Need wire size advise for sub panel

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  #1  
Old 12-23-13, 07:14 PM
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Need wire size advise for sub panel

I am installing a 100 amp sub panel at my detached pavilion/workshop/kitchen. I am in Louisiana. I will be burying the conductors in 2.5" PVC under 18" of cover. The conductor length will be 135'. I will separate the neutral buss from the ground at the sub panel and will remove the neutral bonding screw. I will also install two ground rods at the sub panel. I haven't decided on whether to use a breaker box or a lug. The master cutoff may be convenient, but economics may rule.

I need advise as to the conductor sizes needed. Suggestions as to aluminum or copper will be helpful. Also if you can suggest other economical options, I would be thankful.

Concerning load, my calculations show a 50 amp service would be more than adequate for the time being, but I am looking at installing a commercial fryer which may use as many as 60 amps.

I will be running from is a 200 amp Cutler Hammer loadcenter. If I install a 100 amp breaker what is the largest wire size that will fit the breaker to feed the sub panel?

I hate to clutter this thread, but would it be possible (or advisable) to backfeed from a generator through this sub panel in the future? I live in a storm-prone area.

Thanks, all.
 
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  #2  
Old 12-23-13, 10:21 PM
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Welcome to the forums!

The size of the wire you need for a feeder is determined by the distance and the load. What is the total load, in amps, that you could be supplying from your subpanel at any one time?

my calculations show a 50 amp service would be more than adequate for the time being, but I am looking at installing a commercial fryer which may use as many as 60 amps.
60 amps by itself, in addition to the other loads?
 
  #3  
Old 12-23-13, 11:53 PM
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Wire size for sub panel

#2 copper or #1/0 aluminum at 100amps will have under a 3% voltage drop. However as pointed out by Nashkat1 you are showing loads in excess of 100amps. If you look at 200 amps then 3/0 copper or 4/0 aluminum. I only looked at the 200 amps because you could install feed-thru lugs in your 200amp panel to supply the feeder, the 200 amp main serves as the over-current protection so an additional breaker is not required.
 
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Old 12-24-13, 06:01 AM
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I am looking at installing a commercial fryer which may use as many as 60 amps.
Would it use 60 amps or would it just require a 60 amp circuit?
 
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Old 12-24-13, 07:26 AM
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Max 80 amps at any one time. I won't ever be using all of the shop equipment while using the fryer. The fryer will be used only 4 or 5 times a year.
 
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Old 12-24-13, 07:34 AM
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CasualJoe,

The fryer will pull 59 amps.
 
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Old 12-24-13, 07:41 AM
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As this is a detached building a main breaker or disconnect will need to be installed.
 
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Old 12-24-13, 01:20 PM
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Wire size for sub panel

You mentioned wanting to have a generator back-feed your dwelling using this feeder circuit. This would require some transfer switches and knowing the size of your generator and the load you would have on your emergency panel at your dwelling as well as weather the pavilion/workshop/kitchen would be included in the generator load.
 
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