By "no reason to worry about it below grade," I wonder if he meant the protection of the insulation with the brush-on cement, and not the complete omission of insulation below grade. Related question: what insulation/vapour barrier/geotextile materials should go below the slab and in what...
I just went through this with a portable unit. If you suspect the frost guard switch (it sits on the coils and is easily removed, even if you have to snip a couple of wires) you can connect an ohmmeter to it and stick the frost guard switch in the freezer. As the temp drops, the switch should...