ITC 308 - temperature unstable

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Nov 16, 2018
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I recently installed a thermowell in the top of my 25L fermenter. I've currently got a Märzen sat in my ferm fridge at around 13c. At first I had the probe for the ITC 308 sat in the thermowell, but when I pushed the probe down inside the thermowell last night it read 0.3c lower. I guessed this is probably because there's no solid connection and from air insulating the probe, so I looked for something to make a connection between the thermowell and the probe, the closest thing to me was some alcohol hand gel. After a liberal squeeze into the thermowell and jamming it down with a length of dowel, I pushed the probe in.

That was last night, now when I've had a look this morning the ITC 308 is cycling between a 0.4c range every 10 seconds. 12.8, 12.9, 13... 12.9 12.8, 12.7... etc etc.

I've changed the compressor delay setting to 3 minutes and my high and low temps are 0.5c +/- just in case it tries to cycle on and off over the fridge on/off setting.

Anyone encountered anything at all similar? Should I just leave it alone now (arguably what I should've done in the first place - I've since read oil is a good conductor for the probe)? Or do you think I should get the probe out and go back to taping it to the side for the time being until I can wash the themowell out?



Out of Control
Aug 15, 2013
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North Wales
A heat conductive gel/paste would sound ideal (is "alcohol hand gel" thermally conductive or insulating?). But I simply plug the thermowell with cotton-wool (holds the probe in too). The environment in the thermowell has no choice but to mirror the temperature of what it is in. The probe may not respond as fast as if it was swimming in thermal-paste, but does it need to?

Even if you succeed in stabilising the temperature readings of the probe (and even if the ITC-308 really could measure with 0.1C accuracy) don't put too much faith in such tiny increments as 0.1C - it is unlikely that the reading at the probe is identical to a reading 100mm from the probe. And would it matter if it wasn't identical?