Conduit fill - Three #8awg plus one #10awg in 1/2 EMT?

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kwired said:
Maybe under a slab or something?
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I realized that was a possibility, but the OP never mentioned it. Often times, it's just a desire to not have to dig. Let's wait to hear from the OP about the actual circumstances he's dealing with.

That said, there are ways to pull a new conduit under a slab. Of course, if the conduit is embedded in the slab, the job becomes much more challenging and expensive.
 
If we think about it, and if direct-buriable conductors are used, in a few years, when the EMT disintegrates, it will be compliant.

The important thing is to not depend on the EMT as physical protection or as an EGC.
 
LarryFine said:
If we think about it, and if direct-buriable conductors are used, in a few years, when the EMT disintegrates, it will be compliant.
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But only if the depth of the EMT meets the NEC standards for direct-burial cable. And I doubt there's any 50A-rated direct burial cable that's capable of being pulled through 1/2" EMT.
 
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Besides all the time and ugh work of digging, it would totally disrupt a nice established garden, and it goes under a concrete walkway. This little project is getting out of hand as it is :)
 
therobthompson said:
Besides all the time and ugh work of digging, it would totally disrupt a nice established garden, and it goes under a concrete walkway. This little project is getting out of hand as it is :)
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Neither are serious obstacles. Is this for your own installation or for a client? I've seen underground conductors that literally exploded due to the insulation being damaged while being pulled into conduit. And if you pull a bare EGC in that underground EMT, it will eventually disintegrate and then you lose your bonding from the subpanel back to the service.
 
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petersonra said:
Take a look at table 250.122
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good one, well being that the cut off point of the # 12 is 20A and then it jumps to a #10 for 60A , I suppose it depends on the inspector really, what is the approved ground size for a 40 - 50 Amp .. 40 is right in the middle so maybe a #11 ? .. point being yes, it is always better to have a fatter ground but this existing condition could sure use a little more room in the conduit.
 
Another C10 said:
good one, well being that the cut off point of the # 12 is 20A and then it jumps to a #10 for 60A , I suppose it depends on the inspector really, what is the approved ground size for a 40 - 50 Amp .. 40 is right in the middle so maybe a #11 ? .. point being yes, it is always better to have a fatter ground but this existing condition could sure use a little more room in the conduit.
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You do not get to extrapolate the wire type EGC size. It has to be the minimum size the table says. So anything more than 20 A up to 60 A has to be at least a #10 copper.
 
Any reason why you can't use the EMT as the EGC? One less wire to pull...

250.118(4)
 
drcampbell said:
Long-term performance of steel underground?

Plus, the fill-percentage problem has been solved. (either by using a bare EGC, or by cheating and declaring it "close enough" for the existing circumstances)
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I am normally not a fan of relying on conduit as the EGC but it is code compliant. It does get around the concerns over a tight pull damaging conductors.

Just an option; do as you will.
 
When I was a helper, our company got the job of replacing the EMT that was used to supply every A/C compressor unit at an apartment complex. Every inch of EMT that was buried was completely disintegrated.
 
petersonra said:
So anything more than 20 A up to 60 A has to be at
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How do we know that #12 actually stops at 20A when there is no size mentioned for #8, maybe #8 is up to the installer they can go with #12 or # 10 .. its a freebie. Now #6 better be a #10 because it is written as such. Just messing with ya, although I think its a grey area of choice because its left out.
 
Another C10 said:
How do we know that #12 actually stops at 20A when there is no size mentioned for #8, maybe #8 is up to the installer they can go with #12 or # 10 .. its a freebie. Now #6 better be a #10 because it is written as such. Just messing with ya, although I think its a grey area of choice because its left out.
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Read what the code says about the table. It is clear.
 
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