[jimrod]

The 1/4" dia. probe on my Ranco fits loose in my thermowell   .I think it's made from 5/16" tubing.

I am getting low readings of about 10-12 degrees and I'm not sure if it's a bad probe or should I buy a tighter fitting thermowell?  Say .260 ID.?

 

[kylekohlmorgen]

The poly tubing will provide some insulation, along with the air between your probe surface and the interior surface of the tube.

My LHBS has one made of metal - possibly aluminum? I would try a 1/4" ID piece of copper with a capped end.

[ccfoo242]

I have what may be a dumb idea or may be complete genius...

What about adding a little bit of mineral oil inside the thermowell to act as a heat conductor? I've seen entire motherboards submerged in the stuff so I doubt it will harm the probe.

[jimrod]

I think there is a special lube for the thermowell probes But I 'm beginning to think that this home made thermowell is too loose and made of too thick of a tubing.

[anday6]

I would try a 1/4" ID piece of copper with a capped end.

I'm pretty sure copper in finished beer would be a bad idea.  You really wouldn't want a metallic taste to carry over.

[tjroan]

What are you using for a thermowell (material)?  If poly, not a great conductor and could be an issue especially if not a tight fit.  I agree on no copper.  I use the ss ones from Brewers Hardware.  The probes do not fit snug but the thermowell is a good distance in the liquid and ss is an adequate conductor so the temp inside it is pretty much on.  I have the surrounding temp up to 10 deg colder than fermentation temp and no issues.  If questioning the probe, test it by having it next to a proven temp device at various temps (fridge, freezer, ale box, room, other).  Not a perfect calibration but it will tell you if you have a serious probe issue.

[jimrod]

The home made thermowell is 2 1/2" long and it is made from welded stainless. It screws into the side of my keggle. The tubing is a little over sized so the probe fits loose.  I didn't think that made a difference at the time but now I have to wonder why it's not keeping correct temperature readings?

[tom]

With enough time, it should read correctly either way.  Have you checked the probe with another thermometer?

Has the probe gotten wet in the past?

[jimrod]

With enough time, it should read correctly either way.  Have you checked the probe with another thermometer? Has the probe gotten wet in the past?

Yes, it reads low in the thermowell only. It hasn't been wet but pinched a few times.