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#1
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feeder wire for a subpanel
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? |
#2
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feeder wire for a subpanel
wrote in message ... 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? You can't run conduit? I'd use conduit and THHN conductors. |
#3
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feeder wire for a subpanel
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. s wrote in message ... 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? |
#4
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feeder wire for a subpanel
On Dec 10, 9:59 pm, "S. Barker" wrote:
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. They make romex in a large enough gauge for this? I was guessing it must be huge (e.g. 4 or 6 gauge)... |
#5
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feeder wire for a subpanel
You can't run conduit? I'd use conduit and THHN conductors. 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. |
#6
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feeder wire for a subpanel
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? So #1 SER is what I need? 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. |
#7
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feeder wire for a subpanel
On Dec 10, 10:42 pm, wrote:
On Dec 10, 9:59 pm, "S. Barker" wrote: 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. They make romex in a large enough gauge for this? I was guessing it must be huge (e.g. 4 or 6 gauge)... 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. JK |
#8
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feeder wire for a subpanel
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 wrote in message ... 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? So #1 SER is what I need? 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. |
#9
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feeder wire for a subpanel
On Dec 11, 12:18 am, wrote:
On Mon, 10 Dec 2007 20:51:16 -0800 (PST), wrote: So #1 SER is what I need? #1 aluminum or #2 copper for 100a 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. JK |
#10
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feeder wire for a subpanel
On Dec 10, 10:51 pm, wrote:
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? So #1 SER is what I need? 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. 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. |
#11
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feeder wire for a subpanel
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. Any idea what the right cable is for this? 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. Not unless I can get some kind of thin flexible 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. 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. 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. The reading I've done so far 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. Anthony |
#12
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feeder wire for a subpanel
Yes, i was told (haven't actually bought it yet) by my supplier, that he has
an NM-B 4/3 with ground. s wrote in message ... On Dec 10, 9:59 pm, "S. Barker" wrote: 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. They make romex in a large enough gauge for this? I was guessing it must be huge (e.g. 4 or 6 gauge)... |
#13
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feeder wire for a subpanel
WHO said alum?
s wrote in message ... On Mon, 10 Dec 2007 20:42:49 -0800 (PST), wrote: They make romex in a large enough gauge for this? I was guessing it must be huge (e.g. 4 or 6 gauge)... Romex tops out in #2 that would work for 100a if it was copper but he said aluminum. |
#14
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feeder wire for a subpanel
ACTUALLY #4 can be run for the 100a sub panel.
s wrote in message ... On Mon, 10 Dec 2007 20:51:16 -0800 (PST), wrote: So #1 SER is what I need? #1 aluminum or #2 copper for 100a |
#15
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feeder wire for a subpanel
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? 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. |
#16
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feeder wire for a subpanel
On Dec 11, 5:58 am, "RBM" rbm2(remove wrote:
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 You're right, I think my max is around 70A at 120 volt. I guess I was presuming you feed a subpanel with 240V so that it provides a balanced load to both bus bars. So you're saying I could feed the panel with a 60A 240V breaker using 6/3 romex, and then pull more than 60A at 120V (e.g. install 7 20A 120V circuits with a max simultaneous draw around 70A)? That would make this all easier. |
#17
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feeder wire for a subpanel
In article , fg wrote:
On Dec 11, 5:58 am, "RBM" rbm2(remove wrote: 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 You're right, I think my max is around 70A at 120 volt. I guess I was presuming you feed a subpanel with 240V so that it provides a balanced load to both bus bars. That's one reason. The other reason is to supply 240V loads. So you're saying I could feed the panel with a 60A 240V breaker using 6/3 romex, and then pull more than 60A at 120V (e.g. install 7 20A 120V circuits with a max simultaneous draw around 70A)? Absolutely -- as long as you don't pull more than 60A on any one leg at any time. 30 on one leg, 40 on the other, will be just fine. That would make this all easier. Yep. -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
#18
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feeder wire for a subpanel
On Dec 11, 10:57 am, "S. Barker" wrote:
WHO said alum? s wrote in message ... On Mon, 10 Dec 2007 20:42:49 -0800 (PST), wrote: They make romex in a large enough gauge for this? I was guessing it must be huge (e.g. 4 or 6 gauge)... Romex tops out in #2 that would work for 100a if it was copper but he said aluminum. I think I started the talk of aluminum, saying that I had used it for the cost savings over copper. JK |
#19
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feeder wire for a subpanel
On Dec 11, 11:29 am, wrote:
On Tue, 11 Dec 2007 10:58:22 -0600, "S. Barker" wrote: ACTUALLY #4 can be run for the 100a sub panel. cite that, it sure isn't what 310.15(B)(6) says The Table in 310.15(B)(6) says, for a dwelling, which we are assuming this is, for a "Service or Feeder", which this sounds like, the rating in amps for a #4 copper or #2 aluminum shall be 100A. Are you saying that the problem is that it isn't a service but a subpanel? This should fall under the definition of "feeder" and I'm sure that my AHJ and electrician had that in mind when they allowed & ran my feeder, protected by a 100A breaker, through a piece of 2-2-2-4 Aluminum SE cable. If I'm wrong, tell me how. JK |
#20
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feeder wire for a subpanel
see what big jake said.
s wrote in message ... cite that, it sure isn't what 310.15(B)(6) says |
#21
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feeder wire for a subpanel
On Dec 11, 10:41 pm, wrote:
On Tue, 11 Dec 2007 17:48:25 -0800 (PST), Big_Jake wrote: On Dec 11, 11:29 am, wrote: On Tue, 11 Dec 2007 10:58:22 -0600, "S. Barker" wrote: ACTUALLY #4 can be run for the 100a sub panel. cite that, it sure isn't what 310.15(B)(6) says The Table in 310.15(B)(6) says, for a dwelling, which we are assuming this is, for a "Service or Feeder", which this sounds like, the rating in amps for a #4 copper or #2 aluminum shall be 100A. Are you saying that the problem is that it isn't a service but a subpanel? This should fall under the definition of "feeder" and I'm sure that my AHJ and electrician had that in mind when they allowed & ran my feeder, protected by a 100A breaker, through a piece of 2-2-2-4 Aluminum SE cable. If I'm wrong, tell me how. JK Read the text above the table. It says "feeder conductors that serve as the main power feeder to a dwelling unit". That means if this is the feeder to the main breaker you can use the table. This assumes the diversity of the total house load. You won't be using everything at once. That may not be true in a feeder to a sub panel since we don't know what the sub panel serves. Don't feel bad. A lot of people get confused by this, even inspectors who should know better. Here's a couple more for you - (I don't do this for a living) According to another table in 310-16, my SE cable would have been ok for 100 amps if the wire was rated for 90c. and #4 Copper ok for 95 amps, which would can be "rounded up" to the next common breaker size, no? JK |
#22
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feeder wire for a subpanel
On Dec 13, 7:17 am, wrote:
On Wed, 12 Dec 2007 18:48:45 -0800 (PST), Big_Jake wrote: Here's a couple more for you - (I don't do this for a living) According to another table in 310-16, my SE cable would have been ok for 100 amps if the wire was rated for 90c. and #4 Copper ok for 95 amps, which would can be "rounded up" to the next common breaker size, no? That really doesn't mean anything since you won't find a termination listed for 90c. The 90c column is really just there for derating purposes. An example is if you had 8 THHN conductors in a pipe you have to derate them down to 70% of their ampacity 310.15(B)(2) but since THHN is a 90c conductor you can start derating from the 90c ampacity. So for a #12 you would start derating from 30a, get 21a but you are still limited by 240.4(D) that makes it 20. So the termination at the breaker of the main panel and the connection to the buss at the other end aren't rated for 90c? JK |
#23
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feeder wire for a subpanel
On Dec 11, 4:32 pm, wrote:
On Tue, 11 Dec 2007 09:24:46 -0800 (PST), fg wrote: On Dec 11, 5:58 am, "RBM" rbm2(remove wrote: 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 From what you say there 40a with #8/3 would be more than enough. You will balance 80a across the 2 hot legs but going 60a is just a few bucks more for 6/3. The breakers and panel will probably be the same. So does that mean I would only need a 60A double-pole breaker in the main to feed the subpanel? This breaker will feed two hots (240v) to the subpanel bus bars, and then I can pull up to 96A (80% of 120) of 120v from that subpanel? |
#24
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feeder wire for a subpanel
In article , Big_Jake wrote:
So the termination at the breaker of the main panel and the connection to the buss at the other end aren't rated for 90c? Almost certainly not -- but they're marked. Check 'em. -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
#26
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feeder wire for a subpanel
It means you can pull 60 amps on each leg for a total of 60 amps @ 240 volts
or 120 amps @ 120 volts wrote in message ... On Dec 11, 4:32 pm, wrote: On Tue, 11 Dec 2007 09:24:46 -0800 (PST), fg wrote: On Dec 11, 5:58 am, "RBM" rbm2(remove wrote: 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 From what you say there 40a with #8/3 would be more than enough. You will balance 80a across the 2 hot legs but going 60a is just a few bucks more for 6/3. The breakers and panel will probably be the same. So does that mean I would only need a 60A double-pole breaker in the main to feed the subpanel? This breaker will feed two hots (240v) to the subpanel bus bars, and then I can pull up to 96A (80% of 120) of 120v from that subpanel? |
#27
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feeder wire for a subpanel
So does that mean I would only need a 60A double-pole breaker in the main to feed the subpanel? This breaker will feed two hots (240v) to the subpanel bus bars, and then I can pull up to 96A (80% of 120) of 120v from that subpanel? Should that 60A double-pole breaker be a 120/240v or just a 240v? I would presume the latter, but I see both at the store so thought I'd ask. Thanks to *everyone* who has been so generous with their time and expertise! |
#28
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feeder wire for a subpanel
So does that mean I would only need a 60A double-pole breaker in the
main to feed the subpanel? This breaker will feed two hots (240v) to the subpanel bus bars, and then I can pull up to 96A (80% of 120) of 120v from that subpanel? Should that 60A double-pole breaker be a 120/240v or just a 240v? I would presume the latter, but I see both at the store so thought I'd ask. You want a 240V breaker that has two breakers tied together with a common bar. When you turn the breaker off, you want to turn off BOTH legs of the 240V supply. You DO NOT want the double breakers with two individual switches, as that could still leave one half of the supply powered if you didn't flip both switches. Just to clarify, if you run 6/3 wire with a 60A breaker, that's 60 amps on EACH side of neutral (60 on the black wire, 60 on the red wire). If you balance half of your 120V loads on one side, and the other half of your 120V loads on the other, it should support close to 120Amps total. I'm not sure what the derating requirements are, but it should be more than enough to support the 70A loads you are planning. Anthony |
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