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Thread: Problem with MA-T51 Countdown Timer operation of Bathroom Exhaust Fan

  1. #1
    Junior Member
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    Dec 2022
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    Question Problem with MA-T51 Countdown Timer operation of Bathroom Exhaust Fan

    I have a Lutron Maestro MA-T51 Countdown Timer connected to a Panasonic Whisperfit Ventilation Fan in a bathroom that turns on and off repeatedly when the switch is turned on or timer setting is on. Are the fan and switch incompatible? Is there a problem with wiring installation or other problem etc.?

  2. #2
    I just ran into this too. You need to use the version of the timer with a neutral wire connection.

  3. #3
    Lutron Technical Support
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    Jan 2022
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    When the timer switch cycles the fan on and off repeatedly it is due to the fan not meeting the minimum load requirements of the timer switch. As previously mentioned, you would want to replace the MA-T51 with the neutral-based timer switch MA-T51MN. This switch requires a neutral connection. This timer switch has a lower minimum load requirement and should function properly with the Panasonic Whisper fan.

  4. #4
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    Quote Originally Posted by Jonathan K. View Post
    When the timer switch cycles the fan on and off repeatedly it is due to the fan not meeting the minimum load requirements of the timer switch. As previously mentioned, you would want to replace the MA-T51 with the neutral-based timer switch MA-T51MN. This switch requires a neutral connection. This timer switch has a lower minimum load requirement and should function properly with the Panasonic Whisper fan.
    I also have a Panasonic whisper DC fan and the Lutron MN version of the timer works. It’s a minimum load issue, requiring the MN version.

    Only bothersome thing is that the timer turns the fan off and back on when there is a minute remaining in the countdown. Lutron says this is a warning and can’t be disabled. Fair enough if you’re controlling a light, but I’d don’t care that the fan is going to turn off. Lutron should have included the ability to disable this. I have no idea how it will impact the motor of my fan long-term, especially considering that the fan has a startup pause for a reason I assume is to not turn the Doc motor on and then back off.

  5. #5
    Junior Member
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    Jan 2024
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    layman's term to explain the issue regarding MA-T51

    Quote Originally Posted by Jonathan K. View Post
    When the timer switch cycles the fan on and off repeatedly it is due to the fan not meeting the minimum load requirements of the timer switch. As previously mentioned, you would want to replace the MA-T51 with the neutral-based timer switch MA-T51MN. This switch requires a neutral connection. This timer switch has a lower minimum load requirement and should function properly with the Panasonic Whisper fan.
    The post is correct about using neutral wire, but I want to explain what it means by "minimum load requirements".

    Unlike a manual on/off flip switch, the digital switch needs power to run its own digital circuit. There're two kinds of digital timer switch:

    1. For digital timer with 3 wires (no neutral wire): the digital circuit has series connection with the main device (Panasonic fan, for example), so it shares the total power(voltage, load) with the main device. With smaller voltage (because it shares the 120V with the fan), the timer circuit needs bigger current to run properly. But as technology improves, modern fan use less and less energy thus smaller current. That's why the fan goes on and off intermittently.

    2. For digital timer with 4 wires (include neutral wire): the two devices (digital timer and fan) are parallel connections, so each enjoy the full 120V electric power. So the timer will always work, independent of the fan's energy consumption (load).

    So you should use MA-T51MN. Lucky for me, I was able to find the white neutral wire at the back of the wall box, and connect it to the silver screw. And it works. If your wall box doesn't have neutral wire, then you need to have someone to install it. New house usually has neutral wire. I have a new half-bath with city permit, so it comes with neutral wire installed.

    BTW, the Lutron's user manual may need to change its wording. The instruction says "connect the remaining wire removed from the switch to the brass screw terminal". The "remaining wire" is actually load wire (or downstream wire), it's the wire connect to & power the fan when the switch is ON. I can't search "remaining wire" on google, and that caused me some headache. I was confused that isn't neutral wire the same as load wire? It turns out they are not the same, the load wire first goes to the device, and go back to Electric power plant, and the neutral wire goes directly to the power plant.

    Hope this info help you save some time. I spent 4 hours (not very smart, I guess).

  6. #6
    Junior Member
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    One more thing. Some other digital countdown timer only has 3 wires (no neutral wire), they may work with Panasonic whisper fan. However, it's too bulky compared to the Lutron MA-T51MN, I can't fit it into my wall box. A professional electrician maybe able to put it in (need to go in there and rearrange the tangled wires).

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