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Thermostat issue, help please
Bear with me here, this will take a bit of explaining.
I started out using a Hyrdrofarm thermostat. To get a hot spot of ~90F I had to set it to 80F which makes no sense since if anything it should need to be set higher to offset heat lost. I just chalked it up to being cheap.
Then I got a Herpstat 2, same issue, 80F gave me a 90F hotspot through the PVC of an AP T8. This threw me, this thermostat is supposed to be accurate to something like .01F why would it need to be 10F lower than it should, was it related to the Hydrofarm having the same problem?
Now, I cleaned the cage recently and the temps bottomed out completely, I now have the thermostat set to 100F and it is reading 85F in the cage, nothing changed I pulled everything out and put it back in, this was a few days ago.
Additional details: In both cases the thermostat probe was between the flexwatt and the bottom of the cage. My Accurite thermometer probe is inside the cage under the corrugated wrap. The temp gun I have and the Accurite agree with each other. Nothing has changed in or outside of the cage at all except me putting in new corrugated wrap.
Last note, the temp under the corrugated wrap reads 90F while the surface reads 85F, before it was even and there should be no way it is losing that much through that little cardboard.
Thoughts? I'm afraid its going to go back to the way it was while I'm at work and cook my snake.
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5ºF to a sheet of cardboard sound right to me. The herpstats are accurate to 0.9ºF not 0.01ºF that would be the deal of the century if it were. I would trust the herpstat probe over a accurite (IMO 100% junk +/-4ºF how is that good?) and IR guns.
You started gaining 10ºF then after changing the substrate you lost 5ºF the only explanation I could think of is there is something else causing the gain (fluorescent lighting can do so)
If you met to say when set at 90ºF you get 80ºF inside this makes more sense, if the paper is not in direct and full contact with the floor it may not heat fully. The accurite measures the air temp and IR gun the surface I would be suspect if they were exactly the same. Paper is an excellent insulator all that cellulose blown in insulation is a testament to how efficient. It not surprising to lose a a bunch of degrees what are the ambient air temps in the middle of the enclosure? with the light on and off (40min to cool) ? Ambient air temps will have great impact on the loss to the substrate. It is quite possible that the ambient air temps are the culprit in either case (gaining over the T-stat or loosing)
Last edited by kitedemon; 03-26-2013 at 07:50 PM.
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Thermostat issue, help please
Is the probe attached to the heat tape in any fashion? I always preferred to tape my probes down. I feel it's more accurate.
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Re: Thermostat issue, help please
 Originally Posted by interloc
Is the probe attached to the heat tape in any fashion? I always preferred to tape my probes down. I feel it's more accurate.
The probes transmit a tiny charge to the main unit, is there anything that could be interfering with this signal? Magnetic field or bundles of other current carrying wires?
As much as everyone loves Herpstat it isn't inconceivable that one or two faulty units get out of the shop and into circulation. But, what is very improbable is that not only did this happen but, the less expensive unit also exhibited the same issues.
New units with new probes eliminates broken wires inside the insulation relaying a lower temp than actually measured so, you have me stumped unless there is a placement or interference issue.
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Re: Thermostat issue, help please
 Originally Posted by kitedemon
5ºF to a sheet of cardboard sound right to me. The herpstats are accurate to 0.9ºF not 0.01ºF that would be the deal of the century if it were. I would trust the herpstat probe over a accurite (IMO 100% junk +/-4ºF how is that good?) and IR guns.
It's just strange that the temp gun and accurite say the same thing... Plus if the Herpstat was right, when I set it at 80F the temp would be a bit lower than that and I think there would have been some digestion issues.
 Originally Posted by kitedemon
If you met to say when set at 90ºF you get 80ºF inside this makes more sense
That would make sense, but it's the opposite, which is why I'm not sure how much I trust the Herpstat....
 Originally Posted by interloc
Is the probe attached to the heat tape in any fashion? I always preferred to tape my probes down. I feel it's more accurate.
The thermostat probe is in the little groove they put in the bottom of the AP T8, it's snug between the Flexwatt and bottom of the enclosure.
 Originally Posted by Raven01
The probes transmit a tiny charge to the main unit, is there anything that could be interfering with this signal? Magnetic field or bundles of other current carrying wires?
No electronics nearby to be causing this.
I just find it strange that the Herpstat and Hydrofarm were off by 10F. And now having to have it set 20F higher than it was before cleaning the cage worries me.
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Does the thermostat probe and the power cord for either the herpstat or the heat source? Electrical interference from an AC power cord can easily effect a low voltage DC signal. That could have been the issue with the hydrofarm as well.
What (if anything) did you use to attach the herpstat's probe in the slot?
Here is a simple test. move the herpstat's probe inside the cage, and place it right next to the acu-rites probe.
Something is seriously wrong here. AP cages are made of thick PVC. I have to set my herpstat to 99-102.5 to get a 90 degree hotspot. The fact that 2 separate thermostats had the same issue tells my that they probably aren't the issue. You need to isolate the issue. If you have anything else in or near the cage that produces heat (like the fluorescent lights sold by AP) turn them all off. Something is adding heat to the cages. You could also try unplugging the heat tape for a day or so and see how cold the cage gets.
Your herpstat hasn't accidentally been adjusted has it? There is a calibration setting in the menus to adjust the probe reading.
Your current thermostat set temperature actually sounds reasonable. but there is no way a herpstat set to 80 could heat a cage to the proper temperatures.
~Aaron
0.1 Pastel 100% Het Clown Ball Python (Hestia)
1.0 Coastal/Jungle Carpet Python (Shagrath)
0.1 Dumeril's Boa (Nergal)
0.1 Bearded Dragon (Gaius)
1.0 Siberian Husky (Picard)
0.1 German Shepherd/Lab Mix (Jadzia)
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What is the ambient air temp? This is the true controlling factor and key to the whole system. if the air temps are warm the T-stat cannot cool off the enclosure. What is the herpstat reading in power %?
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Re: Thermostat issue, help please
 Originally Posted by The Serpent Merchant
Does the thermostat probe and the power cord for either the herpstat or the heat source? Electrical interference from an AC power cord can easily effect a low voltage DC signal. That could have been the issue with the hydrofarm as well.
What (if anything) did you use to attach the herpstat's probe in the slot?
Here is a simple test. move the herpstat's probe inside the cage, and place it right next to the acu-rites probe.
Something is seriously wrong here. AP cages are made of thick PVC. I have to set my herpstat to 99-102.5 to get a 90 degree hotspot. The fact that 2 separate thermostats had the same issue tells my that they probably aren't the issue. You need to isolate the issue. If you have anything else in or near the cage that produces heat (like the fluorescent lights sold by AP) turn them all off. Something is adding heat to the cages. You could also try unplugging the heat tape for a day or so and see how cold the cage gets.
Your herpstat hasn't accidentally been adjusted has it? There is a calibration setting in the menus to adjust the probe reading.
Your current thermostat set temperature actually sounds reasonable. but there is no way a herpstat set to 80 could heat a cage to the proper temperatures.
I was hoping you your engineering brain would stop by. The only thing holding the probe in place is the weight of the cage, its sandwiched into the groove, no tape or anything obstructing it. I should add that underneath the cage is a board covered in an insulating foil, it's flush with the cage bottom. I'll isolate the cage from anything else electronic in the room, I'll just unplug everything but the thermostat/heat tape tomorrow night. I'll also try putting the probe in the cage next to the acurite one, but I'll have to do it tomorrow evening because I want to be able to watch the temps closely.
I also have a calibrated laboratory grade mercury thermometer I can put into the mix (obviously not while my snake is in there).
And to kitedemon, the ambient is at 77F at time or writing, it was steady at 80-81 before this all started. The drop is likely due to me opening the cage quite a bit today. Also the % is holding around 25-27
Thanks for all the help and ideas everyone, I'll give it a try tomorrow and report back with what happens.
Last edited by mackynz; 03-27-2013 at 12:27 AM.
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I've been thinking about this for awhile now. I don't think anyone has mentioned the elephant in the room yet. Could it be the flexwatt itself? I know that some strips of flexwatt aren't as consistent as others are. It is possible that your probe is on a "cool" spot of the heat tape, and the majority of the rest of the flexwatt is actually hotter. This would explain why 2 thermostats had the same issue and why your thermometer/temp gun also read the same.
~Aaron
0.1 Pastel 100% Het Clown Ball Python (Hestia)
1.0 Coastal/Jungle Carpet Python (Shagrath)
0.1 Dumeril's Boa (Nergal)
0.1 Bearded Dragon (Gaius)
1.0 Siberian Husky (Picard)
0.1 German Shepherd/Lab Mix (Jadzia)
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The Following User Says Thank You to The Serpent Merchant For This Useful Post:
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The Flex is always a possiability. A second thought is the the probe cable running along the flex power supply? This also could cause odd issues. I have never seen an issue like this. What % does the herpstat read most of the time.
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