Trying to Build Ferm. Chamber

So I have been staring at the computer for days looking at various fermentation chamber builds and I am at a crossroads.
The build I am doing is going to have interior measurements of 44WX27HX24D, which comes out to approximately 16.5 cubit foot. I was planning on cooling it with a mini fridge, but I am concerned that a 4.0 cubit foot fridge just isn't going to cut it.
Can someone give me pros & cons of using a window AC unit for this build? I don't have either a fridge or AC unit, so I have to buy one regardless. Space is an issue, so my measurements aren't able to be changed much as this is going under my workbench.
Any help is appreciated.

If you add the window AC unit on the side, will it cut down on the interior dimensions?

No. The width is the one dimension I can actually increase. The height and depth are predetermined by my workbench, but the length can be increased. It is designed just for 2 carboys with a divider so that I can have dual temp control.

I'm also getting ready to build one and found this thread to be fantastic:
https://www.homebrewtalk.com/f51/my-mini-fridge-fermentation-chamber-build-256068/

I think it has the same size fridge you are talking about.

That's what I'm trying to figure out. Is everyone having success with these mini fridge builds, or should I go big with the window AC unit?

I'd go with a chest freezer and fermwraps. Set the thermostat on the chest freezer to be as low as your coldest lager and then use the fermwaps to raise the temps as needed.

I can't use a chest freezer. Space constraints.

i use two vissani wine cooler fridges and stc-1000's. They fit perfectly under the work bench and fit a carboy in them no problem without any mods. Got the coolers off CL for about 80 each. Could be another option.

Cubit or cubic? A cubit is 1.5 feet

huntb said:

Cubit or cubic? A cubit is 1.5 feet

Click to expand...

Really? pfft

An AC unit isn't going to take up ANY interior space... scroll through the Brew McQ build in my sigline.


Actually.. it starts here: https://www.homebrewtalk.com/f51/beginnings-brew-mcq-251929/#post5466784

Is your workbench in a confined area, or is it in a space with outside access? The A/C will put a large amount of heat out into the surrounding air, so winter in the garage might be a bit warmer inside, but summer in the basement will be an oven. A 16.5 cu.ft. fermentation chamber will definitely need a large amount of BTU's, especially if almost full. I would find an online calculator to figure out how many BTU's would be needed to do the job. It is always better to go a little bigger than smaller, as a unit that is too small may want to run 24/7 to keep up with the heat produced by fermentation.

It is in my garage with no outside access. I live in SoCal, so summer will make for a hot garage with the AC unit.

huntb said:

Cubit or cubic? A cubit is 1.5 feet

Click to expand...

My apologies on the "cubit foot". It was not my intention to use an ancient unit of measurement....

I don't think it would heat things up that much, especially if your closet is well-insulated.

jeetaman said:

I can't use a chest freezer. Space constraints.

Click to expand...

Ok, a mini fridge will be fine here. The main point was don't go the AC unit way.

A mini freezer will work better, it has a much larger cooling coil..
Like this - http://www.amazon.com/gp/product/B000QFDNOE/?tag=skimlinks_replacement-20

Here's my 'Workbench" with the mini freezer in the bottom left cabinet, controlled by an stc-1000. I can maintain a 35 degree variation from ambient temp fairly easy - freezer only cycles 3 or 4 times an hour..

So I also see that most people use an STC 1000 for temperature control. Is there a dummy's guide on how to wire this bad boy up? I'm not an electrician, so some idiot-proof instructions would be awesome.

jeetaman said:

So I also see that most people use an STC 1000 for temperature control. Is there a dummy's guide on how to wire this bad boy up? I'm not an electrician, so some idiot-proof instructions would be awesome.

Click to expand...

There are many I will see if I can dig one up.


ON ANOTHER NOTE.

DAMN YOU ZUBIUS for your *king cool looking cabinetry skills on that... AMAZING.


https://www.homebrewtalk.com/f51/stc-1000-wiring-333680/

An A/C unit isn't going to be very large to cool the space. Usually, 16-22 cube refrigerators that are foamed in place, high density urethane insulated, use a 1/3 HP low temp condensing unit putting out 1.8K-2.5K BTU at -15F evaporator. What needs to be considered is an A/C unit is designed to operate at 55F evaporator. Running the A/C down to 25F evap to get you a 35F space beats the unit up. Same thing happens when running a freezer unit at 35F in the space. Running a freezer at medium temp application never alllows the system to reach equilibrium that it is designed to run within. A mini freezer condensor is usually 1/5HP with 400-600 BTU output at 0F evap. Heat from product respiration is nill with a couple of buckets of brew fermenting. Over sizing is the worse thing to do when it comes to designing refrigeration systems. Biggger is better if it is in the wallet or somewhere else. If you choose an A/C unit, something like 3K BTU will be in the park. The BTU output will be less than 3K when running at a 35F space. Reason: The lower the temp, the less heat available to squeeze out. The lower the temp, the lower the pressure of the refrigerant in the evap. The lower the evap pressure, the harder the compressor has to work to reject the heat. If the ambient temps surrounding the box are going to be 100F and if you are using HD foam insulation, a mini freezer won't keep up with the cooling demand. If you dump the air off the condensor of an A/C unit into the garage it will add to the ambient temp. At 110F air across the condensor, the condensing unit loses 10% of its rated cooling capacity.

Vlad
So is there some calculator we could use to get the right size fridge or A/C unit for a certain size space?
Also, does this mean a coil that is sized for a fermentation chamber to maintain a temp of around 65 deg would not be suitable to lager or cold crash at much lower temps?

What does this mean?

VladOfTrub said:

...-15F evaporator. What needs to be considered is an A/C unit is designed to operate at 55F evaporator. Running the A/C down to 25F evap to get you a 35F space beats the unit up.

Click to expand...

Thanks

Quick question for you all. Is there an "easy" way to make my ferm chamber dual zone? I have a freezer hooked up to my chamber and it's big enough for 2 buckets/carboys with a divider in the middle. My thinking was that if I installed a fan in the lower corner of the divider I could blow cold air into the second "warm" chamber. I could also put a fan in the top of the divider blowing the warmer air back into the "cold" chamber.
Is there already a thread for this somewhere?

Here's mine. I'm able to get a differential between the fridge and second (middle) chamber that is suitable for fermenting a lager and an ale at the same time. The third zone is not temperature controlled at this time and I just use it for aging.

https://www.homebrewtalk.com/f51/my-large-fermentation-chamber-cheap-427471/

For whatever it's worth you can check out my dual chamber build in my sig.