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Greg
07-13-2015, 05:39 PM
I have a question for an Electrical Engineer

I want to run 100 amp 220V to a detached Garage, it is approx 80 feet between service entrance and fuse box in the Garage…

what size wire do I need;

I prefer Copper

of course aluminum would be cheaper, but I’ll buy Copper wire. and install in gray plastic

last question; it needs to have a ground rod at the garage also ?

I called the Power Company Engineering Dept, they no longer (provide/advise) the needed wire size !

thanks in advance

daniel lawecki
07-13-2015, 05:48 PM
Use 1awg wire for the service two hot one neutral use ground rod at garage with # 4 bare for ground. Mark neutral with white phasing tape.

JonB_in_Glencoe
07-13-2015, 05:48 PM
I am not an engineer or a lic. electrician...but I've built and wired industrial controls panels for a few decades.

It should be safe for me to tell you, 1 gauge.

But, depending on the type of wire/cable and it's type of insulation it has, you may be able to get by with 2 gauge.

farmerjim
07-13-2015, 05:56 PM
copper as above or 1/0 aluminum

Greg
07-13-2015, 06:04 PM
thank you for the help

P.S. wood shop tools, and of course casting, so no reason to scrimp on the wire, # 1 it is

again thanks for the help

Wolfer
07-13-2015, 11:19 PM
I am a licensed electrician and #3 copper is all you need to run 100 amp 80' away. Two hot wires colored black or black and red with a third wire phase taped white.
You should have a ground rod drove at the garage with #6 AWG bare solid copper going to it.

At the new panel you need to bond the neutral and ground wires. This is usually done with a green screw that comes with your panel. This should be the only place your white wire and your ground wire are connected.

I generally run 1-1/4 conduit in these applications.

bangerjim
07-13-2015, 11:25 PM
You do NOT need an electrical engineer!

Listen to the above electrician. That is his job!

Lloyd Smale
07-14-2015, 07:37 AM
lineman here and we used to run 1/0 underground with a #2 neutral (aluminum) for a 100 amp service. When the customer did his own we allowed 1/0 aluminum or #2 copper. We required two ground rods with #6 solid copper for grounding. Keep in mind that this is for underground installs. You can get away with smaller wire if its open to the air (overhead) I agree with wolfer. Install it in electrical rated pvc pipe (gray pipe) if it ever goes bad its much easier to replace and is also a lot less likely to ever go bad if its in conduit. Don't scrimp now. Do it right the first time.

doc1876
07-14-2015, 08:04 AM
I F you use aluminum, remember to tighten the lugs every year. Heat causes aluminum go get loose.

Wayne Smith
07-14-2015, 12:49 PM
You almost certainly have some local codes that specify the minimum required. Check them first.

popper
07-14-2015, 01:18 PM
Direct burial cable is EXPENSIVE. Put it in sched 80 pvc, stub above ground level about a foot, seal both ends with good RTV. Copper coated Al is OK, plain alum is poor because of bends - I'd use solid copper. Put a good strong rope in the PVC when you put it together - before burial as a puller. Or put the wire in first before gluing. I used 1/0 on my son's garage. You will need to get a licensed electrician to CONNECT it (think INSPECTION). Go with the larger gauge due to start currents in your machines. Low voltage start is hard on motors.

Duckiller
07-14-2015, 02:20 PM
Install the PVC then blow a rag attached to a pull rope, small cheap poly. Blow it through with a compressor , borrow/rent a larger portable construction compressor. For a single install it may be simpler to put the rope in as you install the PVC ,

Flexy
07-14-2015, 02:57 PM
Just how much I want to reply, I'll just keep it short. Google some wiki page, you will get the answer, provided the answer is around the same neighbourhood... Allways opt to bigger dia. Savings on that are minimal, compared on the leighbour... atleast around my corner of the world.

HATCH
07-14-2015, 03:04 PM
use copper only.
Use direct burial and put in conduit.
No matter how good you are, water will get into the conduit if its underground.
Pull a string in so you can pull something else in later.
I have coax run in with my power and have no issues.
#1 copper is what you want.

popper
07-14-2015, 03:17 PM
Don't try pulling 300 or 500 MCM with a rope.

garym1a2
07-14-2015, 03:57 PM
Being an EE, for my own need I always double what I need in capability so I can upgrade later to use more current.

You may want to add A/C, Heat, a welder or other items down the road.

Lloyd Smale
07-15-2015, 07:42 AM
Aluminum wire is just fine. You just need to use some allox on the conections and tighten it good. Go back in about a year and retighten and it will be fine from then on. If aluminum is such a bad deal do you really think the power companys would use it? One trouble call caused by aluminum use would more then offset the cost of going with copper. Bottom line is its cheaper and works fine. I did my own service in aluminum and its been fine for 25 years now. I did this for a living and think ive got a bit more experience then most.

Easy way to pull rope through is to cut a pices of 2inch foam rubber to a round cylinder that matches the size of the pipe (just a bit smaller) put a hole through it and push a piece of twine through the hole and tie it off on the other side. (you may need to make a plastic washer to keep it from pulling through. Take your shop vac and it doesn't take a big one and tape the suction to the far end and it will easily pull the foam and twine through the pipe. Then use the twine to pull in your rope. One poster did hit this right though. You have to look at your electrical codes for your area. they vary and some are very specific about what kind of enterence panel you must use, how many amp panel it must be and exactly what wire you are required to use. One bit of advice another poster touched on is your needs. I allways tell people to figure out your expected load and then double it. It doesn't cost all that much in the big picture and its a lot cheaper then upgrading everything later.

TheCelt
07-15-2015, 09:14 AM
Thought I'd chime in here on the "ground" as you have the wire size pretty much covered. DO NOT SINK A GROUND ROD!!! You will be grounded through the rod at your main panel and if you ground at a separate rod at your detached garage you have created a ground loop. It's laborious to explain why a ground loop is a bad idea but you'd find out during the next electrical storm.

tomme boy
07-15-2015, 10:25 AM
Pulled lots of 300 and 500 with rope. And a skid loader to pull!

popper
07-15-2015, 11:30 AM
And a skid loader to pull! with a bucket of soap, steel cable with basket, pulling machine that bogged down. Most states will let you do the labor work but it must be connected and inspected by licensed person, keep the inspection report for any insurance claims. Problem with Al is stress cracks and cold flow. Copper clad doesn't show the same problems, nor does copper. KCI terminal buildings were done with Al, the redone with Cu clad which did work (cost + 10%, a good profit). Residential allowed Al in the 70's but builders are using Cu now even with push-in terminals. They do tend to undersize long runs to AC.

Wolfer
07-15-2015, 07:06 PM
Thought I'd chime in here on the "ground" as you have the wire size pretty much covered. DO NOT SINK A GROUND ROD!!! You will be grounded through the rod at your main panel and if you ground at a separate rod at your detached garage you have created a ground loop. It's laborious to explain why a ground loop is a bad idea but you'd find out during the next electrical storm.

The national electrical code (NEC ) will require a ground rod at every building. If you run a separate ground wire from your main service to your new panel ( no need to ) then you wouldn't bond the ground and neutral.

TheCelt
07-16-2015, 02:13 PM
The national electrical code (NEC ) will require a ground rod at every building. If you run a separate ground wire from your main service to your new panel ( no need to ) then you wouldn't bond the ground and neutral.

Yeup, you are correct!! Code has changed some in the last 20-30 years. I'm guessing you meant Neutral and Ground bonded at main panel but not at sub-panel. In effect a ground rod at the detached building just enlarges the ground plane of the existing rod in that case.

daniel lawecki
07-16-2015, 02:34 PM
You have to use deoxidation paste on all aluminum wire by the way I wire for a living.

Lloyd Smale
07-16-2015, 04:42 PM
you will already have your ground loop with the utility pole in your front yard. All primary voltage poles are ground and have a ground rod. At least they do in our utility. Adding a ground rod at every enterance gives a shorter path to ground if you have a lightning strike. In our untility and going by our electrical standards for the county EVERY entrance to a building that has a panel has to have two ground rods. Tak my yard. I have a great big pole barn right near the house. Its metal and if lightning is going to hit its going to hit it first Its much taller and metal. Having a couple ground rods to have a path to ground may keep it from damaging things in my home. I don't want the full brunt of the lightning traveling through my service wire back to my panel in the house.
Thought I'd chime in here on the "ground" as you have the wire size pretty much covered. DO NOT SINK A GROUND ROD!!! You will be grounded through the rod at your main panel and if you ground at a separate rod at your detached garage you have created a ground loop. It's laborious to explain why a ground loop is a bad idea but you'd find out during the next electrical storm.

Lloyd Smale
07-16-2015, 04:45 PM
that is the allox I was referring to in my post. Its just a brand name for it. Most electrical codes demand you use it and they will check.
You have to use deoxidation paste on all aluminum wire by the way I wire for a living.

lightman
07-16-2015, 05:23 PM
It looks like I'm late to the party. The OP posted that he is buying #1 and has not been back in a few days. It looks like we are building his job after the fact. But its fun, so I'll play. I ran the numbers and #1 copper or 1/0 aluminum will carry a full 100 amp load with an acceptable voltage drop for the distance the OP stated. I added a few extra feet for up and down the wall. I would put the wire in conduit if given the choice. The #1 would go in 1-1/4 but the 1/0 would be a tight pull. I probably would go 1-1/2 or even 2 inch. The proper fittings on each end (think LB) would provide an easy way to enter and exit the buildings. Cost; the copper would cost me about $450 and the al would be about $110. 2 inch conduit would run about $55 and the required fittings would add maybe another $20. These are local prices and are just off the top of my head, but will be close.

There are as many ways to do this as there are electricians. You can blow or suck a paper towel and a string through with a shop vac, but I would just use a fish tape. I'm not a fan of aluminum, but I've been trained to install it and have used it for 35 years. You need to wire brush the ends, treat it with an oxide inhibitor and torque it to the specs on the lug. The lug also needs to be rated for use with aluminum, but most are. Copper is much more forgiving and would be my personal choice. I would drive a ground rod at the shop and the shop panel would have the neutral and ground separated. A piece of 12-3 added for a 3-way switch from the house to shop would be a nice touch!

I'm a retired Journeyman Lineman and a Master Electrician. Yeah, I hold both cards and was active in both trades!

lightman
07-16-2015, 05:25 PM
LLoyd, thats the stuff most Linemen have on the fronts of their shirts! Around the belly!

Greg
07-16-2015, 11:07 PM
hey -

I'm still here, just watchin and learnin

I do appreciate all the responses

again, thank you for your help

MaryB
07-17-2015, 02:01 AM
Chep insurance, add a whole house surge suppressor at the panel. It won't stop a direct hit but it will keep a near miss from frying motors, lights, etc in the shop

Lloyd Smale
07-17-2015, 08:04 AM
ive still got a few shirts in the closet with those stains because all the connectors we used on the pole came with it in them. really though our meter techs did most of the wiring at the house. Once in a while when they were busy we did it for them.[
LLoyd, thats the stuff most Linemen have on the fronts of their shirts! Around the belly!

Akheloce
07-17-2015, 09:12 PM
A few unasked for cents from a Journeyman Telecom guy...

Don't run phone line with the power if you have, or ever intend to have DSL at the house. I can't tell you how many repair tickets I've been on where the customer ran cat 3/5 or whatever in the same conduit as power over to their garage. The power influence kills DSL. The customers get confused because the modem is in the house, not the garage... However if the phone line in the garage is tied to the phone line in the house, they might as well be on the same physical wires.

Also, I was watching this thread with interest in regards to the ground loop issue. In my world, ground loops are bad, and play havoc with G.SHDSL data circuits. In some areas of my service area, the difference of potential between the Wire Center Earth Ground and the customer Earth Ground may be as much as 40V. A technique to alleviate this issue is to remove the earth ground from the equipment, and instead, bond it to the cable sheath (bonding it to the wire center).

lightman
07-17-2015, 09:51 PM
Would a shielded cable laying in the same trench with a little separation work ok? Just curious.

Akheloce
07-17-2015, 10:11 PM
Shielded is better than not, but it still will cause interference. Think about the milliamperes used in communications vs the 100+ Amps used in power. In a perfect world, your phone line would be at least 12-24" from all power when running parallel- or crossed @ 90 degrees.


Story comes to mind...

One customer had 7Mbps ADSL, but was only getting 4Mbps on a speed test. They had a decoratively manufactured log house.

Removed all house wiring, clipped my test set, and got full speed. Reinstalled one line of house wiring, and got 6 Meg. Reinstalled another, and got 5M. As I laid down each line of house wiring (I'm working in the box on the side if the house), I lost more speed.

As I investigated the house wiring, I noticed the phone jacks and the power outlets were located on the same log.

When a log house is wired, typically a router is run along a log as it is built, hidden from view when the next one is stacked. If the power and phone outlets are on the same log, then the wires were run in the same router channel (bad).

The cat 5 house wiring was shielded.

When I explained this to the customer, she was understanding, but unwilling to accept the fix, which was to drill holes in her new log house, and install new phone lines.

TheCelt
07-18-2015, 09:11 AM
you will already have your ground loop with the utility pole in your front yard. All primary voltage poles are ground and have a ground rod. At least they do in our utility. Adding a ground rod at every enterance gives a shorter path to ground if you have a lightning strike. In our untility and going by our electrical standards for the county EVERY entrance to a building that has a panel has to have two ground rods. Tak my yard. I have a great big pole barn right near the house. Its metal and if lightning is going to hit its going to hit it first Its much taller and metal. Having a couple ground rods to have a path to ground may keep it from damaging things in my home. I don't want the full brunt of the lightning traveling through my service wire back to my panel in the house.

I'm not so sure we're talking about the same thing here. There is no ground loop until you create one. If you tie Neutral to ground at the main panel, sink another ground rod at your sub panel and tie neutral to ground at your sub panel you have created a ground loop.

The danger lies in the fact that you now have two points of ground reference for both panels. If there is a lightening strike in the area each ground sees a different potential. The nanosecond difference in potential is what does the damage.

As previously mentioned a ground rod is required at each panel. Neutral and ground are only tied at the main panel and NOT at the sub panel. This avoids the ground loop and the ground rod at the sub panel increases the ground plane of the original ground rod. In the event of a lightening strike both ground rods see the same potential (which is what you want).

popper
07-18-2015, 09:44 AM
http://www.powerstream.com/Wire_Size.htm for reference. Note the difference in current rating for 1/0 = the transmission rating is the one to use in the OPs application.
Safety wire/neutral/ground rod requirements are NOT for lightning protection!! Completely different techniques. As for data, consider the power lines as a long wire antenna, they pick up everything plus transients from everything turning on/off. Only solution is shielding and separation for data lines - and avoiding ground loops.

TheCelt
07-18-2015, 09:54 AM
http://www.powerstream.com/Wire_Size.htm for reference. Note the difference in current rating for 1/0 = the transmission rating is the one to use in the OPs application.
Safety wire/neutral/ground rod requirements are NOT for lightning protection!! Completely different techniques. As for data, consider the power lines as a long wire antenna, they pick up everything plus transients from everything turning on/off. Only solution is shielding and separation for data lines - and avoiding ground loops.

You are correct popper, ground rod are not for lightening protection, I didn't say they were. I did say that if you ground your sub panel and tie neutral to ground (at the sub panel) you will have a ground loop and a difference of potential at the ground points in the event of a strike nearby.

lightman
07-18-2015, 09:54 AM
Akheloce, Thanks for the info. I quit wiring houses before DSL, so my question was for my education only. Inquiring minds, Ya know! Around here we once had a contractor that worked for us ( power company ) and the phone company and there are a lot of phone drops buried in the same trench with the power. Thankfully mine is not.

gew98
07-18-2015, 02:54 PM
I F you use aluminum, remember to tighten the lugs every year. Heat causes aluminum go get loose. And use NO - OX on your lug/wire lugs. I use it like religion and it saves alot of later down the road dissimilar metals corrosion . For the past couple years two ground rods within 10 foot of panel and each other with bare or insulated # 6 awg minimum on such a panel size. You need to check in your AO if this needs an inspection or not. Some local inspectors want more than NEC code and could cause you grief on a do it yourself install "they" deem inappropriate , an dif you argue with them they will show you they can exceed NEC code by law and make it real hard on you getting inspected and passed timely and on budget. And take the advice on bonding.... seen the results of bonding from lineside to panel where a neutral failed and the ground that should not have been there became the neutral and it caused a fire instead of kicking out the supply as it was way undersized to handle that panels max load. Oh and PVC schedule 40 for underground...direct burial is in the code...but you really want to avoid that.

gew98
07-18-2015, 03:02 PM
Don't try pulling 300 or 500 MCM with a rope.


I've pulled up to 750's with a rope on some 600' runs. Gobs of lube and thankfully few bends. Just have to know what you are dealing with. I saw a fella one day cut the manufactured head off a high dollar spool of pool rope...yeah he got canned on the spot !. I've had twined pull rope break and had to reweave the head...time consuming yes.... but gives the feet a rest to reweave and get ready for the pull !. I always jet a pipe run with a compressor before I even put a string & mouse in it. Have found everything from rocks , mud , screws , drillbits and even dead critters ( blown from the undergound lines )

MaryB
07-19-2015, 12:53 AM
I helped my dad(he was an electrician) with a pull like that. We were wiring a roller skating rink and had to do the pull by hand. I was put on the lube bucket and dad told me to waste it, make it wet! We ended up with 6 guys on the rope to pull through 2 90 degree sweeps.

lightman
07-19-2015, 08:53 AM
I usually have 1 or 2 long pulls a year with fairly big wire. These are mostly buried conduit to irrigation wells. Most are over 600 ft up to around 1100 ft. The wire size will run from 4-4/0 to 4-500 mcm. It depends on the HP and distance. I use my tractor, lots of lube, a couple of guys with a radio turning the reel and 1 guy with me on the pulling end. I use a rope and a pulling basket (kellum). The rope is 3/4 inch and something like a Navy Braid or Double Navy Braid. 1200 feet cost me about $1500 with a factory eye on each end. I'd whack anyone that cut it for sure!

A funny story that I remember is my well drilling and shooting buddy was on a job one day and the utility crew was having trouble blowing or sucking their rat thru the pipe and ask him if he had an air compressor on his drilling rig. He told them yeah, a 450 HP, 500 cfm, 200 psi one. When he blew the rat out of the end of the pipe it went about 40 ft in the air along with a bunch of dirt and water. He said the bearings on their string roller got hot! Thats a heck of a compressor by the way!

I like those jobs. The profit is good and we usually start and finish a 1000-1100 footer in day, a long day. That is, if we don't have trouble trenching. It takes some special equipment for sure!

popper
07-19-2015, 05:09 PM
I was just an apprentice for a summer on the PV, Ks. YMCA, just me & the super. Got to run everything including the jackhammer for light pole bases & mix/pour the concrete. Pulling the mains wasn't too bad but the skimmers walked all over the EMT for the pool lights so it took 3 guys (one a really big plumber) and a puller machine to get-er-done. Thought we were going to break the concrete basement wall. Sure did learn a lot that summer. Summers after that I got to do the estimating for those jobs, plus going to job sites for boss's inspection. Neatest compressor I've seen was a ford V8 with one bank as the compressor.