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Old 10-23-2008, 07:59 PM   #1
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My first post. I have been doing research and have some questions. The shed I am wiring is @130' from the main panel. The main is mounted on the outside wall of the house. The house is raised off of the ground @2.5 feet. My house was built in 1977. The panel is a 200 amp FPE. It does have some room left ( I do plan on upgrading soon). The breaker at the main will be a double pole 50 amp. The conduit is 3/4( yeah I know 1" would have been better) run under the house and attached to the joists to a jb box. I have 3 sweeps ( pretty-straight shot). I have 6-19 thnn. Can I run 3-6's and a #10 for ground to a 50-70 amp sub panel ?(or run larger conduit?) I will also be adding a ground rod with #6 to the sub panel ground bus. Also, when mounting the breaker should it be mounted 120 or 240 ? Am I close?

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Old 10-24-2008, 11:22 AM   #2
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My first post. I have been doing research and have some questions. The shed I am wiring is @130' from the main panel. The main is mounted on the outside wall of the house. The house is raised off of the ground @2.5 feet. My house was built in 1977. The panel is a 200 amp FPE. It does have some room left ( I do plan on upgrading soon). The breaker at the main will be a double pole 50 amp. The conduit is 3/4( yeah I know 1" would have been better) run under the house and attached to the joists to a jb box. I have 3 sweeps ( pretty-straight shot). I have 6-19 thnn. Can I run 3-6's and a #10 for ground to a 50-70 amp sub panel ?(or run larger conduit?) I will also be adding a ground rod with #6 to the sub panel ground bus. Also, when mounting the breaker should it be mounted 120 or 240 ? Am I close?
What is 6-19 thhn?
3/4" conduit is plenty big for 3-#6 and 1-#10. No more than four 90 degree turns or maximum 360 degrees or use pull box. Yes. 1" conduit is easier, but not required.
You must be sure the wire has a "W" labeled on it. Like THWN. THHN is usually rated for for both designations. Wire in underground conduit is considered a wet location.
70 amp sub panel is okay with #6 wire. Probably easier to find a 60 amp. The protection will be the 50 amp in the main panel.
The ground rod is a must. You may need two. Depends on the inspector.
A bare #6 is required to go from the rod to the ground terminal strip.
A two pole 50 amp breaker is 240 across each leg. You can still use the 60 or 70 amp breaker in the sub.

Make sure you separate neutrals and grounds in the sub panel. Do not install the bonding screw (green) provided with the panel.
Looks like you are on the right track. Keep us posted.

You do have a permit right? If not get one before you start. You will be glad you did, maybe.

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Old 10-24-2008, 11:26 AM   #3
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What is 6-19 thhn?
3/4" conduit is plenty big for 3-#6 and 1-#10. No more than four 90 degree turns or maximum 360 degrees or use pull box. Yes. 1" conduit is easier, but not required.
You must be sure the wire has a "W" labeled on it. Like THWN. THHN is usually rated for for both designations. Wire in underground conduit is considered a wet location.
70 amp sub panel is okay with #6 wire. Probably easier to find a 60 amp. The protection will be the 50 amp in the main panel.
The ground rod is a must. You may need two. Depends on the inspector.
A bare #6 is required to go from the rod to the ground terminal strip.
A two pole 50 amp breaker is 240 across each leg. You can still use the 60 or 70 amp breaker in the sub.

Make sure you separate neutrals and grounds in the sub panel. Do not install the bonding screw (green) provided with the panel.
Looks like you are on the right track. Keep us posted.

You do have a permit right? If not get one before you start. You will be glad you did, maybe.
6AWG, 19 strand.
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Old 10-24-2008, 02:37 PM   #4
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Wire will fit. Avoid tight back to back 90's.


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Also, when mounting the breaker should it be mounted 120 or 240 ? Am I close?
Double pole breaker=240 volts
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Old 10-24-2008, 03:55 PM   #5
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I picked up a square d 100amp 6 space unit with the separate ground bus kit along with 140 feet of #10 for the ground wire. The way this old FPE panel is designed you can slip a double pole breaker on one section of the bar (I need a pic maybe). I found out the hard way when I pulled the 20 amp dbl pole out to make some room in the panel and my water pump quit. I measured 120volts at the pressure switch on each side( ground to hot) I did not measure across the hots (mistake). So I pulled the pump out and took it to my local pump shop. It tested fine. Reinstalled it and realized what happened. Felt like an idiot. Anyway my question was if I should install it as 240. And I take it that that would be the proper way. Can I increase the amps at the main? If so at @125-130 feet with the 6-3 how high? Can I do 60?

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Old 10-25-2008, 11:55 AM   #6
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#6 THHN/THWN is good for 75 amps. All double pole breakers are 240 volts across each terminal. This is what you need. 240 volts.
You can use any size breaker in the sub panel you want too. But the wire size (feeder) is determined by the breaker size in the main panel. Article 310.16 shows THHN/THWN #6 good for 75 amps.
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Old 10-25-2008, 01:39 PM   #7
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Originally Posted by J. V. View Post
#6 THHN/THWN is good for 75 amps. All double pole breakers are 240 volts across each terminal. This is what you need. 240 volts.
You can use any size breaker in the sub panel you want too. But the wire size (feeder) is determined by the breaker size in the main panel. Article 310.16 shows THHN/THWN #6 good for 75 amps.
Just an FYI, the service disconnecting means in the shed must be rated for at least 60 amps no matter what your feeder is rated for (doesn't matter if its a 40 amp or 50 amp feeder). Obviously if your feeder is more than 60 amps you'd want to put in a larger main breaker/service disconnect at the shed to accommodate the larger service.

I always thought #6 was rated for 55 amps, not 75. That's news to me....
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Old 10-25-2008, 02:14 PM   #8
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#6 THHN/THWN is good for 75 amps. All double pole breakers are 240 volts across each terminal. This is what you need. 240 volts.
You can use any size breaker in the sub panel you want too. But the wire size (feeder) is determined by the breaker size in the main panel. Article 310.16 shows THHN/THWN #6 good for 75 amps.
Are you sure about the 75 AMPS? Were you using the 75 or 90 rating? Wet or dry? THWN or THWN-2?
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Old 10-25-2008, 02:46 PM   #9
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Article 310.16 shows THHN/THWN #6 good for 75 amps.
True for the 90 degree column, but since most if not all terminations are only rated at 60 & 75 degrees, it limits the amperage down to 65 amps.
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Old 10-25-2008, 04:49 PM   #10
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Pulling the wire was a pain. I learned. Bigger is better. Figured because of the distance that I would have to drop it down to either 50 or 60amp. I am glad I got the 100 amp panel though. Thanks for the info.
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Old 10-25-2008, 04:54 PM   #11
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Pulling the wire was a pain. I learned. Bigger is better. Figured because of the distance that I would have to drop it down to either 50 or 60amp. I am glad I got the 100 amp panel though. Thanks for the info.


proper pulling lube and how you lay the pipe are critical. I have never had an easy pull when someone else laid the conduit.
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Old 10-25-2008, 07:53 PM   #12
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I had trouble at the end where the 90 and the jb was. Lube was useless due to the fact I was pulling against 2 90's.
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Old 10-26-2008, 08:37 AM   #13
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I'd get rid of the FPE panel box.
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Old 10-26-2008, 11:21 AM   #14
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True for the 90 degree column, but since most if not all terminations are only rated at 60 & 75 degrees, it limits the amperage down to 65 amps.
Thanks Chris, Just goes to prove that "art.310.16" is the most abused article/table in the code book.
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Old 10-26-2008, 01:38 PM   #15
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I'd get rid of the FPE panel box.
That's coming soon. The panel is a piece of crap. Been planing on it for years. The breakers are expensive ( I have a stash). I like the Square D QO panel -cheap and plentiful.

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