main panel question

[jodil]

Hi, my question has a few parts, but first lets look at the subject:

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The panel where the SEC comes in is a Generl Switch Co. 100 amp panel. It has two pull out blocks at the top and four small fuses below (15, 15, 15, and 20amp)

Then below that four other fuses (15,15,15, and 20amp)

So wheres the main? Are those large pull out block fuses the main? If so how can I tell (and how can you tell what size amps those style of fuses are without pulling the whole thing out?)

Secondly, the panel to the left (breakers) is that a subpanel? How do you know? If it is a subpanel arent the neutrals and grounds supposed to be separated?

The box to the right is just a 30 amp breaker.

[Erby]

I'm sure that one of the electrical guru's will be along shortly to answer, but in my experience:

The pull out fuse block on the left is the main disconnect as that is where the Service Entrance Conductors (SEC) connect. The pull out fuse block on the right usually was originally designed to feed the electric kitchen range with 220 volt juice, though it may now be feeding something else. I'm not sure you can tell the fuse size without pulling the main block (thus shutting off all the electricity) but you can come close on service amps by wire size and meter size. Guess what size those SEC wires are or were they marked.

The 15 & 20 Amp circuits were originally designed to feed all the other stuff, lights, receptacle outlets, etc with 110 volt juice.

The panel to the left is a sub panel because the double taps at the bottom of the top fuse set are back feeding to the top right breaker in the sub panel. Yes the neutrals should float on a bus bar separate from the ground bus bar which should be electrically connected to the sub panel.

The box to the right is NOT a 30 Amp breaker because it's being fed thru one of the 15 or 20 amp fuses.

[John Dirks Jr]

That setup is similar to the one in my house. The pullouts are the main disconnect and main fuses inside them. I don't think you can tell for sure what the main fuse size is unless you actually pull it out and check.

I wouldn't do it though. Maybe I would if the house was vacant. But in an occupied house with computer equipment and whatnot, I would think twice before pulling the main.

You are right that the neutrals and grounds should be separated in that sub to the left. With that alone you have the right to call the electrician out.

Word the report to have the electrician check the main fuses for correct size while they are on site to fix the wiring in the sub.

[jodil]

Originally posted by Erby

I'm sure that one of the electrical guru's will be along shortly to answer, but in my experience:

The pull out fuse block on the left is the main disconnect as that is where the Service Entrance Conductors (SEC) connect. The pull out fuse block on the right usually was originally designed to feed the electric kitchen range with 220 volt juice, though it may now be feeding something else. I'm not sure you can tell the fuse size without pulling the main block (thus shutting off all the electricity) but you can come close on service amps by wire size and meter size. Guess what size those SEC wires are or were they marked.

The 15 & 20 Amp circuits were originally designed to feed all the other stuff, lights, receptacle outlets, etc with 110 volt juice.

The panel to the left is a sub panel because the double taps at the bottom of the top fuse set are back feeding to the top right breaker in the sub panel. Yes the neutrals should float on a bus bar separate from the ground bus bar which should be electrically connected to the sub panel.

The box to the right is NOT a 30 Amp breaker because it's being fed thru one of the 15 or 20 amp fuses.

I see that the red wire coming off of the 15 amp breaker feeds the box to the right that says "30 amp" on the actual breaker. So what does that mean then?

[John Dirks Jr]

Erby is right, the one on the left is the main. I missed that at first. The sub on the right looks to be fed by the same lugs that feed the sub on the left. You can see them double tapped there.

[John Dirks Jr]

I'm not totally sure but I think the lugs that feed both subs are just that...lugs, and they are unfused. They are sitting between the terminals of the 15's, but they themselves are unfused.

Edit...they may be protected by the main. They are not protected by the 15 or 20 that are just above them. Straps run under that block to the main. They are intended for adding subs.

[John Dirks Jr]

As for your question jodil,

I see that the red wire coming off of the 15 amp breaker feeds the box to the right that says "30 amp" on the actual breaker. So what does that mean then?

If a 30 amp sub was being fed by a 15 amp fused circuit it would likely blow the 15 amp fuse. The circuit feeding the sub should be at least as big as the sub itself.

[Brian G]

I'd say Erby and John are correct on the main location, not being able to tell without pulling the block, and on the sub panel requirements. I never pull those old fuse blocks. They can snap in two sometimes. Yeah I know, failed under testing, but not by my hand.

You know it's a sub panel if it's fed from the service equipment, or another panel (you can have a sub from a sub I suppose). I think you can safely say that only the service equipment is not a sub in a given house (anybody know when that might not be the case?). You can have an exception if the second panel is located in a separate building, and it meets the requirements for the exception.

The panel on the right is also a sub panel, but with no 110v circuits there are no neutrals to separate from the grounds. If it'll hold more breakers (it looks like this one will, but does it?), caution the clients that no 110v circuits can be added there without rewiring the panel.

Brian G.

Electrical Antiques Are Not "Charming" [:-thumbd]

[Jim Katen]

Originally posted by jodil

. . . The panel where the SEC comes in is a Generl Switch Co. 100 amp panel. It has two pull out blocks at the top and four small fuses below (15, 15, 15, and 20amp)

Then below that four other fuses (15,15,15, and 20amp)

So wheres the main? Are those large pull out block fuses the main? If so how can I tell (and how can you tell what size amps those style of fuses are without pulling the whole thing out?)

In that panel design, both of the top pull-out fuse blocks are mains. The one on the left cuts power to everything except the one on the right. The one on the right is just it's own main. Some fuse blocks have small viewing windows that allow you to see a bit of the fuse without removing the block. If there is such a window, you can often tell the fuse size by the color. In any event, you won't find a fuse larger than 60 amps in one of those blocks. (Though you might occasionally find a short section of copper pipe in lieu of a fuse.)

If you pull the block on the left, you'll cut power to the house, so if you decide to do that make sure that gramma's oxygen machine has a battery backup. The blocks sometimes disintegrate when you pull on them. Conventional wisdom is that home inspectors have no business pulling these things out. So, of course, I always pull them. (However I also have a half dozen spare ones of various designs in my car.)

Also note that the left main fuse block supplies power to the two auxiliary terminals located just below the four plug fuses. On your panel, these terminals are improperly double tapped to feed the two sub panels. There are also some improper double tapped neutrals at the upper left.

Secondly, the panel to the left (breakers) is that a subpanel? How do you know? If it is a subpanel arent the neutrals and grounds supposed to be separated?

Yes, it's what we colloquially call a sub panel. (That term doesn't exist in the NEC. It's slang.) It's supposed to have the grounding wires isolated from the neutral wires. No one ever complied with that rule back in the bad old days even though the floating neutral requirement has existed since well before the time that fusebox was manufactured.

The box to the right is just a 30 amp breaker.

That box's feeder cable has a black wire, a red wire and a white wire. If the white wire is being used as a neutral, then the box should be grounded. If the white wire wire is being used as a grounding conductor then the color is wrong (though, personally, I don't get worked up over that one). The neutrals in this panel should be floated as well.

Here's a schematic of the 100-amp fuse panel to clarify what's connected to what.

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Here's a picture of a 100-amp fuse panel that shows the little viewing windows in the blocks.

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And here's a view of a 100-amp fuse panel from the back. Compare it to the schematic for better understanding.

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-Jim Katen, Oregon

[kurt]

This is just me being slack, but....

Figuring out those panels used to be exciting for me, but now I could give a sh--.

I always find enough stuff in them to call them crap, and tell folks to tear it all out & consolidate it into a single upgraded panel.

[randynavarro]

Not being slack, Kurt.

I also do it most every time I see fuses left in home, unless its still the original 600 foot Sears-bought box home.

99.9% of the time, the fuses are overloaded, double-tapped, and just insufficient for the needs of the home.

[Sodapop]

I've seen worse. But I would still upgrade the panel and service.

[hausdok]

Hi,

About 11 years ago, James Simmons (Mr. Electric) gave a class that I attended wherein he told folks that if it's an electrical component like a panel that's been in a home 40 years or more it's obsolete. Since that day, all fuse boxes I see and older panels that I know are over 40 years old get termed 'obsolete' and I recommend folks get them replaced. I can't remember anyone ever arguing the point - not even the zoids - and I've seen some fuse boxes that were actually so well done they looked like works of art.

ONE TEAM - ONE FIGHT!!!

Mike