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Thread: Doorbell wiring

  1. #1
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    Doorbell wiring

    I am trying to install the ring pro doorbell. I have an existing doorbell and wiring in place. I measure the voltage at the doorbell and it was reading 14V. I measure voltsge at the transformer and it was 22V. Wierd thing is the transformer is rated at 16V, 10VA. So two questions:1. Why is the transformer outputting 22V? I dont know how to change the meter to peak or rms, but I'm pretty sure it's set to rms because the outlet at my house reads 122V.2. Why is there such a big voltage drop at the doorbell?

  2. #2
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    The reading at the doorbell was measured with the button depressed?
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  3. #3
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    No not depressed. But I touched both screws with the meter leads and read 14V. I also noticed a small resistor tied in series. Are you saying the button must be depressed in order to detect voltage? The breaker was on.

  4. #4
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    Quote Originally Posted by Dennis Alwon View Post
    The reading at the doorbell was measured with the button depressed?
    eta: ooops misread the post
    Bob

  5. #5
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    Quote Originally Posted by minesh21 View Post
    I am trying to install the ring pro doorbell. I have an existing doorbell and wiring in place. I measure the voltage at the doorbell and it was reading 14V. I measure voltsge at the transformer and it was 22V. Wierd thing is the transformer is rated at 16V, 10VA. So two questions:1. Why is the transformer outputting 22V? I dont know how to change the meter to peak or rms, but I'm pretty sure it's set to rms because the outlet at my house reads 122V.2. Why is there such a big voltage drop at the doorbell?
    I think the 16V is the loaded condition and what you are reading is the no load voltage.

    Can you sketch up the circuit and post it?
    Bob

  6. #6
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    Quote Originally Posted by petersonra View Post
    I think the 16V is the loaded condition and what you are reading is the no load voltage.

    Can you sketch up the circuit and post it?
    I dont know how it was wired. Just observing externally. There is a button, a chime and transformer. Typical wiring is most likely the case.

  7. #7
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    Quote Originally Posted by minesh21 View Post
    No not depressed. But I touched both screws with the meter leads and read 14V. I also noticed a small resistor tied in series. Are you saying the button must be depressed in order to detect voltage? The breaker was on.

    What screws...If you measure at the chime between the Transformer Terminal and the front door terminal then you will not get the true voltage as you will only have the true voltage when the button is depressed. I have no idea what you may be reading thru the pro doorbell controller
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  8. #8
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    180503-1619 EDT

    minesh21:

    You list yourself as an electrical engineer. You should be able to answer your own question.

    It is most likely your meter in AC mode provides an averaged value over a number of cycles calibrated in RMS for a sine wave whether it is a true RMS meter vs a full wave rectified type meter.

    For a sine wave the RMS value is about 0.707 the peak value, and the full wave rectified average value is about 0.636 of the sine wave peak. So a Simpson 260 actually measures 63.6 V DC average from a 100 V peak sine wave. The scale on the meter is drawn 1.112 times greater than its actual DC value.

    On a non sine wave signal the Simpson will usually provide an incorrect RMS reading.

    Your doorbell transformer is probably designed with a high internal impedance and rated for output voltage at full rated load.

    Your open circuit voltage is 22 V and the transformer is rated 16 V at 10 VA. This implies a high internal impedance.

    First, is your input voltage equal to the rated input voltage. Assume it is, then you tell us what you calculate the transformer output impedance to be assuming resistive.

    Second, based on that calculated internal impedance, then what current do you expect the doorbell is drawing? How does that compare with actual doorbell current?

    Third, based on your calculated internal impedance, then what is a calculated short circuit current? What is the measured short circuit current?

    These comparisons my not be real close. You can go back and try to determine the actual AC impedances, and redo calculations and experiments.

    .

  9. #9
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    Quote Originally Posted by minesh21 View Post
    Why is there such a big voltage drop at the doorbell?
    Because, a the button, you're measuring the voltage with the chime in the circuit. This is like thermostat wiring without a C wire.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  10. #10
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    I'm really concerned about the depressed button. I "googled" but found nothing about cheering a doorbell button

    (Every DB transformer I ever checked had a higher voltage than nameplate in a no load mode)
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

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