hydrofarm thermostat?

So today I finally got around to wiring part of my larger rack and hooked it up to a simple hydrofarm thermostat. The issue I'm hitting right away is that it seems to run either all or nothing in terms of power, and the probe takes a long time to adjust to the temp changes (probe is attached to THG tape with electrical tape). I have it set to 95 right now since it seemed liked that was about where it was actually giving me 90, which is what I wanted. The temps, on the other hand, fluctuate up to between 115 and 120 while it's heating and down to 87 when it isn't according to my infrared thermometer. These cycles take about 3 minutes or so, and I'm very uncomfortable with these temperature fluctuations. Only 3 shelves are wired up right now so I don't have any snakes on it.

Is it going to keep doing this, or will it eventually balance itself out? Should I just junk this thing and keep up with the ambient room temp until I can get a herpstat?

No that is how they work. It is an on and off stat delivering full power (causing high temp spikes) and no power periods where it cools off.

I would suggest the combination to be a terrible idea. A tub heats very quickly and cools very quickly unlike something like a glass tank that heats slower and cools slower so it regulates the hills and valleys. The rack does not do this at all. Add THG tape that has a higher temp out put than most tapes this increases the spikes and dies even further.

The hydrofarms also have a lot of hysteresis (about 5 degrees) this also increases the range of the spikes. Together it is a dreadful combination.

I would suggest only a proportional stat be used with a high heat element and a tub. Nothing else will accurately regulate the temp with out issue. Personally given the high heat capabilities of the THG tape I would only use a herpstat with safety relay and keep the hydrofarm as a fail safe for it in case the probe is pulled free.

failsafe set up

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Originally Posted by Daigga

So today I finally got around to wiring part of my larger rack and hooked it up to a simple hydrofarm thermostat. The issue I'm hitting right away is that it seems to run either all or nothing in terms of power, and the probe takes a long time to adjust to the temp changes (probe is attached to THG tape with electrical tape). I have it set to 95 right now since it seemed liked that was about where it was actually giving me 90, which is what I wanted. The temps, on the other hand, fluctuate up to between 115 and 120 while it's heating and down to 87 when it isn't according to my infrared thermometer. These cycles take about 3 minutes or so, and I'm very uncomfortable with these temperature fluctuations. Only 3 shelves are wired up right now so I don't have any snakes on it.

Is it going to keep doing this, or will it eventually balance itself out? Should I just junk this thing and keep up with the ambient room temp until I can get a herpstat?

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Well they are on/off thermostats so it's only ever going to be on or off. I don't believe there's a way to set their buffer time between kicking on. An STC 1000 would allow you to change that but is still an on/off controller. (I use a pair of them for my UTH and heat lamp)

Where's the probe located relative to a hot spot? Do you have a second way to check the temps because that's a very huge difference in temperature? Maybe your IR thermometer is being finicky.

hydrofarms are made to heat dirt. They have a slow response probe, a large hysteresis (what foxton called a buffer) that is designed to regulate potting soil that takes a long time to change. This is why they work best with heavy glass tanks it behaves the closest to soil.

the accuracy of them is quite bad as well.

http://images34.fotki.com/v1605/phot...CA_9509-vi.jpgHosted on Fotki

Actual temp (highly accurate thermometer) is 80.42ºF

Good to know, I guess I'll shut it off and start putting money away for a herpstat. Or are there any other comparable thermostats you would recommend?

Herpstat is the best IMO, helix is also good but does not offer a relay system (proportionals units tend to fail on not off but the failsafe protects against this too) Herpkeeper and ecozone are also both very good they both are very flexible but with that comes complicated.