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Lous noise in the furnace when aprilaire 700 on

I have been hearing a loud knocking noise in my furnace area when the aprilaire 700 is set to on. what is the problem and how do i fix it?

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Re: Lous noise in the furnace when aprilaire 700 on

I have had the same problem , off and on, on my two 700 units for over 4 years. It is caused by water hammer which results when a water solenoid valve closes quickly under pressure. Refer to your owners manual or get a copy of it off the internet. Note the areas where they tell you to remove and clean the inline water strainer and the inline orifice restrictor. These are VERY small components and can clog up easily so they need to be cleaned per the manual. While cleaning them won't totally eliminate the problem it has helped mine with the noise. You really need to have a qualified person, like a plumber, install a small, water hammer arrestor in the inlet line. The trick is to be sure it ends up parallel to the water line flow and not perpendicular to it.... a common mistake. If you are not qualified to work on solenoids and piping, don't do will end up costing you more to repair your mistakes. Good luck


Posted on Jan 15, 2008

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