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Thread: Need help with Aprilaire 400M Humidifier, cannot open Saddle valve for water

  1. #1
    DIY Junior Member mtlmonk's Avatar
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    Default Need help with Aprilaire 400M Humidifier, cannot open Saddle valve for water

    Hello,

    I have an Aprilaire 400M humidifier.

    Cannot find a way to open up the saddle valve to let water run.

    I took my parts (overflow part at the bottom and saddle valve) and installed in my neighbor's setup (he has the same model) and it worked no problem.

    I have the same wiring setup as him also.

    From furnace, took White wire and plugged to yellow of valve.
    Other Yellow of valve, into White of Overflow part
    Other White of Overflow part into Black wire from furnace

    In other words, Furnace -> Valve, Valve -> Overflow part, Overflow part to Furnace (-> is a wire)

    With a voltmeter, I have checked that current is passed to the valve.

    When the humidistat is off, it sends 12V to the valve but whenever humidistat is on, it becomes 0 on the valve.

    I have tested current coming out of the furnace when setting the humidistat to On, without plugging to the valve, and it's around 24V.

    What is wrong? Huh?

  2. #2
    Nuclear Engineer nukeman's Avatar
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    Let's clarify. A saddle valve is usually a mechanical valve that pierces the water line and then has a small tube running from that to the device (humidifier in this case). Inside the actual humidifier, there is a solenoid valve that will actually control the flow of water to your humidifier.

    The Aprilaire 400 doesn't drain the water in the same way like some humidifiers (it sits there until it evaporates), but there is an overflow and it uses floats and a water level sensor.

    So:
    step 1: make sure you are getting water to the unit (turn supply valve off, remove tube, put into bucket, turn valve on).

    step 2: check continuity of the float switch. Disconnect the float switch, turn your meter to Ohms (or continuity tester) and check the wires to the switch. It should be if the float switch is up, there is no continuity (it would shut the solenoid valve off). When the float is down, there should be continuity (near 0 ohms).

    step 3: wiring sounds ok. however, if the float switch is ok, water is getting to the solenoid valve, and the wiring is ok, The next possibility is the 24v transformer is overloaded (or has a bad connection) as is not providing the current needed to open the valve.

    When testing voltage, I assume you are measuring across the solenoid valve (two yellow wires)? Is you meter set to AC volts? When the humidifier is off, the supply or common is switched off (no current can flow). Same thing could happen with a bad float switch. Depending where and how you are measuring voltage will change whether having voltage means that the valve is open or closed.

  3. #3
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by mtlmonk View Post
    I have tested current coming out of the furnace when setting the humidistat to On, without plugging to the valve, and it's around 24V.

    What is wrong? Huh?

    24V of current without the valve connected sounds a bit off to me.


    Be careful playing with electricity.
    Theory only works perfect in a vacuum.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If you have 24vac across the two yellow leads to the solenoid valve (from one to the other), then it should open to let water in. Depending on where you are referencing your measurements, you could get 12vac or so from either lead to somewhere else (ground, maybe) and that only means there's potential, but does not indicate there is a complete circuit to operate the valve. A little bit of knowledge when using a multimeter is sometimes dangerous, and can be misleading.


    The overflow valve may be broken...this is often in series with the power, and opens to prevent new water from being added. If it stays open, or is stuck (did you check the float valve to ensure it is not gunked up and can move?) the solenoid valve will never open to add new water.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    Jack of all trades DonL's Avatar
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    It could be that the T-stat and or sensors are not wired or programmed properly.

    Maybe the T-Stat is not calling for humidity.

    The easiest way to check a solenoid valve with only a volt meter, Is to see if it has voltage and see if the coil is warm to the touch, You may even be able to feel the 60hz. A current measurement is better, Current may be high if the valve is stuck.


    Good Luck.
    Theory only works perfect in a vacuum.

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  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by DonL View Post
    The easiest way to check a solenoid valve with only a volt meter, Is to see if it has voltage and see if the coil is warm to the touch, You may even be able to feel the 60hz. A current measurement is better, Current may be high if the valve is stuck.


    Good Luck.
    He said he installed it in his neighbors (identical) unit, and it worked...it's not the solenoid valve, it's more likely a stuck or bad overflow switch, or the humidistat is not actually calling for it to turn on.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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