What determines Amperage?

[Karl Fields]

Not who, what what determines the amperage to a service. Is it a PoCo transformer adjustment, the cable from transformer to meter? Meter base? Meter itself? Must be something stopping someone from simply drawing say 200amp from a stated 100amp incoming.
Inquiring minds want to know!
Thanks

 

[LXCam]

Everything electrical carries a rating. So lets start downstream below your main breaker. So for sake of discussion you have a 100 amp service breaker. The wire supplying your home is rated for that 100 amp load. Now lets say your three neighbors all have the exact same service an all three of you are supplied power from one single transformer. That transformer is rated for a 400 amp load on the secondary side. Now upstream of that transformer has over current protection on the primary side and lets say the primary voltage is 12,000. So those fuses would be 8 amp.

These values aren't reality as derating comes into play but just basic discussion purposes only. So please no grief from the overly nick picky guys.

Now wire is sized to accommodate a specific amount of current flow. This also typical for meter sockets, switches, receptacles...etc. Once you exceed that value, the resistance to flow causes the conductor to heat up. The more it heats up, the more resistance to flow increases causing what is know as voltage drop, so basically you are no longer getting 120/240 volts to your home. Also if you drastically overheat the wire, it'll melt. This is the reason for overcurrent protection such as a breaker or fuse.


NOW, lets say you get greedy and decide that you're just gonna go ahead and install a 200 amp service and not comply with the applicable codes or with your utility provider regulations. So your greed yass starts using more power then the transformer can provide, thus either melting the conductors that service your home and or fault the fuses that protect the transformer resulting in taking out the service to all four homes.

Also all electrical components have a specific voltage and current rating. Exceeding those for either application can and will create a fire.............fire is bad

Does that answer your ??

 

[Petey156]

Short answer, your main breaker or your service disconnect

 

[Karl Fields]

OK. So "I have a friend who ..." has a single user 15,000 volt transformer way out in the middle of nowhere. County then limits new service permit to 100 amp. After a final, could my "greedy friend" simply exchange the 100 amp main breaker for a 200 amp (assuming everything downstream is rated for 200 amp)?

 

[LXCam]

OK. So "I have a friend who ..." has a single user 15,000 volt transformer way out in the middle of nowhere. County then limits new service permit to 100 amp. After a final, could my "greedy friend" simply exchange the 100 amp main breaker for a 200 amp (assuming everything downstream is rated for 200 amp)?

Well why didn't you ask that to begin with. Gezzis man I don't want any practice typing.


The primary voltage does not determine the amount of current that can be drawn off the transformer. It is the size of the transformer that determines what it can handle. Your local utility provider is taking into account all potential users of that specific circuit which include total connected load as well as voltage drop for the primary circuit caused by that load. These calculations determine the wire size and overcurrent protection. In short, they have a legitimate reason.

 

[Karl Fields]

Maybe I like to beat around the bush
However I certainly do appreciate the well thought out responses LXCam!

 

[LXCam]

Maybe I like to beat around the bush
However I certainly do appreciate the well thought out responses LXCam!

Anytime bud.

 

[landyacht]

Are you able to determine the wire size used by the poco? Because this would probably become your new limiting factor- draw well over 100 amps for an extended duration, when that's all the poco expected, and you could end up overheating the poco's conductors and their over-current might not protect as it probably covers more than one home and is cumulative. I know around here, the poco uses the smallest wire they can to provide power - in some cases smaller than we are required to provide by code. However bc hydro are a law unto themselves, and are allowed to use "different" calculations for wire size.

 

[rancherbill]

OK. So "I have a friend who ..." has a single user 15,000 volt transformer way out in the middle of nowhere. County then limits new service permit to 100 amp. After a final, could my "greedy friend" simply exchange the 100 amp main breaker for a 200 amp (assuming everything downstream is rated for 200 amp)?

You have fragments of the story.

POCO want to sell power. I have never heard of counties limiting power usage. Is there more to the story?

 

[rockwithjason]

OK. So "I have a friend who ..." has a single user 15,000 volt transformer way out in the middle of nowhere. County then limits new service permit to 100 amp. After a final, could my "greedy friend" simply exchange the 100 amp main breaker for a 200 amp (assuming everything downstream is rated for 200 amp)?

could he? yes. will it work? maybe. is he exposing himself to a liability nightmare? absolutely. will the poco smack the **** out of him if he damages anything? big time. will the poco find out? not if he doesn't damage anything or give the poco a reason to come looking. is it s a stupid idea? yup.

 

[tdkkart]

Why would the county slap a 100amp limit on a new service??

 

[alfredeneuman]

could he? yes. will it work? maybe. is he exposing himself to a liability nightmare? absolutely. will the poco smack the **** out of him if he damages anything? big time. will the poco find out? not if he doesn't damage anything or give the poco a reason to come looking. is it s a stupid idea? yup.

 

[Stuart in MN]

Did you mean a 15,000 volt transformer, or it is actually a 15,000 VA (15kva) transformer? The utility company may well limit you to a 100 amp service on a 15kva, and may require installation of a larger transformer for a 200 amp service.

 

[sberry]

Mine has a small ****** on a 400A service. It likely isn't a county but the poco, county really doesn't have much anything to do with primary service.

 

[rockwithjason]

Why would the county slap a 100amp limit on a new service??

most likely because the load on that line is pushing the limits already. infrastructure is very expensive and some poco's are pretty poor so they make due.

 

[A_Pmech]

The transformer installed on the pole is the primary limiting factor on how much power you can draw off the electric grid.

Power companies as a matter of basic routine severely undersize transformers for residential services. This is because residences never use anywhere close to what their services will provide and transformers use energy even when no power is moving through them. Larger transformers use more energy. Since the transformer is on the power company side of the meter, transformer losses are paid for by the power company and not the consumer.

 

[theoldwizard1]

Did you mean a 15,000 volt transformer, or it is actually a 15,000 VA (15kva) transformer?

15kva is really small. If you have 100A service, in theory you could pull 24kva.

The transformer installed on the pole is the primary limiting factor on how much power you can draw off the electric grid.

Power companies as a matter of basic routine severely undersize transformers for residential services. This is because residences never use anywhere close to what their services will provide and transformers use (waste) energy even when no power is moving through them. Larger transformers use (waste) more energy.

True !

Also, in rural areas, transformers may nor have been upsized even when multiple new home have been built.

As stated, residential loads are very "peaky". When a transformer is "overloaded" it is really overloaded during those peaks (typically a motor starting, such as a well pump, refrigerator, saw, etc). During those short periods, an undersized transformer may only be able to supply 200V or less !

 

[rancherbill]

I've been thinking about this.

Here the power companies want to sell power.

Here you get permits from the COUNTY and they do the inspections. You have to have underground near the house - we are rural. Depending on your pole location, the length of the wire on the house size is the limiting factor. The COUNTY electrical inspector will only allow the correct size breaker.

I think this is what he is talking about.

 

[Karl Fields]

Well the issue is almost over.
PoCo Project Manager sized transformer for 200 amp. Load calc came out to 150ish but they bumped to 200.

The issue is the county issues electrical permits. This is zoned AG100 - no house in sight. The county limits to 60 amp, frequently they will up that to 100 and very rarely to 200, because there is no house. There thinking is they don't want to enable people to live on the land without all the proper permits and structures in place.

To get the meter permit, friend had to also pay for an address permit. Can't have a meter without an address Of course mail is not delivered way out there, but that's not the point I guess.

Usually the process is electrical permit, then PoCo comes in to size and install based on the permit. Friend went to PoCo first, then permit process. If the permit was denied, he would have a $12k pole and transformer and no power!

His thinking is main breaker will be for the permit, and then change out as needed.
There are no other properties using this new transformer, nor will there ever be.
Thanks

 

[AndyA]

I think there's also a breaker on the high voltage side of the transformer. If you draw too much current it'll pop that breaker.
We've had squirrels get on top of the transformer and short out the high voltage side. The power company rolls a truck. The guy gets out the 20ft fiberglass stick and pushes the breaker closed to restore power. No one else on the line loses power, so I'm assuming there's a separate breaker for each transformer.