On 7/13/20 4:13 PM, wrote:
On Mon, 13 Jul 2020 12:33:06 -0700 (PDT), trader_4
wrote:

On Monday, July 13, 2020 at 11:54:34 AM UTC-4, wrote:
On Mon, 13 Jul 2020 06:23:28 -0700 (PDT), trader_4
wrote:

On Monday, July 13, 2020 at 12:57:50 AM UTC-4, dpb wrote:
On 7/12/2020 10:34 PM, wrote:
On Sun, 12 Jul 2020 21:46:20 -0500, dpb wrote:

On 7/12/2020 6:21 PM, wrote:
On Sun, 12 Jul 2020 16:02:57 -0500, dpb wrote:

On 7/12/2020 1:11 PM, wrote:
On Sun, 12 Jul 2020 11:21:23 -0500, dpb wrote:

On 7/11/2020 10:12 PM, wrote:
On Sat, 11 Jul 2020 12:54:13 -0500, dpb wrote:

On 7/10/2020 11:01 PM, wrote:
...

If it is on the line side of the meter, I suppose it is between the
PoCo and the worms, although you probably do own that service lateral.
FPL wants them in conduit.

Huh. Thought that was the whole point of there being UF-rated cable.

I have no idea what our local rural electric co-op specifies now, I'm
sure it's probably much more stringent than was 40+ years ago when Dad
was redoing the house and pulled the new feed underground and removed
the overhead wire to the house...

They want conduit, just for the extra protection.

Just a note, that is not UF. It is probably USE but I don't want to be
pedantic ;-)

One thing that makes them different is you can use UF inside, USE, not
so much. It is a smoke and product of combustion thing with that
insulation but it does perform better underground than UF.
I am not sure I have ever even seen service conductors direct buried.
It always seems to be in some kind of raceway.
...

It's UF-B I'm virtually positive...altho I didn't climb the loft to go
look at the jacket on the leftover roll end.


I am surprised the PoCo connected to it.

340.12 Uses Not Permitted. Type UF cable shall not be used
as follows:
(1) As service-entrance cable


Huh. I thought that was what "feeder" meant.

Art 100 definition
"Feeder. All circuit conductors between the service equipment,
the source of a separately derived system, or other power
supply source and the final branch-circuit overcurrent device."

Basically think of it as the wires between the main panel and a sub
panel but that sub panel could be what you think of as the main if the
service disconnect is outside.

Well, there is a a disconnect at the pole that is where these run from
to the main inside the house. So what does that make it?

Is the an over current device there? If so it is a feeder but it
should be 4 wires these days. Prior to the 96 code, you could get away
with 3.

Yes, there's breaker there...forget just what it's sized at.


An important difference, like I thought a "service" is not fused.
At least not on the service size, though according to Fretwell
there is a fuse on the primary side, which makes sense. Still
since a given transformer typically serves more than one service, you
could apparently put many times the current rating of the service
conductors through it before it blows. Probably not much of an
issue, since if something happens, a direct short is probably
far more likely, which I guess would blow the xformer fuse before
damage was done to the conductors.


The OC device on the primary of the transformer will be about 150% of
the transformer rating and of no help at all for a fault at the
customer end of the drop. As I said before, Available Fault Current
will be way up in the thousands off amps.

If it's rated at 100KVA, that's only 400A, 150% is 600A. You
would get higher than that for whatever period it takes to blow
the primary fuse. So what happens if there is a direct short? The wire melts before the primary fuse can blow?

Dead shorts (bolted fault) are pretty rare on service conductors but
it would not surprise me if it burned out the crimp on the secondary
or blew the transformer first. I saw a service conductor laying in a
pool of salt water in the keys once and it danced around there until
most of the water boiled away.
We were on a second floor deck watching and it was quite a show.
The insulation on the conductors was mostly gone and the wire was
smoking.

Typical service rated
breakers are rated at 10,000-25,000 amps AIC. It will be printed on
the breaker. Usually the 10k AIC breakers are only 100a and in a lot
of cases, may not actually be enough for the computed AIC. That is why
they changed the rules in 2005. The AIC is supposed to be on a label
on the service although I still seldom see it in residential. PoCos
usually just provide a rounded off guess based on transformer size
instead of a real calculation. If that transformer gets changed, it is
likely to be what the PoCo had on the truck, not necessarily what they
had there before or even what they really need. For a while here, all
new transformers were 50 KVA. I am not sure why but I guess it is what
they had.

That's only 200A, 150% is 300A, but the primary fuse won't
do anything for a direct short because the wire will melt
first?

Dunno. Never saw the primary fuse open tho, maybe there isn't one. I
know there is a recloser on the primary somewhere that can open and
automatically reset but you usually only see that with a fault on the
primary, like a pole down.
I have seen plenty of transformers blow without taking out the
primary.
That is really not my area of expertise but next time I see my FPL guy
I will ask him.

If there is a fuse, it needs to be at the top where that disconnect
ring is.

http://gfretwell.com/electrical/transformer.jpg

I thought neutrals were "always" on the bottom for a little more
safety.