System Design: All Cast Iron Rads; on the right track?

D107 · May 2018

See attached table and notes which are written up by zone. Will write up room by room soon. Had pro heat loss for various outside temperatures. Calculated load by rad EDR. Zones 1 and 2 are cast iron. If I replace zone 3 basement baseboard with cast iron rads, then load will match loss quite well and should work with 130º AWT (supply 140º) on design day. I know a higher ratio of load to loss btu would be better and allow me to run lower SWT, but I've insulated the house as much as possible, so my 1:1 ratio will have to do. The table shows the deficiency of the baseboard. I'm posting to see if I'm on the right track here. I can't see how I could make this system work otherwise (hopefully for mod-con) and still keep it simple.

Rich_49 · May 2018

Are you using baseboard or radiators ?

D107 · May 2018

@Rich I guess I'm open to cast iron baseboard but prefer radiators. I was told baseboard is more expensive to install. We currently have about 29ft of baseboard, out of which 26ft is actual element. And I already have an old ARCO 53 EDR rad we took out of the kitchen.

D107 · May 2018

I should mention that all zones are piped in series--unfortunately that's how the former owner's contractor did the job when converting from gravity system in 1981. Has not been a problem for us--of course that's with an oversized 180kbtu firing on a 75% eff. boiler. This is a small 1800 sq ft house; can't see doing a manifold with this or changing piping. Best in investment seems to be going cast iron in basement to even the playing field.

NY_Rob · May 2018

Since the cast iron baseboard is probably more radiant vs. convection heat of fin tube... you get a nice long stretch of heated "feel" out of the cast iron baseboard sections.
Install a 10' run of CI baseboard... you feel heat along the whole 10' section of wall.
I replaced 18' of fintube with 19' of CI baseboard last summer... after going through the brutal 2017/18 winter I can tell you the area of the house with the CI baseboard was the most stable and comfortable area in the whole house.
BTW- the mod-con absolutely loves the high thermal mass of the CI baseboard and high amounts of water they contain... no more short cycling!

D107 · May 2018

@Rob I was told that CI baseboard is more costly to install but pure price is not the object. I tend to like the look of rads better and baseboard tends to cut down on wall space. However if you install rads where baseboard used to be there might be some additional work to hide some now-exposed copper piping behind the sheetrock. And some sheetrock repair as well. So adding elbows may impede flow--not something you want to do in a series piping setup. But first I have to make sure that my pdf table of gain and loss is in the ballpark.

NY_Rob · May 2018

As a replacement for existing fin-tube the CI baseboard is almost a drop in solution as far as BTU output is concerned. Even though the CI BB has slightly less BTU output vs. fin-tube it more than makes up the the loss once the hot water flow stops.

Think of CI BB as "the gift that keep on giving"

SuperTech · May 2018

I agree with @NY_Rob cast iron baseboard is far superior to fin tube. You will definitely be more comfortable with it and the mod con will perform well with it. If cast iron radiators aren't a good option the cast iron baseboard is a fantastic choice.

D107 · May 2018

Well the reduced ci btu output may remove that from consideration. My goal is to almost double the gain to equal the loss in basement. Configuration of furniture in my room would obstruct any additional baseboard runs above the current 4 six-foot runs.

System Design: All Cast Iron Rads; on the right track?

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