A/C Unit for a Ferm Chamber - How cold can you get?

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

JayInJersey

Supporting Member
HBT Supporter
Joined
May 22, 2009
Messages
595
Reaction score
1
Location
New Jersey
For those of you that use an A/C Window unit for the cooling of your Ferm Chamber, how cool can you get it?


I ask as I'm considering using one on a chamber I plan to build in my garage but my window unit has its own temp gauge and only goes to 60*.

And if I figure on the average of a 5* change from ambient to brew it would only be able to cool to roughly 65*...which will probably be fine, but I'd love to be able to pull off a 62/3 now and then.


And while I've got you here...how do you bypass the units internal thermostat anyway? I get how you would do it in a fridge...but the A?C unit never seems to blow cool air right when it kicks on.
Perhaps just set it to the lowest (60* in my case), mount it at the top of the cabinet and let the whole hot air rising and the internal controls handle it?
 
maybe this website will help...

http://franklinbrew.org/members/sj/walkin.html


you could go that route or even open the front side of your AC (depending on brand and design of course) and look for the thermostat probe. See if you can re-route that probe to the outside of your fermchamber.

That way the AC is getting readings outside the chamber and you can use an external controller
http://morebeer.com/view_product/16663//Analog_Temperature_Controller
to keep it at whatever desired temp you want. (Provided that the outside temp is warmer than 60F)
 
No experience with these builds, but my thought would be to get a ranco/johnson/ebay tempertature controller and set it at your target temperature. Then all you need to do is find the air conditioner's built in probe and mount it outside your chamber. This way it'll keep running until your controller tells it to shut down (provided the temperature outside the chamber is higher than the chamber).

Others here might have more elegant solutions for disabling the thermostat entirely.
 
you could go that route or even open the front side of your AC (depending on brand and design of course) and look for the thermostat probe. See if you can re-route that probe to the outside of your fermchamber.

Man, I need to start typing faster.
 
I have a 5000 BTU unit in the brewery and can chill the entire 12x16 space to 50F. It has a built-in digital thermostat and the constant air/intermittent cooling can keep the room within a 2F band when the outside temperature swings 40+ degrees.
 
It if an analog unit, it is realtively easy to find where the thermostat lead goes into the on/off switch. I took a smal piece of copper and simply inserted it into the place where the therm probe used to be. This in essence will make the AC run continuously when it is on. Then I plug the AC into a controller. For some reason my RANCO will not work with it - only the Johnson- not sure why...

If you have one of the AC's that is digital/circuit board controlled, good luck - I tried and have no clue how to disable it.
 
That's impressive david. The unit I hoped to use is 6500 BTUs and the space would only be at max like 4'x3'...I might give it a go and see what happens.

If it doesn't work I'll only be out the cost of the wood...and the insulation...on second thought
 
I was given a 5k window AC unit and built an insulated wooden box around it - big enough for about 5 carboys - I rewired the compressor to toggle on/off with an auber instruments temp. controller + SSR - I've got it holding 50 deg. for a lager I'm fermenting right now. it has no problem getting down into the mid 30's.. I've never tried pushing it lower than that.
 
the link is for my 4x7 walkin that I keep at 38 degrees with a tiny AC unit. I lager in it but mostly use it for bottle storage and it holds the kegs from which I run lines to the bar from. I also have three ferm fridges that I use for fermenting. Two are on regular temp controllers and the third is geri-rigged with two thermostats. One controls the fridge and the second controls a plug within the fridge that I can then plug a heating pad into so I can control temp up or down. I can lager in that fridge but then also ramp up temp with the heating pad to mid-high 80's for things like saisons.


https://cdn.homebrewtalk.com/gallery/showphoto.php?photo=29445&cat=all&ppuser=20497
 
That's impressive david. The unit I hoped to use is 6500 BTUs and the space would only be at max like 4'x3'...I might give it a go and see what happens.

If it doesn't work I'll only be out the cost of the wood...and the insulation...on second thought

You'll make ice with that many BTU's in that small of a space... assuming the coils don't freeze up on the unit first.

If you're going to do ANYTHING with an AC unit, you need to REALLY make sure the vapor barrier is heavy duty (I wrapped my entire walkin with 6mm plastic) or the AC unit will suck humidity right through the wood and your unit will freeze up on you constantly.
 
You'll make ice with that many BTU's in that small of a space... assuming the coils don't freeze up on the unit first.
Really?
The damn thing barely keeps my bedroom 60* during the summer.
I knew size made a difference just not THAT big a difference :drunk:
This thing might work then.

So for a wall "sandwich"

frame-ply-plastic-ply-foam insulation stuff



And to think I was going to consider building a lagering cooler below it with a soon to be decommissioned mini-fridge kegorator.
 
Really?
The damn thing barely keeps my bedroom 60* during the summer.
I knew size made a difference just not THAT big a difference :drunk:
This thing might work then.
.

well... maybe there's something wrong with your AC unit but I only have a 5k BTU unit in my walk in which is about 7 feet by 4 feet... and about five and half feet tall... and that sucker drops down to mid/high 30's in well under an hour starting from room temp. A 5K BTU unit will chill a closet or a cabinet like you're talking about really quickly.

Really?

So for a wall "sandwich"

frame-ply-plastic-ply-foam insulation stuff

.

pretty much... I went plywood-plastic-frame-foam insulation (the 2 inch thick extruded foam boards) and then just left that. The walls inside my walk in aren't finished. Never really has a reason to finish it other than the ;looks nice' factor... which... I haven't cared too much about for that.
 
Isn't there a post where a guy put computer fans on the front of the evaporator coil (fins) to prevent icing?
 
If you're going to do ANYTHING with an AC unit, you need to REALLY make sure the vapor barrier is heavy duty (I wrapped my entire walkin with 6mm plastic) or the AC unit will suck humidity right through the wood and your unit will freeze up on you constantly.

Out of curiosity, did you wrap the walking inside the studs (on the walking cooler side) or the outside of the studs (exterior room side)?
 
Out of curiosity, did you wrap the walking inside the studs (on the walking cooler side) or the outside of the studs (exterior room side)?

I framed the walls, wrapped the outside of the frame with the 6mm plastic and then laid the plywood over the plastic, for the outside of the wall... so it goes plywood, plastic, frame...

and then I cut the extruded foam boards to fit in between the 2x4 framing on the inside and just tacked them in. Works like a charm.


... and yes you will need to figure out how to keep your coils from frosting up if you are planning on keeping the temp down around 40 or lower.

The computer fans is a great solution.

What I did was I wired my AC unit's fan to run 24/7. It's been running for about two years now. It's a tiny fan and no, it hasn't driving my electric bill up really high (no more than the computer fans would).

I then wired the compressor on the AC unit to a thermostat so that is really the temp control. Once the walk in reaches a certain temp, the compressor kicks off but the fan stays on... which defrosts anything on the coils.

The one area I have to pay a little attention to is cleaning the walk in or doing some sort of bulk keg change, where the door is going to be open for a while. Just having the door open with all of those kegs/bottles and everything will get a ton of condensation on it almost instantly. When that happens, the coils will freeze up quickly....

so I just step the temp down with the unti. If it is 60 degrees, I'll set it for 50... let the AC unit bring the temp down (ten minutes) and have the compressor shut off and it defrosts... then I'll set it to 45... same thing... then 38ish... same thing.

If not... the compressor running that long would freeze up the coils no matter what you do.
 
Back
Top