I didn't want to spend $500+ on a water chiller to cool 260 gallons in a hydro tree grow, so I thought I'd try to build my own. It ended up working very well, and can be done for much less than a store bought chiller, so I thought I'd share how I did it.
Start off by finding a used dehumidifier with your local online classifieds. They usually come in 35 pint or 70 pint designations. A 35 pint model will build a 1/2hp chiller, while a 70 pint can be used to make a 1hp chiller. You'll want to get an old unit that isn't digital, so it will just turn on when you send it power.
I ended up buying a very old kenmore 35 pint unit for $20
Get an aquarium temperature switch from ebay for $15. You'll need to wire the relay from this into the hot (black) line of the plug of the dehumidifier, to give it power when called for (some electrical knowledge required). Leave the dehumidifier on max so it'll always turn on, or just bypass the dehumidistat so it's always on, I didn't bother, just turned it to max.
The temp switch is good for 7Amp, if you use a 70 pint, you'll have to wire the aquarium temp switch to a larger relay to support the Amperage, or get a larger aquarium temp switch.
You then need some grade 2 titanium tubing, 0.5", thinnest wall you can find. Welded is cheaper than seamless. I ordered mine from Online Metals, google the name. $64 for two 4 foot lengths of 0.5". I'm in Canada so they dinged me another $40 for shipping, so it ended up being a little over $100. I'm sure I could have found it for less on ebay, but this was fast, and I needed it fast.
You also need an insulated reservoir to act as the heat exchanger, with a small water pump for circulation. I used a 38L (10 gallon) container wrapped in styrospan, and a very small 8w pump in the tank for circulation. You might need something larger for a 70 pint model. I will now refer to this small res as the "heat exchanger res"
*A brick
Lastly you need a slightly larger pump, I used a 20W (~1000L/hour) to circulate the nutrients through the titanium tubing.
Oh yeah, and an electrical conduit tube bender. You can rent one for a few dollars. I just vaped a big bowl, and finished a 2oz/1oz tequila/brandy margarita, which seemed like a great idea before writing this "guide", but it might end up being a bit discombobulated.
I don't have any pics of the build, but there's not much too it. You gently bend down the cooling coil into a position so it can sit in the heat exchanger res. Be careful not to kink it anywhere. It will try to float, that's why you need the brick.
Grab the 0.5" titanium tube and use the tube bender to make two "U" shapes, which lay on the bottom of heat exchanger res, and then bend the ends of the "U" up so they come out the top of the tank just above water level.
Put the larger water pump in your nutrient res and plumb it to one of the titanium tubes, then loop the end of that tube to titanium tube two, and then the end of titanium tube two back to the res. There are of course multiple ways to do this, the main thing is to have at least 8 feet of 0.5" tubing is the res (more tube will be more efficient). I went with two 4 foot pieces because shipping was easier. If you get your Ti locally, you might just want to bend up an 8 foot piece and not bother with the extra connections. If you use a 70 pint dehumidifier, make sure to use at least 16 feet, but don't put it all in series, make two 8 foot loops and run them in parallel. with twice the flow rate, either a 40W pump water pump, or two 20W pumps. The main thing being to have enough surface area from the tubing to stop the res from icing up, if it can't transfer enough thermal energy into your nutrient res, the heat exchanger res will freeze up. My loop from one titaium "U" to another made of tube is pretty kinked up now, it's gotten worse, so I'm changing it out to the little fitting piece I made by jamming two 90's together you can see in one of the pics. More flow = more efficiency.
To tell how well the system works I used a timer and measured the water volume coming back into the nutrient res. I also measured the the temp of the water going in, and the temp coming back out. This information can give you the BTU/hour of the chiller using this online calculator:
http://www.advantageengineering.com/fyi/288/advantageFYI288.php
I have 3.3 gallon per minute
19.9C (67.82F) input to chiller
17.4C (63.32F) output from chiller
This is 4125 BTU/hour
To compare, Active Aqua 1/2hp chiller is 4100 BTU/hour
http://www.hydrofarm.com/product.php?itemid=7638#tabs-2
Active Aqua chiller consumes 4.4 Amp. The one I built from a 20year old dehumidifier consumes 5 Amp, but if you added another 4 feet of titanium tubing, and/or increased the water flow rate through the titanium tubing, you could get more BTU/hour, and probably equal or surpass the efficiency of the active aqua unit.
Grade 2 titanium is what is used in all water chillers made for nutrient solutions or salt water aquariums because it will not corrode. Even stainless steel will corrode and cannot be used.
I have pics of the unit to help explain.
You might want to put some chlorine or something else in the heat exchanger res to keep it from growing things, or just change it out every few weeks.
If anyone wants to build one I'll be here to help if you have any questions. You can make a 1/2hp - 1hp chiller for $100-$200 instead of $500-1000. In the first pic my top temp is air temp, bottom is water. Lights off at the time.
Start off by finding a used dehumidifier with your local online classifieds. They usually come in 35 pint or 70 pint designations. A 35 pint model will build a 1/2hp chiller, while a 70 pint can be used to make a 1hp chiller. You'll want to get an old unit that isn't digital, so it will just turn on when you send it power.
I ended up buying a very old kenmore 35 pint unit for $20
Get an aquarium temperature switch from ebay for $15. You'll need to wire the relay from this into the hot (black) line of the plug of the dehumidifier, to give it power when called for (some electrical knowledge required). Leave the dehumidifier on max so it'll always turn on, or just bypass the dehumidistat so it's always on, I didn't bother, just turned it to max.
The temp switch is good for 7Amp, if you use a 70 pint, you'll have to wire the aquarium temp switch to a larger relay to support the Amperage, or get a larger aquarium temp switch.
You then need some grade 2 titanium tubing, 0.5", thinnest wall you can find. Welded is cheaper than seamless. I ordered mine from Online Metals, google the name. $64 for two 4 foot lengths of 0.5". I'm in Canada so they dinged me another $40 for shipping, so it ended up being a little over $100. I'm sure I could have found it for less on ebay, but this was fast, and I needed it fast.
You also need an insulated reservoir to act as the heat exchanger, with a small water pump for circulation. I used a 38L (10 gallon) container wrapped in styrospan, and a very small 8w pump in the tank for circulation. You might need something larger for a 70 pint model. I will now refer to this small res as the "heat exchanger res"
*A brick
Lastly you need a slightly larger pump, I used a 20W (~1000L/hour) to circulate the nutrients through the titanium tubing.
Oh yeah, and an electrical conduit tube bender. You can rent one for a few dollars. I just vaped a big bowl, and finished a 2oz/1oz tequila/brandy margarita, which seemed like a great idea before writing this "guide", but it might end up being a bit discombobulated.
I don't have any pics of the build, but there's not much too it. You gently bend down the cooling coil into a position so it can sit in the heat exchanger res. Be careful not to kink it anywhere. It will try to float, that's why you need the brick.
Grab the 0.5" titanium tube and use the tube bender to make two "U" shapes, which lay on the bottom of heat exchanger res, and then bend the ends of the "U" up so they come out the top of the tank just above water level.
Put the larger water pump in your nutrient res and plumb it to one of the titanium tubes, then loop the end of that tube to titanium tube two, and then the end of titanium tube two back to the res. There are of course multiple ways to do this, the main thing is to have at least 8 feet of 0.5" tubing is the res (more tube will be more efficient). I went with two 4 foot pieces because shipping was easier. If you get your Ti locally, you might just want to bend up an 8 foot piece and not bother with the extra connections. If you use a 70 pint dehumidifier, make sure to use at least 16 feet, but don't put it all in series, make two 8 foot loops and run them in parallel. with twice the flow rate, either a 40W pump water pump, or two 20W pumps. The main thing being to have enough surface area from the tubing to stop the res from icing up, if it can't transfer enough thermal energy into your nutrient res, the heat exchanger res will freeze up. My loop from one titaium "U" to another made of tube is pretty kinked up now, it's gotten worse, so I'm changing it out to the little fitting piece I made by jamming two 90's together you can see in one of the pics. More flow = more efficiency.
To tell how well the system works I used a timer and measured the water volume coming back into the nutrient res. I also measured the the temp of the water going in, and the temp coming back out. This information can give you the BTU/hour of the chiller using this online calculator:
http://www.advantageengineering.com/fyi/288/advantageFYI288.php
I have 3.3 gallon per minute
19.9C (67.82F) input to chiller
17.4C (63.32F) output from chiller
This is 4125 BTU/hour
To compare, Active Aqua 1/2hp chiller is 4100 BTU/hour
http://www.hydrofarm.com/product.php?itemid=7638#tabs-2
Active Aqua chiller consumes 4.4 Amp. The one I built from a 20year old dehumidifier consumes 5 Amp, but if you added another 4 feet of titanium tubing, and/or increased the water flow rate through the titanium tubing, you could get more BTU/hour, and probably equal or surpass the efficiency of the active aqua unit.
Grade 2 titanium is what is used in all water chillers made for nutrient solutions or salt water aquariums because it will not corrode. Even stainless steel will corrode and cannot be used.
I have pics of the unit to help explain.
You might want to put some chlorine or something else in the heat exchanger res to keep it from growing things, or just change it out every few weeks.
If anyone wants to build one I'll be here to help if you have any questions. You can make a 1/2hp - 1hp chiller for $100-$200 instead of $500-1000. In the first pic my top temp is air temp, bottom is water. Lights off at the time.
