Replacing cast iron heat pipes in basement

Discussion in 'HVAC Heating & Cooling' started by demar, Oct 6, 2010.

  1. demar

    demar New Member

    Oct 6, 2010
    My 85 year old home originally had a steam boiler. The former owner in the early 80s converted it to gas hot water. The original cast iron radiators are in place, as are the original steam races that circumnavigate the basement at a height just above my head.

    I have a plan to have these pipes removed and replaced with PEX so that they can be run through the joist bays and I can finish the basement. At the same time I'd like to add a second zone for the 2nd and 3rd floors (currently the entire house is on one thermostat). All the first-floor radiators, and it seems, most if not all of the 2nd and 3rd floor ones, have individual supply and return pipes to the basement. I imagine for steam heat regulation this was a requirement, since there are steam valves still in place on the radiators (most stuck wide open), and no evident bypass lines/valves.

    I've had a number of HVAC firms come in - some have refused, others have sounded hesitant and bid accordingly, and one gentleman - a licensed plumber and licensed HVAC guy, bonded and insured, is willing to go forward with the work at what seems to be a reasonable price. He has a design to use 1 1/4" copper mains and branch PEX off of them in order to maintain circulation. I'm impressed with his knowledge and he has done other work for me that I have been pleased with (mostly system repairs).

    Without critiquing his design, I'm wondering if anyone out there has done a similar project and can let me know about the potential pitfalls of this "major surgery". How risky is this job? I would really like to clean up the basement and have better temperature control upstairs (we've already insulated and air-sealed btw) but would just like to know what the risk of major trouble is if we embark on this project.

  2. JSJ96

    JSJ96 New Member

    Jan 23, 2012
    Hey all, two years later I'm about to embark on precisely the same project. Any thoughts on the initial post and Jim, if you're out there, how did it go?

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  4. BadgerBoilerMN

    BadgerBoilerMN Hydronic Heating Designer

    Mar 4, 2011
    hydronic heating designer/contractor
    removing low hanging boiler pipes and radiators the professional way

    We remove low hanging boiler distribution pipes my 6'2" dad calls "head knockers" every week. A gravity or steam boiler system was designed to use the heat of the water and bouancy to drive water to and from the old cast iron radiators. These old turn-of-the-century homes were heated well but split down the middle in order to balance flow.

    As you suggest, zoning may be done, but starts in the basement. Your last contractor is closer than the rest but I fear is still trying to mix the old gravity design with a new, more modern approach.

    Before replacing any boiler or furnace we first perform a computer generated heat load analysis from which, the boiler size (output) can be determined. Further, the minimum flow for the distribution piping can be chosen and installed with confidence.

    Depending on the dimensions of the house, it is very rare for us to install remote or extended manifolds but rather design a distribution system including all pumps, zone valves and controls that hangs on a 5 x 5 foot panel in one room of the basement.

    As most old houses have been upgraded and all most all were originally over-radiated condensing boiler with their built-in weather sensitive controls (outdoor reset) are the perfect match. We often get involved with older homes in which one or more radiators have been removed (kitchen remodels come to mind). From a comfort standpoint this is the equivalent of removing a window pane. Even if PEX is installed below the new kitchen floor it is often done without the benefit of a proper heat load resulting in a perfectly functional kitchen with 10° cooler than the dining room.

    Similarly, a basement of an old Victorian home may have been nicely heated with the waste heat coming off the old 60% efficiency coal fired boiler (not converted to gas), but once removed and replaced with a 95% efficient condensing boiler the basement falls off rapidly. Radiation for any basement finishing or remodel must be incorporated in any new re-pipe as removing the old boiler will even cool off the floors above. With this in mind, we often demo the entire basement floor in order to install a proper vapor barrier, rigid insulation and PEX tubing for perfect comfort and dry usable space. Naturally this would be the time to add a bathroom, address radon concerns and rewire for future entertainment centers etc.

    In short, you may have the right man but it is still uncertain that you have the right plan. Perhaps a professional design for your professional installer would be in order. For that matter, if you have a proper heat load, boiler specification with a drawing, any competent mechanic can bid the job for you.
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