Elec. Sub-Panel hook-up question…
I’m putting two 100 amp sub panels in a new ‘addition’ that is nearly as large as the original house itself. The addition creates two new spaces, one to be used as a ‘shop’ and one as an apt. I’ve been told to use SE #4 wire to carry the load from the main to each of the subs. Also, that this is a line that encloses four wires: two hots, a neutral, and a ground. But when I go to purchase it — SE #4 — they show me a single woven copper cable enclosed in black plastic. So, what is it that I need to know to get the right cable to carry this load …. up to 100 amps from main panel to sub?
Also, is it necessary to have two lines from the main, one to each of the subs? Or is it possible to have one line to the first sub, and then a branch line from this off to the second? I’m just putting all of the lines in place and will have a licensed electrician actually hook everything up in the end.
Thanks!
nb
Replies
I'm just putting all of the lines in place and will have a licensed electrician actually hook everything up in the end.
Why then bother with the electrician? Seattle inspector wil tell you what you need to change if you did not do it right.
If you aint gettin' a permit, well...., then you should not ask a question in an open forum.
BTW, I have gotten a Seattle city permit in the past for a major church renovation, no problem then (10 years ago) with DIY or the inspections
- DIY may actually be part of the WA state constitution <G>
junkhound,
The whole 'electrical' thing makes me very nervous. I'm working on a forty foot structure and I've never really built anything much in my life. At crucial points -- such as hooking up and turning on all the new wiring -- I've been feeling I should go with a licensed electrician. But you may be right .. when i have the electrician come for the first look I'll ask him about that. The thing is, I'm going to have to have the MAIN box upped from the 125 that it is to either 200 or 320 and Im REALLY uncomfortable trying to do that!
Know any good/cheap electricians in the area?
(and yes .. everything I'm doing is permitted/inspected)
n
Find an Electrician that will let you do the dirty work. Drilling holes nailing boxes and pulling wires. Then he can do the smart work as making connections.
that has been exactly my plan.
I'll call someone in to do the hookups .... unless i get 'braver' as that time approaches!
thanks
I have been around the construction business for more years than I want to mention. Electricians are not cheep but neither are Doctors. They have to learn a lot and pass tests. My earlier point is hanging panels, pulling wire,nailing boxes etc. up is time consuming and their is no need for added markups when you buy them. Let the electrician do the smart stuff he is trained to do. You will have a good and very fair priced job when done. I can stack brick but can't lay them. Know your limitations and the risks you want to put your family in. So save money doing the dumb electrical stuff yourself.
this is exactly what I'm trying to do ... drill holes, run wire, set boxes and switches and panels, wire receptacles and switches ... then bring in the 'guy who knows' to hook up the final, actual live wires.
So far so good. And of course I'll be inspected along the way and will proceed with caution taking NO risks with anything 'live'.
thanks-
n
But you are also trying to design it..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
But you are also trying to design it.
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Setting some panels -- setting boxes, and running lines through holes, yes. And all permitted and with inspector's overview.
I see no danger or folly in that.
n
If you are designing it why are you asking all of those questions about what size feeder that you need..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I don't understand the purpose of your question; I am trying to figure out every aspect of a problem as I proceed with it. I have asked for various levels and angles of input from varying sources along the way. This has been one of them.
Actually if you are going with a #2 aluminum to each 100a panel and you have made yourself happy that there is not a voltage drop issue you don't really have a problem with the feeders.I am sorry If I cluttered up the tread with the #4 vs #3 copper thing but that is a common mistake people make.
"I am sorry If I cluttered up the tread with the #4 vs #3 copper thing but that is a common mistake people make."
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No no no ... I was in the process of attempting to make decisions regarding how to proceed ... which way to go about it .. what was best and what was most expensive and what was truly adequate. Your, and most everyones, input was very helpful in supplying me with enough new information to be able to ask the right questions both here and in calling electrical suppliers here in Seattle and in speaking with those electricians who would give me a few minutes here and there. I really began with very little idea of what I was doing. I had not even *considered* aluminum at the outset of my inquiry and only had some vague ideas about which cables to use and how to use them which weren't making sense to me.
Because of the input from you and Jay and Bill and several others I've now got a very clear picture of how to proceed and even of *various* possible ways to proceed. I view this as perfect use of these discussion/sharing-information boards, and I'm very grateful for all of you who are kind enough to reach out here.
Thanks very much to all who responded! -
n b
I live in King County, pulled permits to do the same thing as you did (100A sub panel off of main, 65 ft from the panel). Ran sch 40 conduit on exterior of house, 4 conductors (hot, hot, neutral, ground). Couple of things:
give me til tomorrow and I'll have the correct gauges for you, but I think it was 4 ga for black/red/white, and 6 ga for ground. Ground doesn't have to be shielded. If you want to go Al for cost make sure you use the right gauge (and I think 2 ga is correct) and also that your connectors are for Al. If you don't know, go to that huge electric supply place in SoDo area.
You'll have to do a floating ground (meaning that your neutral and ground will be separate at the sub and will connect back at the main). Make sure you have the grounding bar for that in the sub panel you buy (many already do).
put a breaker off of your main and one in your subpanel - I used the double slot for a 220 off of the main panel from an old electric dryer. This will keep you from having to kill the power to the whole house at the meter. Another one in the sub means that you can wire and fiddle with wiring without having to run back to the main all the time.
buy that plastic flip card "code check" thing from HD. it was useful for sizing conduit and caught a mistake of mine (number of turns in conduit before you need a breakout) prior to inspection.
use the right gauge to your breakers - 14ga up to 15A, 10ga up to 25A
get it inspected - best $130 I've spent. I passed both, and the inspectors were really good guys who knew the former owner of my house so gave me a bunch of tips, too.
I've got some pics of the install, to. Again, full day of soccer tomorrow but give me a few days, k?
Edited 9/13/2008 3:03 am ET by BradG
240.4(D) 14ga-15a, 12ga-20a, 10ga-30a
Ah! a man with the regs ...thx
No problem, this is another place that the NEC can cause some confusion. If you look at 310.16 it looks like you might be able to use some higher values but 240.4(D) nails it down to the 14-15a, 12-20a, 10-30a. (maximum breaker size). This actually is there to build in the 80% limitation on continuous loads for outlets that are likely to be plug connected since the designer has no control over what the user will plug in. They enforce it with the breaker size.
The wire is actually rated higher but we try not to talk about it too loudly to avoid confusion ;-)BTW there are some places where you can actually usually use the 310.16 ampacity but it is generally a hardwired motor load like an A/C compressor.
That brings up a question I have. I am putting in a micro/hood to replace a hood. The existing feed is a 14ga off a bath gfci (have no idea why they did that, it is not that near kitch), basement recpt, deck recpt, and a couple of other things.
Was going to run another ckt and reuse the old for a new light in b'ment. Dug out the manual for the micro and below is first comment:
• ELECTRICAL RATING OF THIS OVEN : 120V, 60Hz.
14 Amps / 1500 Watts(Microwave oven + Cooktop Lamp + Ventilation Fan)
- You need a 120V, 60Hz, AC only, 15A or 20A, fused electrical supply (located in the cabinet above the
microwave as close as possible to the microwave circuit) serving only the microwave.
A few pages later:
1. Locate the grounded electric outlet for this oven in the
cabinet above the oven, as shown in Figure 4 Detail.
NOTE: The outlet should be on a circuit dedicated to the
microwave oven 120V, 60Hz., AC only, with a
20ampere fused electrical supply.
Cook power rating is 1000w. Seems like somewher in another site spec showed grand total 1350w
Guess will jut run 12 and be done with it. At 1500w it works out to .8333 loading but if that 14ga/15A already is .80 then it would be ok.For those who have fought for it Freedom has a flavor the protected will never know.
This is a strange set of instructions. It starts out 15 or 20a then says 20. I would go with the 20 but the 15 will work, this is not a continuous load.
Legally you should also have a 20 in the bathroom too. It might be worth while putting in both at 20a and using the existing 15 in the basement. You could use a multiwire (shared neutral) circuit as long as the bathroom GFCI connects after the neutral gets split out. That would get you two 20a circuits in one 12/3 cable and a double pole breaker.
Thanks, this house was built in early 70's. I am surprised at some of the things done, but then maybe I am not. It was not a DIY project.
The baths survived raising twin girls and I doubt the empty nesters want to worry about that part now. It is fairly doable since the two baths are just above the panel in an open joist part of the basement. Will pass it on. Each bath has a sep 20a ckt doing the lt/ht/fan. I guess back then the hairdryers were not capable of global warming.(;-).For those who have fought for it Freedom has a flavor the protected will never know.
Back then GFCI's where supsect and also more costly.And apparently there was not the requirement for dedicated bath receptacel circuits.This it was common to run one circuit for all bath receptacles, garage and exterior receptacles.Then people wonder by the receptacles in the grage don't work and find that the power room bath GFCI has tripped. And that receptacle has not been used since the house was built..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Yup, and wire was cheap.For those who have fought for it Freedom has a flavor the protected will never know.
Brad, -- everything you've listed here I've finally arrived at through questioning here and elsewhere and through, as I mentioned a few times, the tauntaun book Wiring a House. The only thing I hadn't heard of is "that plastic flip card "code check" thing from HD"... but I'll definitely look into it.
As for inspections, as long as you're permitted, which I am, I don't know how there is any choice but to be inspected! (I, too, have found that the inspectors -- for siting, foundation, slab, sheer framing and plumbing, so far -- are exTREMEly good guys!)
I would LOVE to see some pics of the install --- didju have to 'up' what you pulled in to your main box? And how much did you end up with coming in over all? 200?
You should come by and see this addition ... forty foot high four story tower on the top of the highest hill in the city .. views to Canada and unobstructed in every direction for hundreds of miles. Really fun.
thanks -
n
http://www.codecheck.com/cc/index.html
Pretty good refFor those who have fought for it Freedom has a flavor the protected will never know.
yep, that's it (codecheck)
Edited 9/15/2008 1:00 am ET by BradG
Pictures and comments ..
Here is the sub-panel, done
http://i236.photobucket.com/albums/ff91/bradgobble/DSC_0002.jpg
Here is the main panel
http://i236.photobucket.com/albums/ff91/bradgobble/DSC_0491.jpg
external schedule 40 conduit exiting main
http://i236.photobucket.com/albums/ff91/bradgobble/DSC_0481.jpg
external entering shop
http://i236.photobucket.com/albums/ff91/bradgobble/DSC_0486.jpg
btw, if anyone knows how to put a damn pic in I'd apprecaite it ... feelin' like a tard right now...
Edited 9/15/2008 1:34 am ET by BradG
Edited 9/15/2008 1:36 am ET by BradG
Edited 9/15/2008 1:49 am ET by BradG
Edited 9/15/2008 1:53 am ET by BradG
BradG - Very good to see this! .. thanks. I've done every single aspect of this tower by myself learning as I go. Electrical is the only aspect of building that throws me; so picky and exacting and possibly dangerous that i don't enjoy it like I do all other aspects. Good to see that yours turned out well.
Thanks again.
nb
Know any good/cheap electricians in the area?
Yeah me, I work free for family and give free advice to neighbors (but not do the work) <big GGG>
You should do a load calculation for your two new "100 amp" boxes. You may want to consider voltage drop also.
I'm confused about this: "SE #4 -- they show me a single woven copper cable enclosed in black plastic." Actually I don't understand the word "woven" in this context. I am thinking looms and cotton.
There are some problems with running just one conductor to the first subpanel and then feeding the second subpanel from the first subpanel. Is this your own residence?
The cable from the main to the 1st sub would have to carry all expected loads running at the same time of both panels. Is you 200 amp main enough to carry the loads of the new addition?
~Peter
pm22
1 - I'm putting in two 100 amp sub panels to be sure that, in future, whatever I might want to upgrade to will more than likely be able to be handled by these. I will be using less than their full potential at the outset for sure.
2 - Well .. 'braided'? If you really have no idea what I'm talking about .. I donno how to say it. It is not 'solid' wire .. it is many very thin wires 'woven' together.
3 - In thinking it through after posting this is exactly what I realized. That it is just better to run the two separate lines even though the cost is high. With copper at its highest price ever now, these lines will cost me, with tax, over 4 bucks a foot. I've got close to a couple hundred feet. Yes, it's my own residence. But Aluminum costs about 1.35 a foot -- quite a difference.
thanks - - - - n
Each sub-panel should have its own feed from the main panel circuit breakers. Each will need two hots and a neutral and a ground.
The wire they showed you is correct but needs to be in a conduit to protect the 4 wires feeding the panels. Other types of wire are wrapped in a bundle with the ground around the outside then covered with insulation. (plastic)
hey USAn ..
Thanks for the simple, straightforward response.
I think I've got it (am getting it) all figured out here. I'm now considering aluminum for the feeds.
thanks -
n
Remember ground and neutral are NOT the same. They should not be connected at the sub panel.
Got it .. thanks.
I'm looking closely at a couple of tauntaun books on wiring and at some older articles from the magazine. Rex Cauldwell's "Wiring a House" is a godsend.
thanks again.
n
single woven copper cable enclosed in black plastic
That's "stranded" wire. Think of your Romex, the individual conductors are solid single copper.
If that #4 was solid, you wouldn't be able to bend it.
You might do a search here for "Sub panel" and you'll get hundreds of hits.
Ignore the old stuff, the rules have changed recently.
There's enough info there to get you going.
No such thing as good/cheap electricians.
Joe H
thanks Joe ...
I see two problems immediately. You need 3 ga copper for 100a and you need SER, not SE (that gives you the insulated neutral and a ground).
Each 100a panel needs it's own feeder or you could run a 200a feeder and tap it (3/0 copper).
Personally I can't imagine an apartment and a shop that would need more than 100a but you won't know without a load calc. Are you going to have a kitchen? What kind of heat and hot water are you using?
As long as the cable feeding the sub panels is large enough to handle the combined loads of both sub panels, and all the feeder cables have correctly sized breakers, why can't one sub panel feed a second sub panel?
You can feed another sub panel from a sub panel but it sounded like he wanted 100a on each.