I'm searching for some 2-4ft long 1-2ft wide heat mats to start plant seeds and cuttings on. In shopping around on Amazon I see that most (or all so far) heat mats have polarized 2-prong plugs. Shouldn't an electrical device designed to generate heat and be near water have a third, grounding prong?

Oddly enough most (also all so far) thermostats I've found specifically designed for plant heating mats have 3-prong outlets built onto them for mats to plug into, and the thermostat devices themselves have 3-prong plugs to go into a 3-prong (ideally GFCI) outlet.

Does anyone know the reason for this, or have any tips on where to find grounded heat mats for plants?

  • Not sure if this Q is best suited for here or another site like DIY.SE or EE.SE. I want to keep it pragmatic so I figured I'd ask it based on the intended use of gardening. – cr0 Jan 19 '18 at 15:57
  • I understand the difference between 2 and 3 prong outlets. I infer from my understanding and seeing thermostats for heat mats having 3 prong female and male connectors, that heat mats should have 3 prongs. Yet most heat mats I find online are 2 prong. – cr0 Jan 19 '18 at 21:17
  • 1
    Any aquarium heater/thermostat I have seen has been 2 prong - POLARIZED. – blacksmith37 Jan 20 '18 at 0:49
  • 1
    See electronics.stackexchange.com/questions/337066/… for an explanation. – Niall C. Jan 20 '18 at 3:12