Concrete Encased Duct Bank (under 600V).

[tepres]

I saw this topic when I did a search but could not find a definitive answer.

The question is this:
Can you reduce the minimum amount of cover for an underground duct installation (below 600V) if it is concrete encased? (under traffic)

A point was made in another post about how it was odd that 300.50(A) Exception 2 (over 600V) allows for the reduction of cover but there is no clear allowance for it in 300.5 (600V nominal or less).

[ May 22, 2003, 03:52 PM: Message edited by: tepres ]

 

[sc57ford]

Re: Concrete Encased Duct Bank (under 600V).

Table 300.5 gives you the Minimum cover requirements regardless of concrete encasement, except in Note 5 of the Table where solid rock prevents minimum cover.

 

[bennie]

Re: Concrete Encased Duct Bank (under 600V).

The "under traffic" appears to negate the concrete encasemant dimension. Where two dimensions are calculated the one offering most protection shall be used. (my words)

 

[tepres]

Re: Concrete Encased Duct Bank (under 600V).

I spoke with one of the engineers at work and his interpretation was since the under traffic dimension is given "without concrete encasement", the "below 2 inch thick concrete" dimension (12 inches deep) negates that dimension.

In other words: regardless of location, if the conduit or cable is under two inches of concrete, that will be the dimension you would use.

(The concrete encasement would have to be at least 2 inches thick on top.)

[ May 30, 2003, 07:39 AM: Message edited by: tepres ]