Knob and tube OCP

[drcampbell]

For that we usually use 11kV or greater.

There's very little 11kV used indoors in wood-framed residences here.

 

[jap]

Prior to about 1940, wire was usually often insulated with natural rubber and wrapped with varnished cotton.
Because it wasn't very durable, it was strung in open air and protected/supported with ceramics.

When you find it today, the natural rubber has usually become so brittle that it promptly turns to dust when you touch it, if the varmints and insects haven't chewed through it first. The ceramics keep it safe (almost) even if the insulation disappears entirely and the bare copper is exposed. Problems occur at the terminations (the cut end of the cotton sleeve usually unravels) or when something changes, such as the aforementioned thermal insulation being retrofitted into the attic by a Bigfoot crew, or adding devices for which the amperage capacity doesn't exist.

To further confound things, American practice was to make 10, 15, 20, and 30-amp fuses all in the same interchangeable package. If the fuse kept blowing because you added devices, it was a trivial matter to put a higher-capacity fuse in its place.
(Canadians were a little smarter than this, making the diameter of the button on the base of their screw-in fuses proportional to the amperage rating, and putting non-metallic rejection washers into the fuseholders to make it impossible to put in a higher-capacity fuse)

Knob-and-tube wiring - Wikipedia

en.wikipedia.org

It's still a trivial American practice.

Even today you can swap a 2p 15 amp breaker to a 2p 100 amp if want too.

Most are just smarter than that.

JAP>

 

[jap]

If you ever been around corner grounded systems you might. Sometimes used as a slug for the grounded conductor in fused disconnects, which is sort of ok as you aren't supposed to use a fuse in a grounded conductor. Problem is when a non qualified get ahold of it and thinks it might be ok to replace that fuse that keeps blowing with the slug.

That's interesting.

JAP>

 

[don_resqcapt19]

That's interesting.

JAP>

 

[ptonsparky]

View attachment 2565010

Fuses are cheaper by far. I probably have more of a selection than my nearest supply houses.

Anybody need some?

 

[rambojoe]

You realize you're talking about tearing out walls and ceilings, right? Wiring doesn't usually get fully replaced until there's a remodel. My own house most of it didn't get removed (or decommissioned) until we did a remodel, and there's still three switch legs that didn't get replaced because those walls weren't redone.

I see a lot more K&T than I see fuses. But I still see fuses now and then, often some little 'subpanel' with four fuses in a closet that's now fed by a breaker.

And yes some owners don't care, or know. And some can't afford to do anything about it.

You are are talking about tearing out walls, not me...
If my point was missed, I truly regret not being clear.
BTW, although I never do resi anymore- I could (and have) done a whole rewire w/o tearing out one wall... a few holes but not walls.

 

[xformer]

Some of us are old enough to have seen steel wire run down the center of an attic...

Some of us are old enough to remember steel pennys.

 

[jap]

Fuses are cheaper by far. I probably have more of a selection than my nearest supply houses.

Anybody need some?

Some of us are old enough to remember steel pennys.

And some of us are old enough we saved on fuses and pennies by troubleshooting shorted wiring by unplugging everything and screwing an incandescent light bulb into the fuse holder which would illuminate until the fault was cleared.

JAP>

 

[ptonsparky]

And some of us are old enough we saved on fuses and pennies by troubleshooting shorted wiring by unplugging everything and screwing an incandescent light bulb into the fuse holder which would illuminate until the fault was cleared.

JAP>

Found my very 1st with that method.

 

[jaggedben]

You are are talking about tearing out walls, not me...
If my point was missed, I truly regret not being clear.
BTW, although I never do resi anymore- I could (and have) done a whole rewire w/o tearing out one wall... a few holes but not walls.

Okay, fair enough, a few holes. First, surely you charged a decent rate for such skills. But also it's semantics in my opinion. Whole wall or a few holes, do you do the refinishing yourself? How about if there's wallpaper? Fancy wainscotting in 150-year-old houses that were owned by fairly rich early adopters of electricity, but then left to less fiscally responsible heirs? My point was simply that these are the sorts of things that keep this work from being done. I know that in my area a quality full house K&T replacement might cost as much as a new car. (Of course the customer also wants the car, which is an EV. But then, they have more money than anyone who owned the house since it was built.)

 

[letgomywago]

Its hard to believe that there is still more than a small amount of knob and tube about... and fuses.
I hate to say i classify homeowners/landlords who just dont care about updating things like old wiring but being an electrician, i do. Its getting to a point where those old conductors and loom sleeves at outlets are getting scary.
I understand if it works it works but that rubber crap is getting long in the tooth...

So something to think about on the homeowners side of this (landlords have no excuse unless its a historical building). You buy a house right after ww2 you're 20 you live there just redoing the kitchen and bath but have lived there for so long you don't need more than the 2 or 3 outlets upstairs the kids are long moved out anyway. You have a fixed income and know the nuances of the house. When the kitchen was done you had them swap the panel to a whopping 100 amps something you never thought you'd need. Now your kids inherit it and want to move in or give it to the grand kid who just started a family. Do you now tell this new 20 year old grand kid who is just happy to have a nice clean place to live that they are crap for not being able to immediately update that last circuit to the 3 rooms or can you give them 10 years to save for it?

 

[letgomywago]

Okay, fair enough, a few holes. First, surely you charged a decent rate for such skills. But also it's semantics in my opinion. Whole wall or a few holes, do you do the refinishing yourself? How about if there's wallpaper? Fancy wainscotting in 150-year-old houses that were owned by fairly rich early adopters of electricity, but then left to less fiscally responsible heirs? My point was simply that these are the sorts of things that keep this work from being done. I know that in my area a quality full house K&T replacement might cost as much as a new car. (Of course the customer also wants the car, which is an EV. But then, they have more money than anyone who owned the house since it was built.)

Cheapest one I did was 12 man hours and was only 700 ft^2 rancher that had an existing 200 amp panel ready for the afcis. More often you're looking at 80 to 160 man hours for a normal house with basement main floor and upstairs that used to be attic.

 

[Besoeker3]

A thousand words….

Thank you, sit!

 

[Besoeker3]

There's very little 11kV used indoors in wood-framed residences here.

We don't either - I was referring to the porcelain insulators on HV. We don't use knob and tube or at least I don't recall it.

 

[gadfly56]

I really hope nobody thought that was serious; I've seen enough coins, cartridge fuses wrapped with aluminum foil, etc. Still haven't seen copper plumbing pipe in place of fuses. Yet.

In NYC, that's what's used for the neutral and ground connections in fire alarm panel fused cut outs.

 

[LarryFine]

Still haven't seen copper plumbing pipe in place of fuses. Yet.

I have seen such in the grounded conductor of corner-grounded fused switches.

 

[zbang]

In NYC, that's what's used for the neutral and ground connections in fire alarm panel fused cut outs.

That and in corner-grounded systems is using the pipe in place of a jumper (for convenience, I assume), not using it where a fuse should be; I'm talking about using pipe in place of a proper fuse (which is a d^mn-fool idea).

 

[augie47]

Fuses are cheaper by far. I probably have more of a selection than my nearest supply houses.

Anybody need some?

Lock them in a vault

For years I had a sizable box full of 15-30 plug fuses and "fusetrons" along with cartridge fuses I had salvaged and finally, having not had a need for one in ages, I tossed it..... then last weekend I needed a FRN30.. ran to Lowe's 2 pack FRNR-30 $ 18.00

 

[rambojoe]

Ace hardwares in my town have a grip of discontinued items, from breakers to starters...

 

[LarryFine]

I still have a tackle box of fuses.