Different parts of heat tape heating more than others

I recently purchased a rack system with built in heat tape from a reputable provider. I used aluminum tape to secure my thermostat probe (ve 300x2) onto the heat tape and set daytime temp to 90. I notice that area of heat where the probe is will hover around 90 (according to my thermogun), but other parts of the heat tape, on the next shelf under for example, will be SIGNIFICANTLY higher than the 90degree setting that i have it at(I’ve seen it at 117-130 degrees). I wanted to know if others have come across this issue and what I may doing wrong? I want to resolve this issue before i put any BPs in the rack. Thanks!!

There is usually a small differential between shelf but that is a huge differential and something like that would concern me.

Do you have your T-stat probe on the middle shelf?

Is your heat tape new?

Heat tape failure even with a reliable thermostat can happen.

Hi thanks for your response! the probe on on the top shelf (5 shelves total) but i did initially have it on the middle shelf and experienced similar things. the heat tape is new

hey thanks for responding! the aluminum tape is not covering the probe tip at all

It’s actually somewhat important you have (nearly) the exact same cord lengths off each piece. If they’re plugged into the same power source and cords are different lengths it can deliver a different amount of voltage to different pieces

Ok take the probe off the heat tape and test it separately. Could be a bad probe. Unplug the probe and check to make sure the plug end is good. Since your stat has 2 probes test them side by and make sure they both read the same. Most likey a bad probe. I’ve seen it happen to lots of stats over the years. Also just in case test your temp gun too while your at it. Those can also fail.