I'm trying to replace an old wall heater. I've installed the box and fan deck and hooked up the wires, but when I turn it on there's a burning smell which seems to come from the fiber glass insulation above the box. So I'm wondering if this material should not be touching the top of the box, or if something else is wrong that just causes the heater to get too hot (it seems to get very hot very fast). Could it be a mix up of wires? It's a Marley R1500. Thanks in advance!