Heat issues....

Sometimes the problem is a few small issues that compound each other. The accuracy of the probe (I have not looked at the specs of the zilla but Johnson, Ranco and hydrofarm are +/-2ºF) That in itself isn't a huge issue but then it will alter from the set point some degrees. The better on/off ones are usually 1º but the cheaper zilla maybe more I again do not have specs for it. Again that isn't too big a problem. The last is how quickly the probe and controller responds to the temp is it altered ever second or every min or every 5 mins? Typically on/off styles do not change faster than one min increments.

What all that means is a if you have a poor insulating container (plastic tub for example) the temp changes inside very quickly. The probe may not be correct (set to 90 it may actually be 92 and still be passed by the manufacturer) then it might have a one degree throw so make that a high of 93, and a slow to change probe/electronics and the enclosure has no thermal mass so it changes rapidly, you can add 3 or 4 degrees more to over shooting the mark... so a high of 96-7. That is a good case if the variation off the set point is 3 degrees or 5 degrees you can easily see 100 + then a drop to mid 80S than back up again.

The old pads sounded like they were underpowered and that means the controller ran them more on than off so that did not allow for a swing at all it never hit the set point.

Possible solutions change the heat pad so it is on something that will take a min or two to heat up and cool off to help take the edge of the top and bottom of the swing. leave a small air space under the enclosure (to do the same) Replace the T-stat with something more reliable (in a cool room with unstable room temps a proportional style works better.) Heat the room to a constant 80º that will cause the probe to trigger off faster. There are likely other options but these are what I can think might work. To my mind the solution is a better T-stat, proportional one, the rest are band-aid fixes. The only other real solution is to change the enclosure to one that has more mass but that can create other issues depending on what you went with.

Thank you kitedemon for that post. Anyways, I think I kinda figured out the problem. It was just bad probe placement on my part. I readjusted it in the tank, and so it appears the thermometer is going to where exactly I put it. But it shuts off and gets too low.

I set the dial to 93, cause it will heat it up to 100, which is where I need it to get to 90. The glass only gets to 95, so no fear of burn. So when it shuts off at around 100, it dips down to 93, like on the dial, perfectly. Problem is, that drops the ground temp. for my snake from 90, to 80. If I set the dial higher, it goes past 100, and I dont want it that high. Is there any way to keep the shut off time lower, or is there always going to be that 10 degree discrepancy. I mean, the $12 dimmer was doing a better job, and constantly kept it at 100....ideas?

Can you use the rheostat to control the max output and and use the t-stat at the same time to adjust for smaller changes? I have never tried that but it might work. I hate experimenting with the snake still in the enclosure but I guess there is no help for it.

Yeah, I've been waiting till its nightime to experiment, because he's out and about, and not on the uth.

I'm just going to stick with the dimmer. It has kept a really consistent temperature, mind you it will have to be monitored. But there are no real wild temperature changes in my room, that can't be compensated with fiddling with the dimmer.