Cast iron radiator output

John Mills_3

page was mentioned on HVAC-Talk...

http://www.oldradiators.com/cast_iron_radiators_tips.htm

SM

Cast iron radiator ouput

Trying to size boiler to replace an old boiler. There is 40 ft of baseboard and 3 radiators with 8 section, 2 with 6 sections and 1 with 4 section. What is the heat output of each section with 180 water? Baseboard is approx. 550 btu's/ft?

Thanks

Bill NTSG

Would have

to know the height of your radiator sections to figure the EDR. But if you have hot water and not steam you can size your replacement boiler by doing an accurate heat loss of the building.

You would really have to ASSume the person who installed the heat knew what he was doing. Maybe he did, but ...

SM

Tell me this.

Even with a heat loss calculation, don't I have to know the output of the radiators to determine if I have the means to get the heat from the boiler to the house? If I calculated 105,000 Btu's but only have radiators to give off 85,000 BTUs it would not do me any good. On the other hand if the person is happy with the heating of their home, but wants the boiler replaced, the existing boiler is over sized (cycling on the limits). Couldn't I determine the size boiler needed from the amount of radiators and the fact they are running 180 degree supply water now?

Bill NTSG

Conversely

if you determined that the installed radiation could produce 250,000 btu with 180° water would you put "that" boiler in if the heat loss of the home was only 50,000BTUH ??

In any case I am not arguing with you , but you still need the height of the radiators to determine the EDR. Hot water is the opposite of steam. With steam you size to the connected load , with water the heat loss of the house.

If you are under radiated it will only be a problem at or near design days. Hot water is very forgiving.

SM

Your are correct

The height is 38".

Bill NTSG

How Many?

Columns in the section ? 2,3,4,5,6? it makes a difference.

Assuming 4 column newer style radiators 37.5 " tall you would have 4.125 sq. ft. EDR per section. For a total of approx. 330 sq. ft. EDR. Assuming 180° supply water and an average 170° you would about 150 btuh per sq ft. EDR.

Or 330 x 150 = 99,000. Plus 40 ft baseboard at 550 =22,000. About 121,000 btu. But I flunked math and got expelled from High school so you better double check me.

aaron willsey

I bought and collected a number of old cast iron radiators. I am a home owner doing my own installation of a hot water system. I found a web site that sold radiators, saw what they had and what the output was, they also had charts to calculate output and a formula for each room. Unfortunately, I am at work and don't have the address on this computer. I got it off a google search. My method of sizeing is sort of working backwards, but it gives you an idea. I'll e-mail the web site to you from home.