Rigid metal conduit through concrete wall

[bluedog225]

I’m trying to work out a service line from a conex to my garage. The solar equipment and batteries are in the conex.

Poor planning on my part so I’ll need to go through a 10” concrete wall. I’d like to keep the hole as small as practical. Looks like I can run 4 conductors of 6 awg for split phase through 3/4 pvc conduit underground and switch to rigid metal conduit above ground and through the wall.

The OD of the 1’ rigid conduit is 1.050”.

Will I be able to push that conduit through a 1” hole drilled with a hand held [edit-rotary sds]? I’m hoping/guessing there will be some slop in the hole but I never drilled through something like this. I’d hate to get all set up and have to change course at the end.

Thanks

 

[mike93lx]

I would drill it at 1-1/8 or 1-1/4. No need for it to be super tight.

And I hope you mean a rotary hammer/sds, not a hammer drill. If you don't own one, rent one

 

[bluedog225]

Yes. The bulldog. And thanks.

 

[jack stand]

Conduit, bigger and spare's is a safe bet. (Underground)

edit; of course this was back when the material cost was insignificant to the job!

 

[nadogail]

I have found that saving a few pennies by specifying the smallest possible size conduit has been a false economy, I have come to appreciate more room for job expansion and ease of pulling the conductors.

 

[onetonbb74]

Trade size for a 1 inch rmc is 1-3/8" KO, I wouldn't go smaller than that. I'd use a full size rotohammer, you'll want one for the ground rod anyways...predrill both sides of the core, so no blowouts.

 

[bluedog225]

I can go 2” underground as I have a bunch of schedule 80 laying around. And I’ll scope it down with a bushing for the wall penetration. And there is no issue running 2” up into the conex.

Onetonbb74-Don’t know how I’d predrill both sides as I can’t think of a way to match up both sides of the wall. Maybe drill a 1/4” pilot? Or am I missing your point?

If I do go 2” (likely), and it goes bad in some way, will I likely still have enough strength to use the existing wires to pull the new stuff? Or does the failure mode (short?) burn through all the conductors? Seems like the breaker would trip and I’d be fine using the old wire to pull new stuff.

I was planning on just pounding the ground rod down at the conex with a post hole thumper.

 

[bb29510]

i would core bit it and use pvc

 

[Stuart in MN]

If the hole is slightly oversize, that will leave you adequate space for sealing around the conduit with ductseal, spray foam or similar.

 

[Norcal]

I can go 2” underground as I have a bunch of schedule 80 laying around. And I’ll scope it down with a bushing for the wall penetration. And there is no issue running 2” up into the conex.

Onetonbb74-Don’t know how I’d predrill both sides as I can’t think of a way to match up both sides of the wall. Maybe drill a 1/4” pilot? Or am I missing your point?

If I do go 2” (likely), and it goes bad in some way, will I likely still have enough strength to use the existing wires to pull the new stuff? Or does the failure mode (short?) burn through all the conductors? Seems like the breaker would trip and I’d be fine using the old wire to pull new stuff.

I was planning on just pounding the ground rod down at the conex with a post hole thumper.

Unless you can prove 25 ohms of resistance or less, you need 2 rods at least 6 feet apart and it's cheaper to just drive the 2nd rod because the testing gear is expensive & need to be qualified to operate it. For a run of 120/240V the grounding conductor does not need to be 6 AWG, & if trying to only buy 1 color of wire, not code compliant, since for conductors smaller then 4 AWG, the grounded conductor (neutral) is required to have white or gray colored insulation, & the grounding conductor is required to be green or green with 1 or more yellow stripes.

This thread belongs in the electrical forum.

 

[Augus7us]

If I had to drill a 10"x1.5" hole, I would rent a core drill. 10" of solid concrete with an sds drill will turn your brain into mashed potatoes. I've only used a core drill once but it cut a 4" and 1.5" hole in reinforced concrete and it was amazingly easy.

 

[bluedog225]

Sounds like a core drill is the way to go. A bit of a pain to rent though.

I’ve had pretty good luck drilling this stuff up to 1”. Though it’s 6000 psi, It’s got limestone aggregate. That seems to make a difference.

 

[Augus7us]

If you already have an SDS type hammer drill it wouldn't cost much to buy the bit and try. My experience is telling me it will be an endeavor for that size and depth. That said it will not be a walk in the park setting up a core drill if its horizontal. I think you have to use tapcons to hold it up temporarily.

Myself, i did 4 holes with a SDS+; three 1" holes and one 3" hole that was about five 1" holes and I chipped the center out. It was ugly. I rented the core drill for the holes above because one was for the new shop toilet flange and I didn't want it looking horrible. Now that I've used one, I would rent it again in a heartbeat to do all the holes I mentioned.

On a different note, two of those holes were for ground rods. And as mentioned get you a "ground round pounder thing" off amazon. I forget what its called but it wasn't cheap, like $60 if I remember right but it made short work sinking those long ground rods.

 

[mike93lx]

If I had several to do, I'd rent a core drill, but for just one, I'd use my sds and **** up the discomfort. Maybe have a pump sprayer with water to keep things cool and control dust.

 

[bluedog225]

Thanks all. I can already see it coming out crooked.

 

[mike93lx]

Thanks all. I can already see it coming out crooked.

Checking the bit with a torpedo level or a speed square will help a lot

 

[dogdog]

it’s not that hard google up the chart and drill hole size a bit bigger so you have room for the hydraulic cement and float some caulking in between the wall and conduit. Especially the ones that is under ground. Also they have 1-1/2 up to 2” bits for sds max at least would have make the job simpler. Well at least the drilling hole part.

 

[rayra]

Seconding go bigger conduit to future-proof. And no reason to go metal from plastic, unless safety code requires for that much current.