baseboeard/ radiant question?

tony_16

i read dan's book, how come? which i found to be an excellent book.theres one part in the book where dan talks about not going over 67 feet of element on a baseboard loop,but what if you were using cast iron basboard does the 67 feet still apply or should you go less if your using cast iron basboard? next question is about radiant heat, i done a limited amout of radinat heat usually just bathrooms or kitchens just for floorwarming purposes but i find myself getting more and more involved in radiant heat latley and i have heard people talk about injections loops.not to sound foolish but what is an injection loop,? is it to create a reverse return effect in radiant heat loops? where and when would it be a good idea to use one? thank you for input

John Felciano

Tony

The 67 feet is a rule of thumb.The amount of baseboard that can be on a 3/4" pipe is derived by how many btu's a foot the baseboard puts out.3/4" pipe can carry 40,000 btus at 4gpm with a 20 deg delta t.After that there isn't enogh temperature to produce enough heat.As the water cools off in a loop the baseboard produces fewer btu's a foot.I think Dan explains it as people on a train.As the baseboard gives off heat it's like people getting off the train.After a while there is noone left on the train.

A injection loop is a high temperature feed to a cooler radiant loop.It's just a way of modulating the water temperature.For example a radiant system my be running at 120* and the injection loop will add just enough high temperature water,say 180*, to maintain that design temperature.

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