Getting my tubs hot enough (new guy)

[mapleman]

A little background info:

I just built my first rack using PVC.
I'm using Iris MCBS tubs and flexwatt (8 watt) heating tape, applied to the back of the rack (1 row of tape for each tub). Also using a Helix thermostat. The rack is located in a spare room in my house.

I have the thermostat set at 100 degrees (checked with accurite thermometer and it's accurate).

The inside of the tubs at the back (closest to the heat tape) are only getting to 82 degrees - the front of the tub is getting to 74 degrees.

I'm guessing I need to juice the thermostat up to get the back area of the tubs to 85-90? This will likely require turning the Helix up to 105-110?

One thing I noticed is that the sides of the tubs slant upwards, so the tub is only touching the heat tape at the very top, and the bottom of the tub (where it rests on the shelf) is about 1/2" away from the heat tape. It would seem to me that if the sides of the tubs were straight and not slanted out that they would be closer to the heat source and not require such a high setting of the thermostat.

Any advice would be much appreciated.

Lee

[Dalishar]

I'm not sure if this is what you're supposed to do, but what I've personally done is just upped the thermostat. I believe mine is set at 116 and the hot side temperature in the tubs doesn't go over 92 even with extreme room temp fluctuations.

You may not need to bump that high with a helix though - my thermostat reads 116 but the heat tape is only about ~108-110. I think I buggered something up when I taped the probe down, but it's been working just fine if I keep the discrepancy in mind.

I'm not exactly comfortable keeping it that high and check obsessively throughout the day, but it's been stable for the last ~3 weeks.

I have the same issue with the tub sides. Sterilites are so blah .

[reptidude1]

well i would just up the temps on the tstat but make sure the readings of your hot side temp. How long have you had this temp set at this? And now i have a question. Where the hell do u get expanded pvc? I cant find any...

[mapleman]

How long have you had this temp set at this?

Well, I posted about 30 minutes after I got home with my accurite. Now it has stabilized and the hot side is reading 85 and the cool side is reading 77. I figured I should just up the thermostat, but wanted to make sure that my readings were normal or in the range of everyone else. Just got everything put together and the power turned on last night. Picked up my Accurite and got it hooked up a little while ago.

I got the 48" X 96" sheet pvc from Piedmont Plastics in New Orleans. I'm not sure where you are located but they have several branches across the US. Sean from EbN turned me on to them, that's who he uses. About $85/sheet for 1/2" and $57/sheet for the 1/4". I used 1/2" for the sides and shelves and 1/4" for the back. I'm going to post a pic later this evening, I'd like some feedback to see if anyone has suggestions or improvements for the next one.

Thanks,

Lee

[reptidude1]

cool if the lot side is reading 85 let it stabilize for at least 48 hrs and if the heat tape is reading lets say 98 degrees? Then it the tubs will be at least 96 degrees if not 98