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Thread: boiler size question

  1. #1

    Question boiler size question

    I am converting from oil to natural gas. I have a 2-story old Victorian house, 7 rooms, steam radiators with 1 pipe system steam boiler/burner. I am replacing a Weil-McLain Gold Series 3 Model P-SGO-4. One vendor noted that this is too big it has steam sq ft of 450. I have had no problems.

    4 vendor quotes have similar boiler sizes, but my vendor's is a bit larger. Are they similar enough and so OK? All visited all radiators and looked like they measured. My vendor is a well known local guy named by utility and town hall construction dept.

    My vendor wants to install the Peerless 63-04 or 63-04L - Input MBH 147.5 and steam sq ft 383.

    Other vendors:

    One has the Peerless smaller 63-03 without the "L" (input MBH 118, steam sq ft 308).

    One has the Burnham IN4 (Input MBH 105, steam sq ft 271).

    One has the Utica PEG112EID (Input MBH 112, steam sq ft 292).

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    The fact that the existing boiler keeps the house warm has only a very small relation to whether it is too big or not! Just read some of the other (many) threads here in this section. The easiest thing is to replace it with a similar size, and 95%+ of the time, that's too big, and often WAY to big. Figuring out what is the right size takes some actual calculations, not a guess, not just counting up the radiators, or the square footage, and no two houses are built the same, so you have to take into consideration the windows, sizes, types, insulation, amounts, types, locations, air exchanges (how tight the building is), and your actual design-day temperature requirements (available for free with your zip code). Until you've had that figured, while yes, you can put in a boiler that will heat the house, that is by no means the one that will give you the best economy while doing it...bigger costs more both up front, and every time it runs.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    In the Trades Tom Sawyer's Avatar
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    Steam boilers are a little different than hot water boilers in that you need room (head space) above the water line to stabilize the steam and keep wet steam out of the pipes. So most times the installer is going to slightly oversize the boiler itself and then reduce the input. All 4 of the boilers you listed are good units for steam making.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  4. #4
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    As Tom suggests, steam boilers are a little different. Sizing a boiler for steam is accomplished by sizing the boiler to the radiation. The performance of the system depends on matching input to output.

    Each boiler comes with seldom read instructions for building the proper sized header, from pipe, and should be followed to the tee. Your "vendor" installing contractor should produce a document showing the total radiation connected to the proposed boiler and the boiler IBR output listed.

  5. #5
    In the Trades Tom Sawyer's Avatar
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    Everhot makes an anti surge tank that has saved the ass'es of many an ignorant boiler installer LOL
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  6. #6

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    Can you please tell me what the EDR for my radiators is? To better analyze, as you tell me, the size of suggested boilers by vendors? Attached are photos of my 8 radiators. Each has the height and location on the photo Again, I have a 2-story old Victorian house, 7 rooms, steam radiators with 1 pipe system steam boiler/burner. I am converting to natural gas from oil.

    It takes two posts to post the 8 photos.
    Attached Images Attached Images      

  7. #7

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    Here's the other photos. The height and location is on each photo.
    Attached Images Attached Images    

  8. #8
    In the Trades Tom Sawyer's Avatar
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    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  9. #9

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    I am just a very non-technical person. I tried to calculate the rad EDR based on your link.

    I am attaching photos with the two types of sides, used to determine if type is tubes or column. I had to make exceptions if something was NOT on the chart. Therefore, for height 25 inches I used 26, for 22 inches I used 23 (I went up to the next higher inches). I used tubes as they measure 2.5 inches and must be the newer rads and not columns. Is this right based on my photos? But rad6 is very different, tall and skinny with 1 inch tubes. I just used the tubes chart like for the 2.5 inch rads.

    If I add the total sq ft of all rads, I get 291. Is the below done right and this what I want? Is this the number I compare to the vendor steam sq. ft?

    Radiator # height, tubes, chart's tubes sq ft * sections = total for rad

    rad1 25, 4, 2.75 * 8 = 22

    rad2 22, 5, 3.00 * 10 = 30

    rad3 22, 5, 3.00 * 10 = 30

    rad4 22, 5, 3.00 * 10 = 30

    rad5 38, 5, 6.00 * 8 = 48

    rad6 25, 4 (1 tube), 2.75 * 21 = 57.75

    rad7 22, 5, 3.00 * 15 = 45

    rad8 26, 5, 3.50 * 8 = 28

    NOTES:

    For height of 22 in - used chart 23 in
    For height of 25 in used chart 26 in
    Rad6 is very different, tall and skinny. I also used tubes (not the columns chart)
    Attached Images Attached Images   

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