service size

Old 05-14-04, 03:41 AM
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service size

Hi guys and gals,

Trying to figure out how to ask this question in a reasonable/intelligible way.

Is it the utility which provides the current to the SE, or is it the amount of current being used by the consumer that determines the service size?

What I'm trying to determine, I guess, is this: Does the meter produce a load, and therfore a current on the SE wires coming to the main breaker, or is it, rather, that the main breaker is able to handle more current. I know that the meter and the SE wires need to be sized for whatever amount of current will be used.

For example, if I wanted to upgrade a service panel from 100 to 200 amps, would the utility need to install a larger meter and SE cable (assuming that the original meter and SE cable was rated at only 100 amps - although I think that meters are rated at 150-200 amps), or could I simply replace the 100 amp main breaker with a 200 amp breaker and be able to add to my circuits safely?

OK, to rephrase: does the utility provide a specified amount of current to be used, or is the consumer limited by the size of the main breaker? If I turned off everything in my house (lights, refrig, EVERYTHING), and amp probed the SE wires coming into the main breaker, would I get a Current reading?

I'm having a hard time dictating this, but I hope it's intelligible enough for a reply. Though I am not a schooled electrician, the trade is fascinating to me and am just trying to get some clarifications to the (sometimes poorly written) books that I'm reading.

Thanks in advance for your replies,
Old 05-14-04, 06:44 AM
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Your service is determined by the loads in your home. You perform a demand load calculation to give the required minim size of all service equipment that the homeowner is responsible for.
The utility Co doesn't have to go by your (required by electric code) calculations. If upgrade from 100A rated equipment to 200A, and you electric load in the house doesn't change, then the energy given by the Utility Co remains the same.
When you upgrade, sometimes the utility Co doesn't think the meter and/or service wires require upgrade. Depends on the utility Co. standards, they are not bound by the national electric code.
Old 05-14-04, 07:35 AM
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If you turn off everything in your house, there should be zero current coming in from the utility. The utility does not limit the current--your main breaker does that.

As Brian says, only the utility can answer many of your other questions, and they would base their answers on the equipment currently installed.
Old 05-14-04, 08:57 AM
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In our area most houses have service drops capable of up to a class 320 service (400 amp running at 80% capacity). You are responsible for everything from the point of attatchment on down. 100 amp meter base is not the same as a 150/200 amp meter base and you would be responsible for changing this. At least in my area.

There is a formula layed out by the NEC for the MINIMUM amount of amperage required for the residence. I would find an electrical contractor who is willing to do this calculation for you, taking into account any special needs you may have such as a wood shop. It should take them more than about 15 minutes and most of that is the time on the phone to get the information.

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