Heat tape and thermostat question

SO I have a one continuous heat tape about 12 feet and what I noticed is that I set the on and off thermostat to 92 degrees, but when I checked the tub temperature it reads 110. So I moved the probe closer to the tub and not in the open and the temperature only changed to 100 degrees. So I lowered the temperature to 91 on the thermostat and now it reads 95-96 in the tub. Here's what interesting, the tubs that are on the heat tape upside down (meaning silver metal part on heat tape is pointing down) is a bit hotter than the tubs that are on the heat tape with the silver part up. Anyone have this problem? Also the heat tape is 3inch 10 watt tape.

I tape my probe directly to the heat tape. After that, I start setting temperatures. Also, when you measure be sure to use an accurate temp gun.

Agreed. Put the probe right on the heat tape. I don't think either side gets hotter than the other... but there will be some variance from top to bottom since heat rises.

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Okay maybe I didnt make it clear. The probe is directly on the heat tape and its in the middle of the rack system. Today I checked the temperature with a probe thermometer and a temp gun and each read the ambient temperature exactly give or take .5-1 degree. When I put the thermometer probe on the heat tape, it read the same thing as the on and off thermostat give or take 1 degree. BUT when I put the thermometer probe on the inside of the tub and taped it down onto the tub where the heat tape is going to be at, the reading for my thermometer probe is 85-87 while my temp gun reads 91-100. And the funny thing is that the lower tubs, the higher the temperature. I know that 10 watt 3 inch heat tape gives off more heat but I set my thermostat at 92. The tubs should have a hot spot of 91-100.