sub panel


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Old 10-16-10, 05:51 AM
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sub panel

I am putting in a sub panel for electricity in my garage. I have purchased a 60 amp double pole breaker to go into my house breaker box. I have also bought a siemens 125 amp box for the garage along with 10-3 wire to go to it, along with pvc conduit. How deep do I need to bury the conduit? Do I need to connect the bonding strap? Do I need to run a ground for the garage breaker box? (Bare copper wire to copper rod driven into ground)
 
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Old 10-16-10, 05:59 AM
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Not sure what your going to do with the 10/3 but this can not be used as a feeder for 60 amps. You need #6 copper. (Either THWN or UF-b)

You do not connect the bonding strap. The neutrals and grounds are kept separate.

PVC conduit must be buried 18" deep with THWN wire or UF-b must be buried 24" deep direct buried.

For grounding, these pictures will help you:
http://forum.doityourself.com/electr...-drawings.html
 
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Old 10-16-10, 07:05 AM
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The reason I'm using 10-3 is because thats what they told me to use at Lowes. Afriend had told me previously to use 12-2, but Lowes told me to use the 10-3. It has 4 wires. Can it be used? I spent $150 on the 10-3 wire, 50 ft.
 
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Old 10-16-10, 07:15 AM
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10/3 can not be used for 60 amps. If you want to use the 10/3 the largest sized breaker you may use is 30 amp.

This is UF cable correct?
 
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Old 10-16-10, 07:28 AM
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The 60 amp breaker is the one I'm putting in the house to use to feed the sub-panel. It will serve as the main breaker for the 125 amp Siemens sub-panel. The largest breaker I'm going to use in the garage is 30 amp. Can this be done?
 
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Old 10-16-10, 07:39 AM
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Ok, were getting a little confused here.

The 60 amp breaker in the main panel is fine as long as the feeder from the main panel to the garage sub panel is #6 copper wire (either THWN in conduit or UF-b)

If you want to use the 10/3 (must be UF) as your feeder you may only use a 30 amp breaker in the main panel.

It will go like this if you want to use the 60 amp breaker:

Main-> 60 amp breaker-> #6 feeder-> 125 amp sub panel -> 30 amp breaker-> #10 wire -> equipment.

If you want to feed the sub with the #10 is will go like this:

Main-> 30 amp breaker -> #10/3 feeder -> 125 sub panel -> 30 amp breaker -> #10 wire -> equipment.
 
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Old 10-16-10, 07:52 AM
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Guess I'll see if Lowes will take the 10-3 wire back, ha! It was cut from a spool at 50 ft. length. $150 bucks down the drain. Can't seem to get straight answers from anybody. Thanks a bunch for your help, your way seems more safe, but who's to say you're right either? Oh, wait a minute, there is a double pole 30 amp breaker already in the main panel that is not being used. They must have put it in there trying to put in central air or something. Anyway, can I use this breaker and the 10-3 wire to feed my garage? Man I really appreciate you help!!!
 
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Old 10-16-10, 09:05 AM
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Look at the outer jacket of your cable (not wire) and read what is imprinted. If it says type NM-B you may NOT use this cable underground or outside. If it says type UF (or UF-B) then you may use it but you will have a terrible time pulling it through the conduit unless you have at least 1-1/2 inch conduit.

Some definitions: Wire or conductor is a single piece of wire whereas multiple wires contained in an overwrap are called cables.

Type NM cable can ONLY be used inside.

Personnel at the big-box mega-mart homecenters RARELY are qualified to give expert advice. Treat any advice you receive from these people as you would any advice from a drunken bum on Skid Road UNTIL you check it out on this forum.

Since your purchase was based upon incorrect information provided by their associate the store SHOULD take back the incorrect cable and issue a refund along with an apology.


You CAN trust the information you read on this forum as many of the members are licensed electricians AND there are licensed engineers that also contribute.
 
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Old 10-16-10, 09:28 AM
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Here is National Electric Code table 310.16 for wires: Houston Wire & Cable Company - NEC Table 310.16 That is just general other factors such as distance and bundling can lower the amount of amps a wire can handle. Equipment being fed such as a welder or AC compressor can also affect wire size so a chart is useful but needs to be combined with the situation to determine wire size. However in general if you follow the chart and have a run of less then 100 feet you will be ok.

When I worked for Home Depot Electrical was next to Gardening. When projected profits for the day were calculated based on early sales some associates were asked to go home to improve the profit ratio. Sometimes that left the gardening associate taking care of electrical. That could also happen if the electrical associate was at lunch and there was only one in the department and of course the associate in electrical could be a new hire with little or no training.
 
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Old 10-16-10, 09:34 AM
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Originally Posted by gearhead59 View Post
Thanks a bunch for your help, your way seems more safe, but who's to say you're right either?
The NEC code book says I'm right

Originally Posted by gearhead59 View Post
Anyway, can I use this breaker and the 10-3 wire to feed my garage? Man I really appreciate you help!!!
Yes, you could use the 30 amp breaker to feed your subpanel, as Furd and I posted, ONLY IF the cable is UF.

What are you planing to run in your garage? I am wondering if 30 amps will be enough for you.


Originally Posted by gearhead59 View Post
Man I really appreciate you help!!!
No problem! Happy to help.
 
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Old 10-16-10, 11:32 AM
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sub-panel

Ok, they took the 10-3 wire back and they gave me 4 seperate nylon coated #6 stranded THHN and/or THWN-2 rated wires. Will this work for the 60 amp breaker in the house breaker box?
What is the equipment grounding bar? Don't see one in the sub-panel I bought. There is a bar there with one big connection at one end, then the rest of the way it's full of screws. It's a Siemens 124 amp Main Lug indoor breaker box.
From the looks of your diagram, I need to connect the bond bar from the equipment grounding bar and run a ground wire outside and connect it to a ground rod, right?
What is the line in the diagram from the sub-panel, that goes up to a box that says "Neutral not to be bonded to ground", then it goes on to a thing that says "NEC 250 24(AX5)?
Much thanks! Mike
 
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Old 10-16-10, 11:45 AM
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Yes, the THHN/THWN wire is the correct one to use. You MUST use it in conduit all the way from the service (main) panel to the sub-panel.

An equipment grounding bar is a separate bus bar that will cost about $5. and is bolted to the back of the box in the sub-panel with included machine screws or self-tapping screws into holes already provided. You do NOT want to "bond" the neutral bus to the box. You need to supply a #6 "Grounding Electrode Conductor (GEC) from the equipment grounding bar to the ground rod.

The "line" on the diagram is simply a directional linking the text to the part of the diagram to which it pertains.
 
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Old 10-16-10, 11:57 AM
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Originally Posted by gearhead59 View Post
Ok, they took the 10-3 wire back and they gave me 4 seperate nylon coated #6 stranded THHN and/or THWN-2 rated wires. Will this work for the 60 amp breaker in the house breaker box?
Yes.
What is the equipment grounding bar? Don't see one in the sub-panel I bought.
They are not usually included with the panel. They must be purchased separately. There are pre tapped holes. You must get one made for your panel. Be sure the bonding screw or strap of the neutral bar in the panel is removed.
From the looks of your diagram, I need to connect the bond bar[sic] from the equipment grounding bar and run a ground wire outside and connect it to a ground rod, right?
Ground wire from house and ground wire from ground rod go to the ground bar as do all garage fixture grounds. Neutral from house goes to neutral bar.
What is the line in the diagram from the sub-panel, that goes up to a box that says "Neutral not to be bonded to ground
Neutral bar is isolated on insulated posts and bonding screw or strap not used. House neutral and all garage fixture neutrals go to it.

Are the wires black-black or red-white-green?
 
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Old 10-16-10, 12:38 PM
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Ok, thanks for everything! One more question,... I have already purchased 1" pvc conduit, is this the best way to do this underground, and is 1" big enough for the 4, #6 wires?
 
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Old 10-16-10, 01:02 PM
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1" big enough to be legal, but it'll be a rough pull if there's more than 180 degrees of bend in it. If possible, upsize it to 1 1/4" or even 1 1/2 or 2", and it'll make it much easier to pull the wires through. Going larger (2") now will also leave you an upgrade path later on, if you need larger service to the garage for say a future welder or something. You would just have to pull larger wires into place.

Underground is the only way to do it if it is a detached building, but if it is an attached garage you can run it along the surface of the siding. Underground has to be at least 12" below the surface. It is best to install a LB (pull ell) at the point of entry of each building for ease of pulling. You must install a LB after every 360 degrees of bend.
 
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Old 10-16-10, 01:28 PM
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Yep, I will upgrade asap, and I will probably upgrade my existing 100 amp service to 200 amp. I am a mechanic/machinist, and will have one or two welders, air compressor, etc., etc. in my garage, so, what size conduit do you recommend? Lowes will take it back since guy made mistake. Also, when I do change to 200 amp service, what wire will I need for the feeder? Maybe they will take this wire back and I can get the wire I'll need to run the 200 amp service, if it would work for what I'm doing now also!
 
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Old 10-16-10, 02:36 PM
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Originally Posted by gearhead59 View Post
The reason I'm using 10-3 is because thats what they told me to use at Lowes. Afriend had told me previously to use 12-2, but Lowes told me to use the 10-3. It has 4 wires. Can it be used? I spent $150 on the 10-3 wire, 50 ft.

3 dollars a FOOT?????????????????????????????
 
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Old 10-16-10, 02:54 PM
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Heck, I can get about 250ft of 10/3 nmb for that amount.
 
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Old 10-16-10, 04:23 PM
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sub-panel

Ok, now I have the #6 wire and I went and exchanged the 1" pvc conduit for 2", dang, that looks like extreme overkill! Is this what is needed to pass code, and to be big enough for an upgrade when I decide to go to 200 amp service. If I don't need the 2" pipe, I can still exchange it. I was thinking more along the lines of 1 1/2 ". Would 1 1/2" work later if I decided to go to 200 amp service?
 
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Old 10-16-10, 04:47 PM
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According to a couple of the other guys on here, 10-3 will not meet code for running a sub-panel from a Double pole 60 amp breaker in the house.
 
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Old 10-16-10, 04:58 PM
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The proper size for four #6 THHN/THWN conductors is 3/4-inch PVC although using 1-inch will make it a bit easier to pull. If you plan on someday increasing the power to the garage to 200 amperes (that's a HUGE amount of power for a home shop) then you need to lay 2-inch conduit now. If the plan is to increase the service to the house to 200 amperes in the future but leave the garage/shop at 60 amperes then run 1-inch conduit.

Be sure to also pick up a quart of wire pulling lubricant and use it liberally when pulling the wires in the conduit. You need to have the conduit complete before pulling the wires and pull all four at the same time.
 
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Old 10-16-10, 05:21 PM
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Yep, thats what I plan on doing, putting in 200 amp service to the house, but I will be running at least one welder, an air compressor, a lathe, mill, press, tire machine, computer, and a P.A. system for the band I play in out in the garage. So, will the 60 amp double pole breaker work for my garage service after the 200 amp upgrade?
 
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Old 10-16-10, 05:26 PM
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Assuming that you won't be running all the machines at the same time as you and the band are jammin the 60 ampere supply should be sufficient.

Sixty amperes at 240 volts is 14,400 watts. Add up the rated watts input for everything that might possibly be running at the same time, including lighting, and see what you get.
 
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Old 10-16-10, 05:26 PM
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Suggest you slide a string into the conduit as you assemble it. After the glue drys you can pull a heavier cord then the wires. Also you may want to bury a second 3/4" conduit with string a foot above the conduit for future LV and/or communication wires. Or use the 1" for that and buy 1-1/2 conduit for your main power.
 
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Old 10-16-10, 06:19 PM
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In a machine shop, there could easily be situations where multiple machines are running at once with only one person. A MIG welder alone usually requires a 30 or 50A circuit. Then if there's something in the CNC mill or on the lathe (which can run unattended) while you're welding, that could tax the sub feed. He may be looking at a 100A/125A service to the shop at some point. 100A service requires 2ga, which would require a 1 1/4" conduit, and 125A requires 1ga and 1 1/2" conduit, but again, upsizing will give you an easier pull and more room in the LB's
 
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Old 10-16-10, 07:40 PM
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Perhaps the Op could give more detail about the future upgrade to 200 amps. Is the 200 amp panel going in the house and the feeder for the garage staying the 60 amps or are they planning 200 amps to the garage and upgrading the house also?
 
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Old 10-16-10, 08:02 PM
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sub-panel

This is a reply and thanks to all the guys that helped me with this! This forum stuff is great! I hope I can help someone with something someday soon! Obviously not anything electrical though! Ha! Much thanks again guys!
 
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Old 10-16-10, 08:15 PM
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Thanks for replying pcboss! I am going to go with 1 1/2" conduit, the double pole 60 amp breaker in the house with #6 wire for a feeder. I think that will serve my purpose best for now. When I get around to upgrading, I'll get on here before buying anything now that I know how to get to this website and forum. I just wanted to make sure what I'm doing now will pass code and be safe. I'll worry about upgrading when I get to that point. If you're bored, you can tell me how a small jobing shop/house should be done right though. I appreciate your time! Mike
 
 

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