. Running both circuits to each quad box and splitting the receptacles between them is also good design. This plan also allows you to install a 220V receptacle in any box, if you should eventually need that.

You do not need a double pole CB just because there are two circuits in each box, even if you use a multiwire (Edison) circuit with a shared neutral. If you do have a 220V receptacle in the circuit, or split a single duplex between the circuits (ie: two circuits feeding a device on the same yoke), then you need a double-pole CB. However, there's nothing to prevent you from using a double-pole and it's not a bad idea.

As to multiwire branch circuits: I happen to like them, they save copper and help with box and conduit fill. However, they have the drawback that if the neutral becomes disconnected, and you have devices plugged-in to both circuits, the connected devices will be "two-twentied". Just make your neutral connections carefully, particularly at the panelboard neutral bus.

The other drawback to Edison circuits is that GFCI receptacles will not work on them. In a residential basement, you should be using GFCI protection. You can only run the common neutral to the first pair of GFCI's - from then on the neutrals must be split. On the subject of GFCI's: The most economical design is to use a pair of them in the first box and then use their Load terminals to feed conventional duplexes in all the other boxes. This protects the downstream receptacles, and costs much less than GFCI CB's. However, if you want to install a 220V receptacle anywhere "after" the GFCI's, this won't work. In that case, you'll need a 110/220V GFCI CB to protect the circuit.

One additional thing to consider for a workshop is whether you should run a feeder to a "sub-panel" in the shop, and then run your branch circuits from there. If you think you might eventually expand this installation with additional circuits, it might not be a bad idea, particularly if it's a long run to the main panel.

I should probably give you the standard caution about contacting the "authority having jurisdiction" for the specific requirements in your area, pulling a permit, inspection etc. Nonetheless, I'm aware that sometimes electrical work is done without this legal requirement, and sometimes it's even safe and workman-like. Do some reading on the proper installation for the wiring method you choose. There are plenty of good books on home wiring. The place to learn is definitely not Home Depot. Be wary of advice in this NG as well (including mine for that matter). There's a lot of scary misinformation posted on electrical questions...

Good Luck,

Kenneth

Reply to
KJS

Not on a 240/120 circuit, you can't. Doesn't work.

Reply to
Doug Miller

It can if you do it right. It won't work if you need a GFCI protected

240V device. Otherwise, you can even mix 240V unprotected outlets and 120V GFCI outlets and 120V-outlets-connected-to-the-GFCI-load-screws, all on one edison circuit. (it may not meet local codes to mix 120V and 240V outlets on a branch circuit, but that's not the point.)

As long as the only return path for the hot LOAD wire of a GFCI is back to the neutral LOAD screw of the same device, it will work. The GFCI will not even know it is sharing a neutral LINE wire.

Bob

Reply to
zxcvbob

Well, I am far from an authority, so don't take my word on it, but I would be curious to know what you find out. I think what I had read was not to loop conductors around a screw terminal on a device (receptacle, switch, and so on). But even if that's true, looping the EGC around a ground screw may be fine.

Cheers, Wayne

Reply to
Wayne Whitney

Emt is the easiest and most efficient way to go.

No. The only time a breaker has to be common tripped with another is when the 2 circuits are connected to the same device YOKE.

IOW - a 220v receptacle is on one yoke. It's breaker must have a common trip.

A duplex receptacle split into 2 circuits by removing the jumper tab would be considered 2 circuits on one yoke, and the breakers would have to common trip.

A combination device at your back door, with 2 switches on it both on the same yoke, one fed by one circuit for the back door light and the other for the power to your backyard shed which is on it's own circuit, would have to be common trip.

Nope just pass it through.

In residential both hots can be black, but you could use a black for one circuit and a red or blur for the other if you desire.

You will have 2 neutrals and they must be white.

No.

Reply to
HA HA Budys Here

This is Turtle.

Reply below and try to sort it out.

This is a bit of over kill here but your not paying for labor so go for it.

Now the wires run for the jointer & dust collector. i would just run one set of wires for the 230 volt service wire to the two of them and have a receptical for each. Both can share the wire / breaker as they both will be connected very near each other. Wire size / breaker size will have to be dealt with other than this talk.

Now the table saw and the planner in my opinion should have their own seperate service of 120 volts and have each a breaker by theirself. Planner one set of wires and breaker and a set of wires just for the table saw's 120 volt service.

You will have 2 service sets of wires for the table saw and Planner. Then one set of wires / breaker for the DC and Jointer with 2 recepticals. You will have

2 black wires / 1 green or nake ground wire to be joined at the 2 receptical. We have not cover wire size yet.

NO and NO

Now tring to figure out what set of wires go to each of the 120 volt services or equipment. you can paint one set of wires for one of the pieces of equipment with spray paint about 1 foot at the end to tell which is which. Now really it will not make much difference for your only going to have 2 blacks / 2 whites and 2 ground wires. The two whites and the ground at the switch box are going at the same place and then one black wire to each of the equipment. It don't take much to figure it out for there is only 3 wire for each and different colors to boot. Just get one black to each piece of equipment and the white & Ground to the receptical. To each piece of equipment you will have ground/common/ Black.

You will have 2 black wire , 2 white wires, and 2 Green or Nake ground wires. Then 1 Black [hot wire]/ 1 white [common ] / 1 Green or nake [ground wire ] will go to one piece of equipment and the other set left will go to the other. DON'T FORGET TO HAVE A GROUND WIRE TO EACH. It can be green or Nake wire.

We will have to cover the rating of the wire / breaker size by the way you run it and go by a wire chart for what you call derating the circuit or wire. I have wire charts to tell you what will fit in the conduit and what rating of the number of wire / amp draw of each / size of conduit. Tell me what way your going to run the wire like all in one or seperate conduits. If you like you can e-mail me and I can look up the wire rating verses the conduit size for you or post back here.

TURTLE

Reply to
TURTLE

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