What determines my electric service amperage?

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Old 09-10-15, 07:59 AM
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What determines my electric service amperage?

What determines the ‘electrical service amperage’ delivered to the house? Is it a device on the electric pole near the street (the service drop), the meter itself, or the breaker in the main service panel?
 
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Old 09-10-15, 08:07 AM
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"D" all of the above. In most cases there is ample power available at the pole. Then the service is limited by everything downstream from that including the wire connecting the pole to the house to the circuit panel and it's master breaker. Sometimes a house may have a 200 amp service from the pole but only a 100 amp panel so the limiting factor would be the circuit panel.

Many of my rental houses are older homes. When I upgrade them with central HVAC, add extra circuits for what the modern world demands the old 60 or 100 amp service is not sufficient. In some cases there already exists the wire from the pole and meter base for 200 amps so all I have to do is upgrade the breaker panel. In other cases the power company has to run a new wire to the house.
 
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Old 09-10-15, 08:10 AM
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How does the meter base limit the current?
 
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Old 09-10-15, 08:17 AM
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In the same way the service drop does -- melting if you overload it. The meter itself can also explode if overloaded, but those are almost universally good for up to 200A.

The size of the service is the least of the ratings of the drop, entrance, meter, meter base, and main panel(s). In the case where you have only one main overcurrent protection device, (a main breaker or fuses) it should be set equal to or less than the service size. There can be multiple mains on a single service, in which case there are calculations to do to determine how to protect everything.
 
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Old 09-10-15, 08:25 AM
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How does the meter base limit the current?
It isn't designed to, that is the job of the breakers and fuses, but if you overload the meter base sometimes it fails with smoke sometimes with fire. There are fuse links at the pole but they are to protect the transformer not the service to your breaker box.
 
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Old 09-10-15, 10:30 AM
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But if determining your electrical service amperage I generally look at the main cutoff breaker in the panel. It's usually something like 60, 100 or 200 amps. Everything else upstream like the meter base and wire to the pole has the same or higher capacity.
 
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Old 09-10-15, 01:16 PM
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I live in an old house that was once used as a duplex. I have 2 electric meters. The house had two old fuse boxes (4 fuses per box) and I was told I had ’60 amp service’ per fuse box. I had the fuse boxes replaced with breaker panels. The electrician ran new wire from the service drop, installed new meter bases, and ran new wire from the meters to the panels. He installed 100 amp main breakers in each panel. I was under the impression that I still had 60 amp service from the street. More recently I asked another electrician what needed to be done to upgrade to 100 amp service. He looked things over from the service drop to the main panels and said ‘You already have 100 amp service.’ Is he correct?
 
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Old 09-10-15, 05:32 PM
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If you are talking about the wiring from the street to your house..... that is completely under the power companies control.

Inside a house we are bound by the Electrical codes. The power company has their own code. For the most part... 100A service cable is run from the street to your house. You upgraded from two 60A services to two 100A services. The power company would more than likely use the same wire. Since their wire is in "free air" they can allow it to supply a lot more current then if the wire was enclosed in a sheath or conduit.

I'd say your electrician friend is correct.
 
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Old 09-10-15, 06:34 PM
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I had the fuse boxes replaced with breaker panels. The electrician ran new wire from the service drop, installed new meter bases, and ran new wire from the meters to the panels. He installed 100 amp main breakers in each panel.
It sounds to me more like you have two 100 amp services. I believe the electrician should have combined the two services. To have two meters for one residence would be pretty rare unless one is for special rates such as electric water heating or electric heat. Most power companies have done away with the special rates encouraging more useage. Do you get two bills every month too?
 
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Old 09-11-15, 06:37 AM
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In my area the power company rarely installs drops rated for less than 200A. There's a decent chance your existing drop from the pole is more than adequate. They also don't upgrade unless you actually add a big load like a tankless water heater rather than just a bigger panel with similar usage.
 
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Old 09-11-15, 06:52 AM
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I would agree that you got what you paid for. I would not worry about the size of the power company lines. They probably looked at since you did not add load, only potential load, there was no reason to make changes on their end.
 
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Old 09-11-15, 08:37 AM
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I mentioned in an earlier post the house I am in was used for many years (decades) as a duplex. It has 2 street addresses, 2 electric meters, 2 gas meters, 2 furnaces, 2 water heaters, etc. One side was used for the income. But, when we moved in we decided to use the complete house and not rent the one side out. Yes, I get 2 bills for electricity and gas each month, sent to the 2 different addresses. But, we wanted to leave the rental option available if we found we wanted, or needed, the extra income. So when the old fuse boxes were replaced the electrician asked if I wanted to combine all the lines under one meter or leave the two. I said to leave the two. So he installed everything new from the service drop to the panels.
 
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Old 09-11-15, 05:56 PM
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Look at my post #9 again, you have two 100amp services. The service capacity is determined by the service entrance wiring, the meter socket and the main breaker rating of the service disconnect or main panel. The size of your service has nothing to do with the lines the power company runs to your service.
 
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