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Output of Burnham Baseray below 150F?

CharlesR Member Posts: 1
Hi all,

Could someone point me to a resource that will give me some sense of the output of Baseray cast-iron baseboard in low-temperature systems? The spec sheet doesn't go below 150F, and I suspect at some point it's non-linear.

Background: I'm a homeowner in the Boston area and have a Buderus GB142 hooked up to a high-mass radiators (circa 1912; the system originally ran on gravity), using a Tekmar unit for outdoor reset, and even on the coldest days of the year, we don't see water temps above the 140s. It's about 40 outside today, and the system is calling for a temp around 100F (the boiler actually thinks it is hooked up to low-mass radiant). The system is comfortable and very efficient.

Background: During a previous renovation, Buderus panels were installed (on PEX) in the bathroom and kitchen. I'd like to relocate them to a separate (currently unconnected) basement zone, because we've found that at low temps, they simply don't put out much heat and they are located in areas where I'd like to put other things. If the bathroom panel gets obstructed by a towel, the output drops even further.

We are renovating and the additional sealing and insulating may help, but I'm still interested in CI baseboard because it would take less space and I'm guessing that CI baseboard would match up better with the rest of the main zone. (We unfortunately don't have the room to restore the original radiators).

I'm working with a plumber our GC is using for the rest of the job, and it would be great to get a sense of the output in the 105-125 range and how that matches up with the heat loss before going forward, and whether others have had success with similar arrangements.

Thank you!


  • jumper
    jumper Member Posts: 2,282
    Eventually convection coefficient goes non-linear but I would think that even at 105° extrapolation is accurate enough. Rule of thumb for convection to still air is 1 BTU per square foot per Fahrenheit degree difference. So 125° water & 70° room temperature yields 55 BTU per square foot. Cast iron radiators have a superior radiation/convection ratio than baseboards. Even cast iron ones.