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What’s the difference between a steam and a hot water radiator?

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HeatingHelp
HeatingHelp Administrator Posts: 651
edited December 2020 in THE MAIN WALL

It’s the way the radiator sections go together. They may be nippled together at both the top and bottom, or just at the bottom.

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Comments

  • rjobrien
    rjobrien Member Posts: 9
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    Why did contractors specifically seek out hot-water radiators for two-pipe steam?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,157
    edited December 2020
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    What’s the difference between a steam and a hot water radiator?

    .

    Read the full story here

    What's inside!

    Water radiators have water inside,
    Steam radiators have Steam inside.

    Am I right?

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • rjobrien
    rjobrien Member Posts: 9
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    I have two-pipe steam in my house and a mix of steam (bottom-nipple) and hot-water (top/bottom-nipple) radiators, though mostly hot-water radiators. After living in the house for 12 years, my observation is steam radiators are superior to hot-water radiators for steam heat, the reason being in the shoulder seasons during shorter cycles, the smaller volume of steam in the hot-water radiator cools off from the cold iron mass before leasing its full heat potential into the air. By contrast, in the steam radiators, only the first few sections heat up, segregating the steam from the rest of the cold radiator. This also plays out as I insulate the house. I may have improved heating efficiency by 15% or more -- not enough to replace all the radiators in the house but enough to reduce the number of times the steam fills the oversized radiators. The segregated sections of steam radiators allow for shorter cycles of the boiler without compromising on performance. Just my humble observation...
  • motoguy128
    motoguy128 Member Posts: 393
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    I have mostly steam only radiators on my 1 pipe system.  The universal radiators perform poorly  with steam.  The steam races across the top and never fully heats the whole radiator.  I suspect they would have worked ok with the original very very slow Hoffman #2 vacuum vents and a slow warm up and modulating coal boiler.  

    The wall radiators do ok.  

    One thing I don’t like about steam is that it has so little mass compared to hot water.  Except in colder weather where radiators will be partly hot all the time, temps seem to swing a bit and you only get rediant effect about half the time.   

    A hot water radiator might only swing by 20 degrees and will stay warm all the time.  

    Might be better if my total radiation closely matched my heat loss instead of being oversized by about 50% or more. 
    rjobrien
  • Jamie Hall
    Jamie Hall Member Posts: 23,565
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    Radiators connected across both the top and the bottom can be used -- quite successfully -- on both steam and hot water, with much the same results (except that you'll get a lot more heat out of the radiator on steam!). The problem which @motoguy128 mentions can be essentially eliminated by placing the vent no more than half the way up -- preferably no more than a third of the way up. The problem doesn't exist on two pipe steam.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • motoguy128
    motoguy128 Member Posts: 393
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    Radiators connected across both the top and the bottom can be used -- quite successfully -- on both steam and hot water, with much the same results (except that you'll get a lot more heat out of the radiator on steam!). The problem which @motoguy128 mentions can be essentially eliminated by placing the vent no more than half the way up -- preferably no more than a third of the way up. The problem doesn't exist on two pipe steam.
    Both vents are located near the bottom.  Steam shoots across the top and barely heats the bottom of the sections before closing the vent.  

    Same model.  Short Arco.  One is 26 sections the other 17.  Both have ventrites on them.  Smaller set at 3.  The big one at 7.  I’d guess they only put out about 2/3 rated output

    a short 8 section one upstairs seems to heat ok.  It’s has a TRV with a Groton 4.  

    All of the other steam radiators head evenly based on venting rate and lateral size.    

    Might just be the odd short proportions.  
  • motoguy128
    motoguy128 Member Posts: 393
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    The 3 mentioned are radiators 4, 5 and 10 out of 15 on the header.  They start heating at the same time.  No difference in evenness whether all TRVs are calling upstairs or not.  

    Pressure was running around 1-3”
    last year.  Been around 10” lately.  Might need a good long skim again after changing some piping on my indirect.