BOILER SOURCE & RETURN LINE SIZING

MODEM

So I am adding new zones to my boiler baseboard heat system -- 1 is splitting two bedrooms because one of the rooms is always too warm or too cold, while the other three are new rooms. I already verified my boiler is large enough to handle it. My boiler has a 1-1/4" source & return. My heat lines are 3/4". I know I want to use 1-1/4x1-1/4x3/4 tee's for my source, but do I want the same for the return, or do I down size it slightly to 1x1x3/4? I've read "theories" on both, and I can understand both lines of thought. Thank you!!

Jamie Hall

my take? If that return main is 1 1/4, use the 1 1/4

EBEBRATT-Ed

Don't put more than 65' of 3/4 baseboard on 1 loop or you will run out of heat.

I agree with @Jamie Hall if your supply is 1 1/4 off the boiler and the return going into the boiler is 1 1/4 that's where you should connect