Hi.

I have an old 1920s Bungalow (single story). I recently had the old 1960 split bus panel and 1980 era subpanel replaced with a 30 slot pictured below with existing 100A service (backfed). I didn't opt for a service upgrade to 200A as the house is only 900 sq ft plus doing so would have triggered a mast relocation according to the electrician.

What I really wanted was an independent main breaker separate from the panel so I could de-energise the entire panel but the electrician said this is only allowed when the panel is exterior mounted plus touching the service wiring between the meter and panel would have trigger the above service change/mast relo scenario (+$1800).

I just abandoned the fabric coated 12ga (red arrow in picture) that ran from a 20A breaker to a single 2-pin receptacle in a bedroom. I'm planning on wiring 4 existing and 2 new bedroom receptacles off this circuit using 12/2 (the 3 other existing receptacles in the bedrooms were all chained off the washing machine and basement lighting circuits!).

In addition to this, there is a fair bit of k&t in the attic that I was planning on abandoning this winter (once it's not so hot up there) and the basement wiring is a disaster, at least 3 abandoned circuits got transferred over to the new panel plus what's wired onto what breaker makes little sense .... so lots of incremental changes.

I'm comfortable doing the wiring changes and really enjoy it (I've read all the basic texts and am currently reading Electrical Wiring Residential (Ray Mullin)).

What I'm not so comfortable about is working close to the service lugs. What can I do here to enhance my safety here? Obviously don't touch the lugs , don't wear jewelry, wear long sleeved shirt and leather gloves but is there anything else? I've seen references to making some form of shield to cover the lugs but I'm not sure how practical that is?

 

With the main breaker off the only live parts in the panel will be the wires connected to the breaker.

 

I realize that the only live parts are the lugs on the 100A breaker.

I'm worried (probably irrationally) that I'll slip and touch one, or drop something onto one. The area where I'll be working is only 3" above the live lugs.

This is why I was asking about additional safety precautions.

I was thinking maybe a 2'x3' piece of switchboard matting and possibly gloves? I realize this is massive overkill and a professional wouldn't bat an eyelid at working in this area but a) I'm not a professional b) have a first child arriving in 2 months and I'd rather be paranoid when it comes to safety when I'm working anywhere near live power.

I'm assuming skin touching one of the lugs would generate a fatal shock and touching something metallic onto one is an arc-flash hazard.

 

Not necessarily a fatal shock, but you'll jump!

Rather than a high dollar voltage rated floor mat, I'd rather turn off the main breaker and just be careful, but you could shield the two lugs and the small bit of copper wire exposed at those lugs with a voltage rated blanket, but I really think that is overkill if you are wearing leather gloves. The very worst thing you could probably do is to accidentally cross the panel box to a hot lug with a screwdriver. If you do, you'll get a close-up of what arc-flash is all about.

Myself, I wouldn't turn off the main breaker, but I would be careful.

 

I'm a professional. I've worked inside switchgear where the conductors are 5/8" X 4" copper bars, while the gear was live, and I'm sitting here to tell you about it.

You're right. It's about taking the proper precautions. For one, wear safety goggles or, at least, safety glasses. For another, if I had to work directly above the power feed in a panel like yours, I would cut a piece of cardboard that I could slip around the feeders and protect against contact with the live lugs. Just let it hang out the front like a shed roof.

 

Thanks for the replies.

I always find the "just be careful" bit funny as I assume most people accidentally electrocuted thought they were being careful.

Anyhow. Is there a particular brand of leather gloves that offer reasonable protection (obviously they won't be rated class 00/0 etc).

I can get 2'x3' piece of ASTM D178-93 Type 1 Class 2 switchboard (floor mat) locally for $40.00. To me that seems like cheap peace of mind however I can't say I'm super familiar about forms of electrocution though I did once get 120v across my chest (arm to arm) which wasn't pleasant and obviously no mat is going to help here, rather stick to working one arm behind back.

Thanks. I'd seen using cardboard suggested elsewhere. I understand what you're saying about the "shed roof".

Hopefully I don't have to redo any of the ground/neutral wiring that runs directly behind those feed wires.

I assume it's fine to just tape the cardboard onto the 100A breaker to ensure it stays in place.

 

I guess it would be. I cut keyhole slits in it so that I can get it to go all the way to the back of the panel box. No tape needed then.

 

Hmmn, having difficulty visualizing, maybe we're not on the same page after all. Picture is worth a 1000 words [edit: sorry, wasn't trying to be a smartass]

 

A keyhole slit, or slot, looks like the older keyholes for doors. It's a straight cut with a circle cut out at the end. Just hold the piece of cardboard - pieces of cardboard boxes are handy for this - in front of the place where you want to insert it. Mark the center of each wire it touches. Pull it away and cut a slit at each mark. Guesstimate the length and cut a circle at the end. Then fit it back in around the wires.

If you're suggesting that I should open a panel, set up a camera, and record making a work shield, no thanks. That would take longer than doing the work and I can't think of any other use for it.

You'll just have to use your imagination, I'm afraid.

Yes. If you'd like to post pictures to help us see something you're dealing with, please do.

 

I carry Gorilla tape for when the mains wires are a little long like that.

It's pretty thick and has good stick.

 

I wasn't asking you to open up a panel. Thought maybe there was an existing pic floating around the web? I get the slit bit so it fits between the service wires but I'm not understanding the "circle at end" part.

 

Here.......check out the illustration.



The hole and slot is called a keyhole.

 

pjmax, thanks very much!! appreciate the illustration.

Nashkat1, thanks also!!

 

My pleasure ..........

 

Seems to me the greatest risk is attaching your safety shield
I think I'd go with the Gorilla tape stuck to the breaker & a couple inches over the wires.

Either way--or doing nothing--the risk is extremely small in a back-fed panel.

 

You're welcome.

The way your panel is made, you may have some risk of contacting power to the right of the main breaker and at the bottom of the two columns of breakers. You can check those areas with a multimeter to see.

Both of those may be dead with the main breaker off.The area at the bottom certainly will be. You can tape over them if they are live and it worries you and you don't want to kill the power to your whole house. Just make sure to leave nice long tails to grab to get the tape out.

It would be nice if the person who landed the feeders had trimmed them so the insulation ended at the breaker lugs. Oh well. Make the shield that I described and PJ illustrated. It goes in by pushing the slots over the feeders. Because your breaker is side-fed, make the end that will be up long enough to fold over the top of the main breaker and the uncut edge long enough to reach across the breaker and an inch or two past the right-hand end and you should be fine.

 

Can someone educate me as to why this would be? Is it just a case that it's only 100A (versus 200A with a standard main-breaker style) or is there something to the different panel designs?

As a slight tangent. Obviously it makes no difference for the main service panel (as they are bonded together) but I thought it was considered good wiring practice to have all the neutrals go to one bus bar and all the grounds to the other .... or is it just a personal preference thing?

 

Guy called your panel a back-fed panel because the feeders enter the side of a breaker. "Back-fed" actually refers to feeding the power into one of the breakers mounted on the branch supply buses. That isn't what you have but, because your main breaker is mounted crossways at the top of one of the columns, it looks like one.

I think that what Guy meant was that having the main breaker mounted and fed the way it is reduces the chance of accidentally contacting unfused power while working in the panel, relatively working in one that's top fed and/or, worse, has the feeders terminated to exposed metal lugs.

There's something to that. It would, of course, be better if the installer hadn't left so much exposed conductor.

In the enclosure with the main overcurrent protection device, which this is, the grounding electrode conductor is created by bonding the incoming neutral to one or more low-impedance paths to ground - cold water inlet, gas service inlet, driven ground rods. That protects your service, your house and you from damage from external "high-voltage transients." Lightening, IOW.

All of the branch circuit neutral and grounding (equipment grounding) conductors and the panel enclosure are also bonded to the GEC at this point. That protects everything and everyone from damage from internal high-voltage transients - direct shorts in an appliance or the wiring.

From this point on, all grounding conductors in the house are bonded together and to every metal enclosure. The neutrals never again touch anything grounded. In any subpanel they are isolated from the panel itself and only connected to the neutral feeder for that subpanel. That helps insure that the lightening or other external surge won't see an easier path to ground somewhere inside your house.

There was just a thread on this. See Neutral/ground separation in subpanels.

 

I thought it was backfed and that the breaker is attached to one of the supply busses. Here is a better picture. I asked the electrician whether it was possible to use the breaker slots to the right and he said technically yes but in this application it was normal to not populate them. I couldn't tell if it was safety or just to clearly indicate the location of the master.




I understand the neutral/ground differences between main panel and subpanel. My question was that on previous panels I'd seen they had always been wired where all the neutrals went to one side and all the grounds to the other. In this case the electrician mixed them. Obviously for a main panel it doesn't make any difference, I guess aesthetically I always preferred to see all the neutrals on one side and all the grounds on the other.

 

You're right, it is backfed. Not only that, there appear to be a pair of open spaces above the main and four at the top of the right-hand column. Thanks for the better picture, and my apologies to guy48065.

Your main breaker isn't attached to just one of the supply buses, though; it's attached to both of them. It has to be to supply your 120/240V single-phase service. Looking at this, turning off the main should definitely kill everything except the two wires feeding it. Good.

IDK why some folks do that. Is there anything on your panel schedule that indicates that it should be done this way? The four open slots above the main are particularly puzzling. To avoid bending the feeders in too short a radius, probably. The bond bushing at the entry from the meter is a nice touch too.

And I'm in the habit of landing them opposite their supply breaker, and numbering each conductor. Different folks develop different habits.

 

It looks like a backfed breaker to me, it even has the main breaker hold-down kit installed. I believe this is the way Cutler-Hammer does their 100 amp BR series main breaker loadcenters. If you look closely at the 2 spaces across from the main breaker, you'll see that the stabs have been altered to keep breakers from being installed there.

 

I thought something looked kinds funny about those tabs. Those look like aluminum buses too, FWIW.

 

I'm not sure about the "stabs being altered" to prevent breakers being installed. The electrician said I could install breakers there if I wanted, didn't sound like he'd altered them.

As far as the space above, that's not usable. Here's a pic from the outside so there's no knockouts for those. It's a 30 slot panel. It's a testament to the crazyness of the house wiring that I don't have a single free slot



What section in the NEC describes the use of conduit exiting the panel? I'm abandoning this old fabric cable that used to go up through the notch in the joist to a single 2-pin. It's now going to feed 2 bedrooms (reuse 20A breaker, 12/2, six 15A sockets). There was never a clamp on the old cable, it was free upto the old socket. Should I keep the old length of conduit and just clamp the cable to the joist or remove the conduit and install a new clamp into the panel knockout?

 

Actually, they're like that to accept tandems.

 

And in this picture I see knockouts there. To get to 30 slots you have to use the two to the right of the main.

Chapter 3.

In your picture you have what looks like EMT, flexible metal conduit. a fabric-covered cable extending out of an EMT sleeve and, maybe, some Type AC or AC cable.

If you're asking about the black fabric-covered cable hanging out of the stub of EMT, get rid of all that and bring new cable through the existing knockout. Use reducing washers to mount the cable clamp if you need to.

Does your jurisdiction require conduit and metal-jacketed cable, or can you use Type NM (Romex)?

 

I know LOL. You'd said you thought there were slots above the breaker, there aren't. That was my point. Just the two on the right that I'd been told not to use.

The fabric covered cable is actually going into an old length of solid (but bent) conduit.

There is plenty of NM. I think I've probably answered my own question as the sparky who did the panel upgrade added all the flexible conduit so I'm guessing there is a requirement for it, I'll call the city.

The solid conduit was from before which he managed to reuse. You can see the remains of the plywood for the old subpanel on the other wall to the right and he spliced the old wires that terminated in the subpanel in the plastic junction box mounted to the joist.

 

Correct, stabs that accept tandems are purposely keyed to prevent tandems from being installed where they aren't "allowed". You can usually confirm the tandem population allowance with the PB's model number. A "BR1220B100" for example is a 100A PB with 12 spaces that allows for 20 circuits, or 8 tandems.

 

That "solid (but bent) conduit" is a short stub of EMT - Electrical Metallic Tubing. Is that what you're replacing?

In these pictures we can see the flexible conduit ending and multiple cables coming out of them. Looking back I can see the multiple cables coming into the panel with no cable clamps.

Have fun correcting that. Might take a J-box or two.

Oy.

 

Yes, that's what I'm replacing initially (the fabric wire that's running into the short section of bent EMT).



Correct, there seem to be no clamps on the wires entering the panel either via flex conduit or legacy EMT. Some of the lengths of EMT/solid conduit are pretty long, 20' or so. The only one thats short is the above as the old 2-pin outlet was only 2' above the panel through the joist.

I think on the old split-bus main panel the NM just ran straight into the panel but I can't recall if there were clamps. When the electrician did the panel upgrade, for each case of this it looks like he added the short length of flex conduit.

The panel change was inspected by the city so I assumed it met muster though I recall the inspection being rather cursory.

I'll have to call the city tomorrow, I've spoken to the head inspector and he seemed to know his stuff (a different inspector did the panel change inspection).

 

Cutler-Hammer BR loadceneters usually have aluminum bus, but they also offer copper bus in selected catalog numbers, copper is not available through their entire line. The BR series copper bus is tin plated and looks like aluminum. I still think the stabs to the right of the main breaker are too short to accept breakers. It maybe be a 30 circuit panel, but I don't think it has 30 slots. To be 30 slots you'd have to count the two spaces to the right of the main breaker to get 28 and the two spaces the main breaker is using to get 30. The two spaces to the right of the main breaker also have twist-outs in the cover, but that is normal for a 100 amp BR series loadcenter even when no breakers go in those spaces. Out of curiosity, I'd like to know the catalog number of the panel.

As I recall, the slots that allow tandems are usually at the bottom of the panel unless all slots accept tandems like in a "20-40" or "8-16" panel (assumes the panel is installed with the main breaker at the top and not inverted for bottom feed application).

 

You've lost me. All I see are cables & wires coming into the panel via conduit. Have I missed something?
Is there a requirement to clamp cables at one end or both when run inside conduit?

 

Cables should not be sleeved through open-ended conduit into a panel. There are more conductors in some of the sleeves than can be run in one raceway without debating. The cables need to be inserted through, and secures by, cable clamps. Up to two cables per clamp for most common sizes of Type NM cabling.

 

If you look closely, you can see he terminated the flex into appropriate connectors with bushings on them.

 

Yes, but they're still open-ended and they're overstuffed and the cables aren't secured.

Doing a good job of something that shouldn't have been done does not lead to a good outcome.

 

Nashkat,
I need to see what you're talking about. Can you post a picture that shows conduit + clamps at at the panel?

I see your point about the number of cables in that one flex but given the extra space surrounding the conductors provided by the nm jacket & paper they might not be as close as it seems.

 

No. Maybe I wasn't clear before. The clamps need to be installed instead of the conduit.

The NM sheath, the paper (if any) and the insulation on the conductors are not rated for installation in conduit. But that's closed conduit and it's not the point. The point is that any time you put more than three current-carrying conductors in one raceway you have to start derating them. Yes, there's some leeway in the ampacities but there are so many current-carrying conductors in the stuffed one I doubt if they would make the cut.

And the open-ended conduit sleeves are still just so many chimneys leading out of the panel.

The panel needs to have all of the conduit sleeves removed and the cables brought in through approved cable clamps.

 

I don't see it on the label stuck on the inside of the door. Maybe it's inside the cover, I'll check for it next time I take it off.

These bushings? Are these the threaded connectors at the end of each length of flex conduit?
Were these added to the end (to screw some kind of clamp onto and they just forgot) or does it come this way? Obviously not withstanding the following:

There are 5 pieces of flex conduit, each 18-24" long.

1: 1x 14/2
2: 4x 14/2 (or could be older white 12/2)
3: 2x 14/2 + 1x 12/2
4: 3x 12/2
5: 2x UF

I called the city, waiting to hear back from the head inspector.

 

So I talked to the chief inspector. He said there is no issue running 4 romex through conduit, I forget the max# that can be run but it's irrelevant as he said the rule doesn't apply to < 36" length of conduit.

He did say that code requires that the conduit should be filled with duct seal at both ends to contain any fault to the panel. He said this was a code addition within the last 2 years.

Clamping requirements are that the conduit itself be clamped within 12" inches of the panel, which it is and that the cables leaving the conduit be clamped within a certain #inches after leaving the conduit, which hasn't been done in the case of the wires running perpendicular through the floor rafters.

Also I was told, due to the panel location I have to use some form of conduit when exiting the panel to protect the top of the panel, I can't just run the NM directly into the panel with a clamp.

 

OK. All codes is local. He's the boss.

That answers the concern about the chimney effect. Glad to learn that's been added.

It's actually a support requirement. Running cable through a hole drilled in a framing member is support. You may be good there.

Do what? This is something I, for one, have never heard of. If you find out more about the reason, and the code, behind that, it would be very interesting to hear it.

 

No clue (in the case of 3 or 4 strands of romex) how you're expected to insert the duct seal. There is barely room to insert a toothpick. Would seem possible only with less strands of romex or wider diameter conduit ... but yes this was specifically to address "chimney effect".