Calcium chloride as anti-freeze

[Gudwyn]

I'm considering building a geothermal loop to help cool my tank. My yard is going to be redone and they are taking off the top 8 inches of the soil, so it would be easy to lay down the pex at that time.

Here in Redmond, WA the building code says the frost line is 12" and the year-round ground temp is 50F down a few feet. So technically I would be above the frost line.

I'm thinking of just using RODI water in the loop with peladow added to it as the antifreeze (less toxic in case of leaks).

As nearly as I can tell, a 20% solution should reduce my freezing temp down to -20C (-5F). And it's pretty much impossible for the ground here to get that cold - as nearly as I can google, the record low for Seattle is 0F back in 1950.

Question: can I pump a 20% solution of Calcium Chloride around? Or will it encrust on the powerhead impeller and the walls of the pex pipe?

I think that 20% solution of CaCl is probably about 26oz of peladow per gallon. Is that right? That's about twice what I use in my Calcium supplement (DriZair is repackaged peladow sold in 13oz packets here in NW, so I fudged your recipe a little to take one packet).

If 2-3 gallons of that mixure leaks into my yard, will it be ruined? Roughly 78oz (~5lbs) of peladow.

What about 2-3 gallons into 250 gallon reef tank? It would definitely snow in the tank, but would all life end? Reef calculator says my Ca will be at 1200ppm.

Maybe I'll use a 10% solution. Still would reduce freezing to around 20F which is well below any sustained low here in the Seattle area.

I plan to use two powerheads, a small 5w eheim to circulate the loop 24/7 (bypassing the heat exchangeer) and a larger one on a temp controller that pumps thru the heat exchanger and around the loop. So to freeze, the average temp of the yard has gotta get pretty low - not just one spot.

Thoughts? The "you are freaking insane" thought is fine. But my wife has that one pretty much covered. :)

[Hydro Therapy]

I am not a chemist, but I do know that calcium chloride when reacted with water will produce chlorine which is very corrosive to metals and such. A 10 or 20% solution may reduce the chlorine to an insignificant amount but I have not tried it.

[palmerc]

Sorry I only know metric, so 20% will be 200 g/litre. 26oz per gallon sounds right though based on my very rough conversions.

As for the chlorine story.......... No comment!!!

[Randy Holmes-Farley]

My suggestion is to talk to Greg Hiller. He went through all sorts of thought processes before he picked fluids for his system, and in the end he didn't find it worked well enough (too much back pressure).

The calcium chloride will be denser and a little more viscous, so will cause some difficulty pumping. Chlorine is not a concern, IMO.

[Hobster]

I don't know how much tubing you are planning to put down, but couldn't you just dig down the foot or so to where it maintains 50 degrees??

[Gudwyn]

Thanks for the mention of Greg Hiller. I found this thread http://www.reefcentral.com/forums/showthread.php?s=&threadid=814514

Sent Greg a PM. Hopefully I can learn from someone else who has done this type of stuff before.

Hobster, I have to do it fast between the time the contractor strips the top 8" of the yard and when he pours the new patio and brings in the new topsoil. Can't be out there hand trenching in 300' of pipe.

Could have the contractor do it, but then it would cost real money and I'd be upset if it didn't work.

[Greg Hiller]

>My suggestion is to talk to Greg Hiller. He went through all sorts of thought processes before he picked fluids for his system, and in the end he didn't find it worked well enough (too much back pressure).<

Well, not exactly. When I first set up my cooling loop I found that the tubing I had buried in the yard had too thick of a wall. There was too much resistance to heat transfer THROUGH the wall of the tubing, and therefore the loop did not cool enough. That original loop was buried below the frost line, and entered the house though a concrete wall that was also below the frost line.

A few months ago I decided to try again on the cooling loop idea (mostly since the weather was decent enough here to work outside again). This time I buried four aluminum heat exchanger tubes (http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/9248/cid/2224, only $9 each!) and plumbed them together in parallel to minimize back pressure. Instead of running my water to them through the concrete fountation, this time I had to run water to them out a small opening in the structure above ground. Because of this I considered whether I might want to put something into the heat exchange fluid (tank water is not running in the loop) to make it less likely to freeze. I considered adding salts, sodium chloride, and many others, but I decided I was more worried about corrosion in the aluminum tubes (I looked up the corrosivity of the various solutions WRT aluminum), so I chose to just use DI water in the cooling loop. Every fall when it starts getting cold I will just drain, and blow the water out of the loop and refill it in the spring.

I have also wired the aluminum tubes to some sacrificial zinc anodes to minimize corrosion on the outside of the tubes.

I still have some additional pumping work to do on the system, but plan to test it this weekend. I'll let you know if it works. If it doesn't, at least I didn't spend much on the hardware. :)

[Greg Hiller]

There is some more discussion of this in this thread:

http://www.bostonreefers.org/forums/showthread.php?t=22751

but you may have to scroll down a bit

[Gudwyn]

Thanks Greg, I appreciate the info.

Sounds like your contractor didn't use the PEX pipe which is what all the geothermal guys use for heat pumps. Not sure if PEX works for us since heat pumps have much higher delta T and really long runs of pipe.

I look forward to seeing any updates from you or anyone else who is trying this.

Sounds like I should just try to get the loop down below frost line to get rid of that issue. One less thing to worry about.

[Greg Hiller]

FWIW, I tested my 'new' cooling loop today. It works, but not as good as I was hoping. After running the loop for an hour or so, I was able to measure water coming out of the loop at 72 F, not as cool as I was hoping. Water running into the loop was at 74 F, and running at about 1 1/3 gallons per minute. My tank was running about 82 F. This works out to about 1300 BTU/hr, which is what you get with a small chiller. Still, the pump only draws 95 Watts. That can be compared to electrical power to the small chiller which would be 289 W, plus the electricity of a pump to run water to it. So, my loop is about 3X more efficient than a small chiller. Of course, early in the cooling season it would be a bit more efficient, and late it would be less. The cost for the parts of the loop was about $65 or so, plus the cost of the pump. The pump was on the expensive side, I think it was about $200. So....if the loop were to run for 5 months continuously, compared to a chiller, I'd save about 846 kWH, which where I live is about $93 a season.

If I'd been smart I'd have put more of the aluminum tubes in the ground, but I was getting kind of tired of digging!!

[BeanAnimal]

Greg in increased water flow rate may give your more BTU/h. It would appear that the earth itself is going to be the limiting factor, as well as the efficiency of your in sump heat exchanger.