Less heat with new boiler

Discussion in 'Boiler Forum' started by Mad Plumber, Dec 26, 2013.

  1. Mad Plumber

    Mad Plumber Mad Skills

    Aug 13, 2005
    I had a gravity-fed hydronic system with cast-iron radiators. It was completely gravity-fed, with no pump. My boiler was a coal-fired boiler retrofitted for oil. I recently replaced it with a high-efficiency boiler with a circulating pump. There were no radiators in my basement. The heavy cast-iron pipe and the boiler itself provided sufficient heat in the basement. With the new system, the boiler itself puts out no heat and the water temperature is lower, so that the cast iron pipes in the basement do not put out as much heat as they used to. Now with the new system the basement is very cold. Short of cutting the cast iron pipe and installing a couple of radiators, is there a cheaper way to go? I was thinking of putting some kind of heat diffusers on the cast iron pipe, similar to the plates that are found on baseboard heaters. What do you think?

    Thank you
  2. Soapm

    Soapm Member

    Dec 18, 2013
    Aurora, CO
    How hard is it to add a new zone? The water temp is already lower so add fins to the supply you'll be cooling the water to the radiators and the water in the return may be too cool to use for heat. Our manifold has a place for two more zones, maybe yours has them also.

    I am in no way knowledgeable about this stuff, so take my advice in the spirit it was offered.
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  4. Tom Sawyer

    Tom Sawyer In the Trades

    Nov 29, 2010
    Why do you want to heat the basement?
  5. Dana

    Dana In the trades

    Jan 14, 2009
    Most existing basements old enough to have once had coal-fired gravity systems leak air like sieves and have no foundation insulation. Rather than adding radiation, lower the heat load.

    To start with, air-seal that large skinny hole that is the crack between the foundation and foundation sill, and the corresponding band joist seams (if that's how it's built.) In a small basement you can do that with a coupla 12 board foot FrothPak kits, in a larger basement in a colder climate you may want to go ahead and seal/insulate the band joist and foundation sill with an inch of closed cell spray polyurethane applied by a pro. The foundation sill and band joist is usually the single largest air leak in mid-20th century or later homes, and at an optimally-bad location, being at the bottom of the "stack" driving stack-effect infiltration. (In balloon framed 19th century home with leaky plank sheathing there may be other leaks big enough to compete for first place.)

    Seal up any un-used flue ports air-tight with bricks & mortar or metal vent-caps & duct mastic, and check the weatherstripping on all doors/windows etc. Any flue or electric chases that run from the basement to the attic (or any higher floors) can be sealed at the bottom as well, to prevent parasitic de-pressurization of the basement, sucking in outdoor air 24/365.

    You should be able to do a decent air-sealing job for under $200 in materials, and is usually the cheapest load-reduction you can buy. Fulling insulating the basement may still be worthwhile, but it depends on just how difficult the job is, and your local climate. (Local climate affects just what you can/can't get away with for basement insulation methods & materials, as does the foundation type. Field stone? Cinder block? Poured concreted?)
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