Originally Posted by thekctermite
Also, be sure that you use electrical conduit, not plumbing pipe.
Excellent point. You will need to buy type DZYR grey
electrical conduit (referred to as RNC in the NEC). The easy way to distinguish is that it will be stamped with a UL listing as opposed to an ASTM listing. This is not sold at the big boxes near me so you may have to get if from an electrical supply house.
I'm tending to disagree with you on the 4" though. According to Table 300.5 in the 2005 code book, I believe that the appropriate depth beneath the slab would be 18" since it will not be encased in concrete as it would seem to fall under the category of
One- and two-family dwelling
driveways and outdoor
parking areas, and used only
for dwelling-related purposes (copied directly from the code book)
Perhaps I'm mis-interpretting the code?