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Posted by HeatPro on May 22, 2006 at 11:28:38:
In Reply to: another question for Heatpro posted by joe on May 22, 2006 at 10:39:53:
Using 1/2-inch to provide 20,000 btuh when you know you have enough radiation to do so at 160F using a 40f drop is OK, because then you can move 1.5 gpm as shown in the Table 7 which provides 30,000 btuh at a 40f drop.
1.5 gpm x 8.33 (lbs per gallon H20) x 60 (minutes = 750 lbs H20 x 40 drop = 30,000 btuh
However, when retrofitting, it gets tricker, because you have to KNOW that your radiation can provide 20,000 btuh at 160F. If so, then the 1.5 gpm that can be provided by 1/2-inch tubing at that distance will heat the attic.