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may need new boiler

Fizz Member Posts: 547
So, my EDR is 478, without piping figured.  Nearest boiler match is Dunkirk PSB6D which is rated 479, my main concern is only 7.5 Gal of water capacity in steam system.  Currently have converted WM SGO6 rated 654, but fired at 186K.  Slant fin is rated at 508, don't know gal of water capacity; Smith rated at 533,m with 12.5 gal cap, Crown 533, with 10.7 cap, WM with 521, and capacity of 12g.  Others are Burnham, 542, Newyorker 538 but don't know capacities.  Which is best suited to my set-up?


    RDSTEAM Member Posts: 134
    edited February 2014
    Low content boilers

    What is your current boiler size and water capacity? Low capacity boilers can have a problem if your return water returns slow. A reservoir pipe may be your only option.

    Nevermind i see your current setup now. With a 33% pickup factor! they were just about right there. If your EDR calculated to what you say it is, then with a pickup factor added in i wouldn't go much smaller then the 640 mark.
  • Fizz
    Fizz Member Posts: 547
    Edr confustion

    some posts say match boiler to edr of rads pick-up factor. 
  • The capacity factored in

    We hope the steaming capacity of the boiler has been factored in by the manufacturer with regard to matching the boiler ratings EDR with the amount of steam needed to fill the system. The total volume of the boiler is not able to be used until the final dry-firing event. In my 1,050,000 btu peerless 211A has about 3 gallons from normal waterline to LWCO cutoff point to use for making steam for 55 radiators.

    Just find a boiler whose square foot of steam rating matches your system, and you should be fine. A plus would be a stocking distributor nearby, in case you need a spare part down the road. Even more important would be an installer who feels comfortable opening the installation manual to verify the piping layout!--NBC
  • Fizz
    Fizz Member Posts: 547
    Matching edr

    of boiler to connected load, for argument sake.  Say you have 500edr without pick-up factor added, and Acme boiler has boilerA rated at 500 sq ft of steam, and boilerB rated at 665 sf, which would equal connected load + pick-up factor. This is where my confustion is greatest.  Most boilers state pick-up factor factored in, so that being said, if the 500sf boiler has pick-up factored, then it would match a connected load of 376 + pick-up factor of 134.  Is that right?  If so, then the match for the 500 edr would be boiler 2 rated at 665?
  • Sizing a boiler

    When you have completed your calculations, and have the square feet of radiation (EDR), look in the boiler specs for square feet of steam, with no pickup factor, as it has already been included by the boiler manufacturer--NBC
  • vaporvac
    vaporvac Member Posts: 1,520
    edited February 2014
    500edr = 500sq ft of steam

    500edr (without spick-up factor) = the boiler rated at 500sq ft. The boiler manufacturer has included it, but it isn't written. So really their edr is 500 plu30%, but they don't write that in because it's confusing. Just compare the edr to sqare feet and you'll be fine.ie. My combined edr is 1460. I have two Slantfin boilers so i need 730edr each. This is how we chose them:


    Looking at the chart you can see that the TR50 is the closest with 767sq ft. ,so that's what we went with. That's it. There's nothing else to do. That boiler is able to account for the piping. End of story. (Although it IS confusing!)
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • Fizz
    Fizz Member Posts: 547
    Clarity at last

    Thanks so much for your replies.  Now it makes sense.