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.

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)

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.

Quote:

---

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.

Quote:

---

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.

Quote:

---

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....

Quote:

---

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.

Quote:

---

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.

:confusd:

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.

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 %?

Quote:

---

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.

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.

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.

You may need to switch to interior probe placement it is far far more accurate under erratic conditions. If you do so there are a handful of steps to insure safety however. I know Aaron tested flexwatt to only hit 100ºF but I have a strip that got far far hotter (old style) that would be the first replacement to something that will not get over 100ºF like ultratherm. The next is the probe must be firmly fixed (regardless of placement) and the third is I would use the hydrofarm as a fail safe in addition to the relay setting on the herpstat (if it has them) being enabled. It then will not matter at all if there is hot or cool parts (ultratherms in my experience are super even) and it will account for air temps and any other variations.

I'll feel the flexwatt when I get off work to see if I notice anything. I'll also check with the temp gun, it may not be accurate, bit it would still show a difference.

If I end up keeping the probe in the cage permanently how would you recommend securing it? Hot glue? And wouldn't I have to worry about pee soaked cardboard getting on it or no?

And kitedemon, in case you didn't see it above power usually sits bouncing between 25-27%

I'll update this again after putting the probe in to see what the temp reads.

No I missed that. I use hot melt to secure the probe I tug it to be sure it will not move I also secure the whole cable.

To do so safely the probe must not move. No pee/poo is not an issue the probe is fine.

The second issue is not to use a heat source that becomes very hot even wide open. I use 100ºF as a limit value I do not like seeing a max temp greater by more than a few degrees. I have flexwatt that never gets over 100º and some that gets far over it I would recommend a 'snake free' max temp test the flex it self should not be over 100ºF by much. This means even in the event of a failure the temps inside cannot exceed 100ºF.

The fail safe is the third step using your hydrofarm with its probe where you currently have the herpstats with the herpstat plugged into the hydrofarm and it set shut down before dangerous temps are reached, I again use 97-8º sometimes 100ºF at the flexwatt. This set point should be set so the interior temps cannot get beyond 95-6ºF.

The herpstat then needs to be set (if you have one that has over and under settings) so that it will shut down if the temp on the probe dips below a given point (I use 80ºF as my room can get very cool)

The argument many make is pee/poo on the probe will cause the t-stat to kick on max and cook the snake or the probe may be moved with the same result. This method I described the herpstat would have to fail at the same time AND the hydrofarm as well would have to fail at the same time the heater element shorted out. The chances outside a catastrophic event are so low to not matter. It is safe if you follow these guidelines, it would take something so large to cause all the safety issues to fail at once that there are much larger issues at stake. All the units all being under water or fire would damage all the heating appliances at once but the concern is bigger than holding correct temps. (if your house is on fire you are not likely to be worried that tsats have failed)

Good news everyone! After putting the probe in the cage i was able to get the temps to where they should be furthermore the acurite thermometer only measures 1 degree under the thermostat. This has also further confused me.

As established earlier, when the probe was under the tank I had to have it set to 80F to get the 90F hot spot (as read by the Acurite) so logic dictates that they should not be reading almost the same... There is sorcery afoot!

As far as the Hydrofarm failsafe goes, I'm all for it but a bit confused. It was my understanding that the settings for each probe on the Herpstat were controlled separately. Could you describe exactly how it would be plugged in? I was thinking Flexwatt->Hydrofarm->Herpstat?

Again, thanks for all your help.

Quote:

---

Originally Posted by mackynz

Good news everyone! After putting the probe in the cage i was able to get the temps to where they should be furthermore the acurite thermometer only measures 1 degree under the thermostat. This has also further confused me.

As established earlier, when the probe was under the tank I had to have it set to 80F to get the 90F hot spot (as read by the Acurite) so logic dictates that they should not be reading almost the same... There is sorcery afoot!

As far as the Hydrofarm failsafe goes, I'm all for it but a bit confused. It was my understanding that the settings for each probe on the Herpstat were controlled separately. Could you describe exactly how it would be plugged in? I was thinking Flexwatt->Hydrofarm->Herpstat?

Again, thanks for all your help.

---

Its the other way:

Flexwatt -> herpstat -> hydrofarm -> wall

This works best with single channel thermostats like the herpstat 1 or intro but it will work as well on a multichanel thermostat as well (like the herpstat 2 or 4) but whatever is plugged into the other channel(s) will be held hostage by the hydrofarm in the case of a failure.

This works because the hydrofarm is an on/off style thermostat. It allows power to get to the herpstat as long as the set temperature on the hydrofarm isn't breached. If you plugged the hydrofarm into the herpstat as soon as the herpstat reduced power to that channel the hydrofarm will go dead (or worse start acting erratically)

if the temps in the tub is that much higher than the herpstat setting, and the room temp isn't too high either you're way of measuring the temps is off. you kind of ruled that out with also using a temp gun and getting very close readings with both. then getting higher temps than what the thermostat is set at is most likely a bad reading on the probe. most likely how and where's it's mounted. mine is metal taped to the heat tape where the tub can no way knock it loose or off. if you check these, then you need to call spyder robotics

never place the probe in the tub. if the snake knocks it loose, you can get a hotspot that can burn your snake.

Quote:

---

Originally Posted by don15681

never place the probe in the tub. if the snake knocks it loose, you can get a hotspot that can burn your snake.

---

Which is why I'll be securing the probe and cord in the way mentioned above, plus she has no real way of getting to it anyway.

Quote:

---

Originally Posted by don15681

never place the probe in the tub. if the snake knocks it loose, you can get a hotspot that can burn your snake.

---

If you use the method I described can you explain how this is going to happen?

The herpstat would have to fail, the secondary would have to fail, and the heat tape would have to short all at once. The chances of that are astronomically low. I cannot see anything short of the the home on fire that could manage that all at once.

- - - Updated - - -

http://images57.fotki.com/v505/photo...drawing-vi.jpgHosted on Fotki

Quote:

---

Originally Posted by kitedemon

If you use the method I described can you explain how this is going to happen?

The herpstat would have to fail, the secondary would have to fail, and the heat tape would have to short all at once. The chances of that are astronomically low. I cannot see anything short of the the home on fire that could manage that all at once.

- - - Updated - - -

http://images57.fotki.com/v505/photo...drawing-vi.jpgHosted on Fotki

---

first off that's an excellent drawing. this is in my near future plans, but my probes will be attached to the heat source as in the drawing. attached to the inside of the tubs might work for you. but I have close to 100 balls and I feed live. I never leave my room when I have rodents with my snakes. if a rodent is chewing on one of my snakes, that snake will be all over that tub. (never happen yet) i will hear it and can response fast on it. most hit the rodent right away. but I can't hear that rodent chewing on a probe wire. even tho the herpstat beeps when the probe is unplugged. should also beep with a broken wire. don't want to deal with that. I have my temps where they need to be with my probe on the outside attached to the flexwatt where it is also safe from the tub sliding in and out.

why would the tape have to short, if both probes get knocked off the heat tape is going to max out. even if there's nothing wrong with either thermostat.

The chance of both probe one outside one inside being knocked off (and the herpstat failing as it has the function of the low temp shut down) is crazy low. You have stated it should never be done, It is not for everyone, but when you get erratic temps this is almost always a fix (like the OP).

So you are saying a rat will chew the probe and the one placed on the heat source will fall off and the herpstat will fail and the heat source which under a maxed out test doesn't get hot enough to cause burns (unless you believe heat tape that caps at 100º -2 degrees to the tub so 98ºF) will burn snakes or will suddenly get much hotter than it has when plugged into the wall directly... I am sorry that is far fetched. Or did you not understand what conditions I have suggested to keep the a high level of safety?

Thank you, I try to keep drawings clear. It may not be obvious but a failsafe ALWAYS goes directly on the heat source and I believe that racks have a higher chance of pulling a probe loose than most other set ups, to my mind failsafes are highly advised (in truth, not optional IMO)

The better heat systems these days have limited max temp, most to 100ºF, recently in tests done by other members, have tested some flexwatt to hold 100ºF no more in a max power test. Personally I will not use under any conditions a heat source that will become hotter than 100ºF this means even in a full failure of everything you are still not hot enough to burn.