Starting a DIY Chiller, need info

[jessecnc]

I plan on making a DIY chiller out of an air conditioner. Right now I'm not sure whether I will go the drop-in or flow through route. Most likely the drop-in because of an easier design.
What I need help with from the experts is what metals are safe in saltwater? I know titanium and stainless steel should be ok, but what about Aluminum???
I will post pics and keep everyone updated as the process goes on. The important part, however, is that I should be able to make a 1/4 HP chiller for my 90 for less than $200. If all goes well, way less than $200.

 

[thegrog]

This is a tricky DIY and most likely will cause you many headaches, not to mention more money than you are planning on.
Aluminum is a huge no-no in tanks. Toxic to marine animals.
Titanium and stinless are really your only two options for metals.
Sorry I can't help more than that, it is just that I never really looked into doing this as so many have had problems and never had that big of an issue with heat.

 

[scsinet]

I agree with Grog on all points, and will add that only the highest grade stainless is okay. The cheapo stock won't do, like the stuff they make nuts and bolts out of... you need the food grade stainless.

You'll have to coat the evaporator coils in something.. like a laquer, epoxy, etc, or set up a heat exchanger to transfer the energy to an aquarium safe loop like polyethelyne, titanium, etc.
I especially agree that it's not worth the effort. I'm a die hard DIYer, I've built canopies, stands, skimmers, sumps, wet/drys, controllers, digital timers, etc but I bought my chiller (after failing miserably on two designs, dehumidifier and thermoelectrics). I will concede that in my opinion, a window air conditioner is one of the things that could conceivably work. At least you're not trying a dorm fridge....
I encourage you to run the numbers of what it will cost you to build, the energy consumption because there is no way what you build will be as efficient as an off the shelf model, and incidental costs... for example.. put a price tag on putting up with the noise, the uglyness, and especially the cost of your livestock and the risk you are willing to take on a solution that won't be as reliable as a commercial unit, but nonetheless critical to survival of the system, etc and make sure it makes sense.
I further encourage you to establish exactly how much you are willing to spend, worst case, before you give up and stick to that. I've done too many DIY jobs (both aquarium and otherwise) that ended up costing not only many times what I planned, but more than a commercial solution because I kept thinking I was close... just a little more investment... then suffered another setback...close... setback... vicious cycle. :thinking:

 

[boatbuilde]

been there done that with a window a/c unit and it works like a charm. Use Titanium tubing!!!
E-mail me for the source I got my tubing from (very inexpensive).
I used an elcheapo Wal-Mart 5,000 btu a/c with the digital controls.
ripped the case apart, built an acrylic chamber around the evap. coils filled it full of r/o-d/i
water. Took the Ti. tubing to a fab shop and had them bend it into a coil. clamped some hose to the ends, set it in with the evap coil. use a small Iwaki pump for aquarium water circulation thru the Ti tube. Oh I ended up putting a small powerhead in with the evap. coil.
Take the thermostat sensor and "pot" it in some aquarium safe epoxy not too thick though. and drop it into the sump or tape it to the outside of the Ti tubing's inlet side.
Dropped the temp of my 240gal 9deg while the 800watts of M.H. bulbs are burning maintains 79deg with no problem.
Set the t-stat to its lowest setting and let it run overnight to see what would happen. Tank got to 67deg. This was done during freshwater testing before addin salt and kritters.
been trouble free for about a year now. Aint purdy but beats the hell out of a commercial
chiller on price!!!! If you breakdown the component costs of a commercial chiller you will see they are making more profit than the Gas or Insurance companies!!!!!!!!!!!!

 

[boatbuilde]

Quint do you need a bigger boat? LOL luv that movie.
My .02$ :
I'm not sure "food grade" is the correct description for the type s/s you are talking about. Many types of stainless are food grade.
Alloy composition and method of fabrication would be better.
The most corrosion resistant Stainless normally available tubing is made from alloy 316-L of seamless construction. Welded and drawn tubing construction is not as reliable as seamless.Normally pitting/failing along the weld seam. Other common s/s alloys are 304, 308, 321-(better than 316-L but not as avail.)
I used 316-L seamless in my diy chiller for the better part of a year before stumbling on a cheap source of small dia. Titanium tubing. (the s/s I used was free b.t.w.)
I have been engineering/managing the building commercial offshore oil field boats for many years and have used just about all types of tubing and pipe for engine cooling and exhaust systems. 316-L seamless is dayum near bulletproof. Ti would be best but ouch on the $$$ for large dia.
When I replaced the s/s I inspected it really close even cutting pieces to see the inside in several spots along the length and found no areas of pitting or corrosion, did find some discolored spots but would have given it at least several more years of life expectancy.
My system has no other metals or any submerged pumps in contact with the water to set up any electroylsis (galvanic corrosion) issues. If this were the case then I wouldn't be suprised to see pitting problems.
But now that I have Ti I feel much better about things in general. Ti must have a better heat transfer, temps dropped almost 2 degrees. Wall thickness is slightly thinner than the s/s tubing so maybe that's it.

 

[scsinet]

HAHahah finally somebody gets the joke... Quint... Jaws... sharks... fish...
I always thought it was pretty obvious, but maybe others got it and just never said anything.

 

[boatbuilde]

 

[jessecnc]

Boatbuilder,
I thought about it more today and talked it over with a guy from work, and decided on the same design you used. My e-mail address is below, please send me the link for the titanium tubing, that would be sweet.
BTW...its good to hear some optimism on this subject, but then again being an engineer I can't help myself. I'm also making a 4-way return for my tank. Check out oceansmotions for my inspiration.
relativevelocity@hotmail.com

 

[boatbuilde]

cool

I made a diy 4-way valve out of an American Plastics single union ball valve. found a low rpm high torque motor for the acuator but never got around to putting it all together.
btw, you have mail

 

[boatbuilde]

just want to add that my house t-stat is set at 74. A low ambient temp has a big impact on cooling the tank so if your home gets into the 80's you might not see the same results as me.