How Do I Determine Service Amps to a Meter?

[TXOMFS]

We're looking at buying a piece of property with three single phase meters.

I'd like to know how many amps I have available at each meter for future toys. How can I tell? Do I go buy the size of the master breaker, is it typically written somewhere on the meter, or do I have to call the utility company and ask? I realize I'm limited by the size of the master breaker but is there a chance I have more amps available than the master breaker lets through?

Sorry for using layman's terms.

Thanks!

 

[grantw]

When I was house shopping recently, it was a matter of opening the main panel (during an open house) and looking at the main disconnect. However, as I started reading code and local utility books, it became obvious. If you have overhead service, check out the service riser above the meter. Basically, without fail, I was able to determine service, just by looking at the weather head and riser pipe.

This was the goto assumption for looking at service drops:

2" pipe == 200A service
1.25" pipe == 100A service
1" pipe == 60A service

however, for underground service, you need to check out the main disconnect. The standard issue meters are usually good for 200A, so the writing on the meter body itself will not help.

 

[mm08822]

Typically main breaker rating at each main panel matches the ampacity of the balance of the wiring used in the service up to and including the weatherhead. Typical residential meter pans/meters are either 100a or 200a.

100a meter/meter pan could be used for 60a or 100a service.
200a meter/meter pan could be used for 125a, 150a, or 200a.
The old round style meter pans (I believe) where limited to 60a.

 

[sberry]

What is it you are trying to do?

 

[wyliesdiesels]

You are limited by the main disconnect.

Take some pics post em here

 

[driftpin]

Tell me if I'm wrong, but I suspect the rating is by the rated capacity of the lowest value in the power delivery to the meter can, and the can itself and the meter. By that I mean, 'what is the gauge of the wire drop from the utility pole, what type of conductor is it, and what is the ampacity of the meter can?'

Yes the main disconnect has an amp rating, and that is likely a starting value. You may find the meter can feeding to an outside main disconnect has one value, while the branch circuit panel main disconnect has a lower value. If the branch circuit panel is rated for a higher ampacity, and the conductor can carry it, then you should be able to switch it out for the higher value. In other words, the outside disconnect has a 200 amp breaker, the inside branch panel has a 150 amp breaker. If the conductors from the outside to the inside panel will carry the load, you can upgrade the inside breaker from 150 to 200 amps.

 

[grantw]

Tell me if I'm wrong, but I suspect the rating is by the rated capacity of the lowest value in the power delivery to the meter can, and the can itself and the meter. By that I mean, 'what is the gauge of the wire drop from the utility pole, what type of conductor is it, and what is the ampacity of the meter can?

I wouldn't use the overhead conductor size as any kind of identifier. PoCos rate their wire very differently because free-air.

Also, I wouldn't trust existing meter cans. The one I replaced was a round can, but the Previous Owner had a 100A breaker behind it fed by ~6awg.

I mentioned the riser pipe diameter, as that will give you an indication of the awg in the pipe. Nobody is going to install a 2" conduit for #2 service wire; 99.999% of sparkys will use the right size conduit for the service feed. Except when they don't.

 

[PCustoms]

I wouldn't use the overhead conductor size as any kind of identifier. PoCos rate their wire very differently because free-air.

Also, I wouldn't trust existing meter cans. The one I replaced was a round can, but the Previous Owner had a 100A breaker behind it fed by ~6awg.

I mentioned the riser pipe diameter, as that will give you an indication of the awg in the pipe. Nobody is going to install a 2" conduit for #2 service wire; 99.999% of sparkys will use the right size conduit for the service feed. Except when they don't.

This.

I still don't know what I have at the house. PoCO uses 200A cans by default. I have 2 100A panels that are double tapped to the can (not code, I know). POCO has no record of what they feed me with, their best suggestion is schedule a service call and then maybe they can determine the feed....

Bottom line is they play by different rules

 

[TXOMFS]

What is it you are trying to do?

I anticipate building a shop with various toys (lift, welder, power tools) and probably an apartment which may use electric appliances. I want to know how many amps I have at each main panel so I can determine if I'll need a fourth meter for the shop which could be expensive.

The property has 2 homes, a well, 2 RV hook-ups, a pole barn, lighted horse arena, well pump, and a tack room. All of it is supplied by 3 meters. I'll see it again this weekend and makes notes about what stuff is supplied from which meter and take some photos of the panels & meters.

 

[mm08822]

This.

I still don't know what I have at the house. PoCO uses 200A cans by default. I have 2 100A panels that are double tapped to the can (not code, I know). POCO has no record of what they feed me with, their best suggestion is schedule a service call and then maybe they can determine the feed....

Bottom line is they play by different rules

Most pocos have the customer responsible for all wiring from weatherhead down if overhead service. If underground, customer is responsible from meterpan only into house.

I doubt your poco had anything to do with parallel feeds out of the meter to two panels. So I suspect somebody else(PO?) made up their own rules. The service entrance cable if o/h will tell you size. It would be interesting to see how the two loadside cables are terminated in the meter and exit it. Post a pick please.

 

[wyliesdiesels]

I anticipate building a shop with various toys (lift, welder, power tools) and probably an apartment which may use electric appliances. I want to know how many amps I have at each main panel so I can determine if I'll need a fourth meter for the shop which could be expensive.

The property has 2 homes, a well, 2 RV hook-ups, a pole barn, lighted horse arena, well pump, and a tack room. All of it is supplied by 3 meters. I'll see it again this weekend and makes notes about what stuff is supplied from which meter and take some photos of the panels & meters.

In order to determine if u have enough power, u will hve to do load calcs and know what your main service can supply.

It sounds like u have a jerry rigged setup as most PoCos will not provide multiple meters to single property unless its a multiunit/multifamily dwelling and zoned/permitted as such.

Are all these meters PoCo owned? It may be very expensive to pay for all these as most PoCos charge higher fees and rates for subsequent meters.

Why do u even need multiple meters?

Pics would definitely help

 

[ishamael69]

I have 400A service coming into my house/garage. When they upgraded it, they replaced the meter box with a bigger one, but the meter appears to be the same.

Before we started, the guys from PSO came out for free, looked at the wiring and the transformer, and said "yep, it'll support it." It was my understanding from them that they were actually more worried about the load on the transformer than my wiring. Now, I have the meter, then a 200A main in the house, and a 200A main for the garage.

I guess the moral of the story is, that you might just have to call the power company. My understanding from my reading of the code is that the main breaker(s) tell you your amperage. If you want to know more about the lines before them, you will have to call the power company, because they play by different rules.

 

[grantw]

I guess the moral of the story is, that you might just have to call the power company. My understanding from my reading of the code is that the main breaker(s) tell you your amperage. If you want to know more about the lines before them, you will have to call the power company, because they play by different rules.

I find it hilarious that my 200A upgrade resulted in no new anything from the PoCo. The Original drop from the 60's that supplied a 60A service is now feeding my 2/0 copper and a 200A disconnect. If I follow the overhead back to the pole, the drop looks like it's connected via a small #10 or #8 tie to the tension line. That must be the "fuse" for the drop.

We'll find out once the house is built and my friend is over charging his Tesla.

 

[sberry]

My neighbor got caught with this. His aint bad and he really doesn't load it but its certainly the same wire spliced on to as it was for the original 100. The poco was more than willing to hook on to my old 200 to a 400 that's for sure, I did a design change and a new load calc and talked them in to a better wire.
They were the poco lineman when it was done and the guy commented as they brought new wire spec for the job. It doesn't matter in a practical sense but didn't cost me much to get it. Adds to the problem of disconnecting for power outage though.

 

[sberry]

I anticipate building a shop with various toys (lift, welder, power tools) and probably an apartment which may use electric appliances. I want to know how many amps I have at each main panel so I can determine if I'll need a fourth meter for the shop which could be expensive.

We see some garages with separate service. You need someone knows what they are looking at to take a look. Doesn't mean any of it is overloaded or more cant be added. Generally simple shop work takes relatively little.
You can have a lot of connected equipment and little real load. 400A and no one working at the moment but couple fridges, a fan or 2 and couple lights, 10A a leg or so with some more of another 10 coming on intermittent for heat.

 

[sberry]

My super peak would be 1/4 of the capacity. I got a lot of stuff and would have to work my tail off to hit 100.

 

[bczygan]

Seems simple to me.

Get the POCO service design guy out to look at and tell you what feeds you have from what transformers and what the drops are and could be.

Service drops could be undersized compared to what the transformers could supply.

Then your meters and service entrances might be able to be upsized and made just what you need.

You need to also find out how the services are organized and which properties they are assigned to.

Bill

 

[grantw]

Seems simple to me.

Get the POCO service design guy out to look at and tell you what feeds you have from what transformers and what the drops are and could be.

Service drops could be undersized compared to what the transformers could supply.

Then your meters and service entrances might be able to be upsized and made just what you need.

You need to also find out how the services are organized and which properties they are assigned to.

Bill

this was my backout plan if the poco didn't want to give me 200. I would have left all of the 200a rated gear, but replace the main disco and the sub panel main breaker with 100a gear.