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Alternative to Baseboard Slant Fin Tube

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carsonmccullers
carsonmccullers Member Posts: 4
edited May 16 in Radiant Heating

I want to replace the baseboard slant fin tube in one or two first floor zones with a European product:

https://www.cnmonline.co.uk/central-heating-finn-radiators.html

The 1913-built house once had cast iron radiators that the previous owner replaced with baseboard after an assumed freeze. Ran new copper supply and return lines. Floor holes and footprints of original cast iron rads are still evident.

BTU to BTU, considering the convection qualities of enclosed slant fin tube, how do these compare? 50' of baseboard slant fin in the front living room and dining room would have to be replaced with X' of "FINN" product?

My Burnham Series 2 Gas Boiler is about 30 years old.

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  • hot_rod
    hot_rod Member Posts: 22,491
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    it shows output as 3545 btu/hr?

    Is that for the longest section?

    You would want to match the btu output if the fin tube, around 500-550 btu/ft

    It looks like you can add some fan boosters

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • carsonmccullers
    carsonmccullers Member Posts: 4
    edited May 16
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    3545 btu/hr is for 2000mm length (about 6' 6") which is about 545 btu/ft and equal to the output of the fin tube.

    To the experienced heat tech, does that sound right? Is it not a direct comparison because of the lack of cover and convection heat? Would they be less efficient than the baseboard fin tube? Is it dramatically less efficient to where I should reconsider?

    hot_rod
  • Zman
    Zman Member Posts: 7,607
    edited May 16
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    I'd be inclined to do a heat loss calc on the space and determine how many BTUs you actually need, especially if your are buying spendy new heaters. Chances are the person that installed those heaters WAG'd it (Wild **** Guess 😜). Be sure you do the heat loss and install new heaters in all the rooms on that zone so you don't mess up the balance. https://slantfin.com/slantfin-heat-loss-calculator/

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    mattmia2bburd
  • mattmia2
    mattmia2 Member Posts: 9,970
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  • carsonmccullers
    carsonmccullers Member Posts: 4
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    The website and app are not working.

    I've done webform calculations before (ceiling height, wall dimensions, int. or ext. walls, window size, old or insulated window, room above condition, room below condition, etc.) there are simply too many variables for any of these to be correct if self reported.

  • hot_rod
    hot_rod Member Posts: 22,491
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    fintube in the metal enclosure induces convective currents across the fins. You can feel that air movement above the enclosure. Sometimes see curtains above the enclosure moving. Or black streaks😳 on the wall.

    So the bare fin would probably transfer more energy via radiation, less convection. The opposite for fin tube in enclosures.

    If a fan is added you get forced convection to add additional output. That is the principle behind fan coils and kickspace heaters, generally used to get higher output in a smaller device, size wise.

    The third heat transfer mechanism is conduction. When your feet touch a radiant floor, you are experiencing conduction transfer. Wirsbo used to show the % of each transfer for radiant in a drawing in their design guide, conduction, radiation, and convection.

    Panel radiators sometimes have fins inside, some are just a sheet metal box without the convection boost from the fins

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • carsonmccullers
    carsonmccullers Member Posts: 4
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    Ok. I understand different systems (metal enclosed slant fin, radiant baseboard, cast iron tube, radiant floor) have different properties and heat in different combinations of mechanisms (convection, radiation, conduction). And that a fan or air circulation will increase output (I am not considering this as an option).

    I want to free up my 9" tall, early 1910s, stained, hardwood baseboards in my Living and Dining rooms (all on 1 of 4 zones). I believe these exposed fin tube, when installed 2-high, below windows, will look great. Windows improve convection effect?

    Do I ask a couple heating contractors to run the calculations, heat loss, and provide bids for the work?

  • hot_rod
    hot_rod Member Posts: 22,491
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    either trust a contractor to run some numbers or do it yourself. Find free heat load calculators online

    Yes hot goes to cold, always. So heat emitters under a cold window will drive some convective currents across those fins, and the glass.

    I suspect you will have metric connections to deal with, so be sure to get adapters to U.S. CTS copper tube size. I do like the looks of those.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    carsonmccullers
  • JohnFX
    JohnFX Member Posts: 7
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    Remember to consider the temperature of the boiler water (the "high limit" setting). BTW, where is it set currently? You can "stretch" the output of any Baseboard/Radiator/Panel by increasing the water temp entering. But you gain efficiency by lowering the water temp. Your non-condensing boiler can have a high-limit set as low as approx. 145f

    The specs for the new product you are considering should detail at which water temp they are rated. And should also provide correction factors for other water temps.

    I like to recommend adding additional radiation to any project to use the lowest water temp to gain the highest efficiency

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,176
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    My experience with any baseboard manufacturer… SlantFin, Sterling, Haydon, etc. …is that when you remove the cover of the radiator, you get a significant loss of output capacity.  As much as 60% less heat from the loss of the convection current that is generated by the “chimney effect” of having the cover in place.  By the looks of the proposed radiator design, I am guessing that the fins are made of a stronger material since they are not protected by a cover, and that there are less fins per inch which makes for less surface area for transferring heat.  I’m guessing that you may need more length to accomplish the same result.  

    This is just an observation based on looking at the photograph of the existing baseboard and the proposed product. 


    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    kcopp
  • kcopp
    kcopp Member Posts: 4,450
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    Cast iron baseboard may be pretty competitive.

    It would heat much more comfortably.