Article 300.50 exception #2 indicates that depth of cover can be reduced from Table 300.50 6" for each 2" of concrete cover, (note that the table begins at 600V) yet in the Handbook Table 300.50 (for 0-600V) makes no mention of this exception. Could it be that the exception does not apply for less than feeders 600V? Or is it that if the exception applies for the higher voltage then it will also apply for the lower voltages? Thanks.
Ductbank cover for less than 600V
- Thread starter tscarcel
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Re: Ductbank cover for less than 600V
600 volts is the point at which many NEC rules change. ?At or below 600V? gives you one set of rules, ?Above 600V? gives you another set of rules. Not coincidentally, the ratings of conductors also have a break point at 600 volts. The conductors we use for household applications (i.e., a nominal 120 volts) have insulation systems that are rated for 600 volts.
To answer your specific question, Table 300.50 applies for ?above 600V,? and not to lower voltages. I think the reason is that the lower-rated conductors are not as well protected against physical damage, so that you need more dirt above them to serve as protection.
600 volts is the point at which many NEC rules change. ?At or below 600V? gives you one set of rules, ?Above 600V? gives you another set of rules. Not coincidentally, the ratings of conductors also have a break point at 600 volts. The conductors we use for household applications (i.e., a nominal 120 volts) have insulation systems that are rated for 600 volts.
To answer your specific question, Table 300.50 applies for ?above 600V,? and not to lower voltages. I think the reason is that the lower-rated conductors are not as well protected against physical damage, so that you need more dirt above them to serve as protection.
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