Pipe sizing for secondary loop

chris_93

Hi, How do you determine the proper sizing for a secondary loop. Most new mod con boilers in 120-150k range have a 1 1/4" tappings for the primary loop. The buderus GB142 has 1 1/2" tappings.

1. Is a 1 1/4" secondary loop big enough to deliver all 150k btus.

Thanks

Brad White

Delta-T

Short answer is, yes, you can deliver 150 MBH though 1-1/4" pipe. At a 20 degree drop, 15 GPM will be in an acceptable range (a little higher than I would go, but then, I am conservative.)

You could also deliver 300 MBH in the same pipe if you design for a 40 degree drop... it all depends.

What is the basis for your emitter selection, delta-T, (flow and temperature in and out)?