Need some advice on baseboard BTU and length

[MrMackster]

My plumber is coming in two weeks and I wanted to be able to have an intelligent conversation about this.

I remodeled my second floor, all new insulation, windows, and R60 in my attic. The previous owners converted from steam radiators to hot water baseboard 20+ years ago and I am pretty sure they put down way too many feet of baseboard and now with the remodel its even worse. I need to replace the baseboard in two rooms due to damage. The rooms are small, 12x10 and 11x10 with two windows each. They have 2 six foot sections of fins! Everything is in series and there are the last two rooms in a 5 room loop (all about 2700-3000 BTU required)

I used coolcalc and slant fin's tool to figure out BTU requirements and they both came up with about ~2700 BTU per room which is only about 5-6 feet total of baseboard. Should I downside from 2 six footers to 2 three footers? Anything I should be concerned about? Right now I run at 180 degrees, but I would like to lower it at some point to get it to condense better, but I am sure if that means I should be putting the same amount or less of baseboard. Any advice would be appreciated, my plumber is more of a water/waste plumber and less a heat plumber.

 

[Fitter30]

If your just wanting to lower the capacity the fins can be covered and that will stop the air flow rising . Another way is a boiler reset control that will vary boiler temperature by outdoor temperature

 

[Sponsor]

 

[MrMackster]

If your just wanting to lower the capacity the fins can be covered and that will stop the air flow rising . Another way is a boiler reset control that will vary boiler temperature by outdoor temperature

Yeah, was just reading that. Maybe a good idea to just replace what's there now and cover the fins later if needed. And yes, my boiler has an outdoor reset functionality, but I am skeptical it will work correctly in my configuration.

 

[Fitter30]

Minimum water temp on a cast iron boiler is 140* return. Baseboard really don't start to heat till 120*. Reset will save energy if you need 180* at 0* you won't need 180* at 65*. Easy set point 180* at 0* 140* at 65* 1* change outside temp .6* water temp.

 

[MrMackster]

Thanks @fitter30. Do you know anything about baseboard couplers? Some of the runs are pretty long so I was thinking something to help with expansion might be nice but reading the slantfin docs on their couplers, they mention that they shouldn’t be installed where an accordion action will take place, so I am not actually sure when that wouldn’t be the case. Something like this https://www.supplyhouse.com/Raven-R1644-3-4-x-6-Coupling-x-Coupling-Baseboard-Connector

 

[Fitter30]

Heres a expansion formula
https://www.copper.org/applications/plumbing/cth/design-installation/cth_3design_gencon.html
Those connectors should work