Controlling The Temperature Of More Than One Fermenter In A Fridge

[michael_aussie]

I've finially purchased a fermenting fridge that hopefully will fit all 3 of my fermenters (fingers crossed).

With a single controller controlling the fridge, clearly I can only have one temperature probe, and therefore only control a single temperature.
I always start the three fermenters brewing on the same day, although I'm sure there will be differences in how active the brews are, and therefore how much heat they generate.

Logic tells me that if I put the probe beside one of the fermenters, I will be able to accurately control the temperate of that brew. However, the other brews in the same fridge will only be "slaves".

When you have more than one fermenter in a fridge, how far do the temperatures of your fermenters drift from your fridge set-point???
Will this be an issue for me?

 

[stux]

I've finially purchased a fermenting fridge that hopefully will fit all 3 of my fermenters (fingers crossed).

With a single controller controlling the fridge, clearly I can only have one temperature probe, and therefore only control a single temperature.
I always start the three fermenters brewing on the same day, although I'm sure there will be differences in how active the brews are, and therefore how much heat they generate.

Logic tells me that if I put the probe beside one of the fermenters, I will be able to accurately control the temperate of that brew. However, the other brews in the same fridge will only be "slaves".

When you have more than one fermenter in a fridge, how far do the temperatures of your fermenters drift from your fridge set-point???
Will this be an issue for me?

I'm planning on using two temperature controllers to control two brews in the one fridge.

I've built a wooden shelf which quite successfully limits the cooling which reaches the bottom half of the fridge. so I can have the top half at 17 and the bottom might be 24...

The plan is to put two large CPU fans into the middle shelf one blowing up, the other down.

I have a heat source in the bottom.

Then one controller will control the fridge and the UP fan for cooling/heating the top brew, and the other controller will control the heat source and down fan for heating cooling the bottom brew...

the idea is to run a warmer brew in the bottom half... but perhaps it will work with both set to the same temp... or maybe it will depend on yeast stage... not really sure...

so, as long as I don't get my temps crossed, it should be fine

I'm building the tempmates right now

 

[JestersDarts]

I Only have one brew controlled at a time - due to a NORMAL sized fridge....you crazy bloke..

however, Ive measured the temp swing with a max/min thermometer, and the temperature of the brew only swings by about 1.5 - 2 degrees at most.

 

[unrealeous]

Also - you can put a small computer fan in the fridge to circulate the air - it will keep the temp profile much more uniform [Edit - and you only use 1 temp controller]

 

[zabond]

I brew two batches at a time with the probe hanging between the two fermentors,regardless of yeast activity the two stabelise after a couple of days and stay within 1* of set temp[check hyd sample temps at each reading]as far as trying to use 2 controlers to monitor two dif brew temps at one time,good luck!!I would like to see your wiring diagram as to how you think this will work and not at sometime having the whole system working against itself an causing a major melt down,it would be easier just to use 2 bar fridges

 

[Sammus]

or stick the probe in a bottle of water, tis was I do, works fine.

 

[QldKev]

I've finially purchased a fermenting fridge that hopefully will fit all 3 of my fermenters (fingers crossed).

With a single controller controlling the fridge, clearly I can only have one temperature probe, and therefore only control a single temperature.
I always start the three fermenters brewing on the same day, although I'm sure there will be differences in how active the brews are, and therefore how much heat they generate.

Logic tells me that if I put the probe beside one of the fermenters, I will be able to accurately control the temperate of that brew. However, the other brews in the same fridge will only be "slaves".

When you have more than one fermenter in a fridge, how far do the temperatures of your fermenters drift from your fridge set-point???
Will this be an issue for me?

I run 2 fermentors in my fridge, one on the top shelf and the other on the bottom. I have the probe stuck to the top fermentor but always leave the outside of it open, ie do not cover it up. This will help measure the heat output of the fermenting, but will also monitor the air temp in the fridge. I also use a 120mm pc fan to blow air from the upper section into the lower section. With the fan running using an external temp measurement they are alway within 1 degree of each other. I think huge temp fluctuations are bad for yeast and result in bad tastes, running this setup you will have a fairly stable environment. The key is keeping the temperature uniform, therefore decent air circualtion is needed. With three fermenters I would also look at 2 x 120mm fans. I like to pitch my yeast warmer than the fermenting temp, and always dial up 1 degree lower for the kick off. Ie for a 18c ferment; pitch warm, set temp to 17 for 12-24hrs, then back to 18. This helps force the temps down a bit faster than setting to 18 as the internal temp of the wort will still be warmer than the sorroundings.

Being up here in qld I don't run a heater, but I think the same principle would apply. Do not have the heater directly in contact with any of the fermentors, and ensure your fan is circulating air past it, and past the fermentors.

QldKev

 

[argon]

I can fit 4 fermenters in my all in one freezer. Whenever I have more than one I just squeeze the probe in between 2 of the fermenters and always run a pc fan to circulate the air. I don't really concern myself too much if I have brews in there without probes attached. The environment is pretty steady and doesn't fluctuate more than 1 degree.

 

[jjeffrey]

When I first started brewing in the fridge, I read many posts on AHB and was fooled into believeing I could adequately control fermentation temperatures by controlling the fridge temperature. I found the practice to be rough as guts. Invariably, the 1st day would (slowly) approach the fridge temperature, but it was so slow that if I didn't pitch within 2 degrees of the fridge temp, I may as well have left the bloody thing on the floor; and if I DID pitch with 2 degrees, the temperature wouldn't budge. Days 2 and 3 would be ALWAYS be about 3 degrees above fridge temp, then it would crash leaving me to deal with diacetyl. Further, every 12 hours, I'd get a 1 degree spike owing to the defrost cycle.

Bugger that.

I do suggest you get yourself a temperature logger from Jaycar or Corke so you can actually see what going on in there.

The only way to control your fermentation temperature is to actually measure the the temperature of the fermetation and control it directly. If you can mount a probe in a fridge, you can do it in the fermenter.

I control my brew by setting the fridge at it's highest normal control temperature (which for me is 8 degrees C), insulating the fermenter with a jacket or a couple of towels, and heating it with a belt heater. The fridge needs to be at least 5 degrees colder than the setpoint for the fermenter. The belt heater is controller by a temperature controller in accordance with a RTD which is located central to the fermenter, about 100mm below the surface. My probe is mounted in the lid via a cheapo electrical gland in the lid which a can use to alter the depth of submersion. The belt heater needs to be around the bottom of the fermenter, just above the yeast cake to avoid any autolysis. If you want details of any of the setup- please PM me. The most expensive part is the temperature controller, followed by the plastic box I put it in. It's a very slow process so relays are adequate (although I use SSRs because I hate clicking noises in the garage). I get fermentation control to +-0.1 of a degree, and have measured +0 to -0.3degrees variance throughout the fermenter volume. The coldest point is about 100mm above the belt at the edge of the fermenter, but the bulk is pretty clost to the measured value.

To do more than one fermenter in the fridge is no problem, you just need a control circuit for each fermenter. I have brewed a pilsner at 9 degrees and an ale at 18 degrees simultaneously in the same fridge. They were both flatline for the duration of the fermentation, temperature wise.

Cheers,

jj.

 

[bignath]

I've built a wooden shelf which quite successfully limits the cooling which reaches the bottom half of the fridge. so I can have the top half at 17 and the bottom might be 24...

the question i'm about to pose, seems to ridiculously obvious to me, that i'm sure i'm missing something here, and as a result, will happily be corrected, but here goes.....

"why would you want to have two different zones in your fridge at 17 and 24?" If you're gonna do ales, then 24 would be considered too hot, 17 may be considered ideal (or very close to ideal). Obviously way too hot for lagers, so i'm not sure what you gain by doing this.

If the two temps you were thinking about aiming for were 10/12 and 18/20, i'd understand, but i'm perplexed by this.

As i said, to me it's an obvious question that has me thinking i'm missing out on something :huh:

cheers,

Nath

 

[jakub76]

To do more than one fermenter in the fridge is no problem, you just need a control circuit for each fermenter. I have brewed a pilsner at 9 degrees and an ale at 18 degrees simultaneously in the same fridge.

Please elaborate. What are your two control circuits doing? One controlling the fridge to keep your pilsner at 9C and the other..? Maybe controlling a heat belt attached to the ale?

I use a shielded lamp inside my fermantation fridge during winter, guess I'd need to get a belt or some heater that was exclusively the ale heater for you're idea to work.

I have heard this concept discussed before but maybe I'm missing something.

 

[stux]

the question i'm about to pose, seems to ridiculously obvious to me, that i'm sure i'm missing something here, and as a result, will happily be corrected, but here goes.....

"why would you want to have two different zones in your fridge at 17 and 24?" If you're gonna do ales, then 24 would be considered too hot, 17 may be considered ideal (or very close to ideal). Obviously way too hot for lagers, so i'm not sure what you gain by doing this.

If the two temps you were thinking about aiming for were 10/12 and 18/20, i'd understand, but i'm perplexed by this.

As i said, to me it's an obvious question that has me thinking i'm missing out on something :huh:

cheers,

Nath

Ciders and Ginger beers like it warmer, but I was actually telling you the max differential that I measured. I currently have a lager at 11C in the top zone, I'll measure the bottom zone too

But the idea is to use fans to modify the zones toward each other. Even if I was aiming for the same ferm temp on both zones, invariably you start two brews on a different schedule and th first few days they generate more heat so you end up with a 2-4C differentual

 

[jjeffrey]

Please elaborate. What are your two control circuits doing? One controlling the fridge to keep your pilsner at 9C and the other..? Maybe controlling a heat belt attached to the ale?

I use a shielded lamp inside my fermantation fridge during winter, guess I'd need to get a belt or some heater that was exclusively the ale heater for you're idea to work.

I have heard this concept discussed before but maybe I'm missing something.

Ok. So if I'm doing an ale, I set the fridge to be at it's warmest via it's own inbuilt thermostat. The highest temperature my fridge regulates at is about 8deg. When doing a lager or pilsner, I set the fridge a bit cooler, say around 4-5deg. I've found I need the fridge to be at least 5 degrees cooler than the controlled set point in the fermenter, otherwise the fermentation can generate too much heat. So far, no use of any extra temperature controllers.

Next, I set (each) fermenter up with it's own temperature probe through its lid and it's own temperature controller, which controls the belt heater(s) for each fermenter. I wrap a bit of light insulation (such as a couple of towels) around each fermenter so that I'm not losing too much heat to the fridge (I want the energy from the belt/s to go into the fermenter, not just be lost to the fridge). There is enough heat loss from the fermenter to the fridge via the towels that the belts need to just top-up the energy in the fermenters to maintain a constant temperature. The Temperature control for each fermenter is independant of each other fermenter's setpoint, as well as the fridge temp.

The key is this: To control temperature via cooling you have to be able to effectively control the evaporation of refrigerant (which typically produces local temps of -20deg C) at specific points around/in the fermenter. This is virtually impossible for the scale a homebrewer works on, so in your fridge you rely on air to transfer and even out heat. Air is really bad at conducting heat, and as such its a very difficult media to use to control your fermenter temperature effectively. It's easy to control it via heating, because you can apply heat by simply turning the belt heater on or off as required, and the heat transfer between the belt and fermenter is (relatively) great. The fridges are just creating a cool environment within which to control the temperature via heating.

I'm in Melbourne, so I don't need the fridge to create the cold environment in winter- I just run the same fermenter belt heat control circuits, but they sit in the garage where the temp is typically 2-8deg. I love winter for brewing.

I think you may find that most of the energy from lamp goes straight out the condensing coil of the fridge, rather than into your brew. Belt heaters are certainly more effective at transferring the energy because of the contact area. They are typically about 11-15W. With suitable insulation, 70% of this energy or more can be utilised for controlling the fermenter temp. I've got about a half a dozen, so if I need to use 2 or 3 at a time on a fermenter I can- this happens when the fridge or the garage is way cooler (like by more than 10deg) than the fermenter setpoint.

Cheers,

jj.

 

[jakub76]

OK...so you're controlling temps exclusively through heating. Setting your fridge thermostat/temp controller to the low fermentation temp then hooking up another controller to a heating belt around your high fermentation temp vessel. I can see how this could work now. Thanks for elaborating :icon_cheers: