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Posted by Jack, CVMS on January 04, 2004 at 22:59:10:
In Reply to: Boiler Anti-Freeze posted by Tom Olson on January 04, 2004 at 15:58:57:
Something else to be aware of - be sure that there are no galvanized pipe fittings in your system (there shouldn't be anyway, but once in a while one gets in) as propylene glycol and the zinc of the galvanized coating are not compatible. Also, find out what percentages of glycol you'll need for burst protection as well as freeze protection. For instance: At 35% PG the fluid will begin to freeze (turn to slush) at 4°F, but pipes will not burst until around -60°F. If you need to start the heating system during the winter with the ambient temperature at -20°F you probably wouldn't get any circulation, but your pipes will be protected from freeze damage.
Pure water is a better heat transfer medium by far than the glycol, so keep the mixture as weak as you can get by with.
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