Burial Depth 300.5

[zcanyonboltz]

Im doing a custom home with meter/pedestal at street. I am running 4/0 Aluminum to a 200A disconnect on house. The trench will run under a potential parking area/driveway. Looking at 300.5 I see the required burial depth is 24" deep under the drive and parking area and only 18" not under drive/parking area. In conduit or not this seems really shallow for a service feed. Am I missing something??... because I plan to go at least 36" deep in Schedule 80 PVC.

 

[Dennis Alwon]

24" is a gracious plenty deep. The power company tries to get 30"-36" but often they do not. I have seen so many failures with direct burial cable I would definitely run the conductors in conduit.

I don't believe schedule 80 is necessary but if it makes you feel better then by all means.

 

[ActionDave]

Im doing a custom home with meter/pedestal at street. I am running 4/0 Aluminum to a 200A disconnect on house. The trench will run under a potential parking area/driveway. Looking at 300.5 I see the required burial depth is 24" deep under the drive and parking area and only 18" not under drive/parking area. In conduit or not this seems really shallow for a service feed. Am I missing something??... because I plan to go at least 36" deep in Schedule 80 PVC.

You need 18" of cover so that means a 20" deep trench anyway, I always tell the ditch digger 24" so that I'm sure I'm deep enough. There is nothing gained by going deeper and schd 40 underground is plenty tough enough.

 

[truck41trouble]

Here in the Hudson Valley region of New York, you often will not be able to dig a 36" trench without a breaker on a piece of heavy equipment. At 18" you are starting to scrape the surface of large shale formations that are sometimes impossible to get through. 24" is plenty good, and direct burial done correctly can last a long time. I backfill with stonedust or sand for every direct burial job.
I'm currently building my own home, serviced by a 4800 volt delta feeder. I needed to dig a 950' long 38" trench for the underground primary run, and hit rock at 26". I now have overhead primaries ??

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[electrofelon]

I have always questioned the logic and value of burial depths. I just dont see a 36 inch deep conduit or cable to be significantly less likely to be hit by some sort of future construction project than a 12" deep one. If someone doesnt get a locate and doesnt know its there, they are going to hit it, and as one who has operated digging equipment, I can say that an operator is much more likely to see it the shallower it is.

 

[ActionDave]

I can say that an operator is much more likely to see it the shallower it is.

That is why I don't like going deeper than 24". The deeper you go the harder the conduit is to find even if you do a locate.

 

[Little Bill]

Here, all the POCOs have the say on service trenches. All but one requires 36", the other only requires 30". Most every time they send an engineer or line manager to check the depth before they will pull their wire.
No 36" (or 30" for the odd one), no wire!:happyno:

 

[zcanyonboltz]

Thanks for replies I was just surprised 18" seemed shallow for not being in conduit. As for the reasoning of going schedule 40 the homeowner is an overkill type but yes I agree a tractor or whatever you may hit schedule 40 or schedule 80 with other than maybe a hand shovel the two types will break just as easy, going with schedule 80 gains nothing safety wise underground in this case. The homeowner also wanted to run 4" for this but I talked him into using 2.5 inch. Did I mention overkill

 

[Ponchik]

I would go 3" conduit so it will be a bit easier to pull.

 

[zcanyonboltz]

I would go 3" conduit so it will be a bit easier to pull.

True... I will just go with the 4 inch he wants to buy anyway I mean its his money right I'm just not sure if a 200 disconnect from HD will have a 4 inch knockout I think I remember they only go up to 3 inch or 3.5 inch?

 

[Dennis Alwon]

True... I will just go with the 4 inch he wants to buy anyway I mean its his money right I'm just not sure if a 200 disconnect from HD will have a 4 inch knockout I think I remember they only go up to 3 inch or 3.5 inch?

Most ko's I see are up to 2.5". I seriously doubt it have a 4" ko. It may be hard to punch a 4" hole since the box isn't much deeper-- You need a locknut or something else in there besides the conduit fitting.

 

[Ponchik]

True... I will just go with the 4 inch he wants to buy anyway I mean its his money right I'm just not sure if a 200 disconnect from HD will have a 4 inch knockout I think I remember they only go up to 3 inch or 3.5 inch?

You can use a conduit reducer. 4" to 3". The SQAUER-D panels usually have at least a 3" KO at the bottom. If not you can use a conduit reducer.

View attachment 17654

 

[kwired]

Im doing a custom home with meter/pedestal at street. I am running 4/0 Aluminum to a 200A disconnect on house. The trench will run under a potential parking area/driveway. Looking at 300.5 I see the required burial depth is 24" deep under the drive and parking area and only 18" not under drive/parking area. In conduit or not this seems really shallow for a service feed. Am I missing something??... because I plan to go at least 36" deep in Schedule 80 PVC.

I am seeing your minimum burial depth the other way around - 18" under a dwelling related driveway or parking area, the other parts of your run fit under the "all locations not specified below" category and needs to be 24" deep.

 

[Little Bill]

I am seeing your minimum burial depth the other way around - 18" under a dwelling related driveway or parking area, the other parts of your run fit under the "all locations not specified below" category and needs to be 24" deep.

"All locations not specified below" is also 18" not 24".

 

[kwired]

"All locations not specified below" is also 18" not 24".

Not what I am seeing for direct buried cables/conductors.

 

[Dennis Alwon]

"All locations not specified below" is also 18" not 24".

I think you are talking about non metallic raceways and Kwired is talking about direct burial cable

 

[kwired]

For some reason I thought the OP had direct buried cable/conductors, but went back and I guess he was planning to use PVC raceway, so I guess 18" inches applies to both areas in question for OP.

 

[zcanyonboltz]

"All locations not specified below" is also 18" not 24".

You are right I didn't see the table for under dwelling driveways.... 300.5. Wow 18 inches under the driveway and 24 inches elsewhere. I am just surprised that the depth requirements don't change if cable is in conduit or not in this case unless you used Rigid.

 

[zcanyonboltz]

I have seen so many failures with direct burial cable I would definitely run the conductors in conduit.

Just wondering what types of problems you've seen with direct burial cable...? Just being hit more often? On the tract home projects here I see the POCO and their subcontractor Site Wise going about 4 feet deep.

If we use conduit I'm thinking about how POCO will tie conduit into transformer. Looking at Article 314.30(B) it reads that the conduit shall extend into the enclosure, not sure how POCO feels about this.

 

[zcanyonboltz]

You are right I didn't see the table for under dwelling driveways.... 300.5. Wow 18 inches under the driveway and 24 inches elsewhere. I am just surprised that the depth requirements don't change if cable is in conduit or not in this case unless you used Rigid.

Oops I quoted the wrong quote in my "reply with quote" in my post #18... all locations not specified below is 24" not 18" without being in conduit. 18" just seems shallow even in conduit. I mean when I plant a bush or do sprinkler work or fence work etc... I am usually always going deeper than 18".