??? Uneven temps in new rack

[shelliebear]

We just built our new rack out of melamine and insulted the bottom and everything (http://ball-pythons.net/forums/showt...-in-the-making)
and we bought Flexwatt tape from the Bean farm, insulator clips and cord from Big apple Herp (cheaper prices on different items from each site). We also got a dimmer switch from Lowe's...flexwatt is plugged into a 300 watt capacity dimmer, dimmer is plugged into a 1500 watt capacity thermostat.
When we first set it up we tweaked everything around to get temps right. The dimmer is about 75% of the way turned on, and the thermostat is set to 90 degrees, probe is in the middle tub out of three total tubs right now.
Temps from the bottom of rack keep ranging dramatically. Bottom seems to be perfect at 80 ambient temp, 90-94 degree hot spot, 77 cool side.
Middle tub's hot spot is a little cooler
Top tub's hot spot is about the same as middle
But the very top of the rack we don't have a tub in yet is much hotter than the rest of the shelves, the flexwatt ranges from 90 degrees at the left side of the flexwatt to 100-103 degrees to the right side.
What the heck? What's going on?
Max decided to try unplugging the dimmer and just running the flexwatt directly into the thermostat, do you think this will help?
What do you think is happening that would cause such large fluctuations? i'm worried.

[The Serpent Merchant]

Heat rises. almost every rack is hotter on the top than the bottom

Why do you have a dimmer between the thermostat and flexwatt?

Where is the thermostat probe?

I would try to get the middle shelf of the rack to be at 90 degrees. that way the bottom of the rack can be a little cooler (which it may or may not be due to the insulation that you have down there) and the top can be warmer while still being in the proper ranges

[shelliebear]

So now with just the thermostat connected to the flexwatt, no dimmer, the heat tape is at 110 degrees in some areas. -_- I'm at a loss. I don't know what to do. If we turn thermostat down to 85 ish then it will bring the temps down to 80 and shut off completely after that until temps go below 80...and 80 is too cold for a hot spot...I don't know what to do!

[shelliebear]

Also we -had- a dimmer (it's unplugged now) because I read a story on here recently of someone's flexwatt burning out even when on a thermostat, so I was concerned about that and wanted to dim the wattage so this would be less likely to happen. I am a worry wort.

[Tfpets]

Some variation can be explained by the use of the clips on the flexwatt instead of soldering.

[shelliebear]

There is no shelf above the top area yet so it's just open space, it's where our last tub will go eventually, but that is where the flexwatt is getting hot, even though there's no tub or shelf above it! just open space and air. i'm worried that that means it'll be even hotter in the lower shelves where there is an enclosed tub stuffed between.

[shelliebear]

Some variation can be explained by the use of the clips on the flexwatt instead of soldering.

ohhh but big apple herp said it was ok to use clips and not solder did we mess it up? is it broken now? or can we fix this by adding something?

[Tfpets]

I had clips on a used rack that I purchased. Some of the flexwatt strips stayed much cooler and some didn't work at all. I removed all of the clips and soldered instead and everything works perfect now. Even some of the strips that were hot with the clips are even hotter now. Unregulated, the strips all get to about 135 degrees now!

[The Serpent Merchant]

The clips if attached correctly are perfectly fine. the issue comes when some make more contact than others do with the power rails in the flexwatt. Soldering ensures a 100% connection. Either way will work, but soldering its a little more fool proof if you know how to solder.

[kitedemon]

A rack is an exercise in balance balancing ambient room temps with thermostat set points and heat rising. Typically racks do not have even temps top to bottom. I would expect to see at least 2ºF top to bottom and not be surprised by 4º (middle at 91 top 93 bottom 89 for example) This is normal. Racks are very greatly effected by ambient air temps. The room needs to be stable and warm temp typically 80ºF.

There are a huge number of variables connections air temps type of thermostat probe placement (over or under flexwatt) on and on. It is hard to point to a single point my guess and it is just a guess is it is not just one thing but a combination perhaps a single bad joint and a cooler air temp combining to make larger variations. try to raise the room temp and see if that makes a difference, check all the connections, test the probe... start there.

The use of a rheostat I am not sure I fully support the theory is great if you only are going to get high temp issues it does not protect against low temps at all. For example if everything is perfect at 80ºF room temps but the room temp drops to 70º there is no chance for the heaters to over come the cool air and the snakes will suffer. That last 30% power not being used. I would recommend a second t-stat with its probe on the top shelf set to prevent exceptionally high temps (I use 100º) so if the primary fails open the secondary will kill the power to it and the heaters when the temp hits 100ºF it will adjust if the temp drops and prevent too low temps at least until the heaters run 100% power 24/7 and are still too low.