You absolutely want to ground the metal shelf if you are putting the heat tape directly on the shelf! Due to the very thin insulation on heat tape you can, and likely will, get a small induced charge in the rack itself. This has nothing to do with a crappy installation but rather physics. It will not happen every time but will happen very frequently.
There is also a significant risk of a real shock. Due to the nature of our hobby- tubs sliding in and out all the time- you run a pretty decent risk of wearing through the insulation sooner or later and then you will get a real nice 120V shock when you touch the rack.
I generally recommend you use a layer of pvc sheet (1/4" works great) or 1/4" plywood on the shelf and install your heat tape on that. Besides the benefit of not having to ground your shelf you also get much better heat transfer into your tubs. If you do want to ground the shelf you will need the three prong cord. Black and white wires go to the heat tape and the green needs to be clamped to the shelf.
Reply With Quote