Tankless water heater in attic of house venting question

The Tank Tankless water heater in attic of house venting question

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    Any help or insight that can be provided is much appreciated. I just bought a new Rheem tankless water heater. Below is the exact model/description:

    Rheem EcoSense 9.5 GPM 199,900 BTU Ultra Low Nox Natural Gas High Efficiency Condensing Indoor Tankless Water Heater

    I have the tankless heater set up in the attic and used the previous hotwater heaters’ outtake vent to vent this one. This particular model of tankless has a intake as well. Am I able to just allow the intake to use the air from within the attic to supply the heater? What are the negative effects of using attic air as the intake? There it a direct vent furnace in the attic however it’s over 30 feet away and vented through the roof. I also considered this may be a pressure thing as the manual says to make the intake and outtake vent length to roughly the same size and at least 28 in. apart. So I thought maybe I can have another pipe within the attic which has the same length as the outtake however it just pulls the air from the attic.

    Thank you for any help or recommendations,


    Larry Weingarten

    Hello: It’s always best to have intake and exhaust fairly close together. This way things stay balanced even with temperature changes or wind. I’d extend the intake to outside of the attic, to avoid possible heat and pressure issues. 😉

    Yours, Larry

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