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Picture of the week!™
- Thread starter RF Lighting
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I nearly got a belt from a rodent chewed cable recently - I went to put my bare arm into a ceiling hole with an existing live cable hanging from it, VERY last second I noticed the sheath just inside the ceiling was chewed down to 3 pieces of copper side by side.
Could have easily been a fire there
Could have easily been a fire there
I did wonder if anyone would bring that up. It's not a problem according to the Pyrotenax handbook. And that factory tests on the light duty cable is 2KV.
The book says
It should be noted that surges in excess of the electrical strength of the cable merely produce a flashover between the grains of magnesia insulant, usually with no permanent ill effects to the cable. However, when flashover occurs within a cable at mains pressure a power arc may follow the temporarily ionisd path that is set up between conductor and/or sheath. This arc is usually quenched rapidly by the opening of switch contacts of current overload devices, but when the arc persist, permanent cable damage may occur.
We were messing about with a terminated length, it had no problems with a number of 2.5KV insulation tests.
I remember back on about 1994 working to repair cables damaged by rats. I was lying in the loft trying to reach the damaged cable and a few rats ran over my back. I then heard a noise and creaking from the ladder and was terrified, wondering what was coming and what was going to happen, the restaurant owner had come up the ladder to ask if I was nearly finished as he wanted to open for the evening. I replaced the damaged cable and declined his offer of a free meal. (I drove past a few weeks ago and the restaurant is still open, so either the rats all got electrocuted or the chef found a way to cook them).
Quite amazing that some rodent managed that without being electrocuted in the process. I remember about 10 years ago going to an old place (friend of a friend thing) and the first thing which was noticeable upon opening the hatch into one separate section of the attic (an old addition, full of straw etc.) was the horrible stench. Traced it to one edge of the attic where I found the decaying body of a very large rat, what was left of its jaws still wrapped around the T&E it had decided would make a good meal. Yuck!
K
kai
In the olden days, wiring in houses was run through Earthed metal conduit - maybe that should be introduced again for safety reasons.
I'm up for that!
I tried to do some research into electrical accident statistics. On the NHS database, one incident I looked at was recorded three times by different people. One incident was a toddler with a button cell stuck up his nose, another toddler had swallowed a button cell, an elderly gent had fallen while trying to replace the battery in his clock. All recorded as electrical accidents.
Yes, an excellent idea. I remember as a child, our house (must have been late 19th or early 20th century) having at least some such conduits. As well as protection against rodents, I should imagine replacement of conductors would have been much easier - just pull through.
So why were they discontinued? Money, I suppose.
That, and
a) it was often not proper conduit as we know it now, and the continuity of it as a cpc was often compromised
b) it makes alterations a PITA, so much so that numpty DIYers would end up with no cpc at all.
a) it was often not proper conduit as we know it now, and the continuity of it as a cpc was often compromised
b) it makes alterations a PITA, so much so that numpty DIYers would end up with no cpc at all.
The residential stuff used in the 1920's/1930's was a thinwall conduit, held together with set-screw connectors. There's still something similar sold here in the U.S. by the name of EMT (Electrical Metallic Tubing).
On regular steel conduit, the City of Chicago electrical requires everything to be run in conduit even in domestic work. There are rumors that it became a city requirement after a particularly bad fire many decades ago, while others claim it was really more a union thing for work protection,
On regular steel conduit, the City of Chicago electrical requires everything to be run in conduit even in domestic work. There are rumors that it became a city requirement after a particularly bad fire many decades ago, while others claim it was really more a union thing for work protection,
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Before my forced retirement, I wanted to rewire my house in galv conduit.
No, I think you may have misunderstood me. Sorry if I didn't explain clearly.
I was suggesting that metal conduits to contain and protect normal three core cables, including an earth conductor, might be a good idea. I agree that relying on the conduit, which is likely to rust, as the only earth conductor would be a bad idea. In fact, I've just had a rusty old conduit (that ran under the floor from one end of the house to the other) that contained the main cable from the ancient cut-out to the meter and which was acting as the only earth conductor, replaced (at the expense of the DNO, thankfully) for obvious reasons*.
Bearing that in mind, I should imagine that replacement of the cable would be much easier than chasing into a wall, for example.
*Edit: full details in this thread:
http://www.diynot.com/diy/threads/illegal-cabling-and-strange-box.430930/
Last edited:
That metal tube they used to install in the 1930s which was held together with screws was useless.
To do any rewiring you would have to pull up the floorboards, because the cables couldn't be drawn through with the elbows in place.
Hence why you never see that old tube with newer PVC singles drawn in.
The only bits of that tube system to get re-used were the switch drops buried in the wall, and then twin and earth was used, and the tube wouldn't get earthed.
To do any rewiring you would have to pull up the floorboards, because the cables couldn't be drawn through with the elbows in place.
Hence why you never see that old tube with newer PVC singles drawn in.
The only bits of that tube system to get re-used were the switch drops buried in the wall, and then twin and earth was used, and the tube wouldn't get earthed.
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