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Steam Sizing Question.. what would you choose?

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Joseph_4
Joseph_4 Member Posts: 316
in THE MAIN WALL

Hi

I have a customer whose current steam boiler is a 299 input weil mclein, 20 plus years old that is leaking and needs replacement

The actual OUTPUT required after measuring all radiators is 299K using 1.33 pickup factor or 270k using 1.20 pickup

which means they really need a 330 to 360 input

However they are only willing to pay for a Green Mountain 299K input which pipes from side

or a 282k input which pipes from top like most boilers

A Close friend of mine who does a lot of steam feels the 3" riser of the 282 is superior than the 299 side outlet. He says it causes water carry over problems

We both Never went with an undersized boiler.

I asked the home owner if with the 299k the attic got warm. he doesnt remember. All moved out of house. only Older mother lives there.

I told him you need to realize its undersized. he says he understands and Im making him sign a paper that says he is agreeing to this size against my recomendations.

would u go with the 299 green mountain or 282 williamson

Thx

Joe

Comments

  • mattmia2
    mattmia2 Member Posts: 15,191
    edited December 5

    it would be a lot easier if we were talking in edr, but if it is working with the 299,000 btu/hr it clearly is working with whatever pickup factor that works out to. Unless there piping system is huge, something more like 10% pickup factor is usually enough for 1 pipe. On many 2 pipe systems they can work with a boiler with an actual EDR that is a bit smaller than the actual connected EDR.

    You are mixing units, you aren't giving the actual connected EDR which makes this a little harder. If the Williamson has an output if 1.1 times the connected EDR I would go with that and follow the manufacturer's pipe sizing or use a drop header if you're really worried about it. The side outlet will also work well if the header is done right but they can be a bit more sensitive to surging.

  • ethicalpaul
    ethicalpaul Member Posts: 8,026
    edited December 5

    What Matt said, but also let me ask this simple question: Did the existing boiler ever have any trouble heating the house?

    Never upsize a boiler unless you have a very very good reason, such as an EDR total showing you need it.

    Edit: Steam Doctor has the best answer below. I missed in that post we were only talking about such a small difference.

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
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  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 2,495

    299,000 input and 285,000, are effectively the same boiler. We're talking about an approximate difference of 12,000 BTU output difference between the two boilers. On a system that size, that is negligible and will never be noticed. If you are comfortable with the 299, then you should be equally comfortable with the 285. IMO

    ethicalpaulGGross
  • Joseph_4
    Joseph_4 Member Posts: 316

    The EDR total of Radiators is 937.5. steam outputs 240btu per 1 square foot edr. thats 225000 btu before pickup factor. The boiler that was there WAS undersized. I asked home owner if all radiators got hot. He said he doesnt know cause its years since he has lived there.. This is the reason for my question, The connected load requires a bigger boiler. @Steam Doctors's point would be true maybe if im slightly undersized. I dont agree with him when its 60K undersized.

    What do you think/

    Joe

  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 2,495

    60,000 undersized and 72,000 undersized, is exactly the same thing, IMO. Especially for a system that size.

  • mattmia2
    mattmia2 Member Posts: 15,191

    Is this 1 pipe?

    The radiator not heating is likely some problem other than being undersized. You are only consuming that much steam if every radiator is heated fully and that rarely happens. I would go with either boiler and make sure I have all the near boiler piping correct, drips at the boiler if it is counterflow, mains individually connected to the header rather than teed together at the ceiling, using both boiler outlets if available, possibly using a drop header. Insulating the steam piping.

    You have close to 0 pickup factor at 282k btu/hr but there is also some measurement error in everything.

  • gpjazz
    gpjazz Member Posts: 35

    I'm not a steam guy, but does the current "original" boiler in question still actually function? If so, can you go back to the house and check how the system is performing for yourself? Then you would know if all the rads are getting warm enough or not. Instead of relying on the guy that "doesn't remember"

  • dabrakeman
    dabrakeman Member Posts: 838

    Just curious, what exact model is the current WM boiler?

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