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-   -   Ferm chamber: A/C unit keeps freezing over (http://www.homebrewtalk.com/f51/ferm-chamber-c-unit-keeps-freezing-over-182238/)

ThreeTaps 06-13-2010 02:58 PM

Ferm chamber: A/C unit keeps freezing over
Hey all,

My A/C unit worked fantastic 7 months ago in my last 4 brews. Yesterday, I turned it on again (checked it a week ago, blew cold air) to cool my Centennial Blonde and after being on for 11 hours, i check it. Very little airflow coming out, and ambient temps were 69^F. I pulled it out, took the front and cover off, and everything (well, all the front coils and the compressor) were completely frosted or frozen over. Seeing as this is a crucial time in the yeast activity, I took two strong fans to it and defrosted it in about 30 minutes. After drying up all the water, I put it back in. Blew cold air again with a strong airflow. This morning, I check it again (7 hours later), and it's still on but the airflow is weak again, meaning it's frosted over again. The ambient temp is 62^F and fermometer says 66^F, so the beer should be happy right now at around 67-68^F, but I need to get this thing under control.

ANy ideas of what might be causing this? The filter is clean, no buildup on the coils or anything, and it does blow cold air when defrosted. Is it simply time for a new A/C unit? This one is 2 years old.

x2wdtoyotax 06-13-2010 03:24 PM


This eHow has some good info that you might want to consider. It looks like it could be a couple of things.

ThreeTaps 06-13-2010 03:26 PM


Originally Posted by x2wdtoyotax (Post 2109512)

This eHow has some good info that you might want to consider. It looks like it could be a couple of things.

Thanks for the response. I did see this site (as well as probably 20 others last night), and aside from checking the coolant or hiring a professional, everything else checks out. The cost of a pressure guage and some coolant, or the cost of hiring a professional, doesn't really justify simply replacing the unit with a new one for $99 at sears :)

x2wdtoyotax 06-13-2010 04:46 PM

Another thing you could try... evac the moisture from the lines. Harbor Freight sells and automotive A/C evac pump for pretty cheap.


I am no A/C expert by any means... so who knows if the R134 or R12 fittings will match up... but for 9 bucks it might be worth trying. * Assuming you have an air compressor with enough power.

ThreeTaps 06-13-2010 05:42 PM

Well, I went and bought a new one from Wal Mart:


It's manual, so I don't need to rewire anything this time, which is quite nice. I've got it installed and cooling the ferm chamber now. Anybody think I'll need to do any kind of modification to it? It only has a mechanical knobs that say 'High cool", etc, and for the cooling level it's 1-7. I have it set on high cool for level 7, and the temp controller is controlling the power to it. I shouldn't have to do anything special to keep it running while the temp controller is above the threshold, right? My last one I simply hardwired it so that the compressor and fan were on as long as there was power to the unit (which sucked, since it had an on/off button and digital display). I just hoping that the "high cool" setting isn't going off of a temperature probe that may cut it off too soon, though I don't think that's the issue (the unit is on top of the ferm chamber, blowing air in).

ThreeTaps 06-13-2010 06:02 PM

Dang, just went in the garage and the compressor was off though the fan was on high. I wonder if this is controlled by a temp probe that I can lengthen to outside the chamber, or by an internal mechanism to keep the coils from freezing.

Anybody with more knowledge on A/C units able to chime in here? Think it would be bad for me to extend the probe (assuming it has one) outside the chamber, so that only the temperature controller controls the inside temps, not the built-in A/C one (again, assuming it has one).

EDIT: Ugh, can't find a wiring diagram anywhere. Model number is AEV05LN by GE.

kladue 06-13-2010 07:02 PM

The problem you face is as the chamber is colder than the surrounding area moisture flows in and builds up, then freezes on cold evaporator coil. The evaporator coil tubing runs below freezing in allmost all of the window shakers, so the longer it runs to cool the space the more ice will form. The best advice I can offer is to try and seal any openings that let outside air into chamber to reduce moisture inflow, and use a dehumidifier to control chamber moisture level. Commercial cooler use split systems and heating elements to defrost inside coil.

mmurray 06-14-2010 12:58 AM


Here is an option! It also goes into detail to explain the issue you are having.

Good Luck


How It Works
“Normal” walk-in cooler compressors sell for $2500 + installation – which in our area is another $1000, not including electrical. They use a “brute-force” approach to cooling: using LOTS of coolant (which is bad for the environment), a big motor, lots of surface area and multiple fans (which dry out your vegetables and end up accounting for up to 60% of the cost of operating electricity.).

Here's the crazy thing: that $2500+ walk-in cooler compressor you see on a small 8' x 8' vegetable cooler may only put out 8,500 BTUs of cooling power! That's less than you get from a $300 window air conditioner from Home Depot!

It's not quite that simple, though. Here's the problem with window air conditioner units. First, they are electronically limited so that you can't go below 60 degrees. With some electrical bravery and skill, you could snip, solder and bypass the electrical controls so you COULD go lower. It will work better, but still not very well, because while BTU's are BTU's (it's a strict measure of cooling/heating capacity), your ability to actually ACCESS that cooling power drops drastically as you approach only 60 F. This is because you don't have the fans and extra surface area built into normal walk-in cooler compressor/condensor/evaporator units which dissipate the cold without freezing up.

That's where CoolBot comes in! CoolBot uses new (2006 patent pending) technology to replace the brute force approach of fans and surface area with a micro-controller "brain" that intelligently interfaces with your air conditioner - controlling and co-ordinating its output so that you can access nearly all your cooling power, even as you keep temperatures in your walk-in cooler (or any highly insulated room) in the 30's without re-wiring and without any freeze-ups.

The CoolBot is NOT just a thermostat. The CoolBot uses multiple sensors and a programmed micro-controller to direct your air conditioner's compressor to operate in a such a way that you can run at whatever temperature you want without ever freezing up. And our innovative interface linking the CoolBot controller to your air conditioner allows for 2-minute installations without any training, cutting, soldering or even taping.

The multiple sensors and microcontroller allows the CoolBot to work even during the heat of summer and even when people are opening and closing the door all day long and EVEN if they accidentally leave the door open! (Obviously CoolBot can't get you down to temperature if the door is left open for hours, but it can do the best it can without freezing up the fins of the air conditioner so that when you DO close the door, you'll be able to quickly recover to the right temperature.

CoolBot cannot give you 100% use of the listed BTUs on your air conditioner. You need to buy a 10,000 btu a/c unit even when you could have gotten away with an 8,000 btu walk-in cooler compressor (and we would encourage people to get a 12,000 btu unit. It's not necessary, but it's nice to have the extra power). The price of even a large a/c unit is still a fraction of the cost of a real walk-in cooler compressor.

Most importantly, when it can't access your BTUs of cooling power, CoolBot is programmed to shut off the compressor on your A/C unit, so you do not pay for electricity to make BTUs that you can't use! That saves you money and helps the environment. As long as you sized your air conditioner correctly, you'll have no problem keeping your room as cold as you want it to be.

Here's a chart showing the size of A/C unit we ideally recommend to cool a well-insulated room. (Meaning you have at least 4" of styrofoam in walls, ceiling and floor which is the "industry standard" for walk-in coolers).

Dimensions of Cooler Size of A/C Unit
6' x 8' 10,000 BTU
8' x 8' 12,000 BTU
8' x 10' 15,000 BTU
8' x 12' 18,000 BTU
10' x 12' 21,000 BTU
10' x 14' 25,000 BTU

ThreeTaps 06-14-2010 02:07 AM

Wow, very cool! I might do that if it gets to the point where I can justify the $300 for the CoolBot.

For now I'll watch my fermometers and see how they go. I always give the wort an extra 2^F from what the fermometer says (ex: fermometer says 66, wort should be 68). Even with the compressor turning off frequently, it's staying at 64^F ambient, so I think that should be OK unless I'm fermenting a very active yeast strain (I'm guessing about a 4-6^F increase of temp for the wort compared to ambient).

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