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steam heat sizing

t hardy
t hardy Member Posts: 29
in Strictly Steam
what is the downside of having a steam boiler downsized from EDR??

Comments

  • ChrisJ
    ChrisJ Member Posts: 16,315
    t hardy said:

    what is the downside of having a steam boiler downsized from EDR??

    Assuming all of your piping is very well insulated and the boiler has enough output to compensate for piping losses as well?

    The system will be difficult to balance.

    Aside from that, likely nothing.

    What's your EDR and what size boiler are you considering?

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,477
    If it heats the building there is no downside. You may be able to get away with a pickup factor of less than the recommended 1.33.

    Need info from the boiler name plate, pictures of the piping around the boiler and the total EDR load
  • Jamie Hall
    Jamie Hall Member Posts: 24,856
    However, if you downsize too far, you will get very uneven heat and it will be almost impossible to balance. May I ask why one would want to? Remember that steam is sized to the radiation in the building, not the building heat loss.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PMJ
    PMJ Member Posts: 1,266
    No advantage in being too small - only potential problems. No disadvantage in being too big except up front cost. Too big has control solutions, too small does not.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • jumper
    jumper Member Posts: 2,385
    I suppose one can undersize boiler and then make up difference with electric heaters in occupied rooms. After all radiation was sized for unusually cold days. And maybe tighter windows have replaced original. Some say running undersized longer is less economical than cycling properly matched boiler.

    In the seventies single boilers were often replaced with multiple small boilers. Customers were satisfied when they were installed intelligently and operated intelligently. In Toronto most weekdays only one out of three or four small boilers were running. Around 3:30 PM super fired 100%; cut back mid evening;very early morning back to 100%;cut back around 8:30 AM. Or so he said.
  • t hardy
    t hardy Member Posts: 29
    EDR works out just shy of 163K BTU
    Riello burner with a .85 - 60 - W nozzle
    Current system is good for heating - older Pensotti steam boiler
    new boiler will be a megasteam
  • ChrisJ
    ChrisJ Member Posts: 16,315
    edited March 2017
    t hardy said:

    EDR works out just shy of 163K BTU
    Riello burner with a .85 - 60 - W nozzle
    Current system is good for heating - older Pensotti steam boiler
    new boiler will be a megasteam

    The MST629 has a DOE output of 201,000 btu/h.

    This gives you approximately a 23% pickup factor which is likely plenty. A few guys on here aim for around 15-20%. You'll have 38,000 btu/h extra to play around with for piping losses etc.

    I'd do it.


    Remember, vent your mains very fast and keep radiator venting rates reasonable. If some radiators refuse to heat speed them up and slow the ones stealing the steam down some.



    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,477
    Your way undersized or something. A .85 nozzle will give you an input of 119,000 and an out put of 97,580 (assuming the boiler is 82% efficient. I am also assuming the Riello oil pressure is 100psi which it may not be.

    The rate your firing the boiler can handle 305 square feet.
    305 x 240 x1.33=97,356 btu
  • t hardy
    t hardy Member Posts: 29
    This is EXACTLY my point. If my current boiler input is 120k and 82% efficient sounds about right and the heating is ok (I have 3" FG insulation on all mains with good venting, then why oh why should I go to the 513 megasteam?? and burn 1 1/3 gph oil??
    Thanks to all who have responded!

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