Copper for thermowell

I'm going to wrap a keg in heat tape and put it in my keezer so that i can ferment while serving.

I want to use a thermowell to control the beer temp. I have a coil of soft copper lying around. Is it ok to leave submerged for weeks? I suppose stainless is best but what is the practical disadvantage of copper?

I believe I've heard that the lower pH of beer will start to leach the copper in to the beer. Too much copper can lead to copper poisoning. I wouldn't recommend it. Someone correct me if I'm wrong.

+1 Copper exposure is not good in a ferment. SS or glass is OK. Measuring the outside of the vessel might be OK too.

I'm going to have heat tape wrapped around the outside so i cant really measure the outside temp. I just need a thermowell that i can dangle down one of the keg post holes. If i had a sensor that was for sure waterproof i could just hang the cord down into the beer.

BetterSense said:

I'm going to have heat tape wrapped around the outside so i cant really measure the outside temp. I just need a thermowell that i can dangle down one of the keg post holes. If i had a sensor that was for sure waterproof i could just hang the cord down into the beer.

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Taping to the outside, then insulating will work as long as the probe is a few inches away from the heat source, and a few inches below the liquid level. For your current situation, this should work as good as a thermowell. For traditional fermenting in a fridge/freezer (cooling or heating internal ambient), taping the probe to the outside and insulating actually works better than a thermowell.

Make sure that the heat tape is not of the self regulating type. The stuff for pipes usually is set to heat to a certain temp

I'm going to use flexwatt heat tape which is the same as fermwrap. I guess i could put a strip of heat tape on one side of the corny and tape my sensor to the other side. If i insulate the whole thing it may work but i think the cool freezer air will affect it even under the insulation.

It turns out i had an old racking cane that i never use since i got an auto-siphon. I was able to heat the end up with a torch and smoosh it shut. Plastic isn't very conductive but i think it will be enough for a fermenter thermowell.

BetterSense said:

I'm going to use flexwatt heat tape which is the same as fermwrap. I guess i could put a strip of heat tape on one side of the corny and tape my sensor to the other side. If i insulate the whole thing it may work but i think the cool freezer air will affect it even under the insulation.

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You would only want light insulation over the flex watt, and as much as you can manage over the probe. I assume you keezer is in the high 30's, so it will affect the sensor some, but not much and less the better you can insulate over the top of it.

BetterSense said:

It turns out i had an old racking cane that i never use since i got an auto-siphon. I was able to heat the end up with a torch and smoosh it shut.

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mmmmmm, BetterSense's Burnt Plastic Pale Ale. Include me out.
Seems like it would taste how Mardi Gras beads smell.

I didnt burn the plastic just melt it. That's how they make buckets, racking canes, and better bottles in the first place...melting.

BetterSense said:

I didnt burn the plastic just melt it. That's how they make buckets, racking canes, and better bottles in the first place...melting.

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Yes, but plastic is molded is under fairly well controlled conditions. If you managed to melt it together with a torch without creating any burnt odor, well done.

As long as you live in a moderately sized town, there will be a metal supply that will sell small quantities of stainless tubing. It can be crimped and soldered to make thermowells, even ones that would seal in a corny post if you had a way to flange it.

Uh oh, don't start the "copper in beer" conversation again. There's miles of threads with arguments about that topic.

BetterSense said:

I'm going to have heat tape wrapped around the outside so i cant really measure the outside temp. I just need a thermowell that i can dangle down one of the keg post holes. If i had a sensor that was for sure waterproof i could just hang the cord down into the beer.

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There are plenty of waterproof thermal probes on the market that are waterproof. Ask the vendor if you are not sure.

Waterproof isn't good enough; i also want food-grade. I'm stuck using a certain thermal probe (LM335 diode temp sensor) because it works with my temp controller. Lucky thing that once i get my thermowell made i can switch to pretty much any temp sensor in the future.

Even the cheap probes have stainless steel cases. The cases are 5-6mm and you can stretch silicone air line over the case so that no wires etc are exposed.

Adafruit sell DS18B20 probes with PTFE coated wires.

Also glass encapsulated thermistors are widely available.

Lots of solutions if you have an open mind.

ebay has good 304 stainless thermowells with 1/2 npt threads. I got one there a couple of years ago for my conical so I could control my temp based on the actual temp of the liquid. I just looked and the prices are all over the map. Still, I'd go stainless rather than plastic. After all, you didn't get a conical to introduce plastic to your precious beer.

Side note: take a rubber stopper that fits into the thermowell, drill a hole just the size of the probe cord. Then cut a split in the stopper so you can get it on the cord. Ta Da! Now your probe is held in place on the conical even if you put it on the sloping bottom part.

BetterSense said:

Waterproof isn't good enough; i also want food-grade. I'm stuck using a certain thermal probe (LM335 diode temp sensor) because it works with my temp controller. Lucky thing that once i get my thermowell made i can switch to pretty much any temp sensor in the future.

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The 'food-grade' comment is too funny to pass up. You were willing to do a week+ long soak in your beer of a piece of plastic you exposed to a torch flame, but want to restrict probes to only 'food-grade'?

The whole NSF/FDA/'food grade' thing is often brought up, and is a paper tiger. As long as the materials are known and safe, if it is cleaned properly it will work. Manufacturers won't pay for ratings if there is no market requiring it.

There are several HBT vendors selling custom thermowells for cheap (<$10). One vendor, Bargain Fittings?, also makes dip tubes. He could make you a thermowell with a flange like a corny dip tube, which would allow you to seal things up with a post. Although I seem to remember reading that you don't believe in airtight fermenters or airlocks.

I assume that racking canes are made of neutral, food- safe plastic that will not affect my beer. Although it is charming that you are so concerned about my melted plastic, plastic is still just plastic when it is melted and re-solidified. It does not transmogrify into something else unless you burn it.

Using a corny dip tune is a good idea. Maybe i can get one at my LHBS. However my budget is very small and i do not like to buy something if i can make do with crap i have lying around here.

You are correct that i don't think it's important to seal off primary fermenters. I usually transfer to a keg for lagering or aging or else simply bottle from the primary.

BetterSense said:

I assume that racking canes are made of neutral, food- safe plastic that will not affect my beer. Although it is charming that you are so concerned about my melted plastic, plastic is still just plastic when it is melted and re-solidified. It does not transmogrify into something else unless you burn it.

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What temp do you think a propane flame burns at?
Do you think that 'by feel' you can guarantee not exceeding any temp thresholds for smell/flavor creation or transmogrification?
As for the food 'safieness' of a racking cane, you would have to consult their NSF report for permitted type of contact and time of exposure.

BetterSense said:

Using a corny dip tune is a good idea. Maybe i can get one at my LHBS. However my budget is very small and i do not like to buy something if i can make do with crap i have lying around here.

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Prices for corny kegs parts are obscene. Cheapest I have seen a dip tube is $5, and they are usually $10+. The vendor who makes custom thermowells and dip tubes might be able to sell you a 'combo' (croctopus?) model for <$10. It only involves adding a flange to a well. The tubing alone will cost you $4 at a metal shop.

BetterSense said:

You are correct that i don't think it's important to seal off primary fermenters. I usually transfer to a keg for lagering or aging or else simply bottle from the primary.

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The protective CO2 blanket only has so much magic, and it disappears quickly after ferm slows down- what with diffusion, drafts, expansion/contraction, and what not.

If you are fermenting in cornies, a better system would be to put the thermowell through the lid, and if you make it airtight, maybe even with a post fitting, you can push your beer with CO2 to another keg. You could also just replace the probe/well with a real dip tube after ferm, and do the same thing. I just prefer to keep stuff sealed, plus I seal the last part of the ferm to build some carb to help push and shorten carb time.