Wort chiller from AC unit

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hook_dupin

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I just moved to the California desert, and I'm trying to cut down on my water-usage during the brewing process. Even by using prechilled water for my immersion chiller, I still run the hose for 10 min at a guesstimated 5 gal/min. I've just purchased an old window air conditioning unit so that I can drop the evaporator coils into my wort. The biggest issues I can see is making sure all the evaporator plates are properly sanitized and not damaging the evaporator plates.

Anyone have any thoughts, experience, or war-stories to share?
 

Brew-Happy

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I just moved to the California desert, and I'm trying to cut down on my water-usage during the brewing process. Even by using prechilled water for my immersion chiller, I still run the hose for 10 min at a guesstimated 5 gal/min. I've just purchased an old window air conditioning unit so that I can drop the evaporator coils into my wort. The biggest issues I can see is making sure all the evaporator plates are properly sanitized and not damaging the evaporator plates.

Anyone have any thoughts, experience, or war-stories to share?
You could continue using the immersion chiller with a recirculating pump in a tub of water. Then put the evaporator coil in the tub of water. That way the risk of infection or damage is reduced and you save water.

Put the evaporator coil, pump, and water in a good sized cooler with a lid and you reduce heat capture from the surrounding air.

Just a thought
 

NoNothing

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I would say to just spray the evap down with some star-san before you dunk it in the water. That should sanitize it.

I would love to see pictures of this thing when you have it working.

And +1 on the recirculating pump.
 

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I was planning on taking one of my 5 hp air compressor air temp and moisture condenser seperator units and run the IC thru it with a controllable flow recirculation magnetic drice pump like a March. I know I must modify it preventing condensate moisture from being discharged then run a anti-freeze solution. I have no fear of the anti-freeze breaking thru the copper IC coil getting into the wort, if that's the worry all copper piped houses would be having failures all the time operating at 80 psi years ago. It's an older unit with R12 that has a set 35 degreee F exit temp. Free units nothing lost and simple, worth a try i'm thinking.
 

FlyGuy

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I am certain that your AC unit was never designed to immerse your evap coils in a hot liquid, and I would bet that it will quickly damage your unit. Brew-Happy's suggestion is much safer, although I really don't think that your unit will keep up.

Your better bet by far is to use a recirculating pump and a bucket of ice water. Ice is cheap and safe, and can quickly cool your wort.

There are a bunch of threads on this idea, and here is a good one:
https://www.homebrewtalk.com/showthread.php?t=38235&highlight=chiller
 

CodeRage

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I am with fly guy, and advise sticking it directly into your wort. The system is going to deal with much higher internal pressures than it was designed for. If you are set on using it, do like others say and use it to cool recirculation water in an ice bath.

Just for the hell of it, if the thing should hold up.
there are about 3927 cm3 in 5 gallons of water. 212F to 70F is a 70C difference.
3927*70=274890 calories. 274890 cal/252.16 = 1090 BTUs. So it would take a 5,000 BTU/hr A/C 13 minutes to cool the wort.

I get better results with recirculating with lots of ice and whirl pooling.

EDIT- Regarding your original question, you can sanitize the evaporator like an IC, just throw it in the boil for the last 10 minutes.
 
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hook_dupin

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In a departure from pretty much everyone's (really good and obviously common sense) advice, and as a tribute to scientific method over simplicity, I've decided to test my A/C device. My end goal is to minimize water usage in the brewing process.

The A/C unit itself is a Samsung 12,300 BTU/hr unit, so more than double the output of Virtous's bar napkin calculations

Today was the first test. I started with just hot tap water to test the ability of my A/C unit to handle the cooling load. Technically, I should have had 5 gallons of water exposed to just atmospheric cooling as a control group, but I ran out of buckets.





Here's a quick look at the data from the test:

Starting at a water temp of 120F and an outside air temp of 100F, the A/C unit was able to cool 5 gal of water down to 75F in just under 16 minutes.

That's not the whole story, though. Here's some other observations I made:

-The A/C unit didn't seem to be under stress or strain during the test.

-The simple brewing thermometer I was using remained static and recorded the temp in the upper layers of my simulated wort. I put my hand in the bucket after the test was over and I estimate the water at the bottom of the bucket to be at least 20 degrees cooler than the top layer at the end of my 16 min cooling period

-The compressor took about 2 minutes to kick-on from the time that I pressed the power button on the A/C unit and the cooling rate didn't start to ramp up for another minute or two.

-Finally, only about 60% of the cooling coil surface is exposed to my simulated wort in a standard fermentation bucket (see pic).

A long term recommendation is to switch to a fermenter that is taller and has a rectangular cross-sectional area so that more of my simulated wort will be exposed to the cooling coils.

For Test #2, I will attempt to cool boiling water down to a pitchable temp (75F again). I will also continuously stir my simulated wort in order to achieve more uniform cooling. If you're super-dorky, I will also be determining if this system can be modeled by Newton's Law of Cooling and determining a cooling coefficient.

Stay tuned for Test #2.
 

Bytor1100

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I'm interested in this idea and curious to see if it is worthwhile.

hook_dupin, did you have to re-route evaporator lines, you were you able to bend the existing ones to work?

I would aslo imagine, turning the AC unit on prior to colling the wort would be better. This would drop the "coolant" to a lower level before the cooling begins.
 
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hook_dupin

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I just pulled the evaporator out and bent it sideways. No rerouting of lines required. The input before the expansion orifice has quite a bit of slack built in (about 2ft that was zip-tied in place). However, the current set-up places some non-designed torque on the output. If the design goes "production," I may have an HVAC specialist rework the lines and even see if there are some flexible cooling lines availible. I also plan on eventually mounting this crazy gizmo on a cart if it ends up working.

I definately plan on providing a few minutes worth of warm-up on my next trial to make sure I have steady system. As shown in the test data plot below, there's definately was a lag time before max-rate cooling occured.





Is it worthwhile? I don't know... I think the recirculating ice water systems discussed at length in another thread will always kick the pants off this gadget in terms of total cooling time, sanitizability, and simplicity. Still, I think my time spent on this idea is worthwhile to try to reduce my total water usage and add to the overall body of homebrew research. Yeah...I'm a dork.
 

Drunkensatyr

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This comes up all the time. Do not place any kind of evaporator coil in your wort. Wort is acidic and I would safely guess that over 75% of coils have chemicals in the solder that Will leech into your wort. Use it as a prechiller yes, in your beer - never.
 

Bytor1100

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I was thinking more along the lines of using the AC unit along with a recirculating pump. Ice around here is expensive.
 

Bobby_M

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If it turns out to be effective, it would be best to get the unit reworked to run through a traditionally shaped immersion chiller coil. Yes, you'll have to pay to have it recharged with coolant, but you'd have to anyway if you want flex lines integrated. Anyone know what kind of pressures the compressor generates?

The other idea is to hook the compressor unit into one side of a plate chiller and run your coolant water through the other side. Yes, it would cost you either two plate chillers or a plate chiller and an IC, but without having to buy ice.....IS NICE!
 

CodeRage

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Awesome man, you had the cajones to try it anyway :D

If you put something in there to circulate the wort or just stir it your times would drop dramatically Probably get you closer to my bar napkin math, espescially if you put a fan on the condesor. I REALLY like the idea of replacing the evaporator with an IC style coil. The nice thing is you could use cheaper thinner tubing. That will also eliminate the risk of non food grade chemicals being exposed to the wort.
Keep us updated.
 

BrewBeemer

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Bobby; I just added some R134a to my 1995 Discovery, seems a 134a system will leak out faster than a R12 system, smaller gas particles over time.
On one chart with R134a at 107.2*F the static pressure was 380 PSIG. I would think compressor head pressure would be much higher than the static 380 PSIG operating until the high head pressure limit has been reached.
The cross over temp / pressure equal 134a, 69 PSIG at 68.55*F.
R12 cross over I recall was around 70*F at 70 PSIG.
At lower temps the PSIG became lower than the degrees temp same with R134a systems but a lot less of a difference.
 

Bobby_M

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The thread on morebeer is interesting but it just seems so big and complicated because of the two-exchange process. The AC unit is used almost in its stock form to cool glycol. The glycol is circulated through a plate chiller for liquid to liquid exchange with the wort.

Since I don't know enough about HVAC, I have no idea if it's possible to run the A/C's coolant line through a plate chiller by itself. It may be too restrictive to allow for proper evaporation after the expansion valve. If it would work, it just seems like a way to avoid an extra bulky step.

If that won't work, I could see building a tube and shell exchanger where the inner tubes are the A/C coolant lines and the wort is run through the shell (a reasonably small diameter copper pipe).
 

beerthirty

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Bobby, running it through a plate chiller as the evaporator may not be a good idea. If the charge is a little off by to much it could cause expansion in the chiller instead of at the expansion valve which would in turn cause icing of the chiller. The hot wort would probably keep this from happening but if it didn't the chiller would turn into a block of wort stopping flow. I think your approach of a tube and shell exchanger would work excellent though, maybe something like this, http://cgi.ebay.com/2-Heatcraft-Hea...52|39:1|66:2|65:12&_trksid=p3286.c0.m14.l1318
of course the volume of refrigerant would need to be recalculated to take into account the added system volume.
 

GuateBrewer

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You have to have water to supplement or a resivoir or something. This unit is only 5000 btu, it plugs into 110 AC 15 amp circuit, its basicly the reverse of the guys trying to rig up an electric MLT, on 110 volts, the wire from the wall cannot supply enough power to move, or "make" a lot of heat in a hurry.

Thats why the other guy has a gycol tank and 2 stage system, might work for something like your 90-65 drop, but not your 212-65.
 
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hook_dupin

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Any updates for experiment #2 of cooling 212* water down to pitching temps while stirring the water?
I should have posted this earlier. I accomplished the experiment about two weeks ago.

I boiled up 5 gal of water, transfered it to a bucket and set up the AC rig in my garage. In doing all of that, the water had cooled to 185F (most of the temp loss happened when I dumped the water from my boil pot to the bucket).

I constantly stirred the water to keep uniform temps. The result was that the simulated wort went from 185F to 75F in 17 minutes! I expected an exponential temp drop, but the result was essentially linear at a -6.5 degree (F) per minute cooling rate.



Other folks had the great idea to cut out the evaporator and replace it with a standard immersion chiller. I think I'm going to try that if I can find an HVAC dude who is willing to do it for less than $100. I'll let you know how that turns out
 

CodeRage

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Have you tried putting a larger fan on the condensor? I bet that thing gets pretty hot during the initial cooling.
 
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hook_dupin

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I think this sounds like a much easier and cheaper alternative, IMHO.
Recirculating Ice Water Chiller - Home Brew Forums
But if it works for you then cool.
The recirculating ice-water method is certainly cheaper. However, it also uses 5-10 gal of water plus ice each batch. I live in the Mojave desert where it rains less than 4" a year...I'm trying to see how water-friendly my brewing operation can get. I get seriously guilty when I use massive amounts of water to clean and sanitze equipment. I already use the run-off hot IC water to wash the equipment (and occasionally my car).
 

RobertHSmith

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I had the same idea, but didn't persue it because of a licened AC tech's advice. He suggested that lead based solder is still used in the manufacture of air conditioning units.


If it was cooling a tub of water for a pre chiller then that would work, but for many reasons already mentionted and the one I just mentioned, don't put the coil in the wort.
 
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hook_dupin

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I had the same idea, but didn't persue it because of a licened AC tech's advice. He suggested that lead based solder is still used in the manufacture of air conditioning units.


If it was cooling a tub of water for a pre chiller then that would work, but for many reasons already mentionted and the one I just mentioned, don't put the coil in the wort.
Yeah...my plan is to replace the evaporator with 50' of coiled brass tubing so that there isn't any solder below the water-line in the wort. Using it as a pre-chiller still commits me to using 5-10 gal of extra water and that's not the goal.
 

kladue

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Here is a possible method, use a 30 gallon plastic barrel with removable lid, use 25' of 3/8" od copper wound like a immersion chiller, place coil in barrel and connect to remains of ac unit bolted to lid. operate ac unit until you have ice build up on coils like commercial ice bank ac units operate. Pump chilled water through wort cooling system then you would only need to fire cooling unit a couple hours before use to chill water and build ice reserve. Biggest expense would be having ac tech pull coolant charge and recharge after tubing change, make sure to save capillary tube metering tubing for re-use as it was engineered for the compressor condensor combination.
 

conpewter

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I think he is trying to get away from using water to chill, since there is such a shortage where he is at. I think if you do get some HVAC guy to hook your 50' copper immersion chiller in instead of the coil you should be set. You need to be careful and inspect for leaks since you don't want coolant in your wort, but this is an interesting idea.

I've been looking in to it but if my calcs are right I'll need to pull 12,000 BTU out of my 10 gallon batch to get it down to pitching temps, that either takes a huge AC unit or a lot of time.
 

ChshreCat

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I wonder if there's something you could coat the coils with that would let them work but protect the beer from direct contact.
 

herbmagick

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I just moved to the California desert, and I'm trying to cut down on my water-usage during the brewing process. Even by using prechilled water for my immersion chiller, I still run the hose for 10 min at a guesstimated 5 gal/min. I've just purchased an old window air conditioning unit so that I can drop the evaporator coils into my wort. The biggest issues I can see is making sure all the evaporator plates are properly sanitized and not damaging the evaporator plates.

Anyone have any thoughts, experience, or war-stories to share?
I am doing almost the same thing , i use a tub of water and pump water into a 1/4 inch copper tubing that is imersed in my wort, from that it go's outside into the ac unit evap. coil with ac fan running and then back into my tub of water, i change 2 gals of water every ten min. when the wort is down to the outside temp. i turn fan off and dump ice into the tub. It works fantastic !!!
 

mikescooling

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I can only tell you in commercial chillers, their are a crap load of fans on huge condenser coils, that go to a small chilled water heat exchanger. Water contains lots of heat/energy and air contains very little. If someone asked me about taking on a job that I didn't think would work, I'd pass. Not that this won't work, and if it does tell us about it, so I can do something similar.
 
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