Replacing old cast iron radiator with Runtal Steamview

sjenkins318

Hello! I recently scored a set of 3 lightly used Runtal Steamview radiators for 90% off retail price. I drove all the way from Queens, NYC, to Maine to buy them. The woman I bought them from claimed that that's all she had in her small home, and she ditched the whole steam system for heat pumps. Thus the sale.

These are the radiators, for those who are not familiar with them: https://runtalnorthamerica.com/product/steamview/

My question is heat output. The woman said that the rads put out a ton of heat. I hope they do, because I love the modern look of them and the fact that they mount on the wall.

So, I want to start with replacing one cast iron radiator and see how i like it. My question is, how do I know the new rad will put out enough heat. Do I go by the BTU rating?

My assumption is, if I find the BTU rating of the cast iron rad I want to replace, I have to make sure my new rad has the same BTU or more of the one to be replaced. Do I have that right?

The cast radiator in question is 12 sections, with each section having 3 vertical tubes. Each section is 4.5"x21".

According to this calculator, it seems this rad puts out 1890 BTU. Do I have that right? https://www.expressradiant.ca/pdfs/product_classic_sizing_how_to.pdf

My Runtal puts out 5225 BTU (is is 24"x36")

Something seems off, because its hard to believe this little steel radiator can put out more heat than the cast iron big boy.

See attacehed images of the cast iron to be replaced. Thanks for any input!

sjenkins318

Alternatively, if I look for BTU ratings on this link, it seems like my cast iron puts out 5040 BTU

https://heatinghelp.com/assets/documents/American-Radiators.pdf

Jamie Hall

Ah… double check. Using the .pdf you linked to, I get somewhere in the vicinity of 5000 BTUh for that 12 section radiator…

sjenkins318

Yeah, in the second PDF, which I think makes more sense to reference since it is American Radiators, which is what I have, I get 5040 BTU. So I should be good with my 24x36 Runtal, that puts out 5225 BTU, right? Is that how this works?

Jamie Hall

Yup

Steamhead

@sjenkins318 , be aware that the Steamview is made of steel. Therefore it lacks the thermal mass of cast-iron, and will go cold a lot more quickly then a cast-iron rad when the steam shuts off. This can cause unbalance and comfort issues.

bburd

https://forum.heatinghelp.com/discussion/comment/1808796#Comment_1808796

The problem is mixing different types of radiation with different thermal mass on the same thermostat zone. If you replace all of your cast-iron radiators with Steamviews of equal Btu rating, you should be fine. If you replace only some of them, you are asking for trouble; the rooms with cast-iron will end up warmer than the rooms with Steamview. This is not a difference in energy efficiency; the cast-iron radiators require fewer, longer heating cycles while the Steamviews require the opposite.

mattmia2

If you want it wall hung you could find salvaged wall hung cast iron radiators.

jumper

I suspect Runtal proportion of radiant to convective heat output is higher than cast iron radiator. That may compensate for less thermal mass.

sjenkins318

OK well, I guess I'll install them before this winter and just see how it goes. Thanks!