New circuit in old slab

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  #1  
Old 04-12-05, 10:40 AM
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New circuit in old slab

I am trying to put a new circuit on an kitchen island that I am getting ready to install. I want to run it about a distance of 50-55" from an existing wall(new 15 or 20 amp circuit). The question I have is, the slab is about 16" thick so going under it is out of the question. So how deep a channel do I have to cut? Does it require metal or PVC conduit or even conduit at all. And does it require special boxes in the concrete or is just the conduit sticking up into a box affixed to the cabinet sufficient?

Thanks,
Craig
 
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  #2  
Old 04-13-05, 11:16 AM
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Can't anyone help me?
 
  #3  
Old 04-13-05, 01:44 PM
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So the kitchen floor is actually a 16" thick concrete slab? There's no wood subfloor?
 
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Old 04-13-05, 01:52 PM
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It's probably on an old military airbase runway!
 
  #5  
Old 04-13-05, 02:01 PM
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Correct, there is no wood subfloor! I guess concrete was cheap in florida during the 70's. And nope, no F-18's trying to land in the kitchen.
 
  #6  
Old 04-13-05, 02:02 PM
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Ventilation

Is your kitchen well-ventilated? You could put a gas generator inside the island.

 
  #7  
Old 04-13-05, 02:04 PM
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Code says rigid metallic conduit has to be in a trench 6" deep if covered by 2" thick concrete. If you use 1/2" or 3/4 rigid", the trench has to be at least 6-1/2" or 6-3/4" deep plus the concrete thickness. Use concrete approved conduit fittings.

If you use schedule 80 PVC (i wouldn't use it), the trench has to be 12-1/2" or 12-3/4" deep plus the concrete thickness.

Lay out where the kitchen island will be installed. Stub the conduit up so it will reach inside the island.
 
  #8  
Old 04-13-05, 04:17 PM
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Have you considered a power drop from overhead? With some imagination you could disguise it with an architectural column of some kind.
 
  #9  
Old 04-13-05, 05:11 PM
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Originally Posted by thinman
Code says rigid metallic conduit has to be in a trench 6" deep if covered by 2" thick concrete. If you use 1/2" or 3/4 rigid", the trench has to be at least 6-1/2" or 6-3/4" deep plus the concrete thickness. Use concrete approved conduit fittings.

If you use schedule 80 PVC (i wouldn't use it), the trench has to be 12-1/2" or 12-3/4" deep plus the concrete thickness.

Lay out where the kitchen island will be installed. Stub the conduit up so it will reach inside the island.

t-man,

Did you look at Table 300.5, or did you just type from memory?

This installation would fall in the column "under a building", where the minimum cover requirement is 0" regardless of the wiring method used.

Av8tor,

16" is one awfully thick slab, what makes you believe it is actually that thick?

Regardless, I'd channel out about 2 or 3" deep so as to have a decent amount of concrete on top of the conduit in order to prevent it from cracking too easily over time, would kinda depend on the finished floor being installed on top of the slab. " or " schedule 40 PVC would be my choice unless you need a large oven/range circuit, then I'd go 1" or larger. If this circuit is to serve receptacle(s) for the island countertop, it must be 20 amp and may be tapped from one of the 2 or more small appliance circuits.
 
  #10  
Old 04-13-05, 07:52 PM
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Outstanding posts. Fred, My first idea was a drop down through some sort of column but the wife nixed that one. And the Slab is probably closer to 12-13". I drilled out a spot so see what I was dealing with. Maybe I just hit a thick spot. Thanks much to Thin and Bolted. I am just going with a dedicated 20 amp since the most it will run is a small microwave or such.

Thanks again.
 
  #11  
Old 04-14-05, 06:57 AM
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Talking

Originally Posted by Bolted Fault
t-man,Did you look at Table 300.5, or did you just type from memory?

This installation would fall in the column "under a building", where the minimum cover requirement is 0" regardless of the wiring method used.

So the floor is not considered a part of the building? Guess I see the words 'in' and 'under' as having two different meanings.

Learn something everyday.
 
  #12  
Old 04-14-05, 07:28 AM
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lol....catch 22.....bring in the new ADJ guys..lol

Technically under 2" of slab maybe....lol...6 inches....but wait it is Under the building...0" needed.....but wait...it technically will be unders slab..lol...once you pour it back over the grove...lol

ok...ponder...since the grove is not all the way under the slab stated...is it under the building or within the building...lol..

Sorry..I am not helping the situation...I shall move on
 
  #13  
Old 04-14-05, 07:55 AM
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I think I found it

Table 300.5. Note 2.

Forgot to read the notes! LOL!
 

Last edited by thinman; 04-14-05 at 08:09 AM.
  #14  
Old 04-14-05, 01:35 PM
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Upon closer inspection, yes, I think I would consider the conduit in the building if it's within the slab. But I got lucky because there is no cover requirements for conduit installed in a building , so the answer is still 0". Would Table 300.5 even apply since it only deals with underground installations?

Ah, I love the code......


I guess 300.4(E) Exception No. 1 would apply.
 

Last edited by Bolted Fault; 04-14-05 at 01:42 PM. Reason: added last sentence.
  #15  
Old 04-15-05, 05:18 AM
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2 inches covering the conduit
 
  #16  
Old 04-15-05, 05:19 AM
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Originally Posted by ElectricalMan
lol....catch 22.....bring in the new ADJ guys..lol

Technically under 2" of slab maybe....lol...6 inches....but wait it is Under the building...0" needed.....but wait...it technically will be unders slab..lol...once you pour it back over the grove...lol

ok...ponder...since the grove is not all the way under the slab stated...is it under the building or within the building...lol..

Sorry..I am not helping the situation...I shall move on
. lol .
 
  #17  
Old 04-15-05, 12:48 PM
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Originally Posted by Jedi9
2 inches covering the conduit
If you are saying this is a good idea, I agree. If your are saying it is required, please tell me why.
 
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