Appropriate Size Boiler

Hi, I have had several plumbers come in and look at my system. I am getting mixed opinions on what is the correct size boiler. Brownstone is pre 1900, 4000 SF, 4 family, steam heat with gas and each unit has its own hot water heater. I currently have a 10 year old Burnham IN9 (280k BTU) some plumbers say that is the correct size and others say I can size down to an IN6\. My current boiler is working fine but my issue is actually it was installed/piped wrong and the horizontal lines have a sag in it trapping water. I am going to repipe correctly and fix the sag. The project cost is significant and the additional cost for a new boiler is not that big of a difference. Does anyone have experience on the correct sizing or should I just leave my IN9? thanks Josh

jfeuer22

in Plumbers and Plumbing 11 years and 5 months ago

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Master Plvmber | 11 years and 5 months ago

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Not much market for used boilers, though I’ve had customers have people remove them for free via Craigslist.

jfeuer22 | 11 years and 5 months ago

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Thank you. This makes sense to me. Basically, my boiler and pipes are oversized for the space. Since I am going to have to redo all piping either way, it makes sense to spend the extra money to have the right sized boiler and therefor having the right size pipes. I do plan on adding some radiators but still the IN6 should get the job done. Hopefully, it will save me on some gas too. Is there a market for used boilers? My IN9 is relatively new and has lots of life in it. Thanks for your help. Happy New Year

Master Plvmber | 11 years and 5 months ago

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From my notes, and some information you may find useful: When sizing a boiler in a steam heating system, professionals use a term that is new to many people, Equivalent Direct Radiation (EDR). EDR is applied in two separate ways. First it is a calculation of the surface area of all the radiators and pipes in a building that will fill with steam from the boiler and give off heat to the living space. This calculation is expressed in square feet and gives us a value shown as “sq. ft./EDR”. We calculate this number by measuring all the radiators and some of the pipes in the heating system and referencing old charts that give us the correct numbers to assign to each unit as released by the manufacturers, then we add them all up. Second, the EDR number is a value the boiler manufacturers use to rate the output or express the amount of steam a boiler creates and emits through the piping, sort of like you know a BTU rating does for air conditioners. Most steam heating systems were designed in the early 20th century by someone who was very well informed about how much energy is contained in a specific volume of steam and how best to convey and convert that energy into useable heat within a building’s partitioned rooms and living areas while limiting installation costs by carefully sizing pipe diameters and radiators to their effective minimums. At the time, this was considered to be a very technical job that rarely fell to anyone other than highly qualified engineers and contractors. Today, it’s an installer’s job to match the EDR output of a specific boiler to the system’s EDR within about 10%. This ensures their ability to process that steam effectively, efficiently and quietly. Mismatching these two pieces (the boiler, and the piping/radiator system) creates all kinds of problems: banging pipes, hissing/spitting air vents, high fuel bills, unnecessary fuel usage, unbalanced heating, frequent failures, and the list goes on. Unfortunately, your boiler and heating system are grossly mismatched. Your system can process no more than 434 square feet of steam per hour while your boiler produces 725 square feet of steam. See boiler literature here: http://cdn.usboiler.net/products/boilers/independence/assets/Independence_ProductDataSheet.pdf In more familiar terms, your boiler consumes 280,000 BTUs per hour while your building can only process the steam made by the model of boiler that uses 175,000 BTUs, maximum. Hope this helps.

eman134 | 11 years and 5 months ago

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for a rough EDR calculation, use this link to calculate EDR for your radiators http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCkQFjAA&url=http%3A%2F%2Fwww.columbiaheatingsupply.com%2Fpage_images%2FSizing%2520Cast%2520Iron%2520Radiator%2520Heating%2520Capacity%2520Guide.pdf&ei=uz_EUpj4GsLLsATojYGwDA&usg=AFQjCNEvBiUEWgqVL_SSrULq04tJQfqTBQ&bvm=bv.58187178,d.cWc Add about a 30% pick up factor for the risers, mains etc., and compare it to the output of the IN6 (108 MBH steam) or IN9 (174 MBH steam) http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CE0QFjAB&url=http%3A%2F%2Fcdn.usboiler.net%2Fproducts%2Fboilers%2Findependence%2Fassets%2Fliterature.pdf&ei=0kHEUuavNY7lsATnrILIDQ&usg=AFQjCNG_aSlOArbur3iNF6Vv-l4u9xNrSAamp;bvm=bv.58187178,d.cWc And do not forget to repipe the near boiler piping if it is substandard, since that will make a huge difference