Replies

1. 
   Walt_Pollard | Apr 11, 2001 11:23pm | #1

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   Jason: I have done this with much success. The first step is to figure out the maximum output of the radiator in question at the maximun design temp of the boiler. Once you have your maximum output in BTUs you can figure out how many GPM you need to deliver to the radiator in order to deliver the necessary BTU's (assuming a certain tempiture drop in the water as it travels through the radiator). If you are not familure with these king of calculations I would pick up one of Dan Holohan's books throught http://www.heatinghelpl.com.

   Once you know how many GPM you need to deliver you can find out what diameter PEX will be required. This will differ depending on the manufacturer. Kitec makes a PEX with an aluminum layer that will handle high tempitures so it can be used with cast iron radiators. They have a table that will tell you what diameter to use. http://www.ipexinc.com/kitec.html

   Good luck. Its fun stuff.

1. 
   Jim_Nation | Apr 17, 2001 04:59am | #2

   *It's a little more complicated. The previous post assumed you wanted to serve the existing cast iron radiator. I think you intend to install in floor radiant heating. The temperature of the water for in floor radiant heating should be no more than 130 degrees even better 100-110. Your existing boiler is probably running at 180 to 200. Consequently you need a mixing circuit and secondary pump to provide the lower temperature water to the radiant floor tubing.

1. 
   jason_wise | Apr 18, 2001 05:37am | #3

   *Thanks for the help, this is exactly what I need to know. Do you have any suggestions about where I could find more detailed info about this on line.

1. 
   Walt_Pollard | Apr 19, 2001 01:26am | #4

   *Whoops..Jim is correct...I should have read your question more carefully....sorry for any confusion. You might want to check out http://www.heatinghelp.com. Dan Holohan has a few books for sale there that discuss various piping schemes and give you enough information to be a little creative. "Pumping Away" should have much of the information that you need. Regards, Walt.

2. 
   jason_wise | Apr 19, 2001 01:26am | #5

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   I have been told that your not supposed to mix thin wall(copper base ect.) with cast iron radiators in a hot water system. My clients were told they could replace a cast iron radiator with pex IFR in the bath I'm remodeling. Does anyone have a definative answer on this? Can you suggest a site for sizing and installation guidelines?