2020 code
by shortcircuit - 01/20/20 10:29 AM
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 depth of duckbank
#219490
08/09/18 04:54 PM
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Joined: Mar 2003
Posts: 849
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what is the minimum dept to the top of a electrical ductbank . low voltage , high voltage
Yoopersup
Nec 2014 Code section
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Re: depth of duckbank
[Re: Yoopersup]
#219491
08/09/18 05:16 PM
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Joined: Mar 2003
Posts: 849
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I come up with 2014 NEC page 70-166 Note : Top of Duct or Cable (not concrete) .
Refers you to 300.50 nec page 70-154 . Also see General notes .
What I came up with. Any comments??
Yoopersup
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Re: depth of duckbank
[Re: Yoopersup]
#219492
08/09/18 08:21 PM
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Joined: Jul 2004
Posts: 9,433
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That really looks like the general burial requirements and I am not sure you even need enough dirt to grow grass over a concrete duct bank if there is 2" of concrete to the first raceway.
It does seem that when you go too deep you may be making ampacity adjustments but that is starting to get up in that engineering supervision stuff.
I really only dealt with this once, the ducts were over 6 feet down and they had engineers on site. He showed me stamped plans and I said OK.
Greg Fretwell
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Re: depth of duckbank
[Re: Yoopersup]
#219493
08/10/18 07:16 AM
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Joined: May 2005
Posts: 984
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I'm installing this exact situation now.
The conduits are being laid in a 6" deep trench (there's a buried structure below it) and concrete will be poured just so people won't have to drive over the round conduits.
Ghost307
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Re: depth of duckbank
[Re: Yoopersup]
#219494
08/10/18 09:39 AM
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Joined: Jul 2004
Posts: 9,433
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Traffic is tough on duct banks, That is why they wanted these 6 feet down. Granted this was an interstate tho.
Greg Fretwell
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Re: depth of duckbank
[Re: Yoopersup]
#219495
08/10/18 01:47 PM
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Joined: Apr 2002
Posts: 7,133
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Guys
Looking in the '14 NEC Handbook (Page 272) Figure 310.60
There is a 'Note'
Min burial depth to top of electrical ducts or cables shall be in accordance with 300.50. Max depth to the top of duct banks shall be 30"......etc.
Any specs from the engineer??
John
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Re: depth of duckbank
[Re: Yoopersup]
#219498
08/12/18 05:06 PM
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Joined: Apr 2002
Posts: 7,133
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Just started plan review for an upcoming major project at one of our water utility treatment plants. Two (2) pages of details on the duct banks, some with burial depths of 56" to top of concrete. Details, details, details, which I will 'review' in the next week or so. It is a substantially large project, 350+ page plan set. Funny how the duct bank jumped out as I moved the plan set to my drafting table Saturday afternoon.
John
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Re: depth of duckbank
[Re: Yoopersup]
#219500
08/12/18 08:26 PM
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Joined: May 2005
Posts: 984
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I may have used the word "drive" a bit too loosely.
The conduits need to be driven past to get to the last 4 parking spots at the far end of the lot.
There's no thru traffic and anybody going over them should be traveling at a walking pace (unless they're very late for work).
Ghost307
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