I'm planning to install a subpanel on the 2nd floor that is fed from a main in the basement. I'm guessing it's about a 40' run. The panel will be 100A or 125A. The reading I've done so far suggested I need SER type cable for the feeder run. I couldn't find this cable at any local home store. One store had SER aluminum listed as special order, but they couldn't get it anyway.
Any idea what the right cable is for this? I also hope this comes as a sheathed cable, or would it be 4 separate cables?
If it's 4 seperate cables, they'll have to be in a conduit. What you need is 4/3 with ground. And it does come in romex if you go to the electrical supply house.
You may have to go to a real electrical supply. #1 SER is probably way out of the "hobby" class that the home stores cater to. The other question is, are you sure you really need 100a? Are you using electric strip heat or a tankless water heater?
Not unless I can get some kind of thin flexible conduit. I'll be running this across the basement (through the floor joists), up the inside of the wall, into an attic space, along a roof joist and down a wall stud into the new panel.
I'm running a ton of stuff. I'll install 7 20A circuits. I calc the max simultaneous draw will be in the 70A range. It includes a couple space heaters, two electric griddles, a heat gun (the latter two for encaustic painting), computers, lighting, some tools. Part of what's going on is I'm making up for some homeowner installed way undersuitable wiring. My entire 2nd floor (about 500 sf) is tied into
1 first floor 20A circuit. So I can barely draw from the existing wiring for my needs.
I ran a feeder for an addition on my house, very similar to what you are talking about. It is SE cable or "Service Entrance" cable, and not exactly romex, but the same idea. I bought mine around the time copper was at the all time high, so we went with aluminum. It is
2-2-2-4 cable, with three 2 gauge conductors and one 4 gauge conductor for the ground. I think it was around $1.50 / foot, from a supply house. This was for 100 amps. I assume the copper equivalent would be one gauge smaller, but I don't have my code book in my hands.
My cable is about 1" in diameter, so the copper equivalent would be a little smaller, but still really substantial. You also want to be VERY sure that you don't run in where you might shoot a drywall screw or a nail into it. With 100A going through it, you could have a really bad day.
If you are really using that much up there I doubt you really need any space heaters. I bet you would do fine with 60a. That is a lot. That is 14,400 watts. How big are these griddles?
You are calculating your demand incorrectly. You're max draw is 70 amp @ 120 volt. The feeder you intend to run is 100 amp @ 240 volt. That's 200 amps @
120 Volt. What gfretwell suggested #6 copper, is 60 amp @ 240 volt or 120 amp @ 120 volt. More than enough for your load
I'm not completely up on my code, but apparently there is an exception which allowed me to have 100A breaker with the 2-2-2-4 Aluminum SE cable. All the work was down under permit and has been inspected.
Can you use one inch rigid exterior conduit and go up the outside of the house then back into the house on the top floor? Running it along a downspout maybe so it's not conspicuous. Then it will be easy to just pull whatever wire you want.
If you want to install a 100A breaker for your subpanel, you'll need to run four #2 copper wires (or 1/0 aluminum). I've never seen sheathed cable this large, even at my local electrical supply stores, so you'll probably have to run individual conductors in conduit.
You'll need at least 1-1/4" PVC conduit for the four #2 wires, though I'd go with 1-1/2" as it's a lot more common and would be easier to pull wires through.
The largest flexible conduit I've seen is 1", so you'll probably need to use rigid conduit.
You could run rigid conduit along the underside of the joists if appearance isn't an issue. Otherwise, if the conduit has to run perpendicular to the joists, you'll need to use lots of short sections with couplings. A lot more work, but doable. Plumbers do it all the time.
Keep in mind, the holes you drill for the conduit can't be any larger than 1/3 the depth of the joist, and must be at least 2" from the top and bottom edge of the joist. A 2" hole for the conduit would be too big to fit in a 2x6 joist, but you should be fine if you drill your holes in the center of 2x8 or larger joists. I'd still choose surface mounting if that's an option.
You'll need pulling elbows where you change directions (basically an angle with a removable cover).
Installing conduit would be a lot of work, but it would offer better protection and make changes easier in the future.
However, if you think you can get by with a 60Amp panel, you could use
6/3 romex cable which is commonly available at most home centers (it's frequently used for installing kitchen ranges).
If you really think you'll need 100 amps or larger, maybe you could install two 60A subpanels, fed with two separate 6/3 cables? That would be a lot easier to install, and give you 120A total, assuming you have space for two 60A breaker pairs in your main panel.
I recommend you pick up a copy of "Code Check Electrical". It condenses all the various code requirements for cable sizes, conduits, derating requirements, etc. Be warned though, it's not a "how-to" book, it's more reference material. You'll probably have to read through the important sections multiple times to catch everything.
Good point. I won't need one of the space heaters whenever I'm using the griddles. The griddles draw 12A each, and do release a lot of their heat into the room. The other heater is needed, though, as it's in a different room.
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.