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commercial boiler

Paul S_3
Paul S_3 Member Posts: 1,261
in THE MAIN WALL
Why are so many commercial water boilers are on the roof? Is it because the use of a low pressure boiler on roof instead of a high pressure boiler in basement? And isnt there a substantial amount of pressure on the lower floors than at the boiler?
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Comments

  • njtommy
    njtommy Member Posts: 1,105
    edited February 2016
    I would imagine it's so they take up less space in the building them self. Also not having to install a big chimney that takes up floor space in a building. Things like that come to my mind.
  • SWEI
    SWEI Member Posts: 7,356
    All of the above.

    A bit of extra water pressure in a pumped heating system beats a vacuum any day.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,852
    Vacuums suck... Especially in a closed loop heating system :smile:

    ME

    There was an error rendering this rich post.

  • Jody_S
    Jody_S Member Posts: 9
    There are a few things that play into it. A common answer I get back from engineers is parking spaces.

    Another factor is to get it into a single mechanical room. If I have chillers or cooling towers on the roof, I probably will want the mechanical room on the top floor so the equipment is all in one central location.

    Venting does play a big part in the decision, Although sidewall venting is allowed by most condensing boiler manufacturers, I would avoid sidewall venting a million plus BTU boiler at all costs. The exhaust plume can be quite spectacuIar. If it is on the roof or top floor, vertical venting is easy and inexpensive.

    If I decide on a top floor mechanical room then other good things can happen. At the top of the system, I am going to design around 5 psig of positive pressure. I've suppressed boiling up to 210 F. If I bump it up to 13 psig, then I am covered to 230 F.

    By dragging my Extrol up there it will ensure the pressure on the system never gets below 5 psig, as long as I pump away from the PONPC. Now the added bonus is that Extrol is now going to be smaller because to the lower initial static pressure I can use in it's sizing. Space and cost are saved with a smaller Extrol.

    Additionally, If you look at solubility tables you will find that as the hydronic system gets taller, the point of low solubility shifts to the top of the system due to the effects of low static pressure there. Check out figure 2-12 in Idronics 15. To be effective, the air separator should be at the top of the system in tall buildings.

    Finally, the parking space answer is a real answer I get from engineers in heavily developed cities.

    Jody S .
    SWEI

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