I've been using the same home made pvc rack for about three years now. My thermostat is a Herpstat 1. It's been great for years, but recently I noticed the tape is getting way too hot. I had the Herpstat set to about 85, yet the hot side of my tubs was 100 in some cases! I had the probe tucked under the heat tape on the middle rack. Checking with a temp gun I noticed the heat tape was 10 degrees cooler where the probe sat (e.g. 86 whereas the rest of the tape was hotter).

Thinking something was wrong with that section of heat tape, I moved the probe up one shelf, still slid under the heat tape and taped in place. The problem's still occurring. The Herpstat is currently set to 83.4 yet some tubs were reaching 105. Again (checking the heat tape with a temp gun) the tape is about 20 degrees cooler where the probe is located. The tape was indeed reaching 111. WTF???

This is obviously bad for my snakes and bad for my blood pressure. It's really stressing me out. In the meantime I have the tubs slid a bit forward so they're not getting so hot, but I need a solution.

Has anyone heard of this before? I don't know if it's the probe or the tape acting up.