All the local sources of SER electrical cable I can find only have Al
cable, and I can't seem to find a manufacturer on the web for Cu SER
cable. Can anyone offer a pointer? The only #2 Cu cable
(multi-conductor) I have been able to find is NMB, which I prefer not
to use for my subpanel feed.
I'm planning to go with 125A ampacity to match my Al service
conductors. They are spliced with #2 Cu before the meter and are
bigger than the #2 Cu, so they are at least #1 and probably #1/0.
www.essexep.com shows a current price of about $3.70/ft for #2 Cu SER,
while I have been quoted about $2/ft for #1/0 Al SER locally. So
there is quite a premium, for the 40 ft I need it's $148 versus $80.
Unfortunately, their minimum order is $500, and they don't seem to
have any links to distributors. I'll try calling them tomorrow.
BTW, while I was the Borg today I was comparing the #2 Al SER and the
#2 Cu NMB they had. Besides the conductor material, the only
differences I could see were that the SER has a glass tape separator
instead of a paper separator, and that it had a much bigger EGC. So
that brought up a few questions:
What is the minimum size EGC I need for the 125A subpanel feed from my
Does the separator difference, or some other difference I missed,
matter for my application? I'm going 2 ft outside (through a conduit
stub), 30 ft through a crawl space, and about 5 feet through a
basement. In the previous thread, some people suggested NMB, others
said SER was better.
If the #2 Cu NMB would be suitable, but the included EGC is too small,
can I just run a bare copper wire along side for the EGC?
You cannot use 310.15(B)(6) for NM cable, so you'll only be allowed to put 100A
through the #2 NMB
cable. The EGC and GEC for 100A services is #8 copper, #6 aluminum. For 125A,
you need a #6 copper
or #4 aluminum EGC/GEC. Good eye for noticing the difference in grounding wire
If you want 125A, I'd go with the 1/0 SER or install a raceway and pull
individual THWN wires. If
this is truely a subpanel (i.e. past your main breaker/disconnect), then you can
use flex conduit
(liquidtight or regular). Copper is going to cost a lot more, especially if a
raceway method instead
of cable. I'm not sure its worth it to go copper.
From his previous description I don't know if it's a subpanel or not. It
is the main panel, but 30-something feet from the meter base, and the meter
base has a disconnect (I don't know if it is fused).
I think he needs to check with the local inspector and to find out if he
needs 3 conductors or 4, but it is ambiguous.
If it were me, I'd try to get by with 3 wires in a nonmetallic conduit, or
1/0 aluminum SEU.
Right, thanks for reminding me, you mentioned this before. That's
enough reason to eliminate NMB.
OK, the Cu SER cable is 2-2-2-4, and I expect the Al 1/0 SER has a EGC
of #2, certainly at least #4. Anyway, one would expect SER has the
right size EGC, unlike NMB.
Does "fused" just mean that there is an OCPD in the disconnect? There
will be. I plan to use a Square D C125RB with a 125 amp main breaker
(QOM125VH). It's just a rainproof box with a meter base on one side,
and a main breaker on the other side.
So I'll use either #2 Cu SER or #1/0 Al SER, depending on economics
and availability. The consensus here seems to be that the Cu isn't
worth a 75% price premium.
BTW, the current underground service has a splice box before the meter
base, which feeds the existing meter base from overhead. From an
electrical point of view, would it be a good idea to eliminate that
splice box? I believe I can use an underground feed with the C125RB.
Thanks for all the assistance, everyone has been very helpful.
Yes. I was overly specific when I mentioned fuses.
I still think you should check with the inspector first and find out if
you need 4 conductors (SER) or 3 (SE or SEU). It's ambiguous to me, and
I could make a case for either. This also determines how you connect
the neutrals in the panel, and where you connect the grounding electrode
conductor. I suspect you'll need 4 because it's more than 10 feet from
the meter/disconnect, but it's worth asking about because it will save
some money on the cable and on the ground kit for the new panel, and
maybe a headache when you have to route the ground wire that attaches
near the water meter.
Well, I do have an email into the inspector about my general plans.
But there is a detail that demands 4 wires, as I understand it: I'm
doing this work in two stages. In the first stage the new panel will
be a subpanel off a 60 amp breaker in my existing main panel, and will
just feed my new circuits. Only later will I move the existing
circuits over to the new panel and replace the existing main panel
with a disconnect.
Thanks for all the pointers.
Agreed, but there's always a ground-neutral connection in the meter
socket yet you can run just 3 service entrance conductors to a separate
service panel. The disconnect at the meter and the distance to the
panel are what confuses me. Once you have the disconnect (and OCPD),
are the wires no longer service entrance conductors?
That's the ticket. When you hit the primary overcurrent device(s), that is your
main disconnect. You
can run multiple sets of service conductors from the meter, but the service
disconnects must be
grouped or go to different buildings. Can't have a disconnect outside and one
inside that is not
protected by the outside one.
Also, there are local rules to how far inside a building service conductors can
go. I don't know
anyplace that allows 30' inside a building. Here in Washington, things are
pretty generous at 15
feet. Many areas are 5 feet.
Canadian code is 2 meters maximum (a trifle over 6') from the entrance point
to the main disconnect. The main disconnect must also be within 2M from the
front of the house.
You _can_ get approval for longer lengths, but it cannot be done without
prior approval from an inspector.
[IIRC. It may be 1.5M, but it's certainly not more than 2M.]
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
What is your issue with Al? I have used it for years most new homes
anything above 30 amps is AL. The utilities use it almost exclusively. If
installed properly the wire is not the culprit. Unless your looking for a
100 amp load on #2 copper. I would buy the AL. Easier to install, a bit less
money, and you will never get your investment out of it when you sell the
place. A little grease, NoALOX, or other inhibitor will do the trick. Ok you
have to tighten up the lugs every year or so for the first five years. Big
deal. I just sold a home that was wired in the '70's ALL AL. I was not
concerned, as I have been trained on how to install the wire. On final walk
through I did put a meggar and a DLRO on the panel with the main shut off.
Not a problem then, the house was ~23 years old. And not a problem when I
sold it last month. If you size the wire correctly to the load and keep the
connections tight, what is the problem?
I would probably use aluminum because copper prices are really high right
now, and aluminum is lighter. But if someone really wants to use copper,
he can use a size smaller cable and also not have to worry about
terminating the ends carefully nor periodically retightening the lugs. If
one end of the cable is in the meter base, the lugs might not be accessable
I would not buy a house with 15A or 20A aluminum branch circuits or
lighting circuits. If someone gave me a house with aluminum wiring, I
would replace all the 15A and 20A circuits.
30A and larger aluminum is just fine, but I can't fault someone for wanting
to use copper and never having to bother with it again.
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