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

[Jon456]

Maybe under a slab or something?

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.

 

[LarryFine]

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.

 

[Jon456]

If we think about it, and if direct-buriable conductors are used, in a few years, when the EMT disintegrates, it will be compliant.

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.

 

[therobthompson]

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

 

[Jon456]

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

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.

 

[ptonsparky]

The bare cu will last longer than the EMT ever did or will.

 

[Jon456]

The bare cu will last longer than the EMT ever did or will.

Probably. But that doesn't mean it won't fail.

 

[petersonra]

Probably. But that doesn't mean it won't fail.

Anything can fail. The code does not generally require any special provisions for dealing with a failure.

 

[Another C10]

Take a look at table 250.122

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.

 

[petersonra]

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.

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.

 

[winnie]

The extended version of the table used by the illuminati lets you use #11 Ag for this application

 

[Nuber]

Any reason why you can't use the EMT as the EGC? One less wire to pull...

250.118(4)

 

[drcampbell]

Any reason why you can't use the EMT as the EGC? ...

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)

 

[Nuber]

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)

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.

 

[petersonra]

I wish the code would just require the use of plastic or coated RGS/IMC underground.

 

[LarryFine]

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.

 

[ptonsparky]

I had the pleasure of wiring a gas station in rigid steel back in the 80s. Twenty some years later we did it again. Almost All of it was just red lines in the sand. Wire was still good and everything worked yet.

 

[Another C10]

So anything more than 20 A up to 60 A has to be at

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.

 

[petersonra]

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.

Read what the code says about the table. It is clear.

 

[Another C10]

Read what the code says about the table. It is clear.

I'll let ya have it .. nice job.