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Navien combi domes hot water issue

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danitheplumber
danitheplumber Member Posts: 85
in THE MAIN WALL
Had Navien combi boiler firing up to 210 when a call for domestic hot water was called for but for some reason the domestic cold water was steam hot and domestic hot side ice cold. Anyone seen or know what would cause this? No error code came up...

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  • Ironman
    Ironman Member Posts: 7,376
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    Lack of flow.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • danitheplumber
    danitheplumber Member Posts: 85
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    Ya I assume it's never been flushed...
  • Ironman
    Ironman Member Posts: 7,376
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    I'm referring to the hydronic side.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Ironman
    Ironman Member Posts: 7,376
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    Also, check the inlet screen on the cold.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • danitheplumber
    danitheplumber Member Posts: 85
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    It's a domestic hot water issue. The only thing is it seems hot water is going into cold inlet and cold water into hot outlet side so maybe 3 way valve issue
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,291
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    Hi, I’ve met heaters that were plumbed in backwards. You might want to trace down flow to double check the piping. You can’t assume anything. I was once the sixth plumber to look at a troubled job. Turned out there was insulation on the cold and not the hot.

    Yours, Larry

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