DIY Chiller

[TKO]

Ok, I know this may have been covered here at some point but I could not find it.

My background is in HVAC as a Mechanical Engineer so I thought I would visit the idea of making my own chiller for a newly set up tank I have. It wasn't the money end of it for a new chiller so much as the, "I can do this" side of my ego.

My new tank is a 125 with about a 30gal sump. about a week ago after I completed the set up of the tank and under full load of Lighting and all the pumps it is running a steady 93deg.

My goal was to have this tank under full load and cool it down to and maintain at 76deg.
I had a few hours today to play around with the idea and this is what I have come up with so far.

I went to a buddies house and picked up an old 6000BTU (ie. 1/2hp) window unit that had been sitting in his garage for a few years.

Time for a beer

I took it home and striped the front off it. There were 2 copper lines runing into the evapoator coil. 1 was a small cap tube line that meters the amount of freon through the coil and the other was a 5/16 line that runs back to the compressor.

Time for a beer

I cut these 2 lines at the evaporator coil and removed the evporator coil from the unit.

Time for a beer

Next I took a look at the fan motor. This unit is like most other window units, in that it only had one motor with the shaft coming out on both ends. One side for the blower section and one side for the condensor section. I took my hack saw and cut the shaft off of the blower side as close the motor as I could. At this point I was left with a compressor, condersor coil and condensor fan motor and the original controls.

Another beer

I then sat few about an hour (drinking beer) and thought of how to get this to cool the tank and came up with several idea's. I decided to go with a drop in coil in a manner of speaking and I headed off to Home Depot to get the items I thought I would need.

20' 1/4 copper tubing - $9.87
20' 7/16 clear plastic tubing - $2.79
2 - copper shrader valves - $1.99 ea
Map Gas torch - $19.99
Roll of 45% silver soilder - $4.29

I returned home and rolled the copper tubing around a 3" pipe to give me a coil about 3.5" around.

More beer

We all know that we don't want copper in our tanks so this is were the clear tubing came in. It was just the right size to slide over the copper tube and it took me about 15-20 min to get it feed over my coil. I then cut the clear tubing back on each end so that I had about 1' of copper tubing.

Damn I need a beer.

I used the map gas torch and 45% silver solder and brazed one end of my coil into the copper I cut off the old evaporator coil and then took the small copper cap tube and brazed it into the other side of my coil.

Few more beers

I them had to drill a small hole into each of the lines near the compressor and braze in 2 shrader valves so that I could recharge the system with freon. (R22)
I put my freon guages onto the shrader valves and used my vacum pump to pull a good vacum on the system for about 15 min.

Good time for a beer

I moved my contraption over to an old 90gal tank I got in the garage and brought in the water hose and filled the tank, while having a few more beers.

I placed my coil into the tank and tossed in a small rio pump to move the water around a bit and tossed in an old temp sensor. The water temp was at 76deg I turned on the unit and started to add my freon, I brought my charge up to about 250 on the head and 74 on the suction and let it run whie I finished off the rest of my beers.

By this time I was hungry and needing some lunch, so off I went to McDonalds and to the store for more beer.

I returned about a hour later and that tank was sitting at 69deg and still droping. I figured it was time to do some test. I went inside and scavanged through all my stuff and came up with 1-500watt heater, 2-300watt heaters and 1-250watt heater. I pluged them all in and turned them up so they would all come on and stay on and tossed them into the tank, and went back inside to have a few beers and a nap.

I returned about 2.5 hours later and the with the heaters running the tank was now at 58deg so I shut the window unit off and let the heaters bring the temp back up to about 90, and turned the unit back on to cool it down from 90 with the heaters still running.
It is now about 3pm and I am about sick of looking at this thing or maybe it's all the beers. Oh well have another beer.

Well I checked on it again after a short nap at about 4:30pm (1.5 hours of running now) and the tank was sitting at 72deg. with unit still running and heaters still running.

Ok, I got that end all figured out. Now I started making everything look real nice and moving it outside to the wall were my new 125 is sitting, I drill a few holes into the house, and cut my copper coil loose again. I took my protien skimmer out and rewraped my coil around it and placed it back in the sump.

God I need a beer.

I made sure that only the area of my coil that was encased with the clear tubing was inside the sump or house and routed the ends back through the wall to the outside where I again brazed it back together with the compressor unit. I charged the system again with freon and turned it on. Finally done with the chiller part and after running now for 30min or so my 125 is down from 93deg to 85.9 and dropping while under full load.

I will stop here for today but now I got to somehow rework the controls so that the unit will cycle on and off with the tank temp. but for today I will just put it on a timer to run 15min every hour after it drops to 76 until I figure it out.

So far I got a free window unit and about $40 of money into it.

I will get some pics as soon as I get my damn cam back from my brother in the morning. It would have been great to show step by step pics of all my hard work and drinking today.

Ok now I need your input.
Have you tried anything like this and if so what were the long term problems you came up with?
If you have any experiance with A/C units what do you think my problems may be in the future?
Any ideas on the control side?
Any ideas if my clear tubing idea covering the copper will be ok?


Thanks and

HAVE A BEER

[H20ENG]

TKO,
This may work for you, but a few thoughts.

The copper tubing inside the clear tubing- It may protect it, but the tubing may degrade much faster due to the cold, and the efficiency is totally lost in the plastic tubing.
Your evaporator may not absorb enough heat since its encased in plastic, and you may get liquid back to the compressor.
Control- Get a Ranco digital controller to wire the whole thing into. $60 well spent!
I hope that you are recovering the refrigerant when cutting the lines.....
I love beer during DIY too. Mind Lubricant!! Hope you didnt drive to Mickey Dees and the liquor store;)
The 1/2 horse compressor should do the job, but not sure if it will keep up with the covering on the evaporator. Maybe add another 20'?
Chris

[TKO]

Thanks Chris

I have thought of this and first thing in the morning I will pick myself up about 30' of 316 stainless at the supply house and redo my coil with no need for the covering.
I'm not to concerned about the amount of heat transfer lost from the plastic as the unit is oversized for my size tank anyway, but the thought of having the plastic crack after a few months is enough to make me redo with 316 SS.

Also, yes I have a recovery unit. Guess I should have said that, although this thing only uses 1lb or so.

[em21701]

I like your idea, the plastic tubing reduces the efficiency of the coil but it seems to be ample. If the temperature sensor from the original control unit is still intact, this would be your best bet for control, unless it is an electronic temp sensor it will probably not be easy though. As an HVAC guy you probably know more about how the non-electronic temp sensor opperates than I do. You could create an electronic controller that turns the power to the AC on and off, but the AC unit usually leaves the fan running when it cycles, this would be lost unless you wired the relay directly to the compressor. There are plenty of places online where you can create an electronic thermostat. The design would depend primarily on what kind of temperature probe you have availiable.

[H20ENG]

TKO,
Look for something called "duplex stainless". Suposedly good for saltwater. I have had many things made of 316 just melt away from saltwater, but many that still look new. I dont trust 316, Titanium all the way!;)

[em21701]

316L has greater corrosion resistance then 316 stainless. 321 Stainless contains Titanium and is still weldable. It is specifically designed for corrosive environments, I don't know if it is availiable in a tube though.

[em21701]

You could slide the copper tube inside of the stainless tube to get the corrosion resistence of the stainless with the joinabaility of the copper. You would use the stainless just like the plastic tubing that you already are using. You could do this with the titanium as well which would eliminate the trouble with bonding it to the copper tube already in the system.

[TKO]

There is actually no problem with brazing the 316 SS to the short copper lines from the old evaporator as long as you use a flux coated brazing rod made for this type of app.

[ruck'n'reefer]

Tag... sounds interesting! I have a window unit that I would like to convert!

[eric2524]

Sound good, I'd like to see pics when you get some!!
Now I want to do it too!!!

[jjkahler]

Another thing you might look into is some sort of accumulator to help keep the liquid floodback in check. Makes me want to break out my torches and start ripping stuff apart. :) Good job.

[TKO]

This evening I removed the copper coil I made and replaced it with 1/4 316 SS tubing ($1.10 per foot). I added an additional 10' to the coil making it now about 30' long, of which 20' or so is wrapped around the skimmer. As I no longer need the clear tubing over it I'm getting a much better heat transfer from the water and the unit is cooling it down much faster.
I run about 850gph through the sump so I think I am ok in the area of water movement around the coil. Right now I am still turning the unit on and off with a timer set to run for 20min each hour and the tank under full load is staying right around 74deg. Because of the unit running on a timer the tank temp will come up about 3deg during the off time but drops back to 73-74 in the 20min that it is running. This is to much temp swing for my liking and I will be looking for a controller of some type in the next day or so. (No live stock in tank)
I have also added a small receiver to the unit to stop any floodback I may get (don't know if I really needed this)

What I would really like to do is come up with a way to make a DIY enclosed heat exchanger with 3/4" water inlet and outlets on it so I can mount the whole thing outside with the unit and just run some tubing to it from the sump via a small powerhead.
I have come up with a few idea's to do this but am looking for the cheap way.
Any help?

[Trackz]

How loud is the compressor when it's running?

[H20ENG]

Most commercial chillers for saltwater use about 6-12" pvc pipe, capped on one end. A flange on the other has a flat pvc plate bolted to it that has the tubing going through with nothing more than liquid tite cord grip fittings sealing them. The coil is inside the thing and the water side piping is welded to the top.
You could also run the water piping through the plate. Have the inlet pipe extend to one side and the outlet pipe cut flush with the plate to get a good detention time around the coil.
Nice job! Keep an eye on the coil. I have heard that 316L is the way to go but forgot about it.

[lousybreed]

I just have a couple comments to make. I am a chemical engineer and i work at a salt plant, we make around 800 tons of salt per day. I can shed some light on metals and brine. Our brine lines operate at anywhere from 60F to 230F. At room temp you can get away with carbon steel, no good for reef tanks though. Stainless steel has several different grades: 304, 316, 316L........We have found that 316L is by far the best one for corrosion resistance (particularly chloride cracking), long lasting welds, and relatively cheap. Also you can still bend 316L tubing. On our hottest process equipment we use monel, inconel, hasteloy C, platinum and titanium. Platinium is the most resistant and is very, very $$$. Inconel is the next on deck, a foot of 8in ID schedule 10 pipe costs around $700. Very expensive if you are installing 50 foot sections at a time. Monel is cheaper and resist corrosion. The problem with monel and inconel is that there is copper in the mixture. So you are left with titanium. Impervious to acid, brine, and heat; it is a good choice. Very expensive but it is a great metal for heat exchangers (ie chillers). We are installing 2 inconel heat exchangers with titanium tubes at a cost of $600,000 including install. I personally have never seen flexible titanium tubing, if it is out there it will be very expensive. I doubt if it could be bent because it is brittle (strong but doesnt like to be bent). Go with 316L its your best option.

Just thought that you guys might like to hear about this.....

[inLOVEwitHEATHER]

wow.. i have a window unit i wouldnt mind coverting.. a few questions though...are you using the pump in the unit to pump the feron from the unit to the coil?? wouldnt this slow it down? some picture and maybe a little more detail would cool.. also .. where did you get the tubing?? thanks.

keep up the good work!!

[H20ENG]

Thanks, lousybreed. Welcome to RC!
Ti tubing is coiled in most exchangers, probably heated first to do it though.

[TKO]

I have added a medium temp. controller (same type used in walk-in coolers) to the system made by Johnson Controls for $32. Because the sensor bulb is made of copper I used some heat shrink to make it water proof.
The temp now stays within 1deg of where I set it. I have had the tank at 53 since yesterday under full load, just to see if it could be used for cold water type tanks and it seems to be having little problems doing so.
I plan on building another with a newer unit I picked up yesterday for $25 at a yard sale This unit also has a reversing valve so it will be used for cooling and heating. The one I have now is old and ugly and I really don't want it sitting outside the house looking like that. I will take a bunch of pics and try to be very detailed as I work on the new one. Overall I would say this has not been to hard of a project, and so far I have about $100 into it including the unit I just picked up.
I have decided on this one to make a flat evap coil with 316L SS and lay it flat in my return pump section of the sump. This should be easier than trying to bend it like I did around the skimmer.

I also called the supplier where I picked up my SS tubing to ask about 316L tubing and was informed that the tubing I bought was 316L (When I bought it I told them what it was for) So I am glad I lucked out there.

I would still like to build a heat exchanger and have been looking at several ways to do it, But for now I will settle for a coil in the sump until I can come up with a cheap way of doing so.


Thanks to all who have been a help with input.

[diyreefer]

TKO, have you ever considered using a mini-refrigerator used to cool a container of water cooled to 35 deg.. Then coiling some plastic tubing with tank water flowing through it and returning back to the sump. I have not tried this but I wonder how much cooling capacity it would supply.

[em21701]

I tried this, I put a mag350 in the frige and packed it with ice. The compressor never stopped running, and the tank never even dropped a degree.

[cb747]

The mini fridge will never work--maybe on a small tank but never on a large---This window AC unit has my attention!!! Excellent idea!!

[jeff_s1]

Have you looked at this thread?


Home made chiller (http://archive.reefcentral.com/forums/showthread.php?s=&threadid=177020)


Jeff

[BradR]

Tagging this. Great work!