Posted by Harold Kestenholz - Hydronic Network on April 02, 2001 at 17:56:42:
In Reply to: PEX Tubing posted by Chris on April 02, 2001 at 11:44:38:
Many radiant installers are satisfied with 1/2-inch tubing spaced 6 inches apart held up by aluminum heat-spreading plates with a no longer than 300 feet long loop from supply to return. Using a vapor-barrier pex tube will limit ogygen corrosion to cast-iron boilers.
Domestic heated water does not require the vapor barrier as fresh water from the supply already contains corrosive oxygen.
Pex reforms itself if crimped at 270F. 160F water does not adversely affect Pex.
http://www.astm.org/DATABASE.CART/PAGES/F876.htm
http://www.wirsbo.com/Products/Aquapex/aquapex.htm