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Replace or maintain steam boiler

I have a 6700 sq foot house, built in 1929 in Flint MI. It has steam heat, and I am trying to decide if I should replace the boiler or maintain it.

First the boiler, here is what it say on the metal tag screwed to the side: National US Radiator Boiler No 9-66 Steam 5115 square feet, Input 2,000,000 BTU/HR, Water 1,227,900 square feet, Output 1,600,000 square feet Division of Crane, Johnston, PA

Today, we only heat the house, but originally they heated another 5000 square feet with this boiler (horse stables, garage, staff apartment)

Also, we have added storm windows, insulation and other weatherization.

The boiler seems to work fine, I have had a local guy look at it and says don't replace it. He kept putting his hands on it like it was a real "find". I am looking for ways to lower my gas bill.

My questions:
1. Can you tell from the info supplied how old it is -- I was told around 1960.

2. Now that we are only heating the house, I would think the boiler is much too big -- is there a way to "slow it down" or downsize it?

3. Have there been big efficiency gains in boilers like I hear about with forced air?

4. If we replaced the boiler, can you give me a guess at what size we would need and a ballpark of what it should cost?

5. Any other advice given the situation described.


  • Read this article, from Hot Tech Topics

  • Unless you have an old mega-mansion

    that boiler was sized to also handle the load of the other buildings. 5100 square feet of radiation would probably heat a building the size of the Capitol building in Washington. Find out how much radiation is actually in the house and size the boiler from that figure.

    Not only are boilers more efficient now, but you will gain even more efficiency from a boiler that is properly sized to the load.

    You can gain more efficiency by correcting any steam distribution problrems in the system. BTW, what type of steam system do you have? I'll bet it's a Vapor type of system.....

    The biggest mansion I've ever been in- the Laurier mansion in Bryn Mawr, PA- has a load of about 2700 square feet EDR (Broomell Vapor system).
  • Bob W._3
    Bob W._3 Member Posts: 561

    for comparison sake my house has 1069 sq. ft of installed radiation (EDR) heating about 4200 sq. ft. of floor space (10, 8 and 11 foot ceilings) in North Mankato, MN. W-M 105EGH boiler rated at 1125 sq. ft. steam, input 450,000 BTU. It is sized correctly to the installed radiation but is way too big for the house's actual heating needs. Your boiler sounds like a monster. What are your heating bills like?
  • Mike Hurley
    Mike Hurley Member Posts: 4

    Thanks for the feedback. Is there a way to "scale down" the current boiler. A local guy says he can cap or plug some of the orifaces and that will slow down the boiler and save on fuel. Does that make sense? Any other suggestions to help with fuel consumption. The boiler seems to work great and appears to be in good condition -- it's just so big!
  • That wouldn't be too efficient

    since you'd still have all that extra iron and water to heat up. Your best bet is a new, properly-sized boiler.
  • Steam Bunny
    Steam Bunny Member Posts: 76

    If it's running well, you might want to play with some figures to see if you can cost justify a new boiler. Chances are pretty good- to have a top notch, quality installation- it'd be tough.

    At full throttle our "walk-in" boiler clocks in at 1,500,000 btu- installed in/around 1913, she’s coal converted to gas. We had her overhauled in 1969, lowered the water line, & set her back to 750,000 btu. Although a new one may have been somewhat more efficient, fact was - we could never cost justify replacing her. (To this day my husband has every single gas bill)

    Finally we have no choice- but we got 35 great years.

    Catch the irony here-…… our blueprints size the replacement boiler at 1,170,000 btu’s installed. Do I plan to downsize her??? You bet!!! But on this round we'll formally monitor to make certain we're getting the cleanest possible burn at the lowest possible btu.
  • Mike Hurley
    Mike Hurley Member Posts: 4

    Thanks for the comments. What do you mean by "setting her back"?
  • john_27
    john_27 Member Posts: 195

    another option you might consider is converting the burner mechanism to a stage firing or hi-lo-hi type of firing....this would give you a longer run time(but eliminate extra firing once you have eliminated the"pickup load',ie. the piping in your basement(did you size your load when you gave us edr's?)...but, Steamhead is correct...to get maximum efficiency, you need a correctly sized new bopiler, or remove sections from your exising boiler....in our case, we're going to try the options mentioned above first.
  • She means \"down-firing\"

    running the burner at less than its rated input. But if you go too far with this you'll have trouble generating steam quickly. It's like a pan of water on "simmer"- you get a bit of steam, but it never really boils.
  • Steam Bunny
    Steam Bunny Member Posts: 76
    Re \"setting her back\"

    I learned to cut the input btu’s from 1,500,000 btu’s to 750,000 btu’s by simply reducing the amount of gas. Would keep indoor outdoor temps, wind, time, meter reading, etc. records by the gas meter & eventually learned 750k was 1) the lowest I could turn it & 2) where we got the most heat for the buck. It would’ve probably been smarter to then reduce the number of gas orifices but, back then, we had no way of knowing we’d get another 35 years and having just moved into an overwhelmingly big old house, we were pretty quick to learn “if it ain’t broke, don’t fix it”

    Might also add, back then, the WALL hadn’t been born so I was vulnerable to hearing “Lady, your system’s sooooo inefficient & outdated….” More recently, it’s been a powerful pleasure to be armed & ready with- “You’ve NEVER heard of Holohan and his Wall??? Been nice talkin’ to ya!”
  • Steam Bunny
    Steam Bunny Member Posts: 76

    You’re getting the full spectrum of possibilities, which is an incredible opportunity to do it the right way with your lifestyle needs in mind!

    You should also confirm what type steam SYSTEM you have. If you’re running a vapor system on pounds efficient steam becomes an oxymoron. Ditto if you have traps & they’re not ALL working, etc.
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