conical temp variations and lager yeast

[brain medicine]

so we have two thermowells on our 4bbl conicals, one in the lower area of the cone and one at the upper edge of the cone. the lager yeasts we use will throw up a good size krauzen, so i assumed this was the spot with the most activity and put the probe in the upper thermowell. (we've been doing 2-2.5bbl batches while we work out the kinks)

after a few very slow starts and some gravity samples that were a good 3-5 degrees lower than the probe reading, im wondering if i should reverse course and use the lower thermowell that's closer to the cone bottom for the temp probe.

i know that "bottom fermenting" isnt a true depiction of lager yeast, as evidenced by nice big krauzen heads. but our strains do tend to floc pretty well, so im wondering if more of the activity is happening closer to the cone bottom where the floccs settle? should i be more concerned with getting a good reading of whats down in the cone? worry less about the floaters in the krauzen?

[brain medicine]

bump. anyone?

[MoonBrews]

Calibrated Thermometer

Stupid starting point -- have you checked that the thermometer is reading accurately?

[rdcpro]

Stupid starting point -- have you checked that the thermometer is reading accurately?

Yes, check this for sure! And if they are reading accurately (or even close), it sounds like the real problem is temperature stratification, probably because you're only using the cone jacket due to the small batch size. Just a wild guess. But moving the thermometer position won't change that. If it's mostly covered, maybe you can run just the top jacket. Or does the vessel have only one jacket?

Regards,
Mike Sharp

[brain medicine]

Yes, check this for sure! And if they are reading accurately (or even close), it sounds like the real problem is temperature stratification, probably because you're only using the cone jacket due to the small batch size. Just a wild guess. But moving the thermometer position won't change that. If it's mostly covered, maybe you can run just the top jacket. Or does the vessel have only one jacket?

Regards,
Mike Sharp

No, i havent had a chance to calibrate the probes recently. (i'm in NoCal, nano is down in Baja) I picked up a few spare probes in case there are issues with the existing probes. Will be down there this weekend.

The FV has two jackets, cone and upper. There's little to no contact with beer on the upper jacket. Why would i run that and not the cone?

[BrewinLou]

We have had a strange time with Lager yeast. As we crash it slowly and the yeast begins to floc, it flocs so slow that it covers the well and they no longer read correct temps. We end up with 28 degree Lager. So far no problems other than that. I have JVNW 60 bbl tanks with 3 thermawells each.

[rdcpro]

No, i havent had a chance to calibrate the probes recently. (i'm in NoCal, nano is down in Baja) I picked up a few spare probes in case there are issues with the existing probes. Will be down there this weekend.

The FV has two jackets, cone and upper. There's little to no contact with beer on the upper jacket. Why would i run that and not the cone?

Well in this case, obviously you wouldn't. But you could still be getting stratification. If the probes end up reading relatively close to one another, what else could it be? I guess you have to pick your poison, so to speak. Control on the lower temp in lower position probe in the cone, or control on the higher temp in the higher position probe. Or recirculate, which might be ok on a temporary basis while you dial in your process. I think once you can get the top jacket covered and chill with that and not the cone jacket, this problem will go away.

Regards,
Mike Sharp

[brain medicine]

i'd be pretty hesitant to turn off the cone cooling, i'd think the yeast that has flocc'd to the bottom but is still active and is resting on top of trub in a cake would generate quite a bit of heat all bunched up together. i feel like i've read /seen countless references to yeast as great insulator and retaining alot of heat, etc.

unfortunately recirc isnt really an option as our racking arms are fixed pointing down, not much movement gets generated. and not a permanent solution either.

im hoping that i can dial in our HX and cooling systems this trip, and then start to do double batches to fill the tanks. maybe the extra vertical height will generate some movement and circulate the wort?


on a kind of related note- the temp probes are two wire, resistive type. if i connected their bare leads together at the temp controller would it simply average the two readings? i assume the controller would read the resistance from all of the wiring in the whole circuit, i.e. both probes. anybody know if i'm off base here?

[rdcpro]

i'd be pretty hesitant to turn off the cone cooling, i'd think the yeast that has flocc'd to the bottom but is still active and is resting on top of trub in a cake would generate quite a bit of heat all bunched up together. i feel like i've read /seen countless references to yeast as great insulator and retaining alot of heat, etc.

unfortunately recirc isnt really an option as our racking arms are fixed pointing down, not much movement gets generated. and not a permanent solution either.

im hoping that i can dial in our HX and cooling systems this trip, and then start to do double batches to fill the tanks. maybe the extra vertical height will generate some movement and circulate the wort?


on a kind of related note- the temp probes are two wire, resistive type. if i connected their bare leads together at the temp controller would it simply average the two readings? i assume the controller would read the resistance from all of the wiring in the whole circuit, i.e. both probes. anybody know if i'm off base here?

I'm not suggesting turning off the cone jacket unless you have the upper jacket covered. But if you cool only at the bottom of a vessel, you'll get temperature stratification. You need to cool near the top, so the colder beer (which is now denser) moves down along the walls to the cone, displacing the beer up through the center of the fermenter. I think most people only use the cone jacket when they're ready to crash and harvest. When you think about the geometry of the cone, the yeast in the middle isn't going to get cooled by the cone so much anyway. I'm sure someone will chime in here on this, but you can test this out with plain water.

As for the probes, by 2 wire resistive, do you mean thermocouple? You rarely, if ever, see a 2 wire resistive type, because the lead resistance factors in. If they are two wire, they're probably thermocouples. The wires will be color coded either red-white (type J) or red-yellow (type k). There are many others, but these are the most common. RTDs will be either 3-wire or 4 wire. In general, RTDs are more accurate than thermocouples. It's possible that your probes are thermistors...these suck. They are not inherently linear, and they tend to drift. If that's what you have, I'd suggest switching to RTDs for anything where temperature is critical. Edit: This might mean changing the controllers...I don't know what you have.

Regards,
Mike Sharp

[brain medicine]

The accuracy on these is pretty solid. Calibrate when installing and they hold well. Have never had one drift by more than one degree. Good enough. However one thing I forgot is the difficulty getting good contact between probe and the thermowell at the very end of the well. Another thing to check on when I get there.

But I think the likely culprit is the half batch. It barely reaches the top of the cone, so no real updraft movement.

As to turning the cone off, I have never seen or met anyone who does that. Although to be fair, I've obviously never asked anyone if they did it either. Is that really a thing? I'd be worried about not having cooling on the yeast cake for lager yeast. It seems you be betting the farm on good wort movement to keep the temps in line.

[rdcpro]

The accuracy on these is pretty solid. Calibrate when installing and they hold well. Have never had one drift by more than one degree. Good enough. However one thing I forgot is the difficulty getting good contact between probe and the thermowell at the very end of the well. Another thing to check on when I get there.

A little white thermal heat sink compound may help. High quality sensors sometimes have a spring-loaded end that keeps a steady pressure on the end of the thermowell.

But I think the likely culprit is the half batch. It barely reaches the top of the cone, so no real updraft movement.

As to turning the cone off, I have never seen or met anyone who does that. Although to be fair, I've obviously never asked anyone if they did it either. Is that really a thing? I'd be worried about not having cooling on the yeast cake for lager yeast. It seems you be betting the farm on good wort movement to keep the temps in line.

Well, you are depending on good wort movement to keep the temps in line, regardless of how you cool. No movement means stratification, and it can be quite a few degrees of difference between top and bottom.

http://discussions.probrewer.com/showthread.php?38621-Single-jacketed-fermenters-vs-Dual-jacked-fermenters

Regards,
Mike Sharp

[brain medicine]

we've got thermal paste in there already, was just worried maybe something had come loose.

so i was able to put in a full batch, and do some measuring and testing. the racking arm- which is fixed in down position-- has a 1F difference from the temp probe/thermowell that is towards the top of the cone but not too far away. seems like good news. sample valve seems to put about 5-7F extra degrees on the wort, which i assume is because it extends outside the jacket. seems normal.

but just for kicks i measured from the bottom outlet and it was like 10or 12F colder. i'm wondering if the actual bottom of the cone is putting my yeast on ice. for 4bbl we use a whole brick of dry yeast, which is towards the top of the pitching range. but with 1.5" bottom tube, i could be getting alot/most of my yeast settled way down in the "extra" cold zone of the cone bottom/bottom tube. especially since i always dump trub/hops before i pitch. so that has me thinking if my probe says 54, and the bottom cone is like 44, or even 42, then i'd have to think that aint helping the little guys get to work. possibly even cold shocking them as they get whirled around and float towards the bottom. and then they stay on deep freeze....

so maybe i should re-plumb the glycol lines to cool with the top jacket only. and have some basic manual shutoffs for the cone so we can use it to crash when necessary, but otherwise use the top jacket for cooling and hopefully good wort movement.

sound reasonable?

[rdcpro]

[...]
but just for kicks i measured from the bottom outlet and it was like 10or 12F colder. i'm wondering if the actual bottom of the cone is putting my yeast on ice.

[...]
so maybe i should re-plumb the glycol lines to cool with the top jacket only. and have some basic manual shutoffs for the cone so we can use it to crash when necessary, but otherwise use the top jacket for cooling and hopefully good wort movement.

sound reasonable?

Yep, that's temperature stratification. If the beer in the cone is colder than the beer above, it can't possibly move up. The colder your beer is, the denser it is, and so it will sink down and stay down. I know Timm and others do not generally cool the cone. You should at least have a manual valve there so you can turn off the flow to the cone jacket if need be. Make sure you don't close off both supply and discharge ports on the cone, because glycol trapped in there will expand if you heat the vessel during CIP. This can damage your fermenter.

Regards,
Mike Sharp