I am trying to design a radiant floor heating system for my house. I
think that I have enough knowledge to just go ahead with what I know
so far but I really want to design this system with all aspects of
efficiency in mind.

This brings me to the difficulty of pump sizing. After scouring the internet I was finally able to find a pdf document that did a fair job of explaining how to calculate feet of head loss but I still have questions. http://www.robur.com/images/resources%20images/PUMP%20SIZING%20BROCHURE.pdf

How do you calculate for parallel circuits between headers? I'll attempt some ascii art here to explain.

_______________________________________ | | | | | | | | | | | | | | | pump | | | | | | | | | | | | | | | | | | | ---------------------------------------

The first problem I have is which came first; the chicken or the egg? You have to know the flow to calculate head loss but you have to know the amount of head to see what the flow is for a given pump curve.

Sorry, back to the drawing. Assume that all pipe is 3/4" copper; the supply and return headers are 100' long each and each parallel circuit is 25' long. (This is not the actual design just a simple example).

The headers elbows and tees are easy enough to calculate but I can't figure out the circuits. According to that pdf I think they would say to just include the circuit with the most head loss. I don't think that's right though. Other things I have tried are to combine the pipe areas and calculate the equivalent diameter of pipe; divide the given flow by the number of circuits and add their head losses together; and I've thought about calculating for equivalent circumfrence of the combined pipes. None of the options really jumps out at me as the answer. Can somebody please help clarify?

This brings me to the difficulty of pump sizing. After scouring the internet I was finally able to find a pdf document that did a fair job of explaining how to calculate feet of head loss but I still have questions. http://www.robur.com/images/resources%20images/PUMP%20SIZING%20BROCHURE.pdf

How do you calculate for parallel circuits between headers? I'll attempt some ascii art here to explain.

_______________________________________ | | | | | | | | | | | | | | | pump | | | | | | | | | | | | | | | | | | | ---------------------------------------

The first problem I have is which came first; the chicken or the egg? You have to know the flow to calculate head loss but you have to know the amount of head to see what the flow is for a given pump curve.

Sorry, back to the drawing. Assume that all pipe is 3/4" copper; the supply and return headers are 100' long each and each parallel circuit is 25' long. (This is not the actual design just a simple example).

The headers elbows and tees are easy enough to calculate but I can't figure out the circuits. According to that pdf I think they would say to just include the circuit with the most head loss. I don't think that's right though. Other things I have tried are to combine the pipe areas and calculate the equivalent diameter of pipe; divide the given flow by the number of circuits and add their head losses together; and I've thought about calculating for equivalent circumfrence of the combined pipes. None of the options really jumps out at me as the answer. Can somebody please help clarify?