Need help finding out capacity of recessed convectors

Andy Stack_3

Working in a closed Church in the city of Cleveland and need some help finding out the capacity of 14 recessed convectors.

Thanks for the help

Ironman

You might try...

Contacting ADP Products or First Company.

Just wondering: are you replacing these or the boiler? If you're doing the boiler, I'd recommend sizing it from a load calc., not the radiation's capacity. The convectors may be over-sized.

Brad White

Will you accept

an "it depends"?

Some questions if I may?

1) Copper tube/aluminum fins or cast iron elements?

2) Steam or HW?



Where this will get fun is in the height. It is not unusual to get 20 to 25% more capacity when going from say a conventional 20 or 24" high enclosure to 32 inches or more. This is due to the chimney effect and the greater amount of air it will draw when warm. Your enclosure at over eight feet is one for the books. Most tables for convectors go to 32, 36 or 48 inches, some to 60 inches. I suspect once we settle on the element type and assume a comparable tall height even less than yours, it will be conservative.



Ironman is right though, if HW, size the boiler to the heat loss. If steam though, go by the EDR of the radiators as best you can determine.

Andy Stack_3

You would think I would know better. (getting old)

The coils are steel pipe with steel fins, and the system is steam.

 

Andy Stack_3

You would think I would know better. (getting old)

The coils are steel pipe with steel fins, and the system is steam.

 

Brad White

A bit thin on information at my end...

But I did get a range, Andy, if you will bear with me.

Steel fins on steel pipe is a hard one to find data for. I checked Dan's book "EDR" but also Vulcan and Ted Reed Thermal catalogs in the office. Not a lot of steel out there which applies. But for copper with elements nominally 36 inches long and 7 inches wide for 8 inch cabinet depths, I get the following per-element EDR numbers in a 32 inch high convective enclosure, slope top, for comparison:



53.4, 49.0, 50, 60, 59.5. 50.2. 37.5 (I suspect steel on this one), 57, 58.4, 61.4.  Remember, this is per-element and you have two per installation.



So now there is some triangulation to do.



Without overstating, I would still start with a heat loss, just because you have to know what you are up against. That is one number.



Secondly, I would "bracket" all of the radiation numbers. Call this the "what-if" set of numbers. What if all of the convectors added up to the highest of your possible EDR factors (say those in the 60 EDR range. Then, what if they were in the middle, say, the low 50 EDR range, then the real low ones, those in the 40 EDR range.



Which one of these sets, total heat output, best matches your heat loss? This is where you try to get into the head of the Dead Man who installed it. (And if not a Dead Man, maybe very, very old, but secure in his knowledge.) But you can at least come up with the most plausible estimate from what you can find. Not perfect but most likely outcome.



Now, are you planning on replacing a boiler with this information? Given section differences and such, now at least you can see if one selection versus another drives you in a direction up or down. And do not forget the piping too. The big old stuff adds up fast and there goes your safety factor. Could be a 1.5 vs. 1.33 gross/net factor.



Anyway, that is my $0.02



Oh, I forgot to add a reminder about that enclosure height. One selection as an example jumps in output from 42 EDR to 56 EDR when increasing from 20 inches high to 60 inches high. Yours are over eight feet, so your conservative approach (that your actual EDR could be higher!) should be considered in all of this. Good Luck!