I am trying to figure out how to calculate the total equivalent length of a loop with cast iron radiators. The pipes and fittings are easy to calculate because pipe is calculated linearly, and the fittings are just looked up in a table, but how should the radiators be included in this? How does one figure out how many feet of head to add to the loop to account for the radiators?

  • A quick and simple google search gives : runtalnorthamerica.com/commercial_institutional/… – Solar Mike Jul 17 '19 at 7:29
  • That link is for the new style runtal radiators, as opposed to the old style cast iron radiators. – zelinka Jul 17 '19 at 14:52
  • But if you understand the theory and the formula (like how to calculate pressure drop using the friction factor) then it is possible to adjust or re-work for any type of radiator or device that causes a pressure loss. – Solar Mike Jul 17 '19 at 14:55

The standard way to treat a radiator is to pretend like it is a piece of straight pipe, so if the radiator is 4 feet long it counts as 4 feet of straight pipe.

I got this information when I asked a hydronic heating specialist how one does this calculation.

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