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Thread: 6 AWG to 100 amp subpanel?

  1. #16
    Electrical Contractor/Instructor jwelectric's Avatar
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    Balvalve

    I don’t know why nor do I much care but you are quick to jump on the bandwagon condemning items that are made in other countries but in your last two post here you have pointed out the failures of equipment that is made and assembled here in America at the same time pointing the blame on others.

    This shows a lack of knowledge of what you are trying your best to discriminate against. I would recommend that if you have a problem with items made in other countries that you address this issue with the elected officials and let them know if there is not something done to remedy the issue you will vote differently next election than you did in the last election.

    This is how to get action about what you are so quick to post about. The way you are addressing the issue by posting on a DIY web site is gaining nothing.

    Balvalve

    Here is a link to 33 vinyl tape
    http://www.alliedelec.com/Images/Pro...ES_6174725.PDF

    Read it carefully.
    Last edited by jwelectric; 11-17-2011 at 07:30 AM.

  2. #17
    DIY Member bsperr's Avatar
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    I might be missing something, but you should be able to find a 100A main lug only (mlo) subpanel that accepts 6 gauge wire. You might even be able to convert your current subpanel with the right size lugs. It seems like that would be easier unless you really want the convenience of a main breaker on your sub, in which case you can backfeed the mlo panel w/ a 60A breaker like ballvalve suggested (of course you would lose two potential spaces in your panel).

  3. #18
    DIY Junior Member SteinEE's Avatar
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    Not to overcomlicate things but if you are using 75 Degree rated equipment you could use #8's THHN with a 50A C.B in stead of #6's.

    You can change out the lugs. I am sure you can go to a local electrical shop and find these.

    What I don't like about this is the coordination issues. I think it is bad practice to have overcurrent devices upstream trip before local overcurrent devices. You would need to make note of where this new sub panel was fed from in case it trips.

    If this addition is a seperate building or structure you will need to look at NEC 250.32 for Grounding and Bonding Requirements.

  4. #19
    Electrical Contractor/Instructor jwelectric's Avatar
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    If using NM cable it must be sized from the 60 degree column not the 75 degree.

  5. #20
    General Engineering Contractor ballvalve's Avatar
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    Quote Originally Posted by jwelectric View Post
    Balvalve

    I don’t know why nor do I much care but you are quick to jump on the bandwagon condemning items that are made in other countries but in your last two post here you have pointed out the failures of equipment that is made and assembled here in America at the same time pointing the blame on others.

    This shows a lack of knowledge of what you are trying your best to discriminate against. I would recommend that if you have a problem with items made in other countries that you address this issue with the elected officials and let them know if there is not something done to remedy the issue you will vote differently next election than you did in the last election.

    This is how to get action about what you are so quick to post about. The way you are addressing the issue by posting on a DIY web site is gaining nothing.

    Balvalve

    Here is a link to 33 vinyl tape
    http://www.alliedelec.com/Images/Pro...ES_6174725.PDF

    Read it carefully.
    I think you started this with mention of "Canadian" drugs. But if a few get the message, its better than 1000 disposed letters to congress. I had 2 congressman partners, and I can tell you that only paid lobbyists have any pull with them.

    Writing to a politician has the value of perpetual motion devices. I am addressing national security, patriotism, and the education of our children in mechanical matters. Electricity and death fits right in there. These cannot be legislated into the national personae. Kids from farms, immigrants and the Amish, and variations therof provide our only hope for craftsman of the future. I do not have the time to write to each school in America and ask that they re-open the metal and wood shop that is now filled with computers.

    So whats with your latest conundrum about Scotch 33? Ask the electricians on the street if they know of any better? And my '33' boxes all have American flags on them, so this must be especially esoteric.

    I DID notice the part where they suggest putty under it in splices.

    I Do buy imported items, but try and find alternatives. Your electrical students are not getting work in Hong Kong, so what stays here, circulates here. Worked on a monster bridge replacement years ago. Buy American requirement. But no foundrys exist any longer for such heavy castings in America, so we had to go to China. Every piece was off spec, holes misdrilled, and some metallurgy-welding made monstrous pieces unuseable. 6 months of onsite repairs. Every third gigantic bolt failed testing, and all were trashed, finally found them in Ohio. That should explain my scepticism of Mexican circuit breakers and Chinese rivets. Here is my Scotch 33 link.

    http://www.grainger.com/Grainger/SCO...226?Pid=search
    Last edited by ballvalve; 11-19-2011 at 01:08 PM.

  6. #21
    DIY Junior Member seattle_steve's Avatar
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    Default So, back to the topic...

    Thanks for all the suggestions. I do prefer to have a main cutoff on the sub-panel. It seems like Siemens 100-amp panels all require #4 minimum for the main breakers. So, I'm thinking I might take the suggestion to return the panel I bought and just get a "main lug" panel (without a main breaker) and backfeed a 50 or 60amp breaker to use as the main breaker in the sub-panel. Anyway, that's how I read one of the suggestions.

    And, from a little research, it sounds like backfeeding means simply attaching the feeder wires (red & black) to the 50 or 60amp breaker (instead of the panel's lugs). Is that correct? And I assume the neutral and ground attach to their normal lugs/terminals. Although, now that I think about it, will I have the same problem with the neutral: minimum #4? Hmm...I'll check the panel specs again.

    Thanks.

  7. #22
    Retired Defense Industry Engineer jadnashua's Avatar
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    You could just trash the 100A breaker and replace it with a 50A one, too. Since you already have the panel, and would have to buy a 50A breaker anyway, it seems like the easiest. that would have to proper sized lugs.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #23
    DIY Junior Member seattle_steve's Avatar
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    Quote Originally Posted by jadnashua View Post
    You could just trash the 100A breaker and replace it with a 50A one, too. Since you already have the panel, and would have to buy a 50A breaker anyway, it seems like the easiest. that would have to proper sized lugs.
    Yeah, unfortunately (or not?), Siemens builds the main breaker into the panel -- it's physically attached at the top of the panel and isn't a regular breaker that slides into one of the slots. Same with the breaker's lugs -- they don't seem replaceable.

    In the meantime, I bought a Cutler & Hammer panel today to check it out, even though I wanted to stick with the same brand (Siemens) as my main panel, since I have extra Siemens breakers, it will be easier to swap the breakers between panels, etc. The C&H panel's lugs do seem to take smaller gauge wire (and its main breaker does just sit in one of the regular breaker slots, unlike the Siemens). However I'm not impressed with the apparent quality of the C&H innards. It just looks cheap compared to the Siemens.

    So, plan for tomorrow: take back both the Siemens and C&H panels and get a Siemens main lug panel + a 60amp breaker to backfeed as the main.

    As far as the neutral lug wire size: I've noticed at the store that they sell these separately, so I'm guessing if the Siemens neutral lug says min #4, I can add a new neutral lug that accepts a smaller wire?

  9. #24
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by seattle_steve View Post
    Yeah, unfortunately (or not?), Siemens builds the main breaker into the panel -- it's physically attached at the top of the panel and isn't a regular breaker that slides into one of the slots. Same with the breaker's lugs -- they don't seem replaceable.
    So, plan for tomorrow: take back both the Siemens and C&H panels and get a Siemens main lug panel + a 60amp breaker to backfeed as the main.

    As far as the neutral lug wire size: I've noticed at the store that they sell these separately, so I'm guessing if the Siemens neutral lug says min #4, I can add a new neutral lug that accepts a smaller wire?
    There is a reason why the main is mounted to the panel.
    408.36(D) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.

    When you get this50 or 60 amp breaker, in order to back feed the breaker it MUST be secured to the panel to prevent someone from pulling it out while it is still energized. So don't forget to get the lok-down kit that goes with it.

  10. #25
    DIY Junior Member seattle_steve's Avatar
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    Quote Originally Posted by jwelectric View Post
    There is a reason why the main is mounted to the panel.
    408.36(D) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.

    When you get this50 or 60 amp breaker, in order to back feed the breaker it MUST be secured to the panel to prevent someone from pulling it out while it is still energized. So don't forget to get the lok-down kit that goes with it.
    Interesting. Makes sense. After a little more research it sounds like I'll also need a "breaker retaining clip" to meet this requirement. I've added it to my list.

  11. #26
    DIY Junior Member seattle_steve's Avatar
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    Ok, I've given up on Siemens. I took a look at the documentation for the 125A main lug. Turns out they only (apparently) support 3 specific breakers for backfeeding the panel. Not surprisingly, none of these was available at Home Despot. In addition, the 3 breakers were all in the 100-125Amp range, so even if I was able to find one, no doubt I'd be back at square one with the wire size issue.

    So, I bought a 100amp Square-D Homeline main breaker panel. Its main breaker lists a wire range from #12(!) and up. The quality of this panel still seems somewhat inferior to the Siemens (e.g., aluminum "connector plate" (?) instead of copper), but definitely a step up from the C&H panel.

    So, I think I've resolved the panel/breaker/wire-size issue. Thanks again for all the responses.

  12. #27
    General Engineering Contractor ballvalve's Avatar
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    You have resolved it, but it seems a shame for the next guy unless you leave him a big tag in the box saying the main breaker will not operate as a protective device, but only as an on-off switch. With all the rules in that big NEC book, I think they really missed one here.

  13. #28
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by ballvalve View Post
    You have resolved it, but it seems a shame for the next guy unless you leave him a big tag in the box saying the main breaker will not operate as a protective device, but only as an on-off switch. With all the rules in that big NEC book, I think they really missed one here.
    The breaker that supplies the feeders will do the protecting and as you pointed out the main is nothing more than a switch to turn the panel on and off

  14. #29
    Electrician ActionDave's Avatar
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    Quote Originally Posted by ballvalve View Post
    You have resolved it, but it seems a shame for the next guy unless you leave him a big tag in the box saying the main breaker will not operate as a protective device, but only as an on-off switch. With all the rules in that big NEC book, I think they really missed one here.
    I would argue that it is one example of the code behaving as it should. There is nothing unsafe about the set up.

  15. #30
    Retired Defense Industry Engineer jadnashua's Avatar
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    One way to think about this is the wall switch, rated at 15A that is controlling a 100W light bulb...works fine, lasts a long time, perfectly safe.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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