Page 1 of 3 123 LastLast
Results 1 to 15 of 36

Thread: Jeez, another electrical question

  1. #1
    Join Date
    May 2007
    Location
    Fort Smith, Arkansas
    Posts
    1,985

    Jeez, another electrical question

    Pictured is the electrical panel in my garage of the house we purchased some months ago. I added a single 220 breaker for my compressor and a vfd to as yet unbuilt dc with 3 phase motor. The power to both go to separate fused shut off boxes. I added the grounds to where the existing grounds and neutrals were. Now, I'm thinking maybe the neutrals and grounds should be seperated? There is a separate ground bar on the opposite side of the box. Just want to keep things safe although this has probably existed for many years. Thanks.
    Attached Images Attached Images

  2. #2
    Join Date
    Oct 2006
    Location
    Mid Michigan
    Posts
    3,559
    Michael,
    If this box is a sub panel the neutral and ground must be separated. If it is the main house panel the neutral and ground must be joined.
    I am curious about all of the wires coming out of individual breakers. Not sure that this is correct. Another thing, the number of white wires attached to breakers???? The image isn't large enough for me to make out all of the details in the breaker box.
    If it was my breaker box I would replace the box with one that has many more breakers with the current rating of the circuits I needed.
    David B

  3. #3
    Join Date
    May 2007
    Location
    Fort Smith, Arkansas
    Posts
    1,985
    Thanks David. It is a subpanel and may be a subpanel off another subpanel which is up in the attic. Don't have it all figured out yet. Not sure if this one is feeding the one in the attic or the opposite. It's a bit of a mess and a previous owner has used two conductor w/ground for 220 volt circuits with the bare ground attached to the neutral/ground bar. Not sure thats legal. That explains the white wires coming off the breakers.

  4. #4
    Join Date
    Nov 2006
    Location
    Sebastopol, California
    Posts
    2,319

    Some thoughts

    Quote Originally Posted by Michael Weber View Post
    Thanks David. It is a subpanel and may be a subpanel off another subpanel which is up in the attic. Don't have it all figured out yet. Not sure if this one is feeding the one in the attic or the opposite. It's a bit of a mess and a previous owner has used two conductor w/ground for 220 volt circuits with the bare ground attached to the neutral/ground bar. Not sure thats legal. That explains the white wires coming off the breakers.
    If the subpanels are properly set up, you can tell which is upstream by turning off the breaker servicing the panel - that is, there should be a breaker which cuts off current to the subpanel. Ideally, there will be two: one in the upstream subpanel, to cut off all current exiting the box toward the secondary (downstream) subpanel; and one serving as a main breaker in the secondary subpanel. This seems unlikely in this layout, since there look to be several code violations there, but I hope you'll find there's at least one (in either subpanel). Look for the breaker(s) with the biggest wires, and turn off those breakers; then check to see which circuits are turned off.

    As David Baker mentioned, the neutral and ground are bonded (attached to the same bus bar) at the main panel ONLY, and separate at every subpanel. You can buy add-on isolated neutral bus bars, though a lot of panels will come with them already installed; the ground bus bar, if I recall correctly, is bonded to your panel (to provide an equipment ground on the panel itself). I wonder what that object is in the bottom left of the subpanel in your picture.

    From the picture, it's hard to tell whether there are mixed wires going to the bus bar at the right side. Clearly, there are some white (neutral) wires going there, although it seems like far more than make sense.

    If the 220 circuits involved are pure 220 - no part of the circuit is providing 120 current - then I believe using 2 wire plus ground NM is OK for a 220 circuit, with the bare ground wire serving as the equipment ground. It's good practice, though, to wrap black or red tape around the white wire at both ends, to signal that it's carrying a hot leg, not a neutral leg.

    Go to your local public library, and check out at least one book on basic electrical practice. Fine Homebuilding has published some good ones, but there are other good sources too. If there are several choices, lean toward the book with the newest copyright date (codes change), but check all of them out. You need a comprehensive understanding of residential electrical practice in order to tackle what looks like a rat's nest of problems.

    In my opinion, residential electrical stuff's not hard - there are a limited number of rules, and anyone who can use basic tools carefully and can distinguish black, white, red, and green can do the basic steps.

    It does require several abilities:

    1. The ability to look at a problem and reason logically. This can be assisted by sitting down and drawing out the problem and the solutions. When we bought our hot tub years ago, I quickly found that the previous owner (or a well-intentioned friend) had used far too small a relay for the controls and had bollixed up the layout pretty badly. It took me a full afternoon to sit down and draw a proper schematic, but, by the end of the afternoon, I understood exactly how it worked, and have maintained it effectively now for 20 years.

    2. The ability to learn by reading. In my opinion, electrical work is among the most intellectual of all the building trades (although nowadays, with green building finally coming into its own, all the trades require a good deal of book learning-type intellectual power). While the basic rules are simple, there are lots of subtle things, like not overstuffing boxes, that are logically obvious once you read them, but not intuitively obvious if you're sitting there, staring at the wires.

    3. The ability to use basic tools with care and an obsessive concern for perfection in the work.

    4. An equally obsessive desire to live a long time and die from something other than being electrocuted after taking a shortcut to save some money or time. In my stupid youth, I used to work circuits "live," because it was macho. I'm still stupid, but not that way anymore. When I'm working on something electrical, I'll check three times to make sure the circuit is off before proceeding, and I'll use my test equipment to confirm it, even if I KNOW that the circuit breaker I just turned off (and then checked twice that it was turned off) serves the circuit involved. I don't have grandchildren yet, and, if my sons ever get around to procreating, I really want to be around to play with the grandkids.

    If you can't honestly say that you've got these capabilities, DON'T mess with these panels. If you feel you've got them, but are uncertain as to what you're finding, you might check around your neighborhood or amongst your friends and see if there's a competent electrician who can inspect what you've got and give you some advice. A couple of hundred dollars to get a good handle on what you've got could save you grief, time, and money. Much as this community will want to help, only so much can be done with pictures on the Internet.

  5. #5
    Join Date
    May 2007
    Location
    Fort Smith, Arkansas
    Posts
    1,985
    Thanks Bill. I think what you see in the lower left of the box is the ungrounded bus bar which I assume would be for neutrals. There are no wires attached to it at all. In fact, all the 115 volt circuits to all the outlets have both the ground and white wire to the grounded bus bar. Also it appears this box is being fed from the other subpanel. The upper right breaker is the main breaker for the box and is 60 amps and the wire is about 10 or 8 gauge stranded. It is two conductor plus ground with the ground wire going to the common bus bar.

  6. #6
    Join Date
    Aug 2008
    Location
    New Brunswick Canada
    Posts
    16
    Quote Originally Posted by Michael Weber View Post
    In fact, all the 115 volt circuits to all the outlets have both the ground and white wire to the grounded bus bar.
    This is a serious flaw and must be attended to right away, Your electrical system is dangerous, your house is not protected. This has potential to place any metalic object in your house in association with the wiring to become live. This also negates the safety ground system. Have this looked at right away.

  7. #7
    Join Date
    May 2007
    Location
    Fort Smith, Arkansas
    Posts
    1,985
    Thanks David. It seems Bozo the clown might have done the wiring. This subpanel and the one that feeds it are in a detached building consisting of two double garages (one of which is the shop) and a small apartment (unrented) above one of the garages. In addition to all the mentioned problems it seems on closer inspection that someone has provided 220 volts to an air conditioning circuit in the apartment using two single pole breakers. There is a red wire on one and black on the other. The white wire goes to the grounded bus bar and the ground wire is clipped off! You would have thought the home inspector might have caught some of this.

  8. #8
    Join Date
    Jun 2007
    Location
    Wichita, Kansas
    Posts
    1,795
    Quote Originally Posted by Michael Weber View Post
    ...a previous owner has used two conductor w/ground for 220 volt circuits with the bare ground attached to the neutral/ground bar. Not sure thats legal. ....
    Yes, that's not only legal, it's the normal way to wire a 240v circuit using NMC. The white wire should be marked at all accessible locations to show that it's not a neutral conductor - colored tape, heatshrink tube, or whatever the local jurisdiction requires. The bare goes to whatever bus is used for the EGC.
    Tom Veatch
    Wichita, KS
    USA

  9. #9
    Join Date
    Nov 2006
    Location
    Sebastopol, California
    Posts
    2,319
    Quote Originally Posted by Michael Weber View Post
    You would have thought the home inspector might have caught some of this.
    Depending on the laws in your state, you may be able to get some relief either from the seller or from the home inspector. Even from the little photo you posted, it was obvious to several of us that there were issues (not all of us being electricians, either).

    It would be nice for you if you could have the major safety issues addressed by a licensed electrician at no cost to you. You might look into what obligations the seller and/or home inspector have in this matter.

  10. #10
    Join Date
    May 2007
    Location
    Fort Smith, Arkansas
    Posts
    1,985
    Thanks Bill and Tom. I may look into seller/inspector liability but I live in Arkansas and it's not likely there is much recourse there. I'm going to go into the attic and check out the other sub panel and see what it looks like with the cover off. I'm guessing it was an earlier addition since it is on the original garage structure so it may be in better shape. After that, I plan to move the 115 volt neutrals over to the neutral bar. I am under the impression that is the only real pressing need since it seems the 220 volt stuff is okay with the exception of the white wires not being marked as not being actual neutrals. The house by the way is about 100 years old. Most of the electrical has been upgraded from the original knob and tube although some of it still exists.
    Last edited by Michael Weber; 02-07-2009 at 8:01 PM.

  11. #11

    Talking

    Quote Originally Posted by Michael Weber View Post
    Thanks David. It seems Bozo the clown might have done the wiring. This subpanel and the one that feeds it are in a detached building consisting of two double garages (one of which is the shop) and a small apartment (unrented) above one of the garages. In addition to all the mentioned problems it seems on closer inspection that someone has provided 220 volts to an air conditioning circuit in the apartment using two single pole breakers. There is a red wire on one and black on the other. The white wire goes to the grounded bus bar and the ground wire is clipped off! You would have thought the home inspector might have caught some of this.
    Hi Mike

    I'm just going to go through a few problems I see (BTW I am an electrician). I don't see anything that is going to electrocute you unless you would have a feeder neutral open. Starting with the backfed breaker being used as the main in the upper right. It is fed with a cable that has black, white and a bare equipment ground and I don't see a hold down kit on the breaker (required for a back fed main breaker). At anyrate the cable should be a different type with two hot conductors a neutral and an equipment ground. The reason it needs to be a four wire feeder to both sub-panels (I'm assuming both subpanels are getting there supply from the house) is because 3 wire feeders to sub-panels in detached buildings that also have a metal water pipe run to them from the house or any metallic path for that matter must be 4 wire. That would seem feasible since there is an apartment out there...

    The next thing is the terminal strip on the left is your grounded neutral/ground bar not ungrounded. I can't see it but it should be set on insulated standoffs keeping it out of contact with the metal of the panel. And it should have the neutral of the feeder from the other sub-panel upstream connected to it. There should also be a green bonding screw through that terminal strip and threaded into the metal of the panel... bonding the neutral and ground. This needs to be done for all three wire feeders like you have at present. doing this allows you to connect both neutral and ground to that bar on the left just like you see over at the bar on the right, except that terminal strip on the right is a grounding bar only and should have no white or grounded conductors connected to it....only equipment grounds. I can't tell if they connected the neutral of the feeder to that bar or not...if they did it is incorrect. It should be on the bar on the left along with all the other white grounded conductors. If the feeder neutral is connected to the bar on the left then as things are now neutral current is using the metal of the panel to get to the feeder neutral to return to the transformer. Looking at this mess I believe the guy that wired this put so many wires in the left hand gutter that he decided to use that grounding bar on the right for all the ground and grounded connections. But I'm not sure which bar he connected the feeder neutral. And speaking of feeder neutral the cable he used as the feeder requires the white wire to be the neutral and he used it for a hot (ungrounded) conductor and the bare equipment ground is being used as the neutral....not supposed to be that way...

    So I can tell you this much the feeder to this sub-panel and likely the other are going to need to be changed to 4 wire feeders because of the water line (if metal) and any other metallic paths like phone or data that have been run from the house to this detached building.

    I'm sorry if this is confusing I just don't know how else to go it any simpler.

    There are much better panels than what you have and I would recommend changing the one you show to a 100 amp panel with more spaces to accomodate all those circuits.
    Finally if this is the down stream sub panel you need to investigate the sub-panel ahead of this one and make sure there is a disconnect for the building in that panel (main breaker) or some sort of disconnect close to where the feeder from the house enters your detached building.

    Finally, finally if you want to correct the existing panels we can tell you how to do that until you get 4 wire feeders and panel upgrades.
    Last edited by Roger Frazee; 02-07-2009 at 10:58 PM.

  12. #12
    Join Date
    May 2007
    Location
    Fort Smith, Arkansas
    Posts
    1,985
    Roger, thanks for taking time to explain. I just got back from inspecting the upstream sub panel. There are 3 large wires into it from the house (not four). All the bare wires and all the white wires in this box are attached to the neutral bar along with the incoming neutral. So, the bare wire for the downstream box is serving as a neutral but is going to the equipment ground bus bar in the downstream box where all the other grounds and neutrals are! I do know the apartment has it's own water supply (from my irrigation meter) so having 3 wires may not be an issue as far as electrical is concerned. Aren't old houses wonderful? BTW I'm not planning on renting the apartment(especially now). It's small, uninsulated and ugly inside and it makes a good storage place although upstairs.

  13. #13
    Mike

    Your welcome. Yeah I was wondering if maybe it had its own water supply. If you move those white neutrals and the feeder neutral over to that terminal strip on the left (you should do that) be real sure that the terminal strip on the left has the green screw through it to bond the bar to the metal of the panel because it should be sitting on insulated stand offs.. If you can do that you could if you want move the bare equipment grounds over to it also. But ya got a lot of wires to negotiate to get to the terminations on the neutral bar on the left. If the grounds are not long enough just leave them on that grounding bar.

  14. #14
    Join Date
    May 2007
    Location
    Fort Smith, Arkansas
    Posts
    1,985
    Thanks again Roger. One question. If the neutral bus bar is supposed to be bonded to the metal of the box whats the difference between it and the already grounded equipment ground bus on the right? Won't they be shorted together? Would be nice to clean this all up. May contact an electrician next week to make sure it gets done properly and have the two boxes replaced with a single bigger box.

  15. #15
    Hi Mike

    The neutral bar on the left should be on insulated stand offs.... And bonded to the metal of the panel if the panel has a three wire feeder. If a hot wire comes in contact with the metal of the panel the fault current will travel to the bonding jumper (green screw) to the neutral bar out the feeder neutral all the way to the service equipment (house main breaker panel) out the service neutral to the center tap of the transformer. This low impedance/resistance path facilitates massive current flow and trips out the circuit breaker. If that bonding jumper (green screw) isn't installed then there is no path to the neutral conductor of the feeder and the metal will come to line voltage and no breaker will trip. touch the metal and you get zapped.

    Now to answer your question. At present you have the feeder neutral connected to the grounding bar on the right. In reality this is pretty much the same as having everything connected to the neutral bar on the left with the main bonding screw installed only because you have a 3 wire feeder. Panelboards are required in residential load centers to have the ability for the neutral and ground to be isolated in non service equipment applications....like sub panels with 4 wire feeders. Therefore they set the neutral bar on insulators so that the green screw or what ever is used as the main bonding jumper can be removed and effectively allow the neutral to be isolated from ground.
    So you don't have a big safety issue with the way your panel is now other than that bar on the right appears to be an add on and may not be bonded to that box with factory mounting screws using factory predrilled holes. So other than an iffy bond to the panel there isn't much difference.

    But if you will lets wire the panel as it should be. Move the feeder neutral over to the terminal strip on the left and install the green screw bonding the neutral bar to the metal of the panel but leave the neutrals and grounds of the branch circuits connected to the grounding bar on the right. Now all branch circuit neutral current from 120 volt loads must use the metal of the panel to get to the green screw then to the feeder neutral to return to the service equipment and back to the transformer. You do not want neutral current flowing on the metal of the panel. You only want fault current using bonded metal because that current is only there for as long as it takes to trip a circuit breaker. I posted a diagram below to show the problem when we connect grounded conductors to a grounding bar in a panel with a 3 wire feeder with the neutral bonded to ground. Note also that if we remove the bonding jumper the neutral and fault current path will open between the grounding bar and the neutral bar. If any hot phase faults from branch circuits occur to the metal of the panel then a breaker will not trip, the metal will come to line voltage or neutral current will load the panel waiting for a path to the transformer. It will use you if no other lower impedance path exists. The danger in this that the 120 volt loads whose neutrals are connected to the ground bar will stop working so you investigate and go over to the panel.. touch the metal.. at that point if the right conditions exist you could recieve a fatal shock. If there is a hot phase fault to the panel metal you will certainly recieve a shock because a breaker won't clear the fault..even if you have a ground rod connected to that ground bar. So you have two issues that can be deadly. I've also included a diagram showing the effective fault path for a ground fault in order for a breaker to trip just to give you an idea of how this all works. Just remember that current always seeks its source (the transformer) it will use every path available to it to get there. However if given a lower impedance/resistance path it will disproportionately take that path. If the low impedance path through bonded metal and ground wires and the neutral getting back to the transformer is taken away... current will use you, the earth or whatever to get back to the source.

    EDIT: I suppose I should add that panels that have the neutral bar permanently bonded to the panel metal are panels that are to be used only as service equipment and not sub-panels. So I suppose if we get technical your sub-panel configured as it is presently is suitable for service equipment only because there is no way to seperate neutral from ground electrically without using the other terminal strip on the left assuming it is set on insulators.

    Service Equipment: Panels or enclosures that house the first means of disconnect for a service. Neutral and ground are bonded here so fault or neutral current can utilize the low resistance/impedance of the service neutral to return to the transformer (center tap). This keeps current from seeking other paths available at the service equipment to get to the transformer in any appreciable amperage. For example in the diagram showing the effective fault path. There are connections to water pipes and supplemental electrodes like ground rods at the bonded neutral bar. If I have a poor connection to the service neutral causing high resistance or a failing service neutral (damaged overhead for example) more current that expected will seek the transformer through these other higher impedance/resistance paths. If you look at the diagram one path is for current to travel to the ground rod through the earth over to the transformer ground rod then to the center tap of the transformer. Another is the metal water pipe bond.

    I apologize for getting a little carried away with this thread but it is critical to me that when DIY are working on their electrical panels that they understand this bonding and grounding so they know the why of what they are doing.

    Carry on Mike
    Attached Images Attached Images
    Last edited by Roger Frazee; 02-08-2009 at 12:35 PM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •