Ferm Chamber - inside or in garage?

Trying to decide the best location for my fermentation chamber (Minifridge + small ceramic heater w/dual-stage controller)

Either inside the house (steady 70* ambient)
or
In the garage, (~40* in the winter, but much more variation)

Which is more power efficient? Using the fridge compressor to cool ~10 degrees or using the space heater to raise ~20 degrees, on average...

in the house is going to be most efficient because the external temp is going to be always closer to the internal temp you want to set.

that being said, if it's not going to be 90 in the summer and 40 in the winter, i think you'll not see much noticeable change in the power consumption because a fridge is built to be an insulated box. so i say put it where it's most convenient with regards to your brewing and where SWMBO is happiest with it.

Thanks, good thought that it won't make much of a difference either way.

I realize that other things equal, the option with the smallest temp differential would obviously be more efficient, was just thinking that a small heater draws far less power than a fridge compressor.

And either spot is just as convenient - out of the way so SWMBO has no preference.

If you run a refrigeration unit with low exterior ambient room temp you risk ruining the compressor. Appliance Talk: Refrigerator in the Garage

william, how does running the compressor less hurt the fridge? obviously he won't need cooling in the winter months, just heat from the heater. he doesn't care about the freezer temp (which his little mini-fridge doesn't even really have), he just wants a set temp in the ferm chamber.

Great article. Not clear why I risk ruining the compressor though?

Yeah unless you are looking to cold crash in it you shouldnt have a problem running it in the winter. That article you linked to talks about using the fridge at normal fridge temperatures, not 60-70F like youd be using for ales.

I keep my ferm chamber out in the garage, with a window AC unit to cool and a small space heater to chill. In the winter I unplug the AC, and in the summer I unplug the heater. Its been working fine for me lately!

TyTanium said:

And either spot is just as convenient - out of the way so SWMBO has no preference.

Click to expand...

Which spot is going to be more convenient for you, or tick the woman off less, when the blow off jar overflows and leaks out onto the floor?

TyTanium said:

I realize that other things equal, the option with the smallest temp differential would obviously be more efficient, was just thinking that a small heater draws far less power than a fridge compressor.

Click to expand...

If you really care, given similar temp diffs, the refrigerator will remove the heat using less energy than a resistive heater will add heat. Refrigerators (heat pumps) have a COP, commonly around 2, which you multiply the energy input by to get how much heat is moved. The motors and cycle aren't 100% efficient, so some heat load will be added to the room. The closer the ambient is to the desired temp, the higher the COP. However, whether heating or cooling, the costs for your application are so low, it doesn't really matter.

That article really has no bearing on your use, assuming you are using a temp controller going off wort temps, and not using the freezer portion to hold vaccines to save a village in Alaska or something. As I mentioned above, in general, the lower the ambient, the better the fridge performs.

Outstanding, thanks for the detailed response.

And I guess I'll have to throw out my village-saving vaccines.

TyTanium said:

And I guess I'll have to throw out my village-saving vaccines.

Click to expand...

Darn, I forgot to include the liability exclusion waiver with that advice. So I guess I am on the hook for the dead villagers?

I blame myself, really.

I shoulda known when I saw water dripping out. But, I now know ~45* ambient is where the freezer section ceases to freeze, as the above-referenced article indicates.

PS - My wife has family in Austin - love it down there.

If you have a temp controller (digital switch) installed you can place the probe where ever you want. If you want the freezer section to freeze you can make it happen. That said, you won't need to.

The electric heater will be more efficient that the cooling cycle of the fridge. Resistive heating is very efficient; energy goes in and is converted to heat. A refrigeration cycle relies of phase changes and mechanical compression ( both larger efficiency losses). Either way the cost benefit is nil in our case (provided the fridge is newer-ish, old fridges can be terribly inefficient).

As was mentioned above, I would put it as close to where you are brewing as possible and where cleanup is easy. You will eventually have beer all over that thing and the surrounding floor. It is awesome if you can just take a nasty towel followed by a mop to the area. On the same note, try to arrange the inside so it is easy to clean.

Another consideration: if the ambient temp is very near or exactly on your set temp, the resistive heater would be a much better thing to have operating. You could potentially run into a short cycling situation there. If your controller has a cycle timer, that may be a good option to use if that situation comes up.

Juubesan FTW.

-Tyzokun

Boerderij_Kabouter said:

If you have a temp controller (digital switch) installed you can place the probe where ever you want. If you want the freezer section to freeze you can make it happen. That said, you won't need to.

Click to expand...

The whole freezer thing is just a joke from the earlier cited article. He is using a dorm/apt fridge just for ferm'ing, if I recall correctly. You may have to trick/disable the original sensor if you want to crash at maximum, though. I am having that issue right now while trying to crash with a fridge, since the fridge thermo prevents if from running even though it hasn't reached the controller set point. I could cause the evap to ice over if I override the sensor, though. All the more reason to get another chest freezer and mount a fan inside for better transfer.

Boerderij_Kabouter said:

The electric heater will be more efficient that the cooling cycle of the fridge. Resistive heating is very efficient; energy goes in and is converted to heat. A refrigeration cycle relies of phase changes and mechanical compression ( both larger efficiency losses).

Click to expand...

I question that, and submit as evidence the heat pumps commonly used for domestic heating. They are rated as being more efficient than resistive heating, and resistive heating is ~100% efficient. Heat pumps are only more efficient than resistive heat when used in temperate areas, or with ground source heat exchange for colder climes. The Carnot cycle doesn't make cold, it only moves heat. Look up Carnot cycle and COP. It would depend on the efficiency of the motor, though, so a really old fridge may not break even, even if its ideal COP is >1.

Boerderij_Kabouter said:

Another consideration: if the ambient temp is very near or exactly on your set temp, the resistive heater would be a much better thing to have operating. You could potentially run into a short cycling situation there. If your controller has a cycle timer, that may be a good option to use if that situation comes up.

Click to expand...

In this scenario, there isn't really an issue with short cycling, in the sense of coming on very soon after a run cycle, or 'hot' cycling as the more proper term, which is what the Anti-Short cycle Delay (ASD) setting is used to prevent. It will also actually cycle less often, since the heat transfer to ambient will be very slow.

As long as the sensor is in/on the wort (or wherever, but on the vessel wall is best) with a similar diff setting, the length of the cycle will be similar regardless of ambient, although the COP will be more efficient at lower ambient temps, so the compressor won't have to run as long to reach temps. Probably a small difference in real world use, though.

Running for short times isn't really an issue. Running for many periods of short duration, instead of fewer and longer ones, is an issue. That can really only be solved by the increasing the temp differential setting, which would be a trade-off regarding ferm temp stability. Adding more passive thermal mass will also help.

With refrigeration and non-active ferm periods, there is a weird control situation when the ambient is barely higher, or within the setpoint + diff. The wort spends much more time at the upper end of the range before triggering, throwing off back of the envelope calcs to determine avg temps. As long as your diff is small enough, it shouldn't be an issue. If it is, there are medications that can help with that.

That said, you can get much more stable and precise temps by using resistive heat in cold ambient, instead of refrigeration in hot ambient. This is because the heat input power can be varied much easier, and the temp diff can be made infinitely small if an SSR is used. It can even be PID'd for even tighter control, but again, there are meds that can help with that.