Coolbot Review

I’ve been meaning to write this review up, and was prompted to do so by another post today. Disclosure: No financial connection or anything similar.

Some of you here have probably heard of the “Galli” method and the “Mighty Kenmore”, the basic idea of which is to “trick” a normal window air conditioning unit into cooling below its typical minimum of 60-64 degrees. It’s easy enough to do with a resistor, a transformer, a bit of soldering and electrical tape, plus some experimentation to get the temperature right. In fact, I did that myself for a couple of years. But after a frozen window AC unit and difficulty keeping the cellar temperature consistently around 55 degrees, I took a flyer on the Coolbot, which is available on this website for $299: You can read on the site about the genesis for the idea, which was to allow farmers to create cheap cold storage based on the same principle: window AC units are able to cool well below typical comfortable temperatures for a room, and are cheap. In other words, the same reason why some of us are using window units to keep our precious wine at the right temperature.

The basic idea is the same as the Galli method, but it’s automated and doesn’t require any real effort to set up. Here’s what the unit looks like:

The Coolbot has three wires (each using a minijack). The first is a temperature sensor to determine the ambient temperature, in order to call for cooling at appropriate times. The second wire is taped together with the temperature sensor from the AC unit, and supplies heat to the temperature sensor in order to call for cooling (i.e., the AC thinks all of a sudden the temperature is 90 degrees). The third wire is a temperature sensor that is tucked into the cooling fins inside the front of the AC unit, in order to detect if the fins are starting to frost up. If they are, it overrides the call for cooling so that the AC doesn’t ice up. The Coolbot plugs into a household outlet using a wall-wart transformer.

Here’s a wiring diagram:

The AC unit is set to the lowest setable temperature, with the fan on high or auto. The Coolbot is set to the desired cooling temperature. And away you go . . . (the Coolbot has some adjustments that I haven’t found to be relevant regarding delay for icing and so forth).


I’ve been using the Coolbot since mid-Fall. It was very easy to set up, and can easily be undone if you want to return it (you’ll end up with a slight bend from the fin sensor in the fins, but nothing you’d see with the cover on). The interface is perhaps slightly less user friendly than one gets in this day and age of Nest thermostats and iPhones, etc., but it’s really not that important once you’ve set it, and the instructions are quite clear on how to change the various settings if you want to tinker. The quality of the unit is solid - I don’t think this is a large production device, so it does have a bit of hobbyist/Radio Shack look, but the quality of the bits is great and the fit/finish is excellent. It’s not meant to be a design statement, but rather a functional control unit.

The Coolbot has kept the temperature of my cellar at the setpoint of 55 within +/- .3 for liquid (with bottle probe) and about +/- 1.5 deg for air temperature, regardless of the temperature in the surrounding basement (which fluctuates more with seasons). I have yet to see the AC unit freeze up or have even some frost. I have the fan blowing constantly (as recommended by Coolbot) but the compressor is running only a small portion of the time. I’d prefer it to keep the air temperature a bit more consistent, but it has been within the claimed variation in the instructions and on the website. Of course, air temperature is less important than liquid temperature, so it’s not much of an issue. Ideally, however, one could adjust the acceptable deviation to a lower number.

$299 is a bit pricey, which I think reflects that there’s not a huge market for this and the inventor is trying to recoup what likely took a lot of experimentation and some relatively high costs to get these items fabricated. If you prefer to tinker with the Galli method you can do it for a lot less in parts, some amount of time (your value may differ) and end up with a less attractive look (which may not matter). Or you can buy this and get it all ready for you and spend 5-10 minutes setting it up. Having been not entirely satisfied with my own efforts at the Galli method, I turned to this and am quite happy.

Good summary…

I know how the unit operates with the two probes modulating the compressor, but I can’t figure out how this unit can get the A/C to produce sub 40 degree temps without it freezing up (or at least has a lower limit that the A/C can attain without freezing up)

Especially with the Coolbot’s claims of reduced cycling…

Since I’m 64, I set my cellar at 59 degrees to somewhat accelerate the aging process.
Hence, my fooler circuit method works fine for me and I have no need for this device.
But for people who want to use a room A/C and get the temps at or below 55, this device looks VERY interesting…


I am writing from CoolBot (we created an account at Paul’s suggestion yesterday so we could answer here).

AndrewH: That’s a great and thorough review! Thank you so much!!

Paul, to explain about avoiding freeze-ups: The front fins of the a/c unit will always (eventually) freeze up. What we’re doing with the second sensor is catching it right before it happens and cycling off the compressor off so it can recover… then turning it back on when it’s safe again. Using that method it’s easy for us to step down to even 35F if you want.

Andrew: You can adjust the sensitivity to air-temperature room fluctuations up, but not down… So… like you could allow MORE than 1.5 degree fluctuation of air temperature, but you can’t do less.

We could change that I guess… but even in small rooms, because of air movement, we’ve noticed that temperatures vary at least that much so it doesn’t seem prudent or we’ll end up with short-cycling.

Air temperature changes faster up high in the room than lower-down, so a way to get the same “more sensitivity” effect would be to move our room-air temperature up higher to catch the 1.5F temperature change more quickly. Mostly our wine and beer people are fine with greater air fluctuations, it’s the liquid that concerns them (as you mentioned Andrew).

re: a previous post from PaulMills about exhausting the back of window/through-wall air conditioner outside (which isn’t possible in some people’s basements), you could use a “mini-split” air conditioner (CoolBot works great with those).

Exhausting the back of window units even in commercial wine cellars in restaurants with a lot more traffic in and out of the restaurant cooler has been totally fine though.

That being said: I think it would be horrible if you were exhausting into a living level of a residence not because of heat, but just because of noise… I’d definitely go with a mini-split if I had to be inside a residence and couldn’t put it in the basement.

Please let me know if I can answer any other questions!

Katie (and Ron) at CoolBot

I saw that in the literature and settings, but of course doesn’t go in the right direction for me. You might consider allowing for smaller fluctuations, but leaving the default as is.

For what it’s worth, when I was using the resistor approach the air temperature fluctuations were much smaller, at least in the short term (the problem was the longer term). I don’t think the AC was short cycling in my environment (I could hear it) - it just doesn’t need that much cooling, and I think with the Coolbot it blasts cold air for a period, which overcools slightly, and then cuts off until it gets up there again.

Is it fair to assume that the lower the desired cellar temperature setting, the more the compressor cycles On/Off?


Andrew 1.5º +/- air temp is not something to worry about, and as Katie says, short cycling would occur if you tried to cut that down. It also may require a better (read more expensive) thermostat. My commercial gear has what is referred to as a 1º set point. We maintain 55º, so the air temp goes between 54º and 56º, bottle temp is for all intents and purposes constant.

Hey - if anyone is looking to buy one of these, I got an email telling me they’ll be $30 off on Cyber Monday (Nov. 27) when purchased from Amazon. I’m supposed to get a coupon code . . . let me know and you can use the one I’ll be sent to share with friends.

Follow-up on this - can anyone give a longer term review? I’m considering the possibility of building a small cellar in the crawl space under our house. This seems like an interesting option.

Mike - Original poster on this, but it’s still working as described. Air temp has been within 1.5 degrees, usually less, over time, and liquid has shown <.5 deviation. AC unit is going just fine. Based on my experience I’d still recommend it. Just to show my confidence, I recently mounted it to the wall with screws (I’d just had it propped up on a rack) - that’s commitment because I’d have to fill the holes if I ever removed it.

Only challenge I’ve faced, and I don’t know if it’s AC or a result of interaction with coolbot is that the AC doesn’t seem to remove a lot of moisture. In summer, I get humidity over 80%, and no dripping from AC - I didn’t have this problem with previous setup, which was a different AC and the “Galli” method of using a small transformer to heat the temperature sensor (but that approach created different problems).

Thanks Andrew - I remember reading about the Galli method way back on the ebob forums, but my electrical engineering skills are non-existent.

Sorry - one other question, what size room are you cooling and how many BTUs is the AC unit?

I missed this the first time around, but let me say two things: (a) it’s a great idea for someone to produce these things commercially (and I bet the margins are terrific!); and (b) I am the proud owner of a Galli Original (willed to the Smithsonian when my cellar and I are no more) and I could not be happier. I am on my 3d window a/c (this one just finished its first summer). Like the cooling units in the big split systems, they don’t last forever, but I am extraordinarily happy with the results and extraordinarily grateful to TTT for his kindness in setting me up lo those many years ago.

About 700 cu ft., using a unit that’s 5800 BTU (I think - maybe it’s 6500, but it’s the smallest size). Ambient temp outside the cellar ranges from 65-75 (winter to summer). Plenty of insulation.

This is really cool. I intend to build out a cellar when I remodel my basement in the next year or 2 and this looks like a great option.

Question regarding AC units - is an off the shelf / standard window AC unit much noisier than one of the ones specifically made for wine cellar installs? The unit will end up being through the wall into the garage, so it doesn’t need to be super quiet. But our bedroom is right above the garage and I don’t want to hear it going on at night when the rest of the house is quiet. I have been looking and don’t see much info on noise/dB levels for standard AC units.

I can’t comment on wine cellar units, but my window AC I’m using is pretty quiet in this way. I have it in a basement WC, which happens to be below our kitchen and family room. I cannot hear it running when in those rooms, except if it is totally quiet and then I’ll hear a relatively low hum when it’s running full (compressor and fan) and almost nothing if just the fan. There’s no insulation between the floors (other than the ceiling of the wine cellar).

So, in your situation I imagine you might hear it in the bedroom at night (I can hear our outside AC units then too), although if you have insulation between garage and bedroom (which you may well) then I’d worry less.

FYI - just got an email that Coolbot is planning a 10% off Black Friday deal from Nov. 24-27.

Awesome - I was hoping that would happen. I just ordered an LG 8000btu cooler on Amazon Warehouse Deals for $170. I’ll be starting a thread on my ‘extremely inexpensive garage cellar project’ in a few weeks. Early calculations look like 650 bottle storage for about $1600 all-in.

I use a Coolbot for our tiny winery barrel room. Works perfectly - in contrast to a prior setup with a 5000 BTU AC wired to a Johnson controller (bypassing the thermostat to run the AC below 60F). With the prior setup the AC froze repeatedly, especially around harvest time when the door was opened frequently. The Coolbot’s provision to prevent freeze-up (sensor on cooling fins that shuts AC when close to freezing) works perfectly, and this year it never froze.

I’ve used the Coolbot to regulate the room between 54F-64F. It might also work to cold stabilize (40F) but have yet to try it that low.

The Coolbot doesn’t regulate room humidity which could be a factor for cellaring over long periods. Perhaps a separate humidifying system.

Using a coolbot in my cellar with an 18000 BTU Mitsubishi mini split. It was installed slightly incorrectly at first, but since then the cellar has stayed at 55 right on schedule. Best part is that our HVAC people can service my unit rather than dealing with the wine cellar specific cooling units.

It can’t do anything about humidity, but I monitor that and adjust as necessary.

Discount code of 10% is chill10

Supposed to start today on Coolbot website.