lower temps with more base board

rwhtg

we recently got on the topic of water temps and amount of baseboard in a house. so if you do a load calc and a room calls for 10ft of radiation at at 180 deg water temp. how do you figure the amount of baseboard needed if you want to lower the water temp to say 150 deg?

Jean-David Beyer

how do you figure the amount of baseboard needed

From the length of the wall where you want to run the baseboard, you can get an idea of the maximum length of baseboard you can use. Perhaps you might need more than one wall. The only practical wall for me was 14 feet, and I was lucky. I needed less than 3200 BTU/hour. That is what I would need if it were 0F outside, but design temperature around here is about 14F. You do a heat loss calculation to determine the heat loss.



I use this stuff, and this is a chart as to BTU/hour/foot vs. water temperature for mine. Different brands and styles give slightly different results.



http://www.slantfin.com/images/stories/Technical-Literature/ratings_baseline2000_r.pdf



At 150F, you can get 360 BTU/hour per foot, so if you need 3600 BTU/hour on design day, you would need 10 feet.



I wanted to run 135F maximum, so 275 BTU/hour per foot. so I needed about 12 feet. My room had a 14 foot wall, so I had the contractor put in 14 feet. If course the baseboard was a little shorter for practical reasons, but more than 12 feet. It works quite well. I run 110F water through it when it is 50F or more outside. Mod-Con, so I can afford (prefer) running lower temperatures.



I even run 76F water through my radiant slab those days.

Steve Whitbeck

BTU per ft.

The baseboard manufacturer will tell you what BTU per ft. their product will put out at a given temperature.