Small grow hydro res cooler - I just had an IDEA!

[spadedNfaded]

I have a cabinet that is running 1gal growbags right now as a way to grow out a seed selection and select ladies i'd like to keep around. My goal is to have (2) 10 gal roughneck rubbermaids being DWC buckets, housing 4 plants each in an 8 plant scrog under my 400W CMH.

I have some issues i'm working out, one of them is temps being 75-80 degrees constantly. I know a major factor for any DWC system is the res temps and they're a pain in the ass to keep down, specially if the res is inside the growing area.

I've looked into options that members have shared here in the DIY section. The pain in the ass method of using frozen 2l water bottles.
Taking apart A/Cs, humidifiers and drinking-water coolers.
And finally, the tried and true method of purchasing a water-chiller specifically made to do just what we need.

Which got me thinking. I'm trying to cool about 20 gallons of water. Which isn't very much considering the size of some operations that are going on out there. That's about the size of your average aquarium. I search for DIY aquarium coolers and i found a few results i found interesting.

The parts list is:
1 mini fridge
25-50ft of water tubing
assorted hydro plumbing connectors
1 water pump.

Basically the idea is to cut 2 holes in the fridge, one for in and one for out. Inside the mini-fridge make a spool of 20-40ft. Route the lines in series with your low-gallon DWC buckets and start flowing.

Ive read that a lot of lower quality mini-fridges aren't set up to run 24/7 in extreme conditions, but i figure if you get a nice brand and spend an extra $50 on a quality unit, spool close to 40ft of line in there and possibly insulate the hydro plumbing you could use that cooling power effectively. I don't think it would be a strain on it to keep 15gallons from the res and however many gallons fit in the 40ft of line a few degrees cooler.

pros?
cons?

I wanted to reach out and get some opinions before i try this method. I'm gonna start selecting mothers soon so the buckets are in my near future.

- SubN

 

[Mycro]

What an awesome idea!! Not to mention you could stick a few "refreshments" in there as well to help while gardening??

 

[FreezerBoy]

High temps don't necessarily mean trouble. I just stopped working on a high temp dwc diary because temps dropped to 75-80. Most of the summer, it was above 80 and knockin' on 90's door.

You may want to consider an uncooled run and see what happens ...

 

[spadedNfaded]

I understand the power it will use. If you did have no problems with high temps, this can only help me if it knocks a couple degrees off here and there. The more "windings" i put in the cooler the more efficient it will be. i can even put the fridge on a timer to conserve energy during the off hours. It is approaching on the colder time of year though, so maybe if i can get my ventilation in check there wouldn't be so much need.

I would just like to have a method of keeping my res at or below 72degrees. I am working in tight spaces and cant afford to have trouble of that scale in this area.

I understand your case and it seems like dissolved oxygen and no organics seem to work hand in hand for you. I figure if warmer temps dissolve less oxygen, if you get an over-rated pump it should keep enough oxygen in there to keep it clean.

Anyone else??

- SubN

 

[fatigues]

If you read the hose coils through a bar fridge DIY attempts to conclusion, you'll find there are no solid results that show it working. A guy claims to have done it and given it to a friend, but... it sounds like bullshit to me. I'm not sold.

Another lame ass attempt using a Theromodynamic cooler is noted here. I think he managed a 2 degree reduction. (Cruzer ultimately disassembled the chiller from a bar fridge and put it directly in the rez)

The problem is pretty simple: There is not enough of a temperature exchange happening in the hose coils in the fridge to lower the temp of the water fast enough and low enough using ambient air contact to chill the coil. Could you do it? Yes, you could. With a kick- ass enough fridge and kick ass enough coils, you can do it. Problem is, the amount of refrigeration and tubing involved in that effort - and the cost of that tubing (copper or titanium - hell - even aluminum) is cost prohibitive when compared to the ready made alternatives. Plus, there is little to no fine temperatrue control of the cooled water.

So people try and do the tubing on the cheap using garden hose or vinyl tubing but the proven results just don't seem to be there. The cost and difficuly of all that copper or titanium tubing in order to give it a proper chance on an engineering basis have so far lead people to conclude: "Screw this. Might as well just buy a 1/12 HP chiller. It would be easier and cheaper."

If you can get 20 gallons cooled in a dorm style bar fridge, and have it lower res temps 10-14 degrees below ambient for $150 or less on a reliable and controlled basis - you're a shoe-in for Pontiac's DIY Link o Rama. It's a challenge that nobody has - to date - been able to achieve. That does not mean it cannot be done and it may well be that it can.

So far though, it has not happened. The above summarizes the leading reasons as to why not.

 

[ItsAllOver]

I thought of the same idea a couple months ago and wanted to do it, but realized after looking into it a bunch that it was unlikely that any mini fridge could put up with that over a period of time. Now, that's just my initial take based on some research, I haven't experimented with various fridges to validate that at all. Like fatigues said, there are threads with people trying similar things. I just can't imagine figuring out a way to get it to work.

 

[zenoonez]

Air is a relatively inefficient medium for heat transfer. That is the first problem. The second problem is that mini fridges aren't designed to remove a lot of heat. What is inside of a fridge is non heat producing and thus they only need to be able to maintain a temperature against heat loss through the walls of the fridge and through the door opening. Because of this they are designed to work for only a short period of time periodically. AC units are designed for the exact opposite, removal of a large amount of BTUs fairly consistency. If you took apart an old ac unit and put it into a cooler and then ran coiling tube or another type of heat transfer device through it you would get much better and more consistent results. Used ac units can be found for very cheap so... And in places where the ground temp remains fairly cool all year round, thermodynamic cooling could be a viable option but most likely not for direct cooling of your res water. It would be more efficient to decrease the temps of air going over your lights or of increasing the efficiency of your ac unit.