So ,,, how much heat will a 1" pex run at 180 degrees. if the run is from 1 boiler to another boiler around 150' distance.
Again we are confusing energy and flow, but the parameters are simple enough: 180 degree water or 140 degree water - each must produce a delta T on the supply and return appliance ports, and must do so relative to degree day load, and that changes daily during the season, so supply temps should also - but circulation should not have to - and thats trouble free design flow! You tend your boiler and your mixing valves to match load demand, not the other way around.
Ill post the short cut from page 65 of my remaining "book of golden rules"
"Assuming the system will work on a 20-degree F. temperature drop, you can arrive at the proper flow rate by dividing the net Btuh load by 10,000. For instance, if the net heating load is 40,000, the proper flow rate is 4 gpm"
lets reverse engineer that to address your question:
From the parameters - the "Maximun, Trouble-Free, Design Flow Rate for Hot Water Heating" of 1 inch is 8 GPM - the net heating load best supported is
Easiest way to figure the pump head in that loop - again based on the maximum flow through the system
and the question is for 1 inch pex so 8GPM is the goal but we need to know what pump to achieve this goal.
1. Measure the "Longest" ( highest pressure drop) piping circuit in feet
2. Multiply this by .06
3. The answer is in feet of pump head.