Thermometer Stem Length

[swanwick]

When a thermometer is listed as having a 4" stem, is that

1. 4" from the back of the dial to tip
2. 4" from the threads closest to the dial to tip
3. 4" from the threads furthest from the dial to tip

My keggle (bought on Craigslist) has a 3/8" weld so I need to add a "Reducing Adapter" to get up to standard 1/2" NPT. The length of the adapter and the weld together is probably about 3".

Depending on the answer to the above, I think I maybe should go with a 6" stem. Want to keep it as small as possible so it doesn't get bashed by copper chiller.

 

[rambler]

I'm pretty sure (90%) it's option #2 It may depend on the manufacturer. You should be able to go to thier website and find the specs for your particular brand.

 

[swanwick]

So, if it is #2 then assuming it is not going to screw all the way into the female port on the keggle, I will lose an additional ~1/4" of length beyond what it already has to cover to get to the inside of the keggle.

I have non-standard 3/8" ports so that distance includes the ports and a 3/8"->1/4" bushing so that I can connect the 1/4" NPT thermometer.

I think I will go with a 6" stem for my HLT, see how that works and then decide on whether I want 4" or 6" for my BK. I want to make sure the stem is long enough to get good readings, but short enough to not block the wort chiller.

I mash in a cooler so that will be a whole different story.

BTW: I have looked at a LOT of thermometer specs online and I have never seen any of them mention where the stem length is measured from. Once I get mine, I will measure it and report back here for posterity.

 

[BargainFittings]

NPT threaded thermometer stems are measured including the thread length so a 4" stem is 3.5" long with .5" of thread.

 

[SixFoFalcon]

ProTip:
Many thermos have a notch or indentation in the middle(ish) of the stem. This is the minimum insertion depth to get accurate readings. You really want that notch to be fully visible inside the kettle or tun, rather than buried inside the bulkhead or fitting, where the liquid may be cooler.

 

[swanwick]

How far is that notch normally from the tip?

 

[Bobby_M]

2 inches on the ones I have.

 

[swanwick]

Bobby and BargainF, Thx for the definitive answers. Have ordered a 6" stem for my HLT. will see how that works. Then will decide if I need one for my BK. Bit overkill since only real value is to tell when getting close to initial boil.

Would love one for my mash-tun, but that will mean drilling another hole and adding more parts into that hole on my cooler.

Just changed fly sparge process to sparging up from top of grain bed. Used to drip, but was losing too much heat. Sitting on grain bed didn't clog sparge holes at all. Biggest challenge is maintaining consistent water level. Might have to get a BobbyM T for therm and sight glass.