Sub Panel off a Sub Panel

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  #1  
Old 03-09-16, 05:36 PM
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Sub Panel off a Sub Panel

Hello,

I want to add a 60 amp sub panel in the attached garage. The feed will come from a 100A sub panel ( 2 spaces available in this panel) which draws from a 150A main.

The sub in the garage is for 240 v 20 amp table saw and future 240v equip. The total wire length through EMT will be approx 90 ft. I was told by an electrician that 4 wire #6 THHN copper wire will work, but i have read in other forums that #4 is appropriate.

The wire will dictate the EMT conduit size. With #6 THHN i can use 3/4" EMT, I do not want to use 1" due to the difficulties in bending.

Any help here would be much appreciated.


Ed
 
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  #2  
Old 03-09-16, 05:55 PM
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#6 THHN is okay for 60 amps. It is rated for 65 amps at 75. The ground would be #10. EMT will take up to four #6 so three #6 and a #10 should be okay in " EMT.
 
  #3  
Old 03-09-16, 06:50 PM
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Ray thanks for the reply. #6 THHN even though the run is 90' ? I am worried about voltage drop or other problems that wouldn't think to ask.

Wire colors to code are: Red, Black White and #10 green or (bare copper) ?


Ed
 
  #4  
Old 03-09-16, 07:12 PM
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Distance in an average residence is not enough to worry about voltage drop. Even at 100 feet u=you wouldn't need to worry under normal circumstances.
Red, Black White and #10 green or (bare copper)
Yes, or Two Black, One White and #10 green or (bare copper). It may be cheaper to use two blacks because sometimes longer lengths cost less per foot if you can buy a whole spool.
 
  #5  
Old 03-09-16, 07:58 PM
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Great, I really appreciate the help.

Any tips on pulling this through 3/4 EMT? I know about de burring before connectors installed, I will have about 20' between LB's. I will probably use the conduit pulling compound.

Thanks in advance,

Ed
 
  #6  
Old 03-09-16, 08:37 PM
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Any tips on pulling this through 3/4 EMT?
Pull wires as you build your conduit. It is easier that way because you don't have to pull through as much conduit as whole run. Less resistance. You may not even need fish tape if you pull wires in each section. Don't have to pull whole length each section. Push just enough for the wire to come out on the other side, then pull remaining wire.
Pull whole length only when it gets hard to pull.


Ray. Ground wire is still needed when the op is using EMT? Doesn't it get grounded through EMT?

Mod Note: the code requires the conduit to be complete before pulling the conductors. The info as posted is in violation of the code.
 

Last edited by pcboss; 03-10-16 at 05:54 PM. Reason: added Mod Note.
  #7  
Old 03-09-16, 08:53 PM
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Much thanks on the tip, Lambition. I wouldn't have thought of that. Makes a lot of sense. Will the sharp edges of the conduit nick the THHN?

I heard from a retired Master Electrician that the code had changed and a ground was needed in case the EMT separated anywhere along the run. ( I don't know much about much, but it sounded good)
 
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Old 03-09-16, 09:17 PM
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Ray. Ground wire is still needed when the op is using EMT? Doesn't it get grounded through EMT?
No, not needed by code. but often used and O/P mentioned using four wires. Sometimes for one reason or a joint in EMT may loosen or even separate so it is a nice backup.
 

Last edited by ray2047; 03-10-16 at 06:50 AM.
  #9  
Old 03-09-16, 11:53 PM
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Strict interpretation of the code requires the conduit system to be complete BEFORE any wires are pulled. Do not exceed 360[SUP]o[/SUP] of bends between access points.
 
  #10  
Old 03-10-16, 04:55 AM
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Sharp edges will nick any kind of wire. Cutting conduit usually results in inside edges sharper than you would think or would estimate. Some brands of junction box fittings and elbows, etc. will shield the sharp edges if the inside diameter has not been reduced. Be sure to deburr the individual conduit ends and open up the entire inside diameter before assembling the conduit system.
 
  #11  
Old 03-10-16, 04:56 AM
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Furd is correct. NEC 300.18 states that raceways are to be complete between outlets or pull points prior to the installation of conductors.

You can install a pull string/rope as you go to aid in pulling in the wires after the raceway is complete.

Do not use a pipe cutter to cut conduit. Use a hacksaw or power tool (Reciprocating saw, portable band saw) with a metal cutting blade and debur.

3 #6 wires should slide in a 3/4" pipe fairly easy over 90' if you have three 90 degree bends or less. The LB's will be a pain but they always are.
 
  #12  
Old 03-10-16, 03:05 PM
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Again, All good info. Common sense would have it that the safe way would be more difficult, but i could see how it would make sense to have the EMT connected to prevent cuts and nicks in the THHN.

I know that I need 220V in the Sub that I am pulling from, for the new 220V Sub. I assume that I do, because there are 2 heavy gauge wires entering the box, one for each bus. I tried to upload a picture but it repeatedly failed.



I appreciate all the help on this. BTW I have an Electrician to hook my THHN to the Sub, not brave enough or confident enough. I don't care to ride the lightning.( So to Speak )
 
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Old 03-10-16, 04:53 PM
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You shouldn't have 220 volts. Nominal voltage is 240v.
I do, because there are 2 heavy gauge wires entering the box, one for each bus.
Plus a heavy gauge to the neutral.
have an Electrician to hook my THHN to the Sub
Actually it is connected to a 60 amp breaker in the sub. With main breaker off it is safe except for the area around the main breaker.
tried to upload a picture
Did you keep the width to 1000px or less?
 
  #14  
Old 03-10-16, 05:14 PM
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NEC 300.18 states that raceways are to be complete between outlets or pull points prior to the installation of conductors.
From what I understand about that code, it is to be sure that conductor can be pulled or removed in the conduit. It don't really have much do to with damaging the wire. If the conduit is properly deburred, it won't be any sharper than junction box or other pull points.
As long as you don't make bends that wires cannot be pull and you don't have a inspector on your back, don't think it really needs to be followed strictly.

I often have to pull the cable while building conduit because either I forgot to fish tape or don't have long enough fish tape.
To follow the code strictly, installing a pull string is probably the best solution for a long run with multiple bends.
 
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Old 03-10-16, 05:52 PM
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Forgetting the proper tools or saying the inspector won't know how it was done is no excuse to violate the code.
 
  #16  
Old 03-10-16, 06:02 PM
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Lambation Tolyn, AlanJ, Furd, and Ray2047,

Thanks for the help on this.....
Ray2047,

Thanks for the correction.... 240V not 220V

Here is the pic of the sub with and without the cover ( thanks for the resizing tip)

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2nd item Correction, I will have an Electrician connect the THHN to the 100 amp breaker in the sub, as well as the bus in the new sub. Despite the relative simplicity, I have more to loose than to gain by saving $100.00 for an Electrician....



Since there is about 20 ft between LB's would you recommend fish tape or propylene wire pulling twine?

Again thanks in advance.....


Ed
 
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Old 03-10-16, 06:35 PM
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Just to make sure, we have been suggesting you use #6 THHN, 3/4" EMT, and a 60 amp breaker. If you want 100 amps you will need to use larger wire, conduit, and breaker.

I would just try pushing the wire into the pipe with out any pulling aid. You might be surprised how easy the newer wire pushes in. Just group the wires together and tape the ends together with electrical tape. After you get to the first LB you will need to make a loop and pull and push at the same time. After you get the whole run pulled in you will then need to pull the wires tight so that you can install the cover on the LBs.
 
  #18  
Old 03-10-16, 06:42 PM
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As Tolyn wrote you Can NOT use a 100 amp breaker with #6.
 
  #19  
Old 03-10-16, 06:58 PM
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Lol. Sorry mis-communication on my part.

The sub that I am drawing power from is a 100 amp with 3 spaces open. I am going to put in breakers to allow 60 amps to the new garage sub.

What configuration of breakers would you recommend?

Hope this helps to clear things up...

Ed
 
  #20  
Old 03-10-16, 07:08 PM
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You need a two pole 60 amp breaker rated for use in your panel. Approved breakers will be on a label in your panel.
 
  #21  
Old 03-10-16, 09:00 PM
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thank you for your help.
 
  #22  
Old 03-11-16, 01:22 PM
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2 additional questions:

I will be running 10/2 romex from the sub to the (2) 240v outlets in the garage. Can I use the same 10/2 wire for 120v outlets? I will have extra and financially it makes sense to

Secondly:

If I choose to pull a permit, What can I expect in regards to the inspections?

How many inspections?

The process seems easy and where I live I can pull my own permit.

Thanks,

Ed
 
  #23  
Old 03-11-16, 01:34 PM
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Can I use the same 10/2 wire for 120v outlets?
Yes. .
 
  #24  
Old 03-11-16, 01:47 PM
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The permit process depends entirely on your local government, and they'll let you know what the steps are when you file the permit application. Some permit applications are a half sheet of paper and some are pages long; fees vary widely. Small towns and rural areas usually only have a part-time inspector who may have limited days and times he's available, whereas if you're in a larger city they'll have an entire department dedicated to it.

On a small job where you are not covering work with drywall, a single final inspection would be reasonable, but they may want a traditional rough and final inspection. The rough inspection includes all of the conduit, boxes, and cables installed and secured; but no devices are installed and power is not on. At rough everything should be visible to the inspector (no insulation or drywall covering the wiring). The final inspection is once everything is done, walls are finished, all devices installed, cover plates installed, breakers labelled and labelled. If the inspector finds any small problems they will probably just point it out for you to correct after they leave and consider it a pass; any bigger problems, they will fail the inspection and give you a tag with the error indicated and which code section is in violation. A failed inspection usually involves a re-inspection fee.
 
  #25  
Old 03-11-16, 03:26 PM
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Can I use the same 10/2 wire for 120v outlets?
You can, but wiring devices with #10 is a major pain. You are also limited to 20 amps. If you do, pigtail some #12 to the devices.
 
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