Thermostat Problems

I have a Johnson controls t-stat with a ranco as a backup. I'am running 4" heat tape. My question is why would I have to set the t-stat to say 103 to 104 to achieve a basking spot temp of around 88 to 90 degrees??? I have the probe of the t-stat on the heat tape, I have an Accurite in the top, middle, and bottom tubs. I just can't seem to figure this out. I now know I should have gone with 3" heat tape as it heats better.. But I was wondering if there is any way I can make what I have work??? Any help will be greatly appreciated..

Thanks
Alan

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Originally Posted by grunt_11b

I have a Johnson controls t-stat with a ranco as a backup. I'am running 4" heat tape. My question is why would I have to set the t-stat to say 103 to 104 to achieve a basking spot temp of around 88 to 90 degrees??? I have the probe of the t-stat on the heat tape, I have an Accurite in the top, middle, and bottom tubs. I just can't seem to figure this out. I now know I should have gone with 3" heat tape as it heats better.. But I was wondering if there is any way I can make what I have work??? Any help will be greatly appreciated..

Thanks
Alan

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Most tubs have legs that raise the true bottom of the tub off the heating element and causes an air gap. Also how long have you given it to warm up? When I was using a Ranco on a rack I had to have it at 98 degrees to achieve the right temps in my sweater box rack. For some reason the Herpstat pro only has to be at 93 degrees to acheive a 91 degree temp on the bottom of the hot side. Another thing is get a heat gun and put a patch of black electrical tape on the inside bottom of an empty tub. Gun this spot on a regular basis (every 3 to 4 hours) making adjustments until it is at the hot spot temp you want. Then move this tub to another space in the rack and leave it there a couple hours and gun it again. At this point you only want to move the T-stat temp down so that the hottest tub is at the higher end of your hot side temp. The others are what they are and not much can be done to change that other than seperating them onto other T-stats.