Conduit to garage dilema

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  #1  
Old 11-26-06, 07:10 AM
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Conduit to garage dilema

I'm running 1 1/2" conduit out to my garage for a 100 amp panel. I was planning on running PVC, so have been trenching for 18" of cover. I ran into an area that I can't get below 10" or so due to massive tree roots. I really don't want to kill the 60' oak trees, so was looking to maybe transition to RMC for the final 20' or so since that only requires 6" cover. Does code allow that? If so, I would need 2-90 deg elbows to come up from the 18" and turn at the 6". Do those elbows need to be RMC also (since they're above the 18") or since they are basically vertical is PVC ok?

Any other suggestions other than cutting through the roots and potentially killing 2 trees?

Thanks!
Craig
 
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Old 11-26-06, 07:29 AM
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Sch.80 pvc. Make a gentle transition as opposed to the 90deg sweeps. This will make the wire pull much easier. keep it as deep as you can. This is assuming you are in a lawn area and not a driveway etc.
Don't forget the expansion fittings.
 
  #3  
Old 11-26-06, 07:36 AM
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Thanks for the quick response. Yep, lawn area. What are the minimum cover requirements for sched 80 PVC? Or are you just saying to use the sched 80 for the transition, and rmc for the shallow section?

Thanks again!
 
  #4  
Old 11-26-06, 07:39 AM
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One thing to consider is that you can only have a max of 360 deg of bend in any one run of conduit between pull points.

I would suggest more gradual bends at very least. Maybe 45 deg or get your hands on a bender and use 15 deg or 30.

When I run into this problem on a job site I usually make a gradual transition between the two depths that does not require any bends, beyond the flexibility of the conduit itself.

Next I go buy bags of pre mixed sacrete. I cover all the parts of the conduit that are above the min burial depth with at least 4 inches of the mix. Where support was lost because the ditch was too deep, I use rocks or sacrete to fill the gap below the conduit.

I get a garden hose and a shovel and mix water into the sacrete right in the hole before backfilling.

I also add caution tape half way between the conduit and finish grade, but I do that on every underground job.

For a shovel with ditch, figure two bags of sacrete for every bag length of ditch.

Minimum cover for conduit that has 4 inches of more of concrete is 4 inches
 
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