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Thread: Load Center for "new" shop

  1. #1
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    Load Center for "new" shop

    I completed (passed final inspection) last October (2019), and I'm getting ready to start electrifying my shop. I had decided early on pulling a building permit that included electric, was too much for me to do in one pass - I'm very glad I made that decision. I've done some research here and on a different website forum, and wanted to get some additional opinions.

    Here's what I have decided so far:

    100A breaker + feed to barn
    200A panel - 42 slots
    All EMT, use compression fittings and conduit as ground
    All LED lighting

    Here's where I'm struggling:

    1) I located the service entrance in the rear side wall. To run power to the second floor, plus to the other side, will require a lot of conduit if I break out each circuit. Is it common to put a sub panel in upstairs, and one on the other side to minimize wiring?

    2) The more I think about it, the more 42 slots in a panel seems... excessive. I don't know how to go about laying out my electrical on the interior either - I was hoping I could just run power along both sides with sockets, lighting, and the one required GFCI, and add as I need them. But... if I go with a 30 slot breaker, I might regret that decision.

    Ground floor is 20x35, second is 20x30.

    Thanks!

  2. #2
    You could certainly put in multiple subpanels to minimize number of long runs. You could also run big conduit with multiple circuits from your main panel. Running a big conduit with boxes every 10 feet or so is a flexible approach. Running conduit once the shop is full of stuff is more work than running while empty.

    Putting in a 42 slot main even if 30 is more than enough doesn't cost much beyond a little space, and it give you much more room inside the panel to work easily and keep it neatly wired.
    --Certainty is the refuge of a small mind--

  3. #3
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    Quote Originally Posted by Paul F Franklin View Post
    You could certainly put in multiple subpanels to minimize number of long runs. You could also run big conduit with multiple circuits from your main panel. Running a big conduit with boxes every 10 feet or so is a flexible approach. Running conduit once the shop is full of stuff is more work than running while empty.

    Putting in a 42 slot main even if 30 is more than enough doesn't cost much beyond a little space, and it give you much more room inside the panel to work easily and keep it neatly wired.
    Thanks - I like the large conduit idea!

    And I have plenty of vertical space for the larger panel, I just tend to do things overkill, and Iím trying to turn a new leaf.

  4. #4
    Emt conduit with compression connectors and couplings typically make a very poor ground system. Set screw fittings would be better but still not great. I would suggest you pull a ground wire in the conduit.

    In addition you can run 3/4" conduit with a maximum of 8 current carrying conductors, which would give you 4 circuits in each home run. Any more than that and you have to derate the wires according to the codebook.

    While your building is not big enough to need sub panels that would kind of be your call

  5. #5
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    Quote Originally Posted by ray grundhoefer View Post
    Emt conduit with compression connectors and couplings typically make a very poor ground system. Set screw fittings would be better but still not great. I would suggest you pull a ground wire in the conduit.
    I fully agree with the above statements, ground wire is not very expensive and then you know you will have a safe ground. Have not worked in a commercial building in Ohio with new electric work going in without seeing ground wires since early 1990's. This might be due to state code not certain, always see a ground wire going to a ground network.
    As to the sub panels unless you want to shut off one section of machines when not there, I believe it would be cheaper to home run circuit. (example I have a used subpanel for my basement shop that i need to install to be able to turn the main off and all circuits with the exception of lights will be off. This also will create space in the main panel box which is overfull now and I want/need more circuits in the shop as equipment changes from 120 to 240 as it gets upgraded)
    Watch your current carrying conductors in pipe as you have to derate above a certain number, also watch your cubic inch capacity of boxes as you will have to upsize certain boxes as the total wire count climbs.
    Since you are having it all inspected have a conversation with the Electrical inspector before doing anything as HE is the one you have to please not any one on the internet. Will save time and money even if you have to do a few things above basic code requirements.
    Good luck
    Ron
    Last edited by Jim Becker; 04-13-2020 at 12:59 PM. Reason: Fixed quote tagging

  6. #6
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    Gotcha - I'm fine running a ground conductor - I presume I only need one ground per conduit - rather than a dedicated ground per circuit. I was hoping to save a conductor for fill capacity. I assumed compression fittings would make a better connection than set screw fittings, since they make a tight metal-to-metal connection whereas the set screw fittings have the screw and the back of the fitting in tight contact, with the rest a bit loose.

    3/4 conduit gives me sixteen conductors, if I run 12AWG, which is 7 circuits per run. That is significantly more than I would expect to get out of one run, and if I needed more, I'd just add a second conduit. Now... I will have to check for voltage drop for the longest runs, so I might need to size up the conductors to keep it below 3%.

    I'll try to see if I can speak with the inspector, but I would be surprised if the township let me talk with them directly. I was never able to ask questions during the building phase, the answer was always, "follow Michigan code". We follow 2016 NEC, and there are no special provisions. My general plan was to do the bare minimum - light over entrance door, sub panel, feeder wire, sockets along one wall. Eventually I'd do the rest of the work later with a new permit, but this would be something I could accomplish in a few months, assuming the state opens up enough to hand out permits.

  7. #7
    Sounds like a great space. Good luck getting moved into it.

    I do have to ask what your goals are? Conduit is great for armor or pulling new cable through walls in future years, but if you have an exposed ceiling, it’s unnecessary. IMHO I’d much rather have vertical conduit drops for outlets than horizontal runs of conduit. (and you can put NM-B inside conduit for those outlet drops)

    In terms of circuits, I wouldn’t think about running huge numbers of circuits, but about the specific ones you need. Just to call it out, you mention “power with sockets, lighting” above. Just to make sure you know, lighting should be by itself (actually, lighting SHOULD be shared with smoke detectors but NOT with an outlet you are going to plug a planer into).

    You need dedicated circuits for things like compressors and dust collectors. You need to decide where your 240V circuits are for major tools and what plugs you’ll be using. You don’t honestly need that many circuits powering them, though. For general outlets, you don’t really need that many circuits. Honestly, a single 20A 120/240V circuit (where each duplex receptacle is split between each leg) is likely enough, though I would personally want 3, one down each long wall and one down the ceiling.

    Have a lot of fun building your dream shop, but I’d think a lot about detailed requirements before running lots of conduit with multiple circuits and sub panels.

    Bruce

  8. #8
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    Quote Originally Posted by Bruce Lowekamp View Post
    Sounds like a great space. Good luck getting moved into it.

    I do have to ask what your goals are? Conduit is great for armor or pulling new cable through walls in future years, but if you have an exposed ceiling, itís unnecessary. IMHO Iíd much rather have vertical conduit drops for outlets than horizontal runs of conduit. (and you can put NM-B inside conduit for those outlet drops)

    In terms of circuits, I wouldnít think about running huge numbers of circuits, but about the specific ones you need. Just to call it out, you mention ďpower with sockets, lightingĒ above. Just to make sure you know, lighting should be by itself (actually, lighting SHOULD be shared with smoke detectors but NOT with an outlet you are going to plug a planer into).

    You need dedicated circuits for things like compressors and dust collectors. You need to decide where your 240V circuits are for major tools and what plugs youíll be using. You donít honestly need that many circuits powering them, though. For general outlets, you donít really need that many circuits. Honestly, a single 20A 120/240V circuit (where each duplex receptacle is split between each leg) is likely enough, though I would personally want 3, one down each long wall and one down the ceiling.

    Have a lot of fun building your dream shop, but Iíd think a lot about detailed requirements before running lots of conduit with multiple circuits and sub panels.

    Bruce
    A lot to think about! Yes - lighting will be on a dedicated circuit. My hope is I can get the bare minimum installed/inspected/approved and use the rest of the summer to declutter (erm, a 5 year build will generate a lot of useless scrap that I need to deal with!). And with that decluttering, Iíll also have a bit of time to reflect on the layout, and where specific things will go. Iíve played with shop layouts but gave up - decided it would be far easier to use the space first.

    As for horizontal runs of conduit - itís a timber frame (as in mortise and tenon), with a wrap and strap technique. My idea was to run the conduit on the backside of the posts underneath (true) 2Ē girts (or purlins as some call them). Iíll try to remember to post some pictures tomorrow. This would deemphasize the conduit. On the ceiling Iíll likely run any conduit alongside the bent girt. For me conduit will be a cleaner look than romex, and will provide an extra level of safety that will let me sleep at night.
    Last edited by John Pariseau; 04-12-2020 at 11:53 PM.

  9. #9
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    I think any ground wires do not count for box fill. Not sure if they count against conduit fill or not?
    Any chance of welder, electric car, or solar panels in the future? I would run at least 50 amps to subpanel near their future location. Big compressor 30 amp supply from sub panel.
    Make all your panels the same brand so you can move breakers around as needs change.
    Last edited by Bill Dufour; 04-13-2020 at 10:08 PM.

  10. #10
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    Quote Originally Posted by Bill Dufour View Post
    I think any ground wires do not count for box fill. Not sure if they count against conduit fill or not?
    Any chance of welder, electric car, or solar panels in the future? I would run at least 50 amps to subpanel near there future location. Big compressor 30 amp supply from sub panel.
    Make all your panels the same brand so you can move breakers around as needs change.
    No electric car, solar would be neat but impractical.

    Compressor though, maybe. I have a portable unit Iíve been using, but might like something slightly bigger.

    Welder - tough one. This Iím going to have to hold off on, at least for a little while. I know I want one, but if I bought one it wouldnít get the use it deserves.

  11. #11
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    John ,I would suggest that the panel you selected is not overkill. If you upgrade any machines and realize stuff you did not think about at first panels have a way of "filling up". I know mine did.

  12. #12
    Quote Originally Posted by John Pariseau View Post
    Gotcha - I'm fine running a ground conductor - I presume I only need one ground per conduit - rather than a dedicated ground per circuit. I was hoping to save a conductor for fill capacity. I assumed compression fittings would make a better connection than set screw fittings, since they make a tight metal-to-metal connection whereas the set screw fittings have the screw and the back of the fitting in tight contact, with the rest a bit loose.

    3/4 conduit gives me sixteen conductors, if I run 12AWG, which is 7 circuits per run. That is significantly more than I would expect to get out of one run, and if I needed more, I'd just add a second conduit. Now... I will have to check for voltage drop for the longest runs, so I might need to size up the conductors to keep it below 3%.

    I'll try to see if I can speak with the inspector, but I would be surprised if the township let me talk with them directly. I was never able to ask questions during the building phase, the answer was always, "follow Michigan code". We follow 2016 NEC, and there are no special provisions. My general plan was to do the bare minimum - light over entrance door, sub panel, feeder wire, sockets along one wall. Eventually I'd do the rest of the work later with a new permit, but this would be something I could accomplish in a few months, assuming the state opens up enough to hand out permits.
    First off, no electrician I know myself included would consider 16 #12's in a 3/4 conduit a good idea. Secondly as I said before any more than 8 and you are supposed to derate according to table 310-15 B in the code book. Any more than 10 and you need need to derate at 50 percent meaning you would have to run #8 conductors for a 20 amp circuit

  13. #13
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    Quote Originally Posted by John Pariseau View Post
    ...
    1) I located the service entrance in the rear side wall. To run power to the second floor, plus to the other side, will require a lot of conduit if I break out each circuit. Is it common to put a sub panel in upstairs, and one on the other side to minimize wiring?

    2) The more I think about it, the more 42 slots in a panel seems... excessive. I don't know how to go about laying out my electrical on the interior either - I was hoping I could just run power along both sides with sockets, lighting, and the one required GFCI, and add as I need them. But... if I go with a 30 slot breaker, I might regret that decision.

    Ground floor is 20x35, second is 20x30.
    Nice size shop!

    I didn't have time to read the responses but 1, a panel with too many slots doesn't hurt anything. 2, the more sub-panels the better for me - it distributes the load nicely and can save a lot of effort. Consider putting a whole-house (shop) surge protector in the main panel. Keep in mind that there are code limitations when running multiple conductors in one conduit. Remember a sub-panel cannot have the commons and grounds bonded. There are requirements for GFCIs, etc, but note that some equipment will not work with a GFCI, notably certain equipment with certain VFDs. (I have a lathe that will trip any GFCI.) If I had to have it inspected I would have installed the GFCI then removed it later.

    BTW, I am not an electrician but I do all my own wiring. As for laying out the inside, I make two drawings - one a physical layout marking where I want switches and receptacles and the type, the second a logical diagram showing what switches control what lights (and receptacles) and the circuits with the various unswitched receptacles. In general I put receptacles every 4-6 ft and high enough off the floor to clear any work benches, etc, along the walls. I also wired several receptacles in the ceiling for pull-down electrical reels, air filter, garage doors, etc. You want to consider the loads and position the breakers to distribute the load as evenly as possible between both sides of each panel. For lights, consider using 3-way or 4-way switches to control from either end, up and down stairs, and at each physical building entrance. Don't forget outside lighting and receptacles. In my shop I wired one long light circuit from one end of the shop to the other and put enough light fixtures in the ceiling (mostly recessed bulb fixtures with LED bulbs) so I could flip one switch at the man-door at either end of the shop and light the entire building (24x62, several rooms) with enough light to walk anywhere to fetch tools or materials, all without turning on the bright shop ceiling lights. I wired my working lights in zones so if working at the lathes, for example, I don't have to turn on the lights in main shop or wood storage area. If you plan to use any breakers as motor disconnects the breaker must be in sight of the machine. I prefer to use switches rated as motor disconnects.

    Curious, what do you have in the barn that could need 100 amps? Maybe some machines or future plans? I run my barn from a 40 amp circuit but all I have are lights, a small air compressor, and electric watering heaters for livestoci/birds in the winter. Far better to have too much capacity than too little, though.

    JKJ

  14. #14
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    Quote Originally Posted by ray grundhoefer View Post
    First off, no electrician I know myself included would consider 16 #12's in a 3/4 conduit a good idea. Secondly as I said before any more than 8 and you are supposed to derate according to table 310-15 B in the code book. Any more than 10 and you need need to derate at 50 percent meaning you would have to run #8 conductors for a 20 amp circuit
    Sorry, didn't understand your previous comment.

    I looked at Article 310.15(3) Adjustment factors to understand what the code says, and re-read Table 310.15(B)(16) - the heading includes the words "Not More Than Three Current-Carrying Conductors in Raceway" which I did not see initially.

    So - these fill tables are more or less useless - they just provide a "maximum # of conductors to meet 40%" but practically, are useless:

    https://www.stateelectric.com/resour...uit-fill-table

    Correct?

  15. #15
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    Quote Originally Posted by John K Jordan View Post
    Curious, what do you have in the barn that could need 100 amps? Maybe some machines or future plans? I run my barn from a 40 amp circuit but all I have are lights, a small air compressor, and electric watering heaters for livestoci/birds in the winter. Far better to have too much capacity than too little, though.
    Honestly, a 60A feed will be sufficient. I could do a detailed study to determine what equipment I will run, simultaneously and otherwise. Knowing myself this study would never finish, and it would leave me anxious.

    Therefore, the easiest decision point - figuring out the cost difference in feeder wire - which I did - and it was affordable.

    Now - I have peace of mind, will have plenty of headroom, and my voltage drop will be under 2%.

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