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Hydronic zones off steam boiler

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http://steamheating.googlepages.com/zoneheatingwithcondensate

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  • Chris Kraker
    Chris Kraker Member Posts: 4
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    Hydronic zones off steam boiler

    I had a new steam boiler installed last year with a hot water loop to an heat exchanger and expansion tank setup. It is 5 zones with the upstairs using steam with one thermostat and downstairs 4 zone hydronic. The system works well to create heat but i have a concern. When the downstairs calls for heat the system works fine, but when the upstairs calls for steam at the same time the water temp in the hydronic loop system goes beyond its 185 degree limit becuase the pump from the boiler continues to run along with the pump for the zones. This causes the pump from the boiler to the heat exchanger to run very loudly and sound like water sloshing inside that loop. Shouldnt the pump from the boiler to the heat exchanger shut off when the temp exceeds the limit on the auquastat while the pump for the zone loop continues to run to satisfy the thermostats.
  • Ken_40
    Ken_40 Member Posts: 1,320
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    No.

    The problem is in how the HWBB primary pump is piped.

    That primary pump should never "see" water hotter than 190. Instead of taking 212-degree water directly from the boiler coil (or boiler tapping) it should be drawing water from two sources! The 212 water from the boiler AND a blended source that will never see 190+.

    The damage to the primary circ. is probably already done; that being: The eye of the primary pump's impellor is "seeing" 212 degree water and because there is a vacuum at that point, the water is flashing over to steam INSIDE the impellor causing cavitation, and an explosion of water flashing over to steam - making a growling, grinding noise that is damaging the pump.

    When correcting the problem with a relatively straightforward re-pipe, be sure to inspect the impellor and make repairs as necessary.

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  • Chris Kraker
    Chris Kraker Member Posts: 4
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    Thats great information Ken the way its hooked up now is it takes water from a taping off one side of the boiler goes through the pump then through the heat exchanger and then back to another taping on the other side of the boiler. Now the question is where and how do i get blended watet into this loop.
  • Chris Kraker
    Chris Kraker Member Posts: 4
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    Theres nothing comming up with this file Noel. Is there another. Thanks.
  • Chris Kraker
    Chris Kraker Member Posts: 4
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    Wow thats awesome information Noel. Thank you so much, you and Kens help is very much appreciated!
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