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Thread: Any electric meter that needs neutral to register consumption?

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    Any electric meter that needs neutral to register consumption?

    Most meters can register the 120v even if the neutral is not connected to the meter base (because it's measuring the live wire consumption).

    I want to know if there are any meters (especially old) where if the neutral was not connected, it won't register the 120v consumption even if 120v was really used?

    This question is asked not because someone wants to steal 120v from the power company but want to know what if there are cases where the neutral wire was connected to the service entrance without passing through the meter. In such case like this. If the power company would accuse the person of stealing electricity by not having the neutral pass through the meter base (or meter). Defense wants to know if there are any meter models where it won't register 120v if the neutral was not passed through the meter (for the defense of the accused)?

    This is not an actual situation right now but just want to know what is the case for future reference. Therefore don't reply advising that the neutral must pass through the meter base (or meter). I know that is standard operating procedure. But just asking if there are meters where it couldn't register 120v consumption if neutral is not passed through the meter base (and meter).
    Last edited by tersh; 12-02-18 at 09:38 PM.

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    A 208 / 120 V three wire meter recording consumption in a single dwelling unit of a multi-dwelling premises that is supplied by a 208 / 120 V four wire three phase service.
    Another Al in Minnesota

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    Quote Originally Posted by al hildenbrand View Post
    A 208 / 120 V three wire meter recording consumption in a single dwelling unit of a multi-dwelling premises that is supplied by a 208 / 120 V four wire three phase service.
    I was under the impression that a 120/208 three wire service (two of three phases from 208Y/120) was metered with a standard three phase meter that just did not have a connection to the third phase.

    As far as the neutral passing through the meter base, the meter base should have a grounded service conductor terminal which is bonded to the enclosure, but does not necessarily have any connection (neither voltage nor current) to the meter itself (no jaw connected to a neutral terminal). The single phase meter makes the assumption that the current through each L connection acts against a voltage which is exactly 1/2 the voltage difference between L1 and L2 (and of course in phase with that voltage). This type meter definitely would not be able to correctly meter two-of-three-phase service regardless of the presence or absence of a neutral to the meter base.

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    So how does electric meter work.. do they require complete circuit for the consumption to register or do they measure just the hot line (maybe by magnetic field like clamp meter)? Hence even if the neutral didn't pass through the meter base (or meter). The meter can still accurately register 120v consumption? (I was describing the US split/phase 120/240v ac system and meter and not European)

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    My understanding of the standard meter used in Georgia, Virginia, and Jamaica is that it basically takes a coil off around each live wire, like a clamp meter basically, and makes tat aluminum plate turn using this energy.. this then makes the dials turn. If both wires are transferring load through the disc turns correspondingly faster... but the neutral is not actually used. I could be wrong but what I was taught is that the new electric meters..the digital ones.. use a variation of this that is even more similar to the clamp meter.. by using two clamp meter circuits and adding them together... and the power needed for the meter to work is picked up from the metering circuit...

    but, that is all information that anyone probably can get from any old textbook from electricians classes...

    for information sake only... the way it was explained in my uk textbook is the clamp meter works in the same way as the new electric meter works, by sensing the electricity that passes through the coil of the sensor.
    Student of electrical codes. Please Take others advice first.

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    Quote Originally Posted by tersh View Post
    So how does electric meter work..
    Here, consider this Wikipedia article about metering electricity.. In my opinion, your question is too broad to answer.

    Your OP question, being broad, also, did not say you were only asking about 240 / 120 Volt three-wire single-phase supply from a single transformer.

    Quote Originally Posted by tersh View Post
    (I was describing the US split/phase 120/240v ac system and meter and not European)
    My post #2 above is describing the common US multi-dwelling that is supplied from the power company with a three phase 208 / 120 Volt four-wire service, and, where each individual dwelling is supplied with only two phases of three, and a neutral. To accurately represent the energy the electric utility must provide, the meter must accurately represent the phase angle and magnitude of both voltages and currents in the individual dwelling supply. Connection to the neutral is required in this case.

    The local electric utility meter department history and the local public utility regulatory agency, together, will have established the "cash register" meter standard for a given customer. This is not standardized from utility to utility.
    Another Al in Minnesota

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    I've never seen a residential meter that even had a connection for the neutral. Four stabs, 240 line in and out.
    Cheers and Stay Safe,

    Marky the Sparky

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    Quote Originally Posted by K8MHZ View Post
    I've never seen a residential meter that even had a connection for the neutral. Four stabs, 240 line in and out.
    My local PoCo (distributes in seven states) requires the minimum meter base for a stand alone single family residential dwelling supplied by single phase 240 / 120 Volt three wire from a single phase transformer be a five-terminal lever-bypass socket. The fifth terminal is bonded to the grounded service conductor. Here in the Twin Cities we've been required to install nothing less for years now.

    Now, at present, I agree with you, the actual meter plugged into that base, today, that I am aware of, is still a four "stab" device.
    Another Al in Minnesota

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    Quote Originally Posted by al hildenbrand View Post
    My local PoCo (distributes in seven states) requires the minimum meter base for a stand alone single family residential dwelling supplied by single phase 240 / 120 Volt three wire from a single phase transformer be a five-terminal lever-bypass socket. The fifth terminal is bonded to the grounded service conductor. Here in the Twin Cities we've been required to install nothing less for years now.

    Now, at present, I agree with you, the actual meter plugged into that base, today, that I am aware of, is still a four "stab" device.
    Some Googling showed that the fifth terminal is for 120/208. Five terminal sockets can do both 120/240 and 120/208, but 4 terminal sockets can only do 120/240. I have yet to see a five terminal meter.
    Cheers and Stay Safe,

    Marky the Sparky

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    I have done a few services that were 120/208 single phase. The poco here only requires a regular 4 terminal socket with a 5th terminal (usually added in the field).
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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