Power and phone lines for the shop - meeting the NEC

[Bob Davis]

Years ago, I actually owned a copy of the National Electric Code and kept up with it, as an electrical engineer in an industrial situation. I no longer work as an electrical engineer and I've never had to know much about residential applications, so I have some dumb questions.

I'm running a new power feed and two phone lines to my emerging shop. I've settled on running individual #6 power lines with a #12 ground. I'll run all of this through a 1" PVC conduit to get from the existing breaker panel outside to a point where I can bring the wires into the attic and over to the garage shop. I also will have a 4 conductor telephone-type wire. Its cleaner to run the phone line in the same conduit as the power, but I'm concerned about two things - electrical noise pickup and compliance with National electric code. As to the noise, I can always run the cable and if its noisy, just abandon it in place.

If you have any knowledge about NEC with regard to running phone lines and power in the same conduit, please let me know.

Yes, this is related to woodworking. The power will run a complete new set of tools - table saw, dust collector, jointer, drill press, planer, band saw, and coffee pot. The phone line will be used to call my woodworking friends when I get stuck with a problem in the shop.

Thanks in advance for your comments.

Bob

[Bob Gramza]

[BRuce]

no it should not be in the same conduit, run a separate (small) conduit and run the phone, intercom, security and network cable in it.

the ground wire is NOT there to handle the load if the neutral "fails"

ask your electric supplier, he know the scoop for the local area. wire inspectors can, and do, set their own rules.

BRuce

Bob Gramza wrote:

shop. I would run the

current it could burn.

[Doug Miller]

Instead of "should not" be in the same conduit, substitute "must not". This is explicitly prohibited by the NEC, Article 800-52.

True, but he still should use a #6 or #8 equipment ground instead of #12.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

[George Berlinger]

run the phone live seperate.......I needed my once in an emergency....glad I had a phone in the shop to call for help...it wasn,t ;wood related though, slip n fell on the icy drive n broke my ankle, the shop phone was the closest I could get too....have fun....

your shop. I would run the

the current it could burn.

[Bob Davis]

Thanks for the reply, Bob.

Regarding your comment about the neutral, I want to be sure we are talking apples and apples. My plan is to carry three #6 conductors for 120/240 single phase service. The #12 was intended to be just an equipment ground, not a current carrying wire. Does the code require it to be same size? My existing panel would be in violation. I think its got 3 #2's coming in and what appears to be a #10 going to ground rod.

Best regards, Bob

shop. I would run the

current it could burn.

[Bob Davis]

I appreciate all the replies. I'm at the stage where its easier to change and be safe, rather than try to get by. That's why I asked before I actually did the "cannot turn back" part of the installation.

In summary the suggestions/admonitions from the group:

1. Do not run the phone wire in the same conduit with the power.
2. Use a larger ground wire, suggested #6 or #8.

Since the phone wire does not have to be in conduit, I'll just run it outside parallel to the power conduit and hide it behind the conduit. In my area, that's typically how phone wiring is done (exterior grade phone wire stabled to the building).

Best regards, Bob

shop. I would run the

current it could burn.

[Bob Gramza]

: >

: :

[Eric Tonks]

Don't cheapen out -- drop a 1/2" or better 3/4" conduit next to the power line so that you can pull in phone, network, even cable TV or internet connection. You don't know what you will want/need down the road but you will be thankful for having that extra conduit available, especially if it travels underground for any distance. PS. If you are using PVC conduit, the voice/data lines should not be attached to or very close to the power conduit -- vinyl does not provide the shielding that steel conduit would -- keep them a couple of inches or more apart.

[Myxylplyk]

Bob,

Some years ago, about 5, I upgraded the service and communications links to my shop and house. First rule for the power upgrade was to do the labor myself to save money, but do it under the direction of a licensed electrician. Let the electrician make the final hookups and call for the inspection. You'll still save a lot of money, but you'll avoid issues with the inspector and possibily your insurance company. For communications, I ran a separate 1" conduit and placed it 15" to 18" away from the power conduit. (Local phone and cable company recomendation to avoid signal degradation and interferance.) Since I dug a two foot wide trench, I just put them on opposite sides. Further, even though your using undergound conduit, use underground, waterproof cables. I used 12 pair, gel filled for phone/isdn/dsl and heavy ground rated cable for digital cable service. Both cables were provided by the respective phone and cable companies. Both installers were grateful for me doing/helping with the installation. I paid only small reconnect fees.

Good luck,

Myx

[Bob Davis]

Thanks, Myx.

I think I miscommunicated about where I am running this. None of its underground. The original wiring to my 3 car garage went through the ceiling of the first floor from the opposite side of the house (breaker panel). There is no way to add wire through that ceiling, since its a 2 story house. So I'm bringing the wire from the breaker box (interior closet) through an exterior wall and into a conduit that will run along the back side of the house toward the garage.

Bob

but do it under

opposite sides.

[Bob Davis]

I appreciate the wisdom of your remarks, Eric. Years ago, I had an experience working as lead engineer on a plant reconstruction. The electrical foreman taught me a lesson well remembered. I was busy specifying and buying materials and watching the budget. He told me to always buy conduit one or two sizes bigger than the code called for. He told me I'd eat up my dollars paying for labor soaping the cables and pulling it, including some broken wires on long, complex runs. An electrician will practically kiss you when the code says 40% fill and you go for 25% fill instead.

It seems silly that I know so much about the heavy stuff (high voltage, motor control centers, etc) and I'm as dumb as a skunk on residential wiring. I wish I could find my old copy of the code. It would be kind of fun to go through it for old times sake.

Bob

[Doug Miller]

The 1993 NEC (latest one that I have at hand) says "Copper, aluminum, or copper-clad aluminum equipment grounding conductors shall not be less than shown in table 250-95." [Article 250-95]

The table gives the following for copper wire:

*** Please note that more recent codes may have more restrictive requirements. In any event, though, this shows that your plan is clearly a code violation even under the 1993 NEC. Your service entrance isn't in compliance either, but it may have been at the time it was installed.

15A breaker, 14 ga wire

20A, 12 ga 30 thru 60A, 10ga 100A, 8ga 200A, 6ga [higher amperages omitted]

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

[Erik Ahrens]

Bob,

The ground wire cannot be less than two wire sizes smaller than the current carrying wire - #6 = #10 ground minimum. You CAN run the tele wire in the same conduit BUT the insulation rating of the cables/wires has to match the highest rated wire e.g. 600v insulation for power wiring will require 600v insulation for the tele wire (I don't think that is readily available) and noise from the power wiring may crosstalk on the tele wire. I agree to run it separate. Also, modern telephones only require two wires, tip and ring (R&G). I would run 4 though, you may want to have two line or DSL out there some day.

Hope this helps,

Erik

[admin]

One additional comment/recommendataion:

You mentioned using PVC conduit. A lot of PVC, given exposure to sunlight, degrades over time. This is a potential problem 'several years from now'. Also, if it's 'on the surface', it's exposed to all the other "slings and arrows of outrageous fortune", as it were. The "do it right" approach is _ridgid_ conduit, w/ waterproof fittings.

[Gfretwell]

If you use twisted pair for your phone line it won't be bothered by the power. That is also true of CAT5 and LANs. The design on a NIC rejects virtually all "common mode" noise. If telephone lines were bothered by 60hz they certainly wouldn't be putting it on poles next to fat transformers and 13kv cables. The secret is twisted pair tho. Straight through (red,green,yellow,black) will pick up everything from adjacent phone line crosstalk to your local radio station.

As for the EGC (ground) the other posters are on point, #10 minimum and you want #8 min to a ground rod. Anything smaller than #4 requires physical protection.

[Mark]

Exactly. Since your going to be 'up there' anyhow might as well do it now.

My shop has it's own 200 amp service so running power wasn't an issue. But, all self respecting shops and garages have water, since I had to trench for the water line I figured I would also run a conduit so I could operate walk lights switched from both garage and house.

The conduit 'grew' to carrying 3 4 conductor phone lines ( (total 12 wires) just happens I had a spool of wire laying around,) a 4 conductor

16 ga intercom line, CAT-5 LAN, 'TV' cable/ coax, one normal power circuit for motion lights and one 3 way circuit for the walk lights (all 12 ga)

Funny how these things escalate when one has the 'might as well do it now' mentality.

Far as I know there are two conditions for running power (115 volt) and other wires through a conduit, 1) insulation must be rated 600 volts or higher, and 2) the total fill must not exceed 40%.

Fact, fill should not exceed 40% in any conduit, IIRC.

About my memory, I freely admit it could be faulty. Check your codes. Better yet call the inspector. I have found inspectors pretty cool people, (then I'm a homeowner that believes in overbuild) I have yet to meet an inspector that wasn't more than willing to tell all to someone with half a clue that there are codes and what they are.

[Doug Miller]

False. Ground wire size depends on the rating of the overcurrent protection device, and is specified by Table 290-95. [NEC, Article 290-95]

False. This is _explicitly_prohibited_ by the NEC: "Communications conductors shall not be placed in any raceway, compartment, junction box, or similar fitting with conductors of electric light or power circuits..." [NEC, Article

800-52(a)(2)c.1]

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

[Gfretwell]

The only way you can run LV and line voltage in the same conduit is if one of them is in another raceway inside that big one (usually the LV). This is pretty common when you have duct banks between buildings but not that practical for residential or anything you are building to a spec. The duct has to be pretty big to accomodate a raceway plus whatever conductors you run.

[Bob Davis]

Ah, facts I can use. So, since my service is #6 wires (55-60 amps depending on how you interpret the ratings), I need a #10 ground wire.

Bob