temp probe outside or in fermenter?

[vykuza]

Option 'C' for me. Stainless thermowell gets the probe right into the middle of the wort for a super-accurate reading. Easy and cheap enough to do.

This is what I do as well. Just put a stainless thermowell through the side wall of my bunnings fermenter. Takes about 5 minutes to do, and that includes the time getting the drill out of the shed.

 

[Spiesy]

How much difference in temperature does this make compared to reading the temperature on the outside surface of the fermentor thats been insulated with foam?

Quite a few people have noticed a difference, some people have noticed no difference.
Personally speaking, I can't be arsed doing tests - logically it makes sense. It's right in the middle of the fermenter, immersed in wort and less exposed to the changing outside temperatures.

For the $20 or so it cost me, I'll err on the side of caution. I like to give my beer every chance possible to be awesome.

 

[Spiesy]

This is what I do as well. Just put a stainless thermowell through the side wall of my bunnings fermenter. Takes about 5 minutes to do, and that includes the time getting the drill out of the shed.

I'm surprised more people don't do it. Cheap and quick enough to do.

It's odd, some people worry about the resolution of their STC/temp-controller, that it only displays 0.5 resolution - and then leave the probe taped to the outside of the fermenter, or worse, in a water filled beer bottle inside the fridge... :blink:

 

[kiwisteveo]

cheers for all the replies/comments I brought a plastic bulkhead for the probe to go through wall of fermenter and the probe directly into wort cause it was cheaper than SS thermowell so will do that today with a single hop bravo brew but looks like best option will be SS thermowell for other fermenters in the future.

 

[SJW]

Probe in with cling wrap over the top of fermenter.

 

[superjim]

Pics as promised.

 

[TheWiggman]

It's right in the middle of the fermenter, immersed in wort and less exposed to the changing outside temperatures.

In my opinion you're best off having it offset a little from the centre of the fermenter (like post #14) to avoid overshoot with a temp controller like an STC-1000. Only really matters if you're doing temp changes (like stepping a lager), and even then only if you're using a lot of power to heat/cool.

Having it in the middle will allow a temp gradient through the wort from outside in. For example, once the temp might chill to your setpoint of 12°C the freezer/ambient may be -10°C and the outside boundary of the wort might be 9°C. The vessel will continue to get colder after the freezer turns off. Having the sensor closer to the edge will reduce this effect. The outside temps are being used to control the inside temps after all.

Bleeding edge, but it's zero extra hassle for that little bit of improvement in control.

 

[Spiesy]

In my opinion you're best off having it offset a little from the centre of the fermenter (like post #14) to avoid overshoot with a temp controller like an STC-1000. Only really matters if you're doing temp changes (like stepping a lager), and even then only if you're using a lot of power to heat/cool.

Having it in the middle will allow a temp gradient through the wort from outside in. For example, once the temp might chill to your setpoint of 12°C the freezer/ambient may be -10°C and the outside boundary of the wort might be 9°C. The vessel will continue to get colder after the freezer turns off. Having the sensor closer to the edge will reduce this effect. The outside temps are being used to control the inside temps after all.

Bleeding edge, but it's zero extra hassle for that little bit of improvement in control.

Good idea.

 

[Blind Dog]

In my opinion you're best off having it offset a little from the centre of the fermenter (like post #14) to avoid overshoot with a temp controller like an STC-1000. Only really matters if you're doing temp changes (like stepping a lager), and even then only if you're using a lot of power to heat/cool.

Having it in the middle will allow a temp gradient through the wort from outside in. For example, once the temp might chill to your setpoint of 12°C the freezer/ambient may be -10°C and the outside boundary of the wort might be 9°C. The vessel will continue to get colder after the freezer turns off. Having the sensor closer to the edge will reduce this effect. The outside temps are being used to control the inside temps after all.

Bleeding edge, but it's zero extra hassle for that little bit of improvement in control.

Good point

Intuitively it would seem that the air inside the fridge itself would stabilise relatively quickly when heated or colled compared to the fermenting beer so that even though I have a specific heating and cooling sources, their location is unlikely to play a significant effect on the temperature differentials inside the fermenting beer.

Interested if anyone thinks this is not right

 

[TheWiggman]

Largely right I'd say Blind Dog. The liquid will contains a lot more thermal/heat capacity (often referenced here as 'thermal mass') than the air, so energy required to increase the temp of the air in the fridge is much, much less than required for the same temperature difference in the liquid.

If the fridge was cooling and is turned off, the wort will drop in temp and pass some of its heat to the air until they're the same temp
If a belt was heating and is turned off, it will pass its heat into the wort until they're the same temp

As for the speed... well they'll both stabilise at the same rate (because they will both eventually be the same temperature), but the temp difference that the air dropped will be a lot more than the wort dropped.

The location will play a part for the reasons above. The further something is away from the source, the more energy will be passed onto its surroundings first.
If you were in a large cold room would you rather stand on the opposite side and wait for the whole room to heat up or be right next to the heater? And if you stood on the other side of the room and you got warm, what would happen if you realised the heat was turned up too much? By the time you find out the room's already too hot, and you'd have to wait ages for it to cool down. (this is 'overshoot', which can be prevented or minimised using PID control).

The fementer is like the latter example. With the exception that the fermenting wort will generate heat, so to maintain the right temp the ambient air needs to be cooler than the desired fermenting temp.

 

[Coalminer]

In my opinion you're best off having it offset a little from the centre of the fermenter (like post #14) to avoid overshoot with a temp controller like an STC-1000. Only really matters if you're doing temp changes (like stepping a lager), and even then only if you're using a lot of power to heat/cool.

Having it in the middle will allow a temp gradient through the wort from outside in. For example, once the temp might chill to your setpoint of 12°C the freezer/ambient may be -10°C and the outside boundary of the wort might be 9°C. The vessel will continue to get colder after the freezer turns off. Having the sensor closer to the edge will reduce this effect. The outside temps are being used to control the inside temps after all.

Bleeding edge, but it's zero extra hassle for that little bit of improvement in control.

Must agree with this as that is how mine is set up
It is half way between the edge and the center. I figure that will give me an average of the whole system
Bear in mind that there is a lot of movement and mixing of an actively fermenting wort and that should even out the wort temperature
Just my opinion. (for what its worth)

 

[storeboughtcheeseburgers]

I just have it in a cupboard and let the probe sit flush against the inner door of the cupboard about half way down. I figure yeast generally brews at a higher temp once its going, so 18 degrees in a 1.5 X 1m I have had no dramas.

Heat belt is indirect, but close.

 

[Dips Me Lid]

I use the Keg King controllers for my plastic fermentors, the probe fits nice and tight into a SS keg dip tube which I use as a thermowell to get right down into the liquid, I flatten one end of the dip tube with a vice, drill a 20mm hole through the fermentor lid and use a 20mm cable gland to seal it up, I've set mine up just slightly off centre.

 

[Topher]

Tried the thermowell ...... but it kept falling through the glad wrap.

Seriously I do the same, tape and some foam. But I am gonna try the Occy strap method next brew, the bloody tape keeps coming off. Twice the temp probe has fallen right out of the fridge......Had one stout go to 28 degrees and ferment right out in a day, and my current brew had a tropical holiday at 30c but only only for a few hours.

 

[mofox1]

Tried the thermowell ...... but it kept falling through the glad wrap.

Seriously I do the same, tape and some foam. But I am gonna try the Occy strap method next brew, the bloody tape keeps coming off. Twice the temp probe has fallen right out of the fridge......Had one stout go to 28 degrees and ferment right out in a day, and my current brew had a tropical holiday at 30c but only only for a few hours.

I left out the good bit... Big block o' blutack over the sensor, holding it in place, and beefing up the thermal mass around it. The polystyrene/murdered stubby holder goes over that, and held on by tape/ockies.

That way if the tape (or ocky straps) give way, it is still stuck to the side of the vessel, just not as insulated as it used to be.

Also makes it easy to switch it over to my stir plate, or whatever else I'm psuedo-temp controlling at the time. But then I'm sure someones got a thermowell in their stir plate too and will claim this as the superior method. h34r:

 

[storeboughtcheeseburgers]

Depends how cold it gets where you are - I find I'm getting 11 minimums in a closed cupboard with no heating source, so don't really go to much effort (just hang a heat strap from a pipe in the cupboard) and put the probe in the inside, about 50% down and close the doors.

If your in Tassie or vic or whatever u prob could be a bit more pedantic but winter will be over soon anyway - then the madder brewers can start doing lagers, just to go against the seasons and have all different combos of measurements and engineering just cuz they can .

 

[superstock]

Do you guys just slide your temp sensor into the thermowell dry?
Most thermowell controlled devices in industry have oil/liquid in the thermowell to transmit temp more directly, accurately and responsive to the sensor.

 

[vykuza]

I do - I figure it's close enough and not enough air movement in and out of the thermowell's core is going to make a difference. You could also put a plug of play-doh in the end if you want to be super keen on it.

 

[Mattress]

Do you guys just slide your temp sensor into the thermowell dry?
Most thermowell controlled devices in industry have oil/liquid in the thermowell to transmit temp more directly, accurately and responsive to the sensor.

Mate, C'mon.
We're only making beer.
It's not like we get all super anal about our processes.

 

[superstock]

Mate, C'mon.
We're only making beer.
It's not like we get all super anal about our processes.

I totally agree with you. Against the FV wall, insulated & taped does me. However, from the posts, there are others out there with controllers setable to 1/10 degree, using thermowells in the best position for best reading and not using best practice to ensure accuracy. :huh: