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  1. #1
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    Default Mismatched Service Cable Sizes

    I looked at a house yesterday that had a service panel with a 200 amp main disconnect breaker. On the exterior of the house, the cable exiting the bottom of the meter box was a 200 amp sized cable but the service cable entering the top of the meter box from the drip loop was visibly smaller and appeared to be a 150 amp cable based on what I was able to measure (I have a service cable measuring gauge printed on the back of my business cards so it comes in handy in situations like this). The insulation jackets on both cables had been painted so I was not able to view any type of ratings on the cable jackets.

    What are the ramifications/issues associated with this type of setup? The house would have 150 amp service and not 200 amp as advertised but is there any safety issue at play here?

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  2. #2
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    Default Re: Mismatched Service Cable Sizes

    The service entrance cables you describe would be under the NEC and not the Utility NESC. So that said both the cable coming from the point of connection to the NESC and meter and then meter to the distribution panel should both be 200 amp rated.

    As for ramifications one would first have to absolutely determine if the one se cable is under rated. At that point it really does not matter it would have to be replaced.

    But to answer your question and assuming the home electrical usage could exceed 150 amps at a given time, (given that is the correct assumption), with a 200 amp main breaker the possibility does exist that the 150 amp cable insulation could fail resulting in fire or severe heat damage to the se cable.


  3. #3
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    Default Re: Mismatched Service Cable Sizes

    Thanks Roger.

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    Default Re: Mismatched Service Cable Sizes

    Quote Originally Posted by Nick Ostrowski View Post
    I looked at a house yesterday that had a service panel with a 200 amp main disconnect breaker. On the exterior of the house, the cable exiting the bottom of the meter box was a 200 amp sized cable but the service cable entering the top of the meter box from the drip loop was visibly smaller and appeared to be a 150 amp cable based on what I was able to measure (I have a service cable measuring gauge printed on the back of my business cards so it comes in handy in situations like this). The insulation jackets on both cables had been painted so I was not able to view any type of ratings on the cable jackets.

    What are the ramifications/issues associated with this type of setup? The house would have 150 amp service and not 200 amp as advertised but is there any safety issue at play here?
    Entering from the top after an immediately adjacent loop? how high is this loop and drop from grade or walking surface?

    I'm reading this as your concern is regarding cable line side of the service point. That is to say Utility's drop cable.

    Perhaps I'm reading the OP differently, or even incorrectly; however, as I read it, the service drop is the smaller cable in free air from the drip loop to the utility service point - i.e. line side of the utility meter.

    That is utility owned, is it not in your area? That would be NESC not NEC, line-side of the service point regarding ampacity.

    The service entrance conductors, load side of the meter are what you indicated is 200 amps - and that is what your main protects. Load side of the surface mounted meter, that is NEC regulated.

    I do NOT see a problem with what you described and only what you described, as I read your post.


  5. #5
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    Default Re: Mismatched Service Cable Sizes

    No, drip loop was 20+ feet up next to gable vent. Meter box was approximately 4-5 feet above grade level on wall.

    "It takes a big man to cry. It takes an even bigger man to laugh at that man". - Jack Handey

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    Default Re: Mismatched Service Cable Sizes

    Quote Originally Posted by Nick Ostrowski View Post
    No, drip loop was 20+ feet up next to gable vent. Meter box was approximately 4-5 feet above grade level on wall.
    Okay, so you're not describing the Service-Entrance Conductors, or a messenger supported section of the Overhead Service Conductors, but the Service Drop Conductors portion of the Overhead Service. The Service Drop is still line-side of the service point, the point of demarkation, and under NESC/Utility ampacity rules, IIRC the status of regulation/deregulation of utility in your area - and what constitutes the "Service" vs. the Premisis wiring system.

    Utility ampacities in free air/exposed are distinctly different from those of the NEC wiring methods.

    I still see no problem with what you describe (other than the questionably ambiguous description entrance to the meter enclosure from the top,, protected or otherwise building surface still ambiguous in overall description and you have shared no photo, so I won't "go there" as it is a utility/local rules influanced issue).

    Last edited by H.G. Watson, Sr.; 05-24-2011 at 09:55 AM.

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    Default Re: Mismatched Service Cable Sizes

    A cable entering the top of the socket would not be under the NESC as stated by HG. This would be sized according to the NEC. Roger has given you good information.

    All answers based on unamended National Electrical codes.

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    Default Re: Mismatched Service Cable Sizes

    Thanks Jim.

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    Default Re: Mismatched Service Cable Sizes

    Hey, as I said, perhaps I read it wrong.I took him to indicate the cables were bare and painted, not in conduit or old pipe, not via a masthead but a direct cable drop to the box, and without a pic, I didn't and don't find that plausable for other than temporary service on a building not customer owned pole in PPL territory.Either way insulated guessed size doesn't matter if you haven't identified the cable type. Without a demand load history or calcs, its likely a non issue. Lots of wiggle room in Sec. 220 calcs and alternative 220.87..


  10. #10
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    Default Re: Mismatched Service Cable Sizes

    The cable entering the top of the meter could be customer owned as would the cable exiting the bottom of the meter, making both under the NEC.

    Typically (at least where I've been) the connection of the service drop to the conductors coming out the weather head will be customer owned (at the drip loop), not belonging to the utility.

    From that connection out would be utility owned and may well be smaller.

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  11. #11
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    Default Re: Mismatched Service Cable Sizes

    Quote Originally Posted by H.G. Watson, Sr. View Post
    Hey, as I said, perhaps I read it wrong.I took him to indicate the cables were bare and painted, not in conduit or old pipe, not via a masthead but a direct cable drop to the box, and without a pic, I didn't and don't find that plausable for other than temporary service on a building not customer owned pole in PPL territory.Either way insulated guessed size doesn't matter if you haven't identified the cable type. Without a demand load history or calcs, its likely a non issue. Lots of wiggle room in Sec. 220 calcs and alternative 220.87..
    Cables were bare and exposed. No conduit or pipe. This is a normal and very typical (ie - "plausable") installation around here.

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    Default Re: Mismatched Service Cable Sizes

    I'm not sure what "wiggle room" is applicable in any calculations here. In this installation, any and all service wire and cable on the customer side of the "point of service" has to be rated to serve the 200 AMP breaker.

    Calculations are to figure minimum service size required. Once a service is installed with an oversized main breaker, which a 200 AMP ususlly is, that breaker must be supplied with a wire size capable of supplying the 200 AMPs regardless of what the load actually is (unless over 200 AMPs, which is a different problem). In other words, the overcurrent device needs to be the limiting factor, the wire size can't be.

    The point of service is is usually where the overhead service supply wires are spliced to the cable or wire feeding the supply side of the meter, however some utilities insist the POS is where they attach to the meter housing. So, exactly where the utility stops "their" wiring is where NEC sizing begins.


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    Default Re: Mismatched Service Cable Sizes

    Quote Originally Posted by Bill Kriegh View Post
    In other words, the overcurrent device needs to be the limiting factor, the wire size can't be.
    Those conductors which are smaller than the overcurrent protection size are known as "fusible links".

    The point of service is is usually where the overhead service supply wires are spliced to the cable or wire feeding the supply side of the meter, however some utilities insist the POS is where they attach to the meter housing. So, exactly where the utility stops "their" wiring is where NEC sizing begins.
    And that point is typically where the utility pays for the wire/the customer pays for the wire ... if the utility wants to own the part where it attaches to the meter housing, let them pay for "their" wire.

    Years ago, the utility supplied - and owned - the meter enclosures, most, if not all, have gone away from that and they retain ownership of "the meter" but require the customer to purchase and install the meter enclosure and associated wiring - it was one way cutting costs for the utility and there was a lawsuit over this in which a utility was sued for forcing a specific meter enclosure onto their customers and a customer could get a bigger/better meter enclosure for less than the utility was charging, the utility lost and had to give up claiming ownership of the meter enclosure and associated wiring from the point of their splice in toward the structure.

    Not sure if there are any utilities which still claim ownership of the meter unless they provide it as no cost to the customer, and I suspect there are few utilities which do that.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Mismatched Service Cable Sizes

    "Not sure if there are any utilities which still claim ownership of the meter unless they provide it as no cost to the customer, and I suspect there are few utilities which do that"

    Columbus GA US of A, (GA Power)
    The PoCo gives you the meter base (as in FREE). You provide wire from the mast to meter, they provide wire from pole to mast.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  15. #15
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    Default Re: Mismatched Service Cable Sizes

    Quote Originally Posted by Rick Cantrell View Post
    "Not sure if there are any utilities which still claim ownership of the meter unless they provide it as no cost to the customer, and I suspect there are few utilities which do that"

    Columbus GA US of A, (GA Power)
    The PoCo gives you the meter base (as in FREE). You provide wire from the mast to meter, they provide wire from pole to mast.
    Okay, so where is the point of service?

    At the meter base enclosure THEY provided, or ...

    At the connection to the conductors coming out the mast and weather head YOU provided ... ?

    If the want to claim ownership all the way to the free meter base enclosure THEY provided, then let THEM provide the mast, weather head, and conductors between the meter and their splice.

    Jerry Peck, Construction / Litigation Consultant
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  16. #16
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    Default Re: Mismatched Service Cable Sizes

    Around here, the property owner is responsible for the service cable from the drip loop on down.

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  17. #17
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    Default Re: Mismatched Service Cable Sizes

    Quote Originally Posted by Nick Ostrowski View Post
    Around here, the property owner is responsible for the service cable from the drip loop on down.
    I don't think the definition of Service Point has changed in 2011 but I believe I read where they are providing an informational note to clarify the definition.

    If in doubt ask the utility where they consider the Service Point to be located. As far as I am concerned that is the point where you connect wiring you paid for to the utility supplied wiring. Unfortunately what I think never seems to matter and is often considered the meter base even though overhead drops connect to premise wiring at the mast weather head line side of the meter..


  18. #18
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    Default Re: Mismatched Service Cable Sizes

    Quote Originally Posted by Jerry Peck View Post
    Okay, so where is the point of service?

    At the meter base enclosure THEY provided, or ...

    At the connection to the conductors coming out the mast and weather head YOU provided ... ?

    If the want to claim ownership all the way to the free meter base enclosure THEY provided, then let THEM provide the mast, weather head, and conductors between the meter and their splice.
    That I do not know. I only know that was the way it worked on the remodels I've done.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  19. #19
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    Default Re: Mismatched Service Cable Sizes

    Georgia power provides the meter socket free but they do not keep ownership the owner of the structure the meter supplies is responible for any maintanance or repairs. This I know because they are currently upgrading their meters and if any issues are found with the meter socket they will not install their meter until the owner hires an electrician to make the repairs.


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