In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.

# baseboard btu

Member Posts: 46
Can someone help me out by telling me how to figure out how much btus a foot of baseboard puts out and how much btus a pipe can handle.
Foe example: 100' of basebord with 3/4" copper pipe at lets say 170 degree water.
Thanks,
Joe

• Member Posts: 87

It all depends on the the condition of the base board. But most 3/4 " baseboaed puts out approx. 500 btu's per foot at 180 degrees. Check out slantfin.com.
• Member Posts: 688

With all that baseboard your gonna hafta be more specific as to which end of the loop were speaking of. Exceeding 70 feet on a single loop isn't recommended. Depending on the manufacturer I think its around 590 btu @180 and I belive you can do 40,000 btu in one 3/4" pipe. I'm sure I'm gonna get corrected but you'll be close...Robert O'Connor/NJ
• Joe

Most copper fin baseboard has an output ranging from 560 to 600 btuh per lineal foot. These ratings are generally based on a 4 gpm flow rate. As stated, if the element is banged up, if the end caps are missing, or if the air convection opening at the bottom has been obstructed by carpet and pad, then the output will be much less. The btuh capacity of 3/4" copper is approximately 39,000 btuh. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

www.burnham.com
• Member Posts: 110

What's an end cap and why is it important? Many thanks,
• Member Posts: 545
Glenn, I've always wondered

> Most copper fin baseboard has an output ranging

> from 560 to 600 btuh per lineal foot. These

> ratings are generally based on a 4 gpm flow rate.

The data sheet for every BB I've ever seen, including Burnham's CI BB includes this statement, "I=B=R Ratings are determined from tests made in accordance with the I=B=R Testing and Rating
Code for baseboard type radiation, including an allowance of 15% for heating effect permitted by the Code."

What is this 15% bump? I've never felt comfortable using it and have backed it out when I'm sizing BB for a project.
• Member Posts: 545

I usually figure 525-550 btu/ft of BB. You need to look at an IBR chart or figure the head for the flow you need and pick a pump that will match that. You want to keep the velocity in the pipe down to a maximum of 4' per second. So the farthest water should travel in a minute is 240'. 3/4" copper holds pretty close to 2 gallons per 100' of pipe so 240' holds about 4.8 gallons. That tells us 4.8 gpm is the absolute maximum you should try to push through 3/4" pipe. 4 gpm is a safer number.

4 gpm will carry 40,000 btuh with a delta T of 20ºF. Now take 40,000 btuh and divide it by 550 btuh per foot of BB and you can put about 72' of BB on a single run.

So to figure how many btu you can push through a pipe you need to know how much water is in 100' of pipe. Multiply that by 2 to be safe keeping in mind 2.4 wuld be the max. That is how many gpm you can move. How many btu woould then be determined by your delta T. 20ºF is a commonly used number. It could be more or less. But 1 gpm with a delta T of 20ºF will deliver 10,000 btuh.
• Member Posts: 545

I usually figure 525-550 btu/ft of BB. You need to look at an IBR chart or figure the head for the flow you need and pick a pump that will match that. You want to keep the velocity in the pipe down to a maximum of 4' per second. So the farthest water should travel in a minute is 240'. 3/4" copper holds pretty close to 2 gallons per 100' of pipe so 240' holds about 4.8 gallons. That tells us 4.8 gpm is the absolute maximum you should try to push through 3/4" pipe. 4 gpm is a safer number.

4 gpm will carry 40,000 btuh with a delta T of 20ºF. Now take 40,000 btuh and divide it by 550 btuh per foot of BB and you can put about 72' of BB on a single run.

To figure how many btu you can push through a pipe you need to know how much water is in 100' of pipe. Multiply that by 2 to be safe keeping in mind 2.4 wuld be the max. That is how many gpm you can move. How many btu woould then be determined by your delta T. 20ºF is a commonly used number. It could be more or less. But 1 gpm with a delta T of 20ºF will deliver 10,000 btuh.
• Member Posts: 76
baseboard

Embassy has some high output residential baseboard, 870 btu's @ 180 degrees 4Gpm.

http://www.embassyind.com/pdfs/embassyind_system6.pdf
• Member Posts: 94
BTU

At what temperature?? John Manufacturer "Exquisite Heat"
• Member Posts: 545
I'm not sure what you mean

by "at what temperature". BB output? Of course that will vary depending on the deltaT of the room and water temps but generally 70ºF room and 180ºF water temps are assumed. I use a number somewhat less than the manufacturer's because of the 15% they add on to the actual measured performance of the BB. See my question to Glenn above.

If you're asking about the heat delivered by the water it's always going to be pretty close to 10,000 btuh per gpm with a deltaT of 20ºF.
• Member Posts: 2,542
Siegenthalers take on \"heating effect\"...

from his Modern Hydronic Heating of residential and light commercial buildings (first edition)

"The origin of the heating effect factor goes back several decades.At that time it was used to account for the higher output of baseboard convectors placed near the floor level rather than at heights typically found with standing cast iron radiators. Unfortunately, it is a standard that has outlived its usefulness. Since the 15% higher output can not be documented in laboratory settings, it should be discounted from the baseboards actual output capacity by dividing the listed output by 1.15 before selecting baseboard lengths. This bases selection on actual tested performance."

So, in a nutshell, you should ignore the 15% heating effect factor, and derate the baseboard before you choose a size for a given loss factor load.

I wonder when the manufacturers are going to catch on. I suppose its going to take a law suit from someone before they wake up. It usually does.

ME
• Member Posts: 94
BTU

How many systems are running at design. The BTU ouyput will depend heavily on the boiler temp, thermostat demand rate, and the heat loss of the room. Design is based on 100 % circulation at 180. When does that happen? The oil salemans dreams I suspect.

John Cockerill Exquisite Heat
www.Exqheat.com
• Member Posts: 545
Agreed

But we need to make sure the system will take care of the load at design temps.

At least I think that's what the original quesion was about, ie, how many btus to a foot of baseboard and how many btus can you move through a pipe.

You'll get no arguement from me that design is a very tiny portion of the time a system is operating.
• Member Posts: 6,106
Actually

the very best way to size BB is with a program that takes into account the temperature drop. The last elements on the loop will see a lower water temperature and have a lower output that the first ones.

There is an excellent series baseboard sizer on the HDS program, try a demo at www.hydronicpros.com

For a quiet BB system the 1 gpm figure in the sizing charts is commonly used. 4 gpm starts to get a bit of noise. But it does cut down on the amount of board needed

I'd design with a 180 supply so you have some room to adjust up if needed.

Ideally a reset control on the boiler would "nail" the exact temperature needed and be constantly adjusting the supply temperature. A nice even, noise free, fuel efficient BB system this way

hot rod