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hot water loop off steam boiler

STEAM DOCTOR
STEAM DOCTOR Member Posts: 2,199
Good morning. I am running a hot water loop off a steam boiler using the tankless coil. Do I need to mix cooler water into the loop to prevent the water from flashing to steam or is the fact that the water is pressurised and hence a higher boiling point enough to prevent the water from flashing to steam. Thanks in advance for the advice.

Comments

  • ChrisJ
    ChrisJ Member Posts: 16,267
    Yes and no

    The water will not boil due to the pressure,  however you are required by code to use a mixing valve in order to prevent scalding and it also allows the hot water to stay a consistent temperature.  Just think of how hot the domestic hot water can become while the boiler is making steam, 170-180F perhaps? 



    You may also want to consider adding a flow regulator.  I have been thinking about adding one to my setup because if we try to get too much hot water it cools down a lot due to the volume running through the coil.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 2,199
    hot water

    I am not running domestic hot water off the loop. The loop is a heat only loop.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Space heat or DHW???

    Copper or plastic distribution?



    Gots to know...



    ME

    There was an error rendering this rich post.

  • ChrisJ
    ChrisJ Member Posts: 16,267
    my mistake

    Ah,  I thought when running hot water for heat you simply pull water from below the steam line.  Did not know anyone ever used a loop for that?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Got it...

    If you are running plastic for distribution, you will want to protect the tubing from higher operating temperatures. If it is copper or iron, not a problem provided you can maintain at least 5 PSI on the top of the system (.434 PSI per vertical foot above the boiler, PLUS 5 PSI).



    If it were DHW, you'd have to use an antiscald mixing valve. I'd suggest using the same thing if you are dealing with plastic.



    ME

    There was an error rendering this rich post.

  • jonny88
    jonny88 Member Posts: 1,139
    hot water zone

    dans book, the golden rules of hydronic heating.page 77.you will find a piping diagram to make it easy for yourself.
  • Roland_18
    Roland_18 Member Posts: 147
    Another choice

    Roth Mini Shunt.
  • Greg Maxwell
    Greg Maxwell Member Posts: 212
    Heat loop off a coil

    How many BTU's are you going to put on this loop?
  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 2,199
    copper

    There is copper piping. The highest point on the zone is aprox 30' high so I cant come off bottom of boiler.
  • JStar
    JStar Member Posts: 2,752
    I would....

    ...at least put some form of mixing valve, either manual or automatic mixing in the loop's return water. Try to maintain 180 on the loop while the boiler is fully steamed. The worst that happens is you wind up not using the valve; and you get a little more control of the system.
  • wholesalerbill
    wholesalerbill Member Posts: 20
    hot water loop

    You also need a circ pump, expansion tank, aquastat and B&G FB-38 fast fill valve, and a back flow preventor. You have to treat this loop just like you would any hot water boiler loop(zone).
  • wholesalerbill
    wholesalerbill Member Posts: 20
    hot water loop

    one more thing I forgot to add, throw on a Taco SR501 single zone switching relay.
  • Mannu
    Mannu Member Posts: 20
    flow chat

    This is a question.



    On the out part of the tankless coil, you connect a expansion tank, then circulator, then flow check valve, then pressure reducing valve?



    Then the return goes back into the IN part of the tankless coil, with a flow valve?



    Water supply gets tapped into the in part of the tankless coile after the flow valve?
  • Mannu
    Mannu Member Posts: 20
    flow chart

    i meant the title for the post above to be flow chart
This discussion has been closed.