As an electrician, I will offer up a little information in hopes of helping clarify things. First and foremost, controllers should always use grounded plugs into GFCI receptacles or circuits protected by GFCI breakers. After that, it becomes your choice as to how strictly you wish to adhere to the NEC (National Electrical Code). The NEC is written primarily in the interest of safety and satisfaction of requirements for insurance purposes. As soon as you elect to use a product outside of it's rated use (ie: SPT outdoors) a code violation occurs and you have, in essence, given your insurance company a reason to deny a claim in the event of a related incident. I'm not saying it happens, only that it could. The things I've seen in the real world would give a code purist ulcers. Unfortunately, it's usually us as homeowners who show the most disregard for our own personal safety by creating our own violations in the interest of cost cutting. I bit the bullet for my display & have 100% outdoor rated 3-prong cords of appropriate wire gauge for all elements. Having said that, it has been one of my biggest expenses against the budget & I won't begrudge the SPT users of their decisions particularly those in non-snow and drier regions. The rest of the info already posted here on ampacity & wire gauge should answer most of the other questions. To add my two cents on waterproofing, I tape nothing. I use a product called Scotchcote by 3M (#43906) on permanent joints. It's ugly, messy, & smells bad (think molasses colored rubber cement), but it works real well. For on the ground joints, I buy 6' lengths of 1" ID self seal polyethylene pipe insulation from any home center & cut it to length to slip over the connections http://www.lowes.com/pd_21416-1410-S12XB/6_4294765361__?productId=1060007&Ns=p_product_qty_sales_dollar|1&pl=1¤tURL=%3FNs%3Dp_product_qty_sales_dollar%7C1&facetInfo=. While not waterproof, it sheds rain and eliminates snow penetration while elevating the connection slightly off the ground as well. The open ends and mild porousness allow it to breathe and dry out quickly once wet. No nuisance trips yet!