Heat transfer fluid for solar hot water

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454MAG

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I am installing a solar hot water system. The supply houses sell propylene glycol for 20-25 dollars a gallon. could I use longlife antifreeze for this system or regular ethylene glycol. The hot water will be heating the radiant loop installed in my garage floor so it will never come near potable water. Is ethylene glycol compatible with PEX tubing ? Is regular pink RV rated proplene glycol the same as the stuff they sell for this purpose ?
TIA
Ted
 
We make cooling water products. Actually, you should use only water. (perhaps solar power is different though, so make sure you do research) You should also add what is called an extended release charge (which is basically like a bunch of aspirin for your water that release over time) to protect the system.

CC
 
quote:
Originally posted by 454MAG:
Thanks for the input CC. actually I have to run an antifreeze solution or I would have serious problems here in the northeast. I have done some research and foound Propylene glycol is whta is normally used for this function. $20 a Gallon seems really steep for this stuff. I am trying to figure If I can use a longlife antifreeze in its place. The system consists of copper tubing, a bronze circulator pump and some PEX tubing.
thanks
Click to expand...
EG (ethylene glycol) would be a cheaper option for you, but it's very toxic. Personally I would encourage people to use PG wherever they can instead, but as far as $$$ goes... EG is way cheaper.

However, you really should follow what is recommended just to be safe.
 
The "safe" antifreezes, like Sierra, Prestone Low-Tox, etc, are propylene glycol and are about half the price of the special stuff. I don't know how appropriate it would be for a solar system, though.
 
How many gallons do you need? If there is any chance that can come into contact with potable water make sure you use the p-glycol. Like CC said e-glycol is a deadly poison even in small amounts. Also I'm sure the code requires this as well.

I've often wondered if you could run the cheap RV-antifreeze in these systems. I don't know how hot yours runs but I have a wood boiler that runs over 200F. The system has a lot of cast iron so I don't know if there would be problems or not.
 
Thanks for the input. There is no chance of this touching potable water it is an entirely separate system. I have not figured out how many gallons. There are 3 4x8 panels, 100ft 1/2" copper and 1200 ft 1/2" PEX tubing. I am guessing apprx 25 gallons. I have had terrible experiences with pink RV Propylene glycol. I have personally seen 3 v8 boat motors destroyed by this stuff because of freexzing at temperatures no less than -5 degrees. I have also had corrosion problems with this stuff in a volvo penta stern drive where the stuff turned to a nasty pink and white gel with the white being aluminum oxide. This is why I would prefer Ethylene Glycol and its corrosion inhibitors. does anyone know if it is compatible with crosslinked poyethylene tubing ???
Thanks
Ted
 
quote:
The "safe" antifreezes, like Sierra, Prestone Low-Tox, etc, are propylene glycol and are about half the price of the special stuff. I don't know how appropriate it would be for a solar system, though.
Click to expand...
Those would be my choices as well and should work fine in a Solar system.
 
quote:
Originally posted by MolaKule:

quote:
The "safe" antifreezes, like Sierra, Prestone Low-Tox, etc, are propylene glycol and are about half the price of the special stuff. I don't know how appropriate it would be for a solar system, though.
Click to expand...
Those would be my choices as well and should work fine in a Solar system.
Click to expand...
 
Last I looked, Advance Auto had Low Tox for the same as regular, about $7. I highly doubt the $20 a gallon stuff has much better of an additive package for your application. Go with the PG. Do you want gallons of a toxic material running down into your house if an ice storm drops a big tree on it?
 
Thanks for the input CC. actually I have to run an antifreeze solution or I would have serious problems here in the northeast. I have done some research and foound Propylene glycol is whta is normally used for this function. $20 a Gallon seems really steep for this stuff. I am trying to figure If I can use a longlife antifreeze in its place. The system consists of copper tubing, a bronze circulator pump and some PEX tubing.
thanks
 
quote:
Originally posted by 454MAG:
I am installing a solar hot water system. The supply houses sell propylene glycol for 20-25 dollars a gallon. could I use longlife antifreeze for this system or regular ethylene glycol. The hot water will be heating the radiant loop installed in my garage floor so it will never come near potable water. Is ethylene glycol compatible with PEX tubing ? Is regular pink RV rated proplene glycol the same as the stuff they sell for this purpose ?
TIA
Ted
Click to expand...
STAY WITH THE propylene glycol!!!! At one one time I installed and serviced solar hot water systems in R.I. and SE Mass. I would not use any thing from the autoparts store at all. There is a plumping wolesale place about 1/2mile off rt. 95 on Jefferrson Blvd. Just south of Providce. thats sells the stuff if I remember right.

OK after typing all the above I just saw the part about the loop in the floor. You should plumb in a tank for your hot water also. My system in Portmouth RI took care of my hot water all summer and about 85% of the winter.
 
Thank you all for the info. After more research I was able to pick up the proper propylene glycol with inhibitors for $11 a gallon at Lowes. The system I am installing - a Grumman Sunstream from the mid eighties actually used ethylene glycol. There were two separate heat exchangers before the domestic water outlet. One was a 1/2in pipe inside a 3/4" pipe and then a coppeer coil in a storage tank. I plan on using this to heat my garage floor in the winter and then my dhw the rest of the year.
Tom do you think it would be more efficient to just dump the output of the collectors into the floor loop and run a simple pump with a differential controller for the winter then switch to the heat exchanger for DHW ?


Ted
 
454

You might check out what the farmers in your area put into tractor tires for ballast.

Calcium chloride 3.5 lbs to a gallon of water is good down to -50*f.

Don't know about the corrosive nature of this chloride.
 
quote:
Originally posted by Neil Womack:
454
Snip...
Don't know about the corrosive nature of this chloride.
Click to expand...
Used in place of regular salt when it gets too cold. Eats cars just as well or better.
 
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