Fermenting fridge fan

[markp]

Hey people,
Just about to put a fan from a pc tower in my fermenting fridge, my question is do I have the fan running all the time or connect it to just run when the heat/cooling kicks in ?
Cheers in advance,
Mark.

 

[Jack of all biers]

I have mine running all the time (connected to a USB charger) except when I don't want it too (which is rare).

 

[pcqypcqy]

I'd do it just when the heating/cooling is on, but that's just me. I've always figured the point is to distribute the applied heating/cooling evenly. Once this is done, moving the air around seems pointless, and may increase the energy required to maintain the temperature by more efficiently bringing the heat from the outside in. That said, a normal ferment process uses bugger all electricity so it's probably not a real issue.

 

[MHB]

Let it run 24/7.
There a couple points to running a fan, one is to keep the temperature homogeneous - if the fan isn't running the air in the fridge will stratify, like diving into a lake, warm on top and cold down deeper with a really sharp dividing line between the two.
Another is to keep the air moving over the surface of the fermenter, this takes the heat out of the fermenter - a bit like riding a bike on a warm day, or even sitting in front of a fan, you feel cooler in the moving air, even tho its the same temperature.

You are right it does cost money to run the fan, but you get better/closer temperature control, you also wont need a heater. Heat generated by the ferment and the heat produced by the fan will be more than enough to keep the ferment on temp even in the coldest wether. So the little extra cost in summer is probably offset by not funding a heater in winter.
Mark

 

[pcqypcqy]

Let it run 24/7.
There a couple points to running a fan, one is to keep the temperature homogeneous - if the fan isn't running the air in the fridge will stratify, like diving into a lake, warm on top and cold down deeper with a really sharp dividing line between the two.
Another is to keep the air moving over the surface of the fermenter, this takes the heat out of the fermenter - a bit like riding a bike on a warm day, or even sitting in front of a fan, you feel cooler in the moving air, even tho its the same temperature.

You are right it does cost money to run the fan, but you get better/closer temperature control, you also wont need a heater. Heat generated by the ferment and the heat produced by the fan will be more than enough to keep the ferment on temp even in the coldest wether. So the little extra cost in summer is probably offset by not funding a heater in winter.
Mark

I don't disagree, I just don't see it as being significant at our scale and our temperatures, and with our temperature monitoring equipment and probe positions.

 

[RobW]

Is there an optimal level to have the fan - top, middle, bottom?
Or doesn't it matter?

 

[markp]

Thanks for your input guys, much appreciated

 

[pcqypcqy]

Is there an optimal level to have the fan - top, middle, bottom?
Or doesn't it matter?

I'd say it doesn't matter so long as it moves the air around.

 

[MHB]

I don't disagree, I just don't see it as being significant at our scale and our temperatures, and with our temperature monitoring equipment and probe positions.

Well in truth that's exactly why it matters. The smaller the batch the tighter the requirements for temperature control (it takes much less heat to make a bigger change).
I think you need to go and do a bit more seeing (or better yet thinking)!
Mark

 

[pcqypcqy]

Well the proof of the pudding is in the eating, and my beers taste fine.

There's too many variables in our set ups, especially in how the probe is placed and accuracy of said probe / controller.

People who think they're controlling to 0.3 or 0.5°C are kidding themselves.

 

[MHB]

You are actually saying two contradictory things.
First up the argument that "my beer tastes fine" isn't really all that useful, it's predicated that your taste isn't too far up your pucker (evidenced every time people put beers in comps - results often don't reflect personal expectations). Sure brewing is pretty forgiving but the better your control the more you can fine tune your beer to suit your taste and most importantly to good brewing to be able to reproduce the beer.

By running the fan intermittently you actually increase the variation in temperature, saw tooth on a graph, no matter where you put the sensor, if the fan isn't running the air heated by the ferment will rise, will form a layer, will heat up the "fabric" (what the fridge, fermenter... is made of) it will keep heating until the boundary layer is pushed down to the sensor location.

Go have a look at commercial fridges operating in every shop in the country, they all have fans running constantly, some of the more modern ones actually turn the fan off when the door is opened. They run the fan so the product is all at the same temperature and so that warm product put in the fridge cools down as fast as possible.

Without a fan it is pretty common to have a 5oC difference between the top and bottom of a fermenting or keg fridge. with a fan there should be no measurable difference. No matter how accurate (or inaccurate) your sensor is or where it's placed a fan will give you tighter control.
Mark

 

[pcqypcqy]

You are actually saying two contradictory things.
First up the argument that "my beer tastes fine" isn't really all that useful, it's predicated that your taste isn't too far up your pucker (evidenced every time people put beers in comps - results often don't reflect personal expectations). Sure brewing is pretty forgiving but the better your control the more you can fine tune your beer to suit your taste and most importantly to good brewing to be able to reproduce the beer.

By running the fan intermittently you actually increase the variation in temperature, saw tooth on a graph, no matter where you put the sensor, if the fan isn't running the air heated by the ferment will rise, will form a layer, will heat up the "fabric" (what the fridge, fermenter... is made of) it will keep heating until the boundary layer is pushed down to the sensor location.

Go have a look at commercial fridges operating in every shop in the country, they all have fans running constantly, some of the more modern ones actually turn the fan off when the door is opened. They run the fan so the product is all at the same temperature and so that warm product put in the fridge cools down as fast as possible.

Without a fan it is pretty common to have a 5oC difference between the top and bottom of a fermenting or keg fridge. with a fan there should be no measurable difference. No matter how accurate (or inaccurate) your sensor is or where it's placed a fan will give you tighter control.
Mark

I take your point about commercial fridges but these are huge spaces with very concentrated application of cooling. They need the fans to circulate the air otherwise one corner of the gian space will be cold and the rest will be warm.

In a tiny fermenting keezer, I don't think this effect is as pronounced. I put my kegmenter in my small freezer and have about 100mm clear all around.

My other point is that in such a confined space, all of the heat exchange mechanisms will be at work, but radiation will be much more significant in a small space (c.f. a larger fridge or a commercial fridge / cold room). Convection will always be at work, both in the wort and the air surrounding it.

I haven't adopted a fan in mine because I haven't needed to. To be honest I haven't measured the temperature gradient. I will do so for shits and giggles.

I dont' disagree that the top of the ferment fridge / freezer will be warmer than the bottom. What I question is whether this is significant to what we're trying to achieve.

I know what you mean about every idiot on here saying their beer tastes fine to them, but I'm relying on the much more experienced palates of my club and QABC / AABC judges.

 

[markp]

Gotta say after reading the for’s as opposed to the against’s and the cost of running a 12v fan (basically zero) why wouldn’t you run it 24/7 ? Gotta be better to have consistent temp in your fridge !

 

[pcqypcqy]

Gotta say after reading the for’s as opposed to the against’s and the cost of running a 12v fan (basically zero) why wouldn’t you run it 24/7 ? Gotta be better to have consistent temp in your fridge !

You're right of course. It really doesn't matter.

I just don't do it in my keezer because I think it brings the heat in from the lid and sides more efficiently and so causes more on/off cycles of the compressor, and I've applied the same logic to my ferment chamber.

I'm coming from a place where I don't have a fan because it's one extra thing to worry about, power, move out of the way, etc. Keep it simple.