garage Sub panel installation

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  #1  
Old 11-24-12, 11:06 AM
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garage Sub panel installation

hello,

i know there is alot of information already around this forum on sub panel installations however, i cannot find clearly what i am looking for. i am no electrician but understand some basics.

So my garage is detached about 30 feet behind my home. it is a straight shot from my main panel to where i plan putting my sub panel 30-40 feet away. My main service line is 100 amp.

so one of my many questions is... what is the largest size subpanel can i install in my garage if i only have a 100 amp service line?

thanks for the help
 
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  #2  
Old 11-24-12, 11:40 AM
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Note the subpanel can be larger then the feed. Most garages need a 60 amp or less feed but may need a 100 amp subpanel just to have spaces for all the breakers needed.

Edit: This post should be read after PCBoss' but do to a Currilian time warp it posted ahead of his.
 
  #3  
Old 11-24-12, 11:44 AM
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You could install up to a 100 amp subpanel.

You need to supply some information about the tools and usage of the garage so a feeder can be sized. Depending on the usages and loads you may need to upgrade your house service.
 
  #4  
Old 11-24-12, 11:54 AM
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i was hoping i didnt have to upgrade my main service panel but i plan on putting a washer, gas dryer, and as far as tools go...i plan to operate the basic 120v power tools, saws, drills, grinders, air compressor..of course not all at the same time. but i would like the option to install a 240v air compressor in the future.

if i can get a 100amp subpanel back there would i need to install a 100amp breaker at my main panel for the subpanel? and then another main breaker at my subpanel?

thanks
 
  #5  
Old 11-24-12, 12:01 PM
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[Duplicate to try to trick the time warp]
A 60 amp feed would be more then enough so a 60 amp breaker at the main panel. At the subpanel any breaker 60 amp or larger can be used since it only acts as a disconnect. Most 100 amp service panel will come with a 100 amp breaker and that will be fine to use as the subpanel disconnect. As I guess you have already read you will also probably need to purchase a ground bar for the panel as it usually isn't included.
 
  #6  
Old 11-24-12, 12:20 PM
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ok so i can use a 100amp sub panel and a 60 amp breaker at the main panel. will i have the option to upgrade that 60 amp breaker to a 100 amp breaker in the future if i need to? now i understand i need to run 4 wires to the garage. 2 hots 1 neutral and 1 ground correct? what type of wire and what size should i be using?

Also, i understand that i should tie my neutrals together from main panel to my sub panel making sure i isolate my neutrals from the subpanel correct? and my grounds can all be grounded together. main panel grounded to main panel enclosure and tied into the grounds in my subpanel that will also be grounded to the subpanel and a seperate ground rod correct?

thanks for all the quick responses.
 
  #7  
Old 11-24-12, 12:42 PM
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will i have the option to upgrade that 60 amp breaker to a 100 amp breaker in the future if i need to?
Yes. If you use conduit large enough you can pull the #6 and pull in #3 instead if you need to increase capacity. You would need to use at least 1" conduit but 1-1/4" would be an easier pull.
 
  #8  
Old 11-24-12, 04:23 PM
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so for a 60amp breaker i should be running #6 wire? what type of wire do i use? do i just buy them individually red, black, white, and green.

also, do i use a main breaker box or a main lug box?

thanks again this is great amount of help.
 
  #9  
Old 11-24-12, 06:32 PM
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You use THWN. The ground can be #10. You can use two blacks instead of red and black if you just want to buy a single length of black.

Because the box will have more then six spaces you need to have a disconnect. As I wrote earlier buy a box with a main breaker and that will serve as your disconnect. You can often get a box that is sold with breakers cheaper then if bought you bought the components separate. Also as I wrote earlier the ground bar is usually sold separate. You will also need at least one eight foot ground rod.
 
  #10  
Old 11-25-12, 11:30 AM
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great got it! I have most info i need for now to begin purchasing the material and post further questions as i go.

thanks again
 
  #11  
Old 12-04-12, 03:24 PM
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I need some help choosing a circuit breaker panel. I am not sure what kind ineed. I see 10 spaces 20 circuits.. single phase..double phase... can someone shed some light on this to help me choose the correct box.
thanks
 
  #12  
Old 12-04-12, 04:28 PM
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You would pick a panel with enough space for your expected needs, plus some room for future growth.

Your panel should be labeled 120/240, single phase 3 wire.

Your panel will need an auxillary ground bar purchased separately.
 
  #13  
Old 12-04-12, 05:06 PM
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so whats the difference between the amount of spaces and circuits. some panels have the same amount of spaces as circuits. and some have more circuits then spaces.
thanks
 
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Old 12-04-12, 06:18 PM
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You can put two circuits in one space if the panel is rated for tandem breakers. Tandem breakers are either half the size of a regular breakers or two half breakers in a full size breaker housing or a quad, four half size breakers in a two breaker size housing.
 
  #15  
Old 12-05-12, 06:25 AM
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what would be the reason to use double pole breakers rather then single pole?
 
  #16  
Old 12-05-12, 06:32 AM
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Double pole breakers are for 240 volt circuits or a multi-wire branch circuit where the neutral is shared between two hots. Single pole breakers are for 120 circuits.
 
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Old 12-05-12, 06:34 AM
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what would be the reason to use double pole breakers rather then single pole?
Double pole breakers are used for 240 volts. They protect the two hots used for 240 volts. Single pole breakers are used for 120 volts which has only one hot.

Do not confuse a two pole breaker with a tandem. Both take two wires but the latter is for two separate 120 volt circuits.

Extra explanation: "Hot" is an unofficial name for the ungrounded conductor. Neutral is the term often used for the grounded conductor. 120 volts is one ungrounded conductor and one grounded conductor. Only the ungrounded conductor needs to be protected by an overload protection device such as a breaker or fuse so protection is only needed on one leg of a 120 volt circuit. A 240 volt circuit has two ungrounded conductors so both conductors need to be protected.

 

Last edited by ray2047; 12-05-12 at 06:51 AM.
  #18  
Old 12-05-12, 06:44 AM
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oh I see. so the tandem basically is two independent breakers in one. got it makes sense. thanks
 
  #19  
Old 12-05-12, 08:06 AM
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so then when I run my four conductors from my home to my garage I will need to use a double pole breaker at my main panel since i will have two hots?

what about when I reach my sub panel which will also have a main breaker being used as a disconnect, how will I do it there? with another double pole breaker?
 
  #20  
Old 12-05-12, 08:18 AM
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so then when I run my four conductors from my home to my garage I will need to use a double pole breaker at my main panel since i will have two hots?
That is correct.

what about when I reach my sub panel which will also have a main breaker being used as a disconnect, how will I do it there? with another double pole breaker?
The main breaker is a double pole breaker and that is where you connect the feed. The neutral to an isolated neutral bar and ground to a bonded ground bar you will probably need to buy and install.
 
  #21  
Old 12-11-12, 08:12 AM
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so I was at homedepot and did not find any #6 wire that was THWN. All I found was THHN. can I not use this for underground through conduit?
 
  #22  
Old 12-11-12, 09:28 AM
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so I was at homedepot and did not find any #6 wire that was THWN. All I found was THHN. can I not use this for underground through conduit?
Did you actually look at the wire or ask an associate? Better to just look. It will be probably be dual rated THHN/THWN. You can not use wire marked only THHN.
 
  #23  
Old 12-11-12, 10:29 AM
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I was at homedepot and did not find any #6 wire that was THWN. All I found was THHN.
I haven't seen any THHN in years that wasn't dual rated as THHN/THWN. Read the designation molded into the insulation.
 
  #24  
Old 01-05-13, 05:27 PM
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this is a slow build for me so i have my panel, wire, and conduit that i am currently running it through. I ran into something i did not think about. So i have FOUR wires, three #6 and one #8 (ground) and they are all the same length (50ft). Do i really need to run a ground from my home to the garage thats 30 feet away? since i am putting a ground rod for the garage, did i really need to get a ground wire that long? couldnt i just run three wires from the house to garage (2 hots 1 neutral) and just ground the entire garage to the rod which will only be about 6 feet away.

thanks
 
  #25  
Old 01-05-13, 05:38 PM
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Yup, you need 4 wires, the ground and neutral are required, as well as a ground rod at the garage. It's an NEC requirement.
 
  #26  
Old 01-05-13, 05:44 PM
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well i do plan using 4 wires, but do i really need to run a ground from my home to the garage? i am going to have a ground rod at the garage, cant i just run my ground wire from the ground rod to my panel with out running one from my home to the garage?
 
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Old 01-05-13, 06:02 PM
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Code requires both because they serve different purposes. You need both an EGC form the house to provide a low resistance path to clear fault currents and a GEC to bleed off atmospheric electrical potential.
 
  #28  
Old 01-05-13, 06:10 PM
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ok so i am going to run all four from home to the garage, connect the neutrals from my main panel to my subpanel and isololating the neutral on my subpanel, and ground my main panel to my sub panel and to my garages ground bar? correct?
thanks again sorry for all the confusion.
 
  #29  
Old 01-05-13, 07:00 PM
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Sounds like you have it as long as the neutrals and grounds are isolated and the panel does not use the bond screw or strap.
 
  #30  
Old 01-05-13, 07:29 PM
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by isolated you mean at the sub panel right?

okay so my main panel is out of room for my new neutral and ground wires. there is no more room anywhere on the existing ground bar which by the way the grounds and neutrals are all tied together, i am assuming i need to add another ground bar and hook up my new neatural and ground to it?
 
  #31  
Old 01-05-13, 07:57 PM
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You can add a ground bar. Only grounds can be on the add on bar. Neutral need to be on the neutral bar. You can move some grounds to the new bar to make room for the new neutrals.
 
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