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SOLAR HEATING SYSTEM CONSTRUCTION LOG
PROGRESS
REPORT:
December 13, 2004: 
Frozen antifreeze! 
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      When I re-filled 
      the collector loop last fall, I started with about 3 gallons of propylene 
      glycol antifreeze (DowFrost HD) that I had available.  I mixed this 
      with water in a 5 gallon bucket and pumped it into the collector loop.  
      Well, I forgot that my loop takes more than 5 gallons now (since adding 2 
      collectors last year).  So I kept adding water to the bucket until 
      the loop was full.  I ended up with a mixture that was less than 40% 
      antifreeze.  I figured that this would be OK. Well, this morning my collector loop froze - no circulation - even in full sun! The ambient temperature dropped below -13F last night. The high for yesterday was no more than 9F. I checked the specs for DowFrost and found that a 42% mixture only protects to -10F. Oops! I made a quick run to the local plumbing supply and got a 5 gallon pail of Hercules Cryo-Tek-100. By using my fill pump to aggressively push the ice around in my plumbing I eventually got the collectors un-frozen. The collectors themselves were stagnating at 130F while the shaded and insulated return pipe was well below freezing! I drained a few gallons from the collectors and dumped it outside, (remember this stuff is non-toxic) then I pumped in a couple of gallons of the Cryo-Tek. It's interesting that the DowFrost that I used originally looked like green Gatorade, while the Cryo-Tek looks like fruit punch! The mix now looks like prune juice! But hey -- it works! I'm good to -40F now.  |