Venting A/C for fermentation cabinet

[dslater]

Hello -
I am very close to building a fermentation cabinet. I have an old window A/C unti for cooling but I don't have ready access to a window. Can I just let the A/C exhaust to the basement or is that asking for trouble?

Has anyone done this kind of thing?

Thanks,

Dave

 

[Beer_Guy]

Those AC units put off a lot of heat which would build up down there. You need to rig up some way to exhaust it with duct work through a dryer vent or something.

 

[samc]

I think you need to worry about the cooling side freezing up more than the exhaust issues, although that is important. I vent into the garage so no big deal. However I still freeze up the coils in certain situations and it has been an elusive fix for mine.

 

[dslater]

What causes the freeze up on the cooling side -
is it that condensation gets frozen to the cooling fins ?
Does this happen because the A/C is running cooler temps
than it would when cooling a room?

As you can see, in spite of searching this forum and others, I still have a lot to learn

After more reading and thought, I think I may just have to opt for a small cube fridge, although, I'd
really like to use that old A/C for something...

 

[rcrabb22]

When a A/C unit is used for refrigeration the return air recycled through the unit is much colder than it was designed to recirculate and the moisture being removed from the air freezes on the coils and eventually chokes off the cold air flow. Also, the thermostat on the unit is usually bypassed and it will cool the spaces to temps cooler then designed as well.

People have tried several ways to resolve the issue. Some mount computer fans on the inside of the front cover of the unit to blow warmer air on the coils.

Some make use of programmable temperature controllers (like the BCS-460) and program de-ice steps measuring the coil temps and turn off the compressor while allowing the fan to run to melt any ice. Essentially this method cycles the compressor on and off during a cooling cycle so the cooling will take a little longer. Also, this method needs a smarter controller to add waits states to make sure the compressor doesn't run cycle too frequently and ruin it. One person's example uses a 3 minute wait state to protect the compressor.

 

[bmckee56]

Seal your chamber up as air tight as possible. An A/C unit is a de-humidifier and as stated above, it will freeze condensation from the air on the coils. If your chamber does not allow any air to infiltrate, your initial cooling will remove most of the moisture inside thereby decreasing the likelyhood of freeze ups.

With that being said, the primary contains lots of moisture (BEER), right! So now what do you do? Well, most A/C units do not have defrost control on them, so you could shut the unit off periodically to defrost the coil if it begins to freeze up, but that is a pain the butt. An A/C unit can drop the temperature to reasonable fermentation temps. however trying to get them down to lagering temperature will require some level of alteration either to the controller or the persons life controlling the cycles. The best possible solution I can offer is to use a small refrigerator attached to your chamber or a dedicated refrigerator altogether.

Salute!

 

[Moonpile]

I'm building an A/C refrigerated bar right now. My plan is to have an always-on fan inside that can either circulate the air or even blow directly on the coils if I'm having problems. But I've heard that once the area you're refrigerating dries out it's not a problem. Of course fermentation puts off moisture too.

 

[liljimmynorton]

I have an old ac unit mounted in an all styrofoam cabinet that is very sealed. I store it in my garage that is not cooled. While I have an external t-stat controlling power, I did not bypass the internal thermostat. I can run it down to about 50 before the internal t-stat cuts it off. Otherwise I can maintain low 60's very easily with the unit only running for maybe 10 minutes an hour at most. I do keep a container full of water inside as additional internal temperature stability. I am very happy with my results but no lager in my future. Maybe I will bypass the internal t-stat and see what I get.

 

[rcrabb22]

I'm building an A/C refrigerated bar right now. My plan is to have an always-on fan inside that can either circulate the air or even blow directly on the coils if I'm having problems. But I've heard that once the area you're refrigerating dries out it's not a problem. Of course fermentation puts off moisture too.

And every time you open the door of the chamber allows ambient air to enter.

 

[dslater]

Well - I think I lucked out. I've found a $50 fridge on Craigslist - I'll
put the A/C on C/L for $50 and hopefully it will be a wash.

I want to keep this as simple as possible and from the info posted here and elsewhere, it seems like the fridge is the way to go.
I'll try to post some pics as my build progresses -

thanks for all the great info!

 

[samc]

The explanations of the issues above for a/c are pretty darn good and I've got nothing to add. To date my answer has been to get the wort cooled down into the 60's and that works fine, it's when I want to cold crash that I have troubles. I've been able to step the temperature down 1-2 degrees at a time but at some point everything still freezes up. I've tried blocking the front intake with open cell foam to try and warm up the air flow, also using fans, neither of which work for long. Ideally I'd like to find or make some kind of warming coil for the unit to warm the in flowing air, but my skills in that area are lacking.

Your fridge is a better solution - however in my case I have a 15 gallon corny keg fermenter which is hard to fit in your average CL fridge.

 

[Hermit]

I think you need to worry about the cooling side freezing up more than the exhaust issues, although that is important. I vent into the garage so no big deal. However I still freeze up the coils in certain situations and it has been an elusive fix for mine.

Companies sell 'fix kits' for AC's that are nothing more than disk thermostats that clip to the evaporator and open at 35 degrees to keep the coil from freezing up. They go in line with the unit's thermostat.