True Service Amperage Available?


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Old 08-30-10, 12:13 AM
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True Service Amperage Available?

How do you determine the true "amp service" in a residential property? Does a 200a main breaker dictate a 200 amp service to the residence?
 
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Old 08-30-10, 12:35 AM
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Originally Posted by bajafx4 View Post
How do you determine the true "amp service" in a residential property? Does a 200a main breaker dictate a 200 amp service to the residence?
Only direct simple way is look at the main breaker rating the amp rating will be stamped on the handle or near to it and the size of service entrance conductors that will affect both.

So with 200 amp you should have 120mm˛ { 4/0 AWG } Alum conductors or either 70 or 95mm˛ { 2/0 or 3/0 AWG } copper but one serious warning do not touch the main lug where the POCO conductors come in the main breaker it is engerized all the time and unfused as well.

You should able see it if have some question with it just holler and to upload the photo you have to get photobucket or other { The tinyurl do not work in here }

Merci.
Marc
 
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Old 08-30-10, 05:23 AM
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Thanks Marc. That does make perfect sense and is what I would assume to be correct. For some reason I remember hearing stories of homes being built and wired, but then the city/utilitiy company running smaller dia. wire than what's actually required by the main breaker to pass full current capacity. (i.e. a 200a main breaker only being supplied by 4AWG al. wire)
 
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Old 08-30-10, 05:59 AM
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The power companies use a different set of rules to size the conductors that they feed your panel with. It would be rare for the incoming wires to be the same size as the wires feeding into your panel from the meter.
 
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Old 08-30-10, 08:14 AM
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Are there any situations where the power company would use a conducter to the meter that's smaller than the conducter between meter and breaker panel? I assume they would (should) always be larger... how much larger based on distance to pole?

On a side note. If you notice excessive (subjective term) dimming of lights in your home on startup of appliances (refrigerator, a/c, etc.), is there any chance the power company would increase the conducter size feeding the meter?
 
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Old 08-30-10, 08:34 AM
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Originally Posted by bajafx4 View Post
Are there any situations where the power company would use a conducter to the meter that's smaller than the conducter between meter and breaker panel? I assume they would (should) always be larger... how much larger based on distance to pole?
Actually they will be smaller many times. For example even following NEC a conductor in air has a higher ampacity. Also the elecectric company may figure it as never reaching capacity.
On a side note. If you notice excessive (subjective term) dimming of lights in your home on startup of appliances (refrigerator, a/c, etc.), is there any chance the power company would increase the conducter size feeding the meter?
If it was on their side it is more likely they would increase the transformer size. Or shift loads between existing transformers close together.

Of course I have seen a case where a much larger panel was installed with out permit, the electric company never notified, and very sloppy connections to the drop made by the bootleg electrician. In a case like that they may change the drop after the red tag is lifted.
 
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Old 08-30-10, 08:55 AM
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Thanks Ray.

Really... smaller??? So what is the breaker/fused mechanism between the pole and my meter? Say I have a 120 amp breaker panel in my house and I somehow manage to load it to its capacity. What would happen in the instance where the drop to the meter is not adequate to handle a continuous 120 amps?

My personal breaker panel is only 120 amp. My utility pole is ~250ft. from my meter and the line drop is buried. I will check what AWG is coming into my panel later today. In my opinion, I experience "excessive" dimming when my central a/c, refrigerator compressor, or even portable dehumidifier cycles. The dimming is bad enough were guests have noticed and commented.

EDIT: With the exception of adding two 220v 50a breakers to my panel, everything is original from when the house was built in 1991. One of the breakers was for a hot tub, that is gone; the other for a sprinkler pump that draws water from a river, but that only turns on for a few minutes ever few days (when I water the lawn.)
 
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Old 08-30-10, 09:26 AM
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If you were to truly load your panel to the max the power companies transformer may go above its capacity and the wires might get hot. The insulation used is a higher temperature rated insulation than typical house wiring.

There really is no overcurrent protection between the pole and your meter. It is sized for multiple homes all off the same transformer and takes a lot to trip it. The overcurrent protection is provided by your main breaker.

Some dimming is normal but may indicate an overloaded transformer or a loose connection. Do your neighbors experience the same dimming?
 
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Old 08-30-10, 09:55 AM
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What would happen in the instance where the drop to the meter is not adequate to handle a continuous 120 amps?
The insulation will eventually break down and crack off. A major overload like a line-to-line short would melt the wires, maybe blow a fuse on the pole transformer. The power company uses different engineering rules and materials though, so a one-to-one comparison to building wire is not appropriate.

In my opinion, I experience "excessive" dimming when my central a/c, refrigerator compressor, or even portable dehumidifier cycles.
You should complain to the power company about it; this type of service call is usually free. They will probably send a technician out to check the voltage drop and make sure all of the outdoor connections are tight. They might replace the drop or the transformer if it is undersized. One transformer usually feeds several houses so it might need to be bigger if the neighbors had A/C, spas, etc added.

A loose connection or damaged bus bar in your main panel can cause the excessive dimming too. You can look (not touch) in the panel for anything obvious, or contact an electrician for a detailed check of the panel and meter can.
 
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Old 08-30-10, 10:11 AM
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I see how it works. I want to install a few landscape lights (less than 50w total) at my driveway entrance which is 600 feet away from my house. They city is telling me I must run some mongo wire out there (2ga if I remember correctly) just in case some future homeowner tries to run an electric weed whip off the circuit, but the power company can put a big bottleneck between my meter and the pole transformer and it's ok.
 
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Old 08-30-10, 11:53 AM
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Originally Posted by bajafx4 View Post
They city is telling me I must run some mongo wire out there (2ga if I remember correctly) just in case some future homeowner tries to run an electric weed whip off the circuit
Voltage drop is only a design recommendation in the electrical code. Unless you have a local amendment to that effect it is not enforceable. (Although 600' is a very long distance for 120V)

but the power company can put a big bottleneck between my meter and the pole transformer and it's ok.
Every wire is a series resistance. The difference is that the power company sets the tap voltage high at the pole so the resistance of the service drop is accounted for by the time it gets to your weather head.
 
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Old 08-30-10, 12:24 PM
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They city is telling me I must run some mongo wire out there (2ga if I remember correctly) just in case some future homeowner tries to run an electric weed whip off the circuit
Actually if you ran 240v out and used a stepdown transformer you could get away with #6 or even #8 assuming the load would not exceed 15a.
 
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Old 08-30-10, 02:23 PM
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Originally Posted by bajafx4 View Post
... I want to install a few landscape lights (less than 50w total) at my driveway entrance which is 600 feet away from my house.

...but the power company can put a big bottleneck between my meter and the pole transformer and it's ok.
1. Have you checked out an LED system with a substantial battery rack and a solar charger? I'm just guessing that even compared to the cost of 6 AWG that might be cost effective.

2. The power utility and their successors will be easy to find in perpetuity if they screw up the engineering and someone's house burns down or someone dies because of their error. They are regulated by a public utility commission.

However on the customer side of the meter, nobody keeps good track of who did what when, unless permits are pulled and inspections completed. So the records and enforcement level by local authorities are the only hedge that future owners, or more likely their insurance companies, have that something will not go awry due to work by past DIYers or contractors.

That difference may not seem fair, but it can probably be successfully defended with statistical and anecdotal data.
 
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Old 08-30-10, 04:45 PM
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Originally Posted by bajafx4 View Post
I see how it works. I want to install a few landscape lights (less than 50w total) at my driveway entrance which is 600 feet away from my house. They city is telling me I must run some mongo wire out there (2ga if I remember correctly) just in case some future homeowner tries to run an electric weed whip off the circuit, but the power company can put a big bottleneck between my meter and the pole transformer and it's ok.
If you did just run a 120 volt out at 600' you would use #2 copper and have enough power there for a 15 amp circuit with no more than 3% voltage down. It's a lot of money for just those lights but again you could also have a 15 amp circuit for other things down the road.

Jim
 
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Old 08-30-10, 05:20 PM
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Originally Posted by bajafx4 View Post
I see how it works. I want to install a few landscape lights (less than 50w total) at my driveway entrance which is 600 feet away from my house. They city is telling me I must run some mongo wire out there (2ga if I remember correctly) just in case some future homeowner tries to run an electric weed whip off the circuit, but the power company can put a big bottleneck between my meter and the pole transformer and it's ok.
In a situation like this, the City and power company may allow you to install a small service at the driveway entrance.
 
 

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