Herpstat/Heating question

I just finished my first rack and I'm trying to get the temps right now. I have a Herpstat 1 and 4" heat tape. I'm not up to 89 degrees on the hot side of my tubs yet, but I'm finding I need to set the herpstat with the probe on the tape to 106.8 or so to achieve this temp. Being new to rack heating I'm not sure if this is normal?

Can anyone one here help? Rack is in a room set at about 75 degrees...

I have an RBI rack and had to crank my herpstat up to 109.5 to achieve 90* hotspot in my rack, you can turn it up as long as the bottom of the enclosure is not too hot.

how are you checking you temps...i have a herpastat 2 with 11 inch flexwatt and have it set to 90.5 my tub sits directly on the heat tape no space...i use a temp gun and get temps 91-89 deg

seems i needed to give the enclosure more time to come up to temp. XPVC when full enclosed like this must take a while to heat up and a ton of engergy was going into the housing. I have gradually reduced the thermostat to 93 and change (not at home to check) and that is getting me to 89.9%. 3 degrees is a more acceptable heat loss. The snakes seem comfortable and the heating is a much better situation what i had previously.