Fermenting temperatures

[Glot]

I have started a new thread with this as the other one was getting a bit long. Merge them if you want.
I have been monitoring fermentation temps. These are just my observations and it wasn't done as an accurate experiment.
I have two drum fermenters in the one fridge. One on the floor and one on a shelf. I put three temp sensors in each one at different levels. I just manually plug each one into my meter.
With all the talk about accuracy of equipment, where to place your temperature controller sensor etc, in a simple home brew system, it ain't that accurate.
I had up to 2 deg C difference between the top and bottom fermenter.
I had up to 1 deg difference within each fermenter. Swirling the drum to remove stratification altered the reading almost 1 deg
Even with the ferment hard under way, I had my temperature controller sensor just jammed under one of the fermenters between it and the shelf. It was surprisingly close to the reading I was getting from the lower sensor within the fermenter.

 

[Ducatiboy stu]

Hotter at top or bottom..?

 

[Glot]

Confusingly, the bottom fermenter was warmer than the top one but I suspect that is poor air circulation in the fridge and the top one being next to the evaporator. Within the drums, warmer at the top and cooler at the bottom.
Temperature stratification is a big thing. Just look at a storage hot water heater or the ocean.

 

[GeoffN]

What was the difference between the fridge and the fermenter?

I'm busy getting my fermenting fridge going and am looking for some ideas on target temperature for the fridge. From what I've read the difference can be between 0 and 3°C depending on active fermentation and yeast activity. So I was wondering what you have observed.

Thanks in advance.

Sent from my HDC-08 using Tapatalk 4

 

[QldKev]

Confusingly, the bottom fermenter was warmer than the top one but I suspect that is poor air circulation in the fridge and the top one being next to the evaporator. Within the drums, warmer at the top and cooler at the bottom.
Temperature stratification is a big thing. Just look at a storage hot water heater or the ocean.

I did the same test a few years back and found that same strange phenomenon, the bottom fermenter was warmer. I found a pc fan in the fridge helped equalize the temperatures quite a bit.

I've now even got some pvc pipe (left over from the HERMS build) to ensure the air is drawn from the down and vented higher up. Although without the pipe I think it was not that much difference.

 

[Glot]

Fridge temp versus ferment temp. It all depends on where and how you are measuring and of course, how accurate you think your ferment temperatures need to be. I had one of my ferment drums siting on the sensor on a timber shelf. The difference was less than one degree of the average fermenter temperature after I swirled the drum. I wasn't trying to be accurate. Just getting some idea. This was while in strong initial fermentation. I am guessing that the centre of the drum would have been warmer than the outer portion.
Again, I go back to: where do you measure? I actually don't think the plastic drum makes much difference if the sensor is well insulated from the air and in good contact. However, "much" is a very subjective word.

 

[QldKev]

I'm happy with my probe on the outside of the drum, with a wetsuit stubby holder over the top to insulate it form the air.
But when I run both bottom fermenters I just shove the probe in between them.

Sorry I'm filling up your thread with my pics.
Probe in between the bottom fermenters (before I had mounted the fan into the door.)

 

[Glot]

A pic says a thousand words.
I have been a bit perplexed as to why my top drum is cooler than my lower one.
The top drum is about 120 mm away from the evaporator. There is about 100 mm gap between the solid shelf and the rear of the fridge.
I decided to place a bit of heavy ply board between the top drum and the evaporator and sort of "deflecting" to cool air towards the lower section and insulating the top one from the evaporator a bit. It was a spur of the moment thing and to my surprise, when I checked a few hours later, the two temps were more consistent. There are many other variables that I didn't allow for but I really wonder how many people are fermenting at exactly the temperatures they think they are. I realise a couple of degrees can make a difference in taste but without going big money and buying a 2200 litre milk pasteuriser and water chilling plant ( imagine bottling day) it is more beneficial to just get to "know" your set up and its idiosyncrasies in my opinion than trying to work out which sensor is the most accurate down to .001 deg etc. Until I started measurements, I really didn't expect so much difference both within the one drum and between drums.
Please. These are just my observations and there was no attempt to be accurate. Some would say, "why post it then?" It is just to start others thinking.

 

[surly]

A pic says a thousand words.
I have been a bit perplexed as to why my top drum is cooler than my lower one.
The top drum is about 120 mm away from the evaporator. There is about 100 mm gap between the solid shelf and the rear of the fridge.
I decided to place a bit of heavy ply board between the top drum and the evaporator and sort of "deflecting" to cool air towards the lower section and insulating the top one from the evaporator a bit. It was a spur of the moment thing and to my surprise, when I checked a few hours later, the two temps were more consistent. There are many other variables that I didn't allow for but I really wonder how many people are fermenting at exactly the temperatures they think they are. I realise a couple of degrees can make a difference in taste but without going big money and buying a 2200 litre milk pasteuriser and water chilling plant ( imagine bottling day) it is more beneficial to just get to "know" your set up and its idiosyncrasies in my opinion than trying to work out which sensor is the most accurate down to .001 deg etc. Until I started measurements, I really didn't expect so much difference both within the one drum and between drums.
Please. These are just my observations and there was no attempt to be accurate. Some would say, "why post it then?" It is just to start others thinking.

Intgeresting thread Glot.
I use a similar system to QLDKev with the probe mounted to the side of the fermenter (I place it about 1/3 up from the bottom). I am not massively fussed with making perfectly reproducible beers at this stage. I am in the "suck it and see" stage of learning to brew. As long as I am withing a degree or so, I am not too stressed. I tend to aim a bit lower than the recipe calls for as I suspect the outside of the fermenter is a little cooler than the middle.

Don't worry, I doubt NATA will come knocking on your door demanding an improvement to your methodology.

 

[Spiesy]

Put a stainless thermowell in a fermenter so your probe sits smack back dead center in the middle of your wort. Takes the average reading. Easy.