I built a DIY rack with 20 qt tubs and under belly heat with heat tape and I have a 1/4" gap in between the heat tape and the tubs to provide air circulation over the heat tape and the thermostat probe is resting on the heat tape. There is a major heat loss in between the heat tape and the tubs because of the air gap. Should I increase the temperature, remove the air gap, or attach the probe to the bottom of one of the tubs and since I have 3 shelves with independent heat tape and each shelf has 4 tubs I’d be removing 1/4 of my tubs by doing that because I wouldn’t be able to slide the tub in and out. Has anybody built a rack with UTH and comes across this problem, do you provide an air gap or do you use some other method?
I don’t see an issue with your probe placement or 1/4 gap between tape and tub. Every rack I’ve used the set temperature for the thermostat is always set higher then tub temp. You want to raise the temp of heat tape (obviously not real high) until the tub reaches the temperature you want. Every adjustment needs time to come up to temp before you recheck and make changes. If you have a open rack with the sides not enclosed fully, and a low room temperature, those are whats probably working against you. Hope this helps.
The room temperature is 66* F and the thermostat is set at 105* F and the tub is only reaching 73* F. Do I just keep increasing the temperature or should I try something else. Also while I was checking everything I noticed that the tubs have exactly 1/4" rims coming down around the perimeter of the tub. That means that right now I essentially have 1/2" air gap instead of 1/4", if I removed the extra 1/4" then the perimeter rim would be causing an air pocket without any circulation, would that be a problem or would that be better then setting the thermostat at a high temperature?
What kind of device are you using to read your tub temperature? And where in the tub are you reading it? For belly heat the surface of the tub above the heat tape is were you want to read. The front of tub will not reach temperature.
What size heat tape? Is your probe on the center shelf of the rack? Is your rack on or close to the floor? Maybe too much airflow in room? Have you used your reading device on the heat tape to make sure thermostat and device are close in temp reading? Sorry for all the questions just trying to get an idea of what you have going on. Do you have pictures of your setup?
I have 2 digital thermometers reading the bottom surface of the tub that is directly over the heat tape. Right now I have an extra tub that is for temperature measurement purposes and has digital thermometers at different places inside the tub. The measurements I’ve been giving have been on the warm side of the tub on the bottom surface of the tub. I have 3" heat tape and the probe is on the center shelf out of the 3 shelves and is 1 foot off of the ground. I cross-checked the thermostat with a thermometer when I first set it up and the thermostat read accurately then and I assume it does now.
Maybe they are losing heat from the sides/back. So maybe putting a back and sides on the rack, and have the heated end be the far end, insulated by the back, instead of at the front, losing so much heat. I hope that makes sense- basically I suspect the heat loss isn’t so much from between the tape and tub, as from the exposed sides of tape & tub.
I mean, in my new T 10 by animal plastics, there is about 1/8 gap from the heat tape to the bottom of the cage. My heat loss is about 1° to sometimes 2° if I have the fan in my room on.
I agree with @mblaney that the open design is causing a lot of your problem. You could shorten the gap and I think it will help. Also having the heat tape at rear of shelf surrounded by 3 panels will also cut down on airflow taking your heat away.
Okay, I’ll probably start by removing the extra gap so the total gap is only 1/4" and if that doesn’t work then I’ll flip the rack around so the heat element is in the back and insulated. Thank you for your input and help everybody.
I would lean towards the gap being the issue. You can either put some material on top of the heat tape that would touch the tubs I’m not sure what exactly they use but ARS does this to be a conduit for the heat or if there’s any way you can make it 1/8th” that would be something I’d look into
Sorry saw others already weighed in but physics or thermo blahbadeeblah would lead me to agree try and lessen the gap.