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.
Cheers, Wayne
Can't answer your question, but wonder why you want copper.
Essex makes it. Do you need 125A rating, or is 100A enough?
-Bob
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 for retightening.
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.Best regards, Bob
Well, I mostly like the idea of the smaller cable for a given ampacity. The #2 SER I've seen (in Al) is already quite big, and to get 125A in Al I'd have to go to to #1/0.
Cheers, Wayne
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.
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 service disconnect?
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?
Thanks, Wayne
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 size.
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.
-- Mark Kent, WA
100A through the #2 NMB
you need a #6 copper
individual THWN wires. If
can use flex conduit
raceway method instead
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.-Bob
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.
Cheers, Wayne
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.
-Bob
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.
Cheers, Wayne
According to zxcvbob :
If the ground-neutral interconnect and grounding system connection is made in the disconnect box, you'll need 4 wire to the breaker panel, and split the neutral/ground. I think... ;-)
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?
-Bob
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.
-- Mark Kent, WA
According to Mark or Sue :
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.]HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.