Thread: Panel with circuit breakers and pull out fuse?

Hi! I'm new to the forum, and new to the game. Recently got a job with Mueller Services (won't comment on how I feel about them here!) doing home surveys for insurance companies, and came across this circuit breaker panel. I was supposed to figure out the amperage, but was baffled by the pull-out, which I associate with fuse boxes. Was it converted? What would be the amperage? The survey is long gone, but I'm still curious about it.


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This is a common configuration for, I believe, the 40's through the 50's, maybe 60's. Transition time from fuses to breakers. If you are lucky, there is still a label on the panel somewhere with the maximum amp rating. If you pull the fuse block, you will be able to see the rating of the fuses used. Rating of ONE fuse is the present capacity of the panel, but it MAY be capable of carrying more amps if it's under-fused (has smaller fuses installed than the rating). May also be labeling that calls out the max fuse size.
Watch out for creative overfusing. Pieces of copper pipe/tubing have been found in place of a fuse. Pieces of bare copper wire have been used, hidden behind the fuse. Some people will go to great lengths to endanger themselves.

Gary pretty much covered it. The only thing I might add is to also check the size of the wire feeding the panel.

It's a 200A pullout in a ITE loadcenter... (Notice the Bryant/Westinghouse/Cutler-Hammer BR frame breakers).
If the pullout is removed, it should say "ITE Circuit Breaker Company Walker Div.".

Thank you all very much! Interesting (for the likes of a newbie like me, anyway). We're taught not to pull anything, and there's no indication of amperage on the panel, and I'm much too new at this to recognize the panel design. There's so much to learn! That's what makes it interesting.

I don't understand how underfusing would increase the amp carrying capacity. Isn't that why people overfuse?

Thanks again for helping me learn about this!

Kristi

When someone mentioned underfusing it was in reference to a panel that was rated higher than the fuse size installed. For example your panel is rated for up to 200 amps, but it contained 150 amp fuses.

Silly me, must have had a major Sr. moment. I saw the picture and thought, hmm mid 50-s to mid 60s QO non CTL panel how'd they get that sylvania/zinsco breaker to fit in there (? ?)! Glad someone younger and not misfiring noggin' has identified the panel for you, since I must be short circuiting today .

Ahhhh, I understand the underfusing thing now, no longer con-fused! Thanks!

One doesn't have to be a senior to have a "senior moment."

Originally Posted by Gary DeWitt

If you pull the fuse block, you will be able to see the rating of the fuses used.

In some VERY old panels I have seen the current rating on the fuse block as well as the fuse itself. This could help determine the max rating for the panel, especially if it is underfused at the time of inspection.

Originally Posted by Kristi Silber

What would be the amperage?

Regardless of: a) the amperage rating of the panel; or b) regardless of the amperage rating of the fuse block; the amperage rating of the service would be the smaller of a), b) or the service entrance conductor rating.

The rating of the service is always the rating of the lowest rated item, think of it as being links in a chain and a chain is only as strong as its weakest link - the amperage rating is only as high as its lowest rating.

In this panel as long as your wire is 200 amp wire you can not over-fuse the main since a fuse larger than 200 amps will not fit in the fuse holder. You could install the wrong type fuse though...These fuses should be one-time type fuses but in this panel time delay fuses would most likely fit.

[EDIT: THIS WAS POSTED BEFORE I SAW THE PREVIOUS POST - THANKS FOR THE INFO! THIS IS ALL GREAT TO KNOW ABOUT.]

I think for the purpose of our surveys insurance companies are just concerned about fire hazards. We look for overfusing, panels rated below 100 Amps, any fuse boxes, missing breakers, Stab-lok, another brand name I can't remember now... We aren't not allowed to touch anything but the door. Which means, I guess, any panel with pull-outs could be overfused (or underfused) and I'd never know it - is that right? We aren't trained to rate service entrance conductors. I'm such a curious person, though, I like to learn all about this stuff. I really should read up about it.
It's wild seeing the assemblages of panels in old homes, antique things still in use.

They also want us to record panel age and year of last renovation, but give us no clue what to look for. I figure I'm lucky if I'm within 15 years! If it's dirty, it's old, right?

Originally Posted by Kristi Silber

If it's dirty, it's old, right?

Dirt does not necessarily indicate age. I've inspected some homes that were about three or four years old where panels were filthy only because the owners/tenants were slobs and never cleaned the house, properly or improperly. Regardless of how dirty or how old the service panel appears there should be SOMETHING that will tell you the age.

Yeah, I was kidding about the dirt thing. Thus the "winky face." Maybe it just takes time and experience to be able to recognize the SOMETHING that reveals the age of a panel.

Originally Posted by Kristi Silber

Maybe it just takes time and experience to be able to recognize the SOMETHING that reveals the age of a panel.

Typically ... that "SOMETHING" is the age of the house.

If the house is REAL REAL REAL OLD, it may not have had electrical wiring when it was built. Electrical wiring and panels would be newer, but how much 'newer' would be the question.

If the house is just REAL REAL OLD, it may have had knob and tube wiring and fuses in various places (some even in wooden panel enclosures). You will likely find original and newer panels in these houses.

If the house is just REAL OLD, it may have knob and tube and metal fuse panels, or maybe cloth covered NM cable with rubber insulation and fuse panels. You will likely find original and newer panels in these houses.

If the house is just OLD, it may have cloth covered NM cables with rubber insulation and fuse panels, maybe even old breaker panels, and possibly thermoplastic NM cables with thermoplastic insulation (modern NM cable, just old looking ) and fuse panels or breaker panels. You will likely find original and newer panels in these houses too.

If the house is just old, it will likely have modern type NM cables and breaker panels. You may find original and newer panels in these houses too.

If the house is not that old, it will likely have modern type NM cables and breaker panels, and likely the original panels.

In newer and new houses, you will likely have modern NM cables and breaker panels, original to the house.

I say "most likely" because some areas, such as Chicago, do not allow NM cable, in which case it would be in conduit and you would be looking at the type of wiring pulled in that conduit.

How strange that Chicago doesn't allow NM. Does that include wires in the walls, too? Nailing hazard or what?

I just started a folder of the photos I have of breaker/fuse panels so I can compare. I've run across most of the things you mentioned except cloth-covered NM. I see quite a lot of BX.

I have a general idea of which things belong to what era, but my problem is attaching a date to them. I can pretty well determine whether an old panel is original, it's the newer (or renovated) ones on old houses I have a hard time with. What about amperage? Is there a rough date when 200 Amp configurations started being installed? When were Stab-lok panels used? I've seen a few of them. Is it true that the switch from fuses to CBs happened mainly in the 50s?

I'm curious about these pictured puppies. Is the one with a black knob and funky wiring a type of fuse panel for knob-and-tube or something else? (Come to think of it, I have seen cloth-covered wires!) And the other photo - is that a single fuse for a particular circuit or appliance?

Keep in mind that the first time I saw a doorbell transformer-looking-thingy I didn't know what it was (but then again, neither did my manager). This is the state of ignorance I'm starting from!

Thanks so much everybody for your help! I had no idea that my thread would get such attention or so many replies. What a very pleasant surprise!

H.G. Watson posted a link to a really good document concerning the history of a number of residential wiring types & methods a while back http://www.nfpa.org/assets/files//PD...ial_Wiring.pdf.
Gives some good solid dates for introduction of a number of wire types which can help narrow down possible time frames. Also a number of good visuals to help identify types that may not be familiar to you.
Oh, and by the way, Thanks to Mr. Watson for posting this. Another useful piece of data that I will be using now.

Originally Posted by Kristi Silber

How strange that Chicago doesn't allow NM. Does that include wires in the walls, too? Nailing hazard or what?

Trade unions. All wiring is in conduit.

Originally Posted by Kristi Silber

Is the one with a black knob and funky wiring a type of fuse panel for knob-and-tube or something else?

It is just an old telephone terminal. They will often bypass them but use the connectors for attaching new wiring. Notice the light gauge wire. It is all low voltage and harmless. You are correct about the second pic.

Hee hee, a telephone terminal! Gotta laugh at myself sometimes. Thanks for setting me straight!

Trade unions have that much influence over code?! I hope at least there's good reason behind it, more than just making the cost and labor of installation higher.

That's a great link about the history of home electrical materials! Very useful and interesting. Thank you Alton and H.G. Watson both for posting it.

I hope one day I might be in a position to help others in this forum.

Very interesting, that report by the Watson. I was surprised however, the report stated the bonding strip in AC cable was to increase conductivity.

Originally Posted by bob smit

Very interesting, that report by the Watson. I was surprised however, the report stated the bonding strip in AC cable was to increase conductivity.

The increased conductivity referred to is for the fault path. In old BX style wiring, there is no ground conductor nor bonding strip. Consequently, when the insulating material on the conductors themselves becomes compromised, the fault current (caused by wiring "shorting" to the jacket) travels back to the source via the flexible steel jacket surrounding the conductors. The jacket being steel is capable of conducting electricity albeit not very efficiently.

As a consequence of that inefficiency, the steel jacket becomes extremely hot. (I have witnessed such "glowing" cherry red.) The overcurrent protective device, fuse or circuit breaker, interprets this as a load and often will not de-energize the circuit. With the introduction of a "bonding strip" the fault current now has a more conductive path to return to the panel. Remember, all electrical circuits must return to their source of origin.

In the Northeast, where we encounter a great deal of blown-in cellulose insulation, when a fault does occur, we often can see evidence of the fact that the insulation, which is designed to be "flame retardant" smoulders but does not ignite. Ignition and the subsequent fire that results occurs when that smouldering insulation or the BX cable jacket itself comes into contact with wood framing members.

The introduction of the "bonding strip" eliminates that circumstance.

Incidentally, as an electrical inspector, I have seen significantly more fires attributed to BX cable than the older "knob and tube" wiring which is quite prevalent in older homes in the area.

Back in the 80's, with the onset of the energy crisis, blown-in insulation was widely used to combat heat retention inefficiencies in older, often un-insulated homes. The insulation,while performing its heat insulating capability, also compromises the ability of wiring to safely conduct heat build up away from it. Conductors such as "knob and tube" and BX therefore can be subject to overheating for this reason as well.

Codes used to indicate that if "knob and tube" wiring was in contact with insulation, it was required to be removed. Currently, New York State indicates that when such wiring is encountered, regardless of insulation contact, it shall be removed.

As an aside, BX wiring has recently become more noticeable due to the requirements for Arc-Fault protection. Here, when a branch circuit is "altered" it is required to be Arc-Fault protected. (Such as the extension of a receptacle circuit for the purpose of adding additional receptacles.)
BX wiring often becomes the bane of an electrician's existence when attempting to apply Arc-Fault protection to BX wiring simply because the BX wiring is often "leaking" fault current to the steel jacket, thereby "tripping" the Arc-Fault device.

Not sure how any of the above applies to HI's. Just put it out there for informational purposes.

Sorry, the at the end of my post was meant to draw attention to the misnomer that the bonding strip is a grounding conductor. It is not an EGC (equipment grounding conductor) and is not recognized by either UL or the NEC as such.

The bonding strip upon testing the cable does not carry current (don't ask me why, seems it would carry some according to its impedance).
What the bonding strip does do, is reduce inductive reactance due to the spiral method of the armor.

The bonding strip does not share the current carrying chore of the armor.
Long ago... I would run across electricians terminating this strip and I still have to correct home owners today who insist on terminating this strip.

Originally Posted by bob smit

What the bonding strip does do, is reduce inductive reactance due to the spiral method of the armor.

That is one thing the bonding strip does, however, the most important thing that bonding strip does is shorten the current path down the spiral-wound outer metal armor.

Let's say you were to take a 10 foot piece of spiral-wound armored cable, remove the conductors inside, then stretch that spiral-wound armor out, the straightened out armor (the path that most of the current will take) is actually quite a bit longer than that 10 piece of cable. The bonding strip inside the spiral-wound armor contacts the armor and effectively makes the current flow path straight down the armor, no longer around the spiral (which is also why it reduces inductive reactance - the current is parallel with the other conductors, not spiraling around them creating fluctuating magnetic fields where those magnetic fields are not desirable.

For the most part the armor on AC is expected to handle the fault current as the wraps touch each other for the most part. The bonding strip is pretty much there for the reason Bob describes.

As to shortening the path, maybe a little. If the bonding strip (notice it is not referred to as a wire) was intended to carry fault current it would need to be a full sized conductor like MC cable has.

BX is, in my opinion, a problem at least as bad as aluminum branch circuit wiring. Infrared pictures of walls and ceilings in houses that have the stuff are pretty scary sometimes. I'm really surprised it isn't a bigger issue with insurance companies as I've seen a bunch of "glow in the dark" wiring - most often in attics where people keep dragging cardboard boxes back and forth over the stuff deteriorating what little insulation is left even more.

I would agree with J.P. if the AC armor was not in direct contact along its length. However, as B.K. noted, the armor is in direct contact spiral to spiral so that most of the current will flow in a linear fashion. This is not to say that it does not flow in a spiral fashion also. Current will flow in all ways possibly available.
Which has me scratching my head why it doesn't chose to run on the bonding strip also as I stated previously??

Since I started the thread, I'm going to poke my nose into this discussion that's over my head, but which I'm trying to sort of understand anyway.

BS said, "The bonding strip upon testing the cable does not carry current" Does this mean it can't carry current, or it doesn't under normal circumstances?

Further, "What the bonding strip does do, is reduce inductive reactance due to the spiral method of the armor.

The bonding strip does not share the current carrying chore of the armor.
Long ago... I would run across electricians terminating this strip and I still have to correct home owners today who insist on terminating this strip."

I don't get it. How does it change the spiral nature without carrying any current, even over a short distance? And why would terminating the strip make a difference if all it does is change the properties of the armor?

What is the bonding strip made of? I've looked around, all I can't find out is that it's "metal."

It seems to me this contribution by RF makes a lot of sense, as long as the bonding strip is conductive: "The jacket being steel is capable of conducting electricity albeit not very efficiently.

As a consequence of that inefficiency, the steel jacket becomes extremely hot. (I have witnessed such "glowing" cherry red.) The overcurrent protective device, fuse or circuit breaker, interprets this as a load and often will not de-energize the circuit. With the introduction of a "bonding strip" the fault current now has a more conductive path to return to the panel. "

I'd think the bonding strip could at minimum share some of the current, and make overheating less likely (right?).

Wouldn't even a slight twist or bit of corrosion cause current to follow a spiral down the armor? And contact between loops in the spiral must surely be less substantial than the loops themselves - doesn't that make a difference? (Tried to vaguely understand what inductive reactance was, but couldn't figure out where it fit into things here as a safety issue. Does it mean the current would be impaired, so the metal more likely to heat?)

What if there was a fault within the cable, so the armor is carrying current, and it was near a good ground - could it cause a spark?

(Obviously, I know very little about electricity!)

After reading here and elsewhere, I'm really surprised the insurance industry doesn't treat this stuff with more concern.

Originally Posted by bob smit

However, as B.K. noted, the armor is in direct contact spiral to spiral so that most of the current will flow in a linear fashion.

From what I've learned and been told, most of the current flow spirally with the spiral wound armor, that is the reason the bonding strip was added.

Which has me scratching my head why it doesn't chose to run on the bonding strip also as I stated previously??

Current does flow on the bonding strip ... also flows on the bonding strip ... just not entirely on the bonding strip. If the bonding strip did not have any current flow on it when needed for grounding, then there would be no reason to add the bonding strip, which, by the way, was added as it was not part of BX. The bonding strip was added at a later time.

Originally Posted by bob smit

I would agree with J.P. if the AC armor was not in direct contact along its length. However, as B.K. noted, the armor is in direct contact spiral to spiral so that most of the current will flow in a linear fashion. This is not to say that it does not flow in a spiral fashion also. Current will flow in all ways possibly available.

Thanks. I was going to get my DMM out and prove that there would be minimal resistance between the spirals. Just try applying 120 volts to that armor.

Originally Posted by bob smit

Which has me scratching my head

why it doesn't chose to run on the bonding strip also as I stated previously??

Maybe because you told them not to terminate the bonding strip, you think??

Actually, if it is in contact with the armor, sure, it should be carrying some current, too, but I have no proof of that. Anymore than you have proof that the current flows in a spiral.

Originally Posted by John Kogel

Maybe because you told them not to terminate the bonding strip, you think??

The bonding strip does not need to be terminated, it does its job by simply touching the spiral wrapped armor.

Actually, if it is in contact with the armor, sure, it should be carrying some current, too, but I have no proof of that. Anymore than you have proof that the current flows in a spiral.

Both are correct: the bonding strip does carry current and some current flows on the spiral wrapped armor, and both could be proven with the proper equipment. However, being as current takes ALL available paths, which is acknowledged as a true statement of fact, then the current WILL take both paths being discussed.

Doesn't the bonding strip need to be terminated if it's to carry some of the current in order to avoid overheating of the armor? Without termination, wouldn't it just pass the whole load back to the armor at some point?

Can someone please tell me in fairly simple terms what the result of spirally-flowing current would be here?

Originally Posted by Kristi Silber

Doesn't the bonding strip need to be terminated if it's to carry some of the current in order to avoid overheating of the armor? Without termination, wouldn't it just pass the whole load back to the armor at some point?

The bonding strip does not need to be terminated as it does pass its contact and current back to the armor at the end, and through the armor to the connectors.

Can someone please tell me in fairly simple terms what the result of spirally-flowing current would be here?

Think of a contactor draw-in coil for an air conditioner compressor, or any contractor for any motor: pass a current round-and-round through the coil and you get a magnetic field, pass a current round-and-round around the conductors inside the armor and you get a magnetic field. Depending on that magnetic field you could choke off the current flow through the conductors within the armor.

Thank you for the explanation! I thought it must slow current somewhere....Looking around a bit on the net, it seems like the spiraling is like a choke coil, and would reduce conductance along the armor itself. Is that not the case? I'm looking for reasons why the bonding strip is necessary from a safety sense, to avoid overheating, since it doesn't need termination.

I found a blurb in another forum (Armor Clad Cable (old BX) still allowed as ground - The Inspector's Journal Forums) that seems pertinent:

"Article 320 III. Construction Specifications
320.100 Construction.

Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.

The armor of Type AC cable is recognized as an equipment grounding conductor by 250.118. The required internal bonding strip can be simply cut off at the termination of the armored cable, or it can be bent back on the armor. It is not necessary to connect it to an equipment grounding terminal. It reduces the inductive reactance of the spiral armor and increases the armor's effectiveness as an equipment ground.Many installers use this strip to help prevent the insulating (anti-short) bushing required by 320.40 (the “red head”) from falling out during rough wiring."

Originally Posted by Kristi Silber

I thought it must slow current somewhere....Looking around a bit on the net, it seems like the spiraling is like a choke coil, and would reduce conductance along the armor itself.

Usually when I mention choke coil here either no one understands what I am saying or says that would not have that effect. In fact, I had typed 'like a choke coil' but deleted that to avoid those responses - nice to know that you understand a choke coil.

Yes, the choke coil effect doesn't reduce the flow of current current flow along spiral wrapped armor too much (like it doesn't reduce the flow of current through a contactor coil much), but it does create a magnetic field which reduces the current flow in the conductors within the armor. One main drawback for this is overcurrent protection where there is a ground fault and the high current is needed to trip the breaker, but the higher the current through the fault and through the spiral wrapped armor, the lower the current through the conductors within the armor, which in turn reduces the current through the spiral wrapped armor, which reduces the current trying to trip the breaker and the breaker does not trip.

The above all leads to overheating of the conductors and armor itself.

I'm looking for reasons why the bonding strip is necessary from a safety sense, to avoid overheating, since it doesn't need termination.

The purpose of the bonding strip is to make contact between adjacent wraps of the armor and to short-circuit the current going around the spiral and instead follow the armor/bonding strip in a straight line. By having the current (most of the current) flow in a straight line down the armor instead of following around the spiral wrapped armor, there is no coil effect (or a dramatically reduced coil effect) and the inductive reactance from the coil dissipates with the reduced coil current flow.

The reason the bonding strip does not need to be terminated is that it has done its job where it touches the last one or two wraps of the armor, the armor is now in the fitting and there is not coil effect, the current goes from the last one or two wraps of the armor directly into the fitting and into the metal box.

Originally Posted by Jerry Peck

Usually when I mention choke coil here either no one understands what I am saying or says that would not have that effect. In fact, I had typed 'like a choke coil' but deleted that to avoid those responses - nice to know that you understand a choke coil.

......The reason the bonding strip does not need to be terminated is that it has done its job where it touches the last one or two wraps of the armor, the armor is now in the fitting and there is not coil effect, the current goes from the last one or two wraps of the armor directly into the fitting and into the metal box.

Good explanation Jerry. I usually see the the bonding strip bent back on the BX connector, sometimes fastened to the box. I always wondered what the purpose of the strip was as it was too small to carry any current----and the armor carried the ground. Didn't think of the choke coil effect of the armor. Light just came on!

Yes, good explanation, Jerry! Now I understand why the change from steel armor to aluminum hasn't taken care of the problem. This has really been an interesting discussion to follow, from a practical as well as theoretical standpoint. And you have no idea how nice it is to hear, "nice to know you understand a choke coil," when a week ago I would have thought of those crazy neck-stretching metal things women in a small tribe in Asia wear. Thank you all!

Ain't learning fun? Now if I can just get my head around reactance being the imaginary part of complex impedance (Wikipedia)

Best to start with the basics

Basic Electricity - YouTube

Then the technical stuff

Rockwell Retro Encabulator - YouTube

Hee hee, those are awesome. Love the encabulator!

I stated inductive reactance back in post #22 as the issue and resulting need for the bonding strip. Makes no difference how/where its terminated as it touches every spiral along its length.
Since a funny was attempted as to why I have a termination in an enclosure removed.. to eliminate the interplay of copper/alum. i.e. dissimilar metals.

Inductive and Capacitive Reactance results in a form of current flow resistance. In electronic applications, these effects are utilized but are obviously an impedance for a grounding path.

Motors= inductive loads which shift current/voltage out of phase relative to each other.
Capacitors shift in the opposite direction and are used to shift the Power Factor back in phase (toward unity).
Notice on Motors & Ballast nameplates, they have a P.F. rating less than '0', zero being unity.
Notice also that they will be rated in volt amps (V.A.), as opposed to Watts.
Notice that resistive loads are normally rated in watts, (like your toaster), this do to the fact that they have a P.F. of virtually zero (unity, current & voltage in phase = no reactance (or run-on sentences)

"I stated inductive reactance back in post #22 as the issue and resulting need for the bonding strip."

Right you were, and it only took me another 10 posts to figure out what that meant! Now to wrap my head around the rest of your latest reply...uh...give me a while, I'll figure it out eventually...

Correction/addition to my last post, sorry
A purely resistive load has a Power Factor (P.F.) of 1, unity, (not zero).