Ted4 wrote:Ok, another question for u pros. I have a Efm 350 that will sit in my coal shed 60 ft away. I'm ready to pull the trigger and buy the feed and return pipe. I have 3 zones in the house currently. Radiant in slab. 1/2" or 5/8 ID. not really sure. Should I go with 11/4" in trench, or 1"? The extra cost of bigger pipe is about 200.00 and probably a few hundred more between pipe and valves for larger size. The money really isn't the issue, I want to do it right. The question is, if I'm only pulling 3 zones with a total volume less than what a one inch pipe carries, is the bigger pipe overkill?
Leave all the expressed opinion at the curb and do the math!
Sizing is totally dependent on the [fault tolerant] flow in the correct pipe size to carry that load you want to heat. You could put a rocket engine on a straw and do the job or you can do it correctly - It depends!
There are some rules of thumb which have appeared in various threads. For heat transfer, maximum gpm: 1/2” - 1.5 gpm, 3/4” - 4 gpm, 1” - 8 gpm, 1-1/4” - 14-17 gpm, 1-1/2” - 22-25 gpm, 2” - 45-50 gpm.
One gallon per minute of flow (GPM) will move NO MORE THAN 10,000 BTU's of energy in a fault tolerant manor.