How many btu/hr from this cast iron radiator?

kinghoward

Studied all the charts and tables but still need help. This is an old cast iron radiator about 3 ft high. It has three columns and is about 9 inches wide. On one end, about 2 ft up, is a bleeder screw. There are 12 'sections?' along the length of about 30 inchs. Assuming 160 F degree water, what is a good estimate of btu/hr that can be emitted if this radiator is half full of water? I beleive its an old steam radiator…when I try to bleed out air, it fills to the level of the screw and water comes out, so cant fill it any higher by myself? The bottom of this radiator gets quite warm but never so hot that I cant hold my hand on it. Its at the end of the return line. I hope this is enough info. If you want a pic, I can do that. Its a big heavy old one, kinda cool.

mattmia2

there should be a low tapping for a steam vent and a high tapping for a hot water bleeder.

why do you need to know the output?

Steamhead

https://forum.heatinghelp.com/discussion/201871/how-many-btu-hr-from-this-cast-iron-radiator

Definitely sounds like a steamer. Post a pic from the front and the side where the bleeder is, and we'll have a look.

kinghoward

Nope, sorry, somebody put only one bleeder screw on the side. No more at the top. I dont have that many hydronic baseboards on this loop, I am just wondering if this radiator emits more btu per foot of length just in case I replace it with baseboards. Thank u

mattmia2

the output of a radiator is far more than a couple feet of cast iron baseboard. if the radiator is connected at the top so that it is compatible with hot water, it should have a tapping near the top and a tapping about 2/3 of the way down. you plug the top tapping and use the lower tapping for steam, you plug the lower tapping and use the upper tapping for hot water.

kinghoward

Steam-head: here are pics requested.

20250807_220058.jpg

20250807_220041.jpg

20250807_220015.jpg

109A_5

Steam only radiators work poorly with hot water since the top of the sections are not connected together so air is trapped. The sections of the radiator pictured are connected at the top (Red Arrow) so it will work with either Steam or Hot water.

One example, typical places for venting / air bleeding.

mattmia2

being piped in copper that is not the original home of that radiator. that tapping is for the steam air vent. look for a probably slotted plug near the top.

that is a common earlier radiator, others will know it. possibly an arco rococo. (arco is american radiator company, now american standard)

109A_5

That looks like a steam only radiator, the sections are not connected at the top. Even though you can bleed that end section to the bleed port level the rest of the radiator is probably mostly air bound.

kinghoward

The house was built around 1918. I doubt that radiator has ever left that room, I concur somebody attached some 3/4 copper piping later but it fits perfect in one spot. It does put out some heat, doesn't seem to be a way to fill it with water but will look again. No idea how old the radiator is, but thanks again!

mattmia2

https://forum.heatinghelp.com/discussion/comment/1861925#Comment_1861925

it was all the same picture when i looked at it earlier so i couldn't see the top. yeah, that radiator isn't compatible with hot water unless you drill and tap a bleeder in the top of each section. it is steam only.

109A_5

At this point the BTU/Hr may be irrelevant since there is only water flowing through maybe only 10 % of the radiator.

kinghoward

I learned alot. Thanks everyone.

Steamhead

Looks like an American Rococo, and yes, it is steam-only. It cannot have been original to that system.

Please do not desecrate it by drilling and tapping for bleeders on each section. You can probably arrange some sort of trade with someone who has a hot-water Rococo. That one you have is 60 square feet.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1861929#Comment_1861929

it is more that most of it isn't filled. cast iron radiators that are filled with water but only have the bottom tapings used for the supply and return work fine because they heat by convection of the water in the columns.

does the room heat adequately? what sort of baseboard does it share a circuit with, is it cast iron baseboard or fin tube?

looks like someone that didn't know what they were doing tried to convert it from steam to hot water if the return is copper and the supply is black iron.

109A_5

To me 10 % full or 90 % empty accomplishes the same thing, nowhere near the rated heat transfer to the surrounding environment as compared to when it is used correctly, steam. With a correct Cast Iron radiator for hot water, even if the supply and return is at the bottom I find it hard to believe the water at the top is 100% stagnant.

The thing is, if you need much more heat in that room when it is cold out, the best practice is to put the correct radiator in that place.

How that steam radiator got there we may never know. It simply may have been a mistake and it never worked well. It would not be the first time an installer screwed something up. Maybe the home had a steam to hot water conversion that was not done as correctly as it should have. Maybe the owners back then did not care, or did not realize the issue, so it was never corrected.

kinghoward

I think it is a situation where the steam radiator was there, so somebody erroneously thought they could just hook up some water and stick a bleeder valve on it. I have 'fin' baseboards (copper pipe) on a short loop and just ended the loop with this cast iron because it was there, might as well try to use it. I agree do not desecrate this wonderful radiator. Finding someone to take it from upstairs isnt going to happen here, ha! But it should be preserved.

Steamhead

https://forum.heatinghelp.com/discussion/comment/1861963#Comment_1861963

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