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# Figuring out proper radiator size for a room... in laymen's terms

Member Posts: 191
I'm trying to figure out if I can downsize the radiator in a room.
What's the easiest way to do the calculations for a newbie?
It's a small room and I'd like to go from a 13-fin beast of a radiator to a 6-fin.
One-pipe steam system.
Thank you!

• Member Posts: 7,373
The only accurate way is to do a load calc on the entire house and then on the room individually. If the radiation for the entire house is over-sized by 15%, then it should be over-sized for the room proportionately.

IDK why you'd wanna go to the trouble of changing the rad, though. Just slow down the vent rate on it.
Bob Boan
You can choose to do what you want, but you cannot choose the consequences.
• Member Posts: 143
Easiest way to fix this problem is to slow down the vent. A gorton #4 is a great way to keep an oversized radiator tame.
• Member Posts: 616
Is the room overheating, or are you trying to gain space by downsizing the radiator?
Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
• Member Posts: 191
Mostly swapping to regain some space in a small room while still making sure adequate heat.
• Member Posts: 191
Is it possible to just do a calculation on the room size vs size of radiator?
• Member Posts: 7,373
bipbap said:

Is it possible to just do a calculation on the room size vs size of radiator?

I think you missed what I stated earlier about it being sized PROPORTIONATELY.

If you only do a load calc for that room and it needs 10k btus, and then you install a radiator with 10k btu output, what's gonna happen if the rest of your radiation is over-sized by 30%? Answer: that room will be under-radiated by 30%.

This is why you need to do a load calc and radiation survey on the entire house.
Bob Boan
You can choose to do what you want, but you cannot choose the consequences.