what determines the service size ?

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Stevenfyeager

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United States, Indiana
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electrical contractor
Old houses with original 60 amp service panels often get replaced with 100 amp panels and 125 amp panels as the years go by. But many of the outside entrance cables and meters are still the original 60 amp old set ups. When that happens, what size is the service ? 60 ? 100 ? 125 ? What determines the service size ?
Thanks.
 
Stevenfyeager said:
Old houses with original 60 amp service panels often get replaced with 100 amp panels and 125 amp panels as the years go by. But many of the outside entrance cables and meters are still the original 60 amp old set ups. When that happens, what size is the service ? 60 ? 100 ? 125 ? What determines the service size ?
Thanks.
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I would say the service size is determined by the lowest rated cable or piece of equipment.
 
That is a good question. I believe it varies depending on where the power company's responsibility stops. If your riser wire is smaller then the overcurrent protective device then the service would be based on cable size. However if the service from power company ends at the meter, as in underground then IMO the breaker panel and conductor to the panel determines the size
 
It seems like these houses exteriors could be overloaded since the outside was never updated when the inside main breakers sizes were increased. I'm assuming there is basically no limit of power coming in from the POCO, right ?
 
Stevenfyeager said:
Old houses with original 60 amp service panels often get replaced with 100 amp panels and 125 amp panels as the years go by. But many of the outside entrance cables and meters are still the original 60 amp old set ups. When that happens, what size is the service ? 60 ? 100 ? 125 ? What determines the service size ?
Thanks.
Click to expand...
If the 60 amp condcutors are still in place then it's a 60 amp service. Increasing the service disconnect size to 100 or 125 amps with a new panel is a violation.
 
Used to be a real common occurrence locally then POCOs started requiring inspections anytime a meter is pulled (other than for billing purposes) so we catch a lot of those "bootlegged" jobs,
 
Stevenfyeager said:
Old houses with original 60 amp service panels often get replaced with 100 amp panels and 125 amp panels as the years go by. But many of the outside entrance cables and meters are still the original 60 amp old set ups.
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That's the result of a non-permitted/inspected "upgrade" that never gets completed by the POCO.
 
How about actual load calculation being a factor here?

With a single service disconnect you are supposed to have service conductors sized per the overcurrent device.

With the allowed two to six service disconnects your service conductors only need to be sized to carry maximum calculated load.

So you could still have that 60 amp SE cable supplying six 200 amp main breaker panels and sort of are code compliant if the load calculation is 60 or less.
 
In my area you can’t do a service change without a permit from PG&E.

They will send it to their engineering dept to determine if they need to upgrade their end of things, including the transformer.

Building Dept won’t issue the permit without that.
 
We did a service not to long ago I don't remember exactly what it was but I believe we had 10 sets of 500kcmill and Poco fed us with one set of 4/0 I forget I think it was
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I don't remember I was just doing the install at the time I was just working, it was a pretty big built I think 8-9 stories 25 apts

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It was a leed certified building here in NYC that's like a super efficient building honestly probably less then 400 amps if I had to guess

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I have many times done a service upgrade and informed the POCO so they could upsize their service drop. They never do. They just hookup the same drop that was there before. I think they want to see if it burns up before spending the extra money.
 
Con ed does that all the time here they won't fix it unless it break's

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Here the Bldg department issues the permits.
POCOs rarely, if ever know there is a panel upgrade unless the contractor calls Duke, AEP or the dozen or so co-ops to disconnect.
Then there’s the issue of the service guy getting an order for “disconnect for construction”. The inspection comes in from the HO with a picture of the inspection sticker, and the service guys connect it back without telling anyone in engineering about additional loading. Basically falls through the cracks in the name of efficiency.
 
nickelec said:
We did a service not to long ago I don't remember exactly what it was but I believe we had 10 sets of 500kcmill and Poco fed us with one set of 4/0 I forget I think it was
313bfa43a3850bc8a5e5314cb4d54c2d.jpg
e9289766a4182f695362b1bbb7ceee36.jpg


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I had one the other way around once. changed over a single phase service to three phase. Original had like 1800 amps of conductors which was fine in the 2000 amp gear but it went to a 100kVA single phase padmount (which can only deliver ~416 amps) and I honestly don't know how they ever packed all that in there.
 
kwired said:
a 100kVA single phase padmount (which can only deliver ~416 amps)
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That’s at 100% at a specific temp.

It can do way more than that depending on ambient temp, loading time, oil and core temp, etc..
 
Hv&Lv said:
That’s at 100% at a specific temp.

It can do way more than that depending on ambient temp, loading time, oil and core temp, etc..
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Yes it can, particularly when dealing with utility transformers. Still probably not going to deliver 1800 for very long even in pretty low ambient, and certainly wasn't designed to accomodate that much conductor. Can't remember exactly what was there, think it was four runs of 600 aluminum. This one those single phase padmounts with the top hinged wiring compartment door that only stands maybe 30 inches tall, maybe slightly taller on 100 kVA. The 225kva three phase unit it was replaced with had at least 4 foot tall double doors for access, and we went with 1200 amp feeder and only used three of the existing conduits over. Still oversized on conductors and mains as total calculated load probably only around 600 amps, but at least there was room to terminate this time.
 
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