How to size Cast Iron Radiators

Phil May · Post by **Phil May** » Sat. Feb. 02, 2019 5:17 pm

I am looking at a radiator that is 70"longx10"Deepx27"High Any Idea of how many BTU on 180 water it will put out. I am going to be feeding it with 3/4"

Post by **StokerDon** » Sat. Feb. 02, 2019 5:50 pm

The size doesn't help much, with radiators you need to figure out the "Equivalent Direct Radiation" (EDR). You also need to know if it is a column or tube radiator, how many columns or tubes and how many sections it is.

We used to use the Columbia Heating Guide to figure this out but the website seems to have gone extinct. I looks like it exists on this site.
https://docplayer.net/8687383-Cast-iron-radiator- ... guide.html
Got any pics?

Here is a thread devoted to radiators.
My First Radiator

-Don

lsayre · Post by **lsayre** » Sun. Feb. 03, 2019 6:55 am

A few more resources:

https://inspectapedia.com/heat/UticaRadiationTables.pdf

https://www.expressradiant.ca/pdfs/product_classi ... how_to.pdf

http://www.smithfieldsupply.com/company_info/form ... torest.pdf

http://www.kylesconverter.com/power/btus-per-hour ... -radiation

k-2 · Post by **k-2** » Sun. Feb. 03, 2019 9:56 am

Thats one big ass radiator. I have one almost that size in a 570SF room. Does a nice job if that helps.

Post by **Rob R.** » Sun. Feb. 03, 2019 9:58 am

Phil May wrote: ↑
Sat. Feb. 02, 2019 5:17 pm
I am looking at a radiator that is 70"longx10"Deepx27"High Any Idea of how many BTU on 180 water it will put out. I am going to be feeding it with 3/4"

Post a picture of it and we can tell you the btu rating.

Phil May · Post by **Phil May** » Sun. Feb. 03, 2019 12:07 pm

Sweet that will do more than I need. I needed 16ft of Finn And do not have enough wall.

Post by **Rob R.** » Sun. Feb. 03, 2019 12:09 pm

Phil, the output will be much greater than 16' of fin tube.

You are putting this on it's own zone, right?

Phil May · Post by **Phil May** » Sun. Feb. 03, 2019 12:31 pm

No it is going on the end off 23ft of Finn. I was 16ft short

Post by **Rob R.** » Sun. Feb. 03, 2019 12:37 pm

Mixing cast iron radiators and fin tube on the same loop is tricky. The cast iron takes much longer to heat up and cool down than the fin tube.

lsayre · Post by **lsayre** » Sun. Feb. 03, 2019 1:30 pm

I've taken a quick and dirty stab at a spreadsheet BTU calculator for sizing cast iron radiators. Hopefully, it should get you into the general BTU ballpark, but no guarantees (or as they say, trust but verify). Click on the "drop down" cell and then click the arrow that appears to select "Tube" or "Column", then add the number of tubes or columns, the number of sections, and the overall height, and lastly enter the radiators inlet side water temperature.

.XLSX | 6.3KB | Cast iron Radiator BTUH Sizing.xlsx

k-2 · Post by **k-2** » Sun. Feb. 03, 2019 2:47 pm

I have a mix of finned and radiators and it works well,but i also set up the basement so i can bypass the large radiator as i dont always need extra heat in the basement. It does take much longer to cool down ,but as far as heating up ,less than a minute.

Phil May · Post by **Phil May** » Sun. Feb. 03, 2019 4:08 pm

Well I picked it up today and it took 4 people to push it up a small ramp to my truck. It is not going upstairs in my house. It must weight 800lb or more. I have another room that is 12x24 that i can get it to the door with my forks. It should be enough to heat it. It will be on its own zone now.

Post by **Rob R.** » Sun. Feb. 03, 2019 4:13 pm

It should be about perfect for a room that size.

For your other room - have you looked at high-output baseboard? It puts out about 50% more btu's per foot than the regular stuff.

Phil May · Post by **Phil May** » Sun. Feb. 03, 2019 4:20 pm

I am not familiar with that. I only have 12' to get 24' of finn in.

Post by **Rob R.** » Sun. Feb. 03, 2019 4:24 pm

Your local supply house will know what it is.

I had a similar problem in my brother's house. The living room had a high ceiling with lots of windows, but a door and stairwell limited the amount of baseboard that could be installed. We ended up installing Hayden 958 baseboard that we got from Security Supply. 900 btu's per foot with 180F water.