Base board how long can you go and how many gpm

Big Will

Looking for a accurate pump replacement. the existing B+G is missing its tag but I can't count on that any way. The longest zone is a single 3/4" pipe with 45' of base board. so I can figure my head loss I need to know the GPM required for baseboard. also is this too much baseboard in series?

Brad White_191

Personally

I think 45 feet is too long. I like to limit circuits to 25-30 feet.

An exception would be a series loop where the element lengths are taken into account and increase as you go to compensate for lower water temperatures.

If it is so sized in your case and you are confident in that, I could live with it.

45 feet of element and maybe, another 30 feet of tubing, call it 75 LF plus some elbows? If it is 100 to 125 total feet, the heat output is say 600 BTUH average per foot (27,000 BTUH total), that is well within range of most any small circulator, even a Grundfos 15-58 on speed 1.

The flow limitation is that for the tubing size, maybe a bit less because fin bonding forms ridges which impede flow a bit. Figure 2.5 to 3.0 GPM for 3/4", even if some push that to 4.0.

If I had a choice though and wanted better control, I would split the circuit in two if logistically practical. Naturally though, I know nothing of your space.