DJ360

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The earth is the most important conductor, it could save your or someones life, I've been a stickler for earth protection, and I have over 50 years post elec apprentice experience.

 

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21 minutes ago, philmayfield said:

Disgusting! :(

 

How dare you!!!. She is a masterpiece of Art Deco!!!

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You need to earth it well, Col.  She could give you a shock every time you look at her.  :biggrin:

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Hey Phil.  Just wondering do you have some relaties in Atlanta?   There is a Mayfield milk co. there.  They provide a lot of dairy products, milk, cream, ice cream to the stores in North Ga.

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If it's  not wired Col., how about converting it to 12volt. It could then be battery operated or mains transformer plug. Just a thought.

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8 minutes ago, loppylugs said:

Hey Phil.  Just wondering do you have some relaties in Atlanta?   There is a Mayfield milk co. there.  They provide a lot of dairy products, milk, cream, ice cream to the stores in North Ga.

No Loppy. My only relatives living abroad are in Perth WA.

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Col, 

What you describe is a class 1 appliance and needs to be earthed so must have a 3 core flex or cable. The fuse is to protect the cable not the load and  0.75mm cable will carry around 6 amps **  so 3 amps will be fine.

** Cable calcs take many factors into consideration but for a simple table lamp we can safely assume 0.75mm will be fine.

 

Note I don't advise you to go ahead but neither do I discourage you. You're a sensible chap so I leave it up to you.

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Very diplomatic Brew! 

I've just ordered a couple of metres of 'antique gold' 3 core 'retro' flex and a matching torpedo switch.  The flex is modern plastic insulated stuff, with a fabric covering.

I'll post a pic of the restored lamp when done.

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The wind and rain has dropped for now so today we got the cycles out and rode a 10miler on the muddy tow paths, just to keep us in action. So easy to get out of the habit in the winter. Had to do a bit of scrambling under and around a fallen tree, dragging the bikes along the bank  as we crawled. Felt just like a kid again, covered in muck.

 

Yesterday we joined our local gym, £10 a month, concessions for oldies, a bit more than a gym really, its title is 'Leasure Village', going for an induction at 1pm. See how we go? I much prefer being on mi bike in the open air, on the towpaths or country lanes, listening to the birds and looking at the Cows in the fields. Love it.

 

I have had a request from my gang for home made 'Hot Dogs and Burgers with Onions today', So colesterol city here we come. 12 hot dogs and 4 burgers. Good job I only cook these about twice a year. Got to get my pinny on now and get cracking in the kitchen.:biggrin:

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I can't 100% agree with you on a fuse/circuit breaker is to protect the cable, maybe in house wiring, but in industrial circuits we used circuit breakers and HRC fuses to protect the WHOLE circuit, that included motors etc.

Cables we used in mining were 100 to 300 amp rated at 3.3Kv to 11Kv and 440/415 to 550v for "portable" equipment ie shuttle cars to face machinery, conveyors were rated at 1100 to 3.3Kv, and later all face equipment at 1100v. Most trailing cables were rated at 100 amps, and protection was oil filled dashpots for overload protection, later electronic overload circuits, again they were to protect the motors and cables.

On 3.3Kv circuits, each HV contactor had HRC fuses as the final protection in the isolator compartment, I don't recall fuses being in 6.6Kv/11Kv, too high a voltage for HRC type fuses.

The main switch yards, 66Kv , did have blow out fuses to protect the incoming supply from a switch yard fault, so that was 100% protection for the cables owned by the utility.

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I'm not getting into an argument between two electrically qualified people!  :rolleyes:  However my understanding for what it's worth is that the big mains fuse between the street and the consumer unit (I think mine is 100A.. but can't be bothered going to look), protects that section of wiring.

 

Thereafter, each of the main circuit breakers protects sections of the house wiring, such as 'upstairs lighting', (5A) 'downstairs sockets', (13A) etc.. with a separate higher rated feed ( 60A) for ovens.  There are now also as I've mentioned above, assorted Earth Leakage devices which I believe are mostly designed to protect people who decide to grab hold of live wires, or who are exposed to some other wiring fault.

 

From socket to appliance, there is usually also a fuse in the plug, which as Brew states is designed to protect the cable to the appliance, in the case of a short circuit.

 

One area where fuses in plugs create huge controversy, is within sections of the 'hi fi' fraternity.  Some choose to replace plug mounted fuses with either 'poncey' solid silver capped and wired fuses, which supposedly 'sound better', or they effectively by-pass the fuse, with a solid copper, or even silver, 'blank'.

Whether any of that makes any difference to sound quality is a sub set of the endless 'cable wars' which infest the hobby.  I can't hear any difference with fuses, but there does seem to be a benefit from making sure all connections are tight and all plug pins etc., are kept clean and polished.  Also, having a separate circuit or spur for the hi fi can help to minimise interference from the likes of fridges, or other devices which 'put noise on the mains'.

 

Thing is, with most quality hi fi kit, there is seemingly very little risk in by-passing mains plug fuses, because kit always has at least one 'internal' fuse, which will certainly blow before the mains lead is troubled, in the event of any internal fault developing. However, the presence of the internal fuse somewhat negates the point of by-passing an electrically 'bigger' fuse, upstream.  Of course, if the mains lead is of the IEC or 'kettle lead' type, it can conceiveably end up being used to power a kettle, or similar, with the potential for accident if its correct fuse is not  re-fitted.

 

Much of the 'hi-fi' stuff seems to be concerned with minimising or preventing 'RFI', or 'radio frequency interference', from entering the system and damaging sound quality, either by creating audible issues, or by somehow affecting performance in ways which are not directly audible.  Counter arguments seem to say that there is no chance of 'RFI' getting past the assorted transformers and capacitors which sit in the power supply circuit of the kit, so that it cannot become an issue in the audio circuits.  I wouldn't know.. but I have better things to do than getting over exercised about it.

 

I can report that fitting a separate mains 'spur', and later a dedicated 'ring', off a spare section of the consumer unit, did indeed stop clicks from the fridge, and at least psychologically caused me to be happier with the mains supply to my kit. 

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I was probably trained in a totally different environment than you DJ. Mine was the mining side of the trade, where cable size has to be ample for the load, in fact a motor would burn out well before the cable would get warm.

The only times I saw cable failure was due to insulation failure causing a hazardous blow out. Most of the time cable failures were due to mechanical failures, something hitting, trapping or roof falls on armoured cables, and trapped or pulled on trailing cables.

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Although Ohms law is valid to the whole trade the mining industry does have some very unique situations that those of us trained above ground will likely never meet.

 

Regarding hi-fi I'm a middle of the roader.  I enjoy good sound, but could not be bothered with some of the extremes that some go to.  I doubt I would hear much difference anyway.

 

I couldn't have that lamp anyway.  It would put me BP up every time I looked at it.   LOL.

 

Edited to add.   Why can't somebody invent summat that would lower your BP by just looking at it?  It would sure beat meds.  ;)

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industrial circuits we used circuit breakers and HRC fuses to protect the WHOLE circuit, that included motors etc.

 

No, think about it. Circuit Protection is rated for the cables, it does not matter what the load is. CP is calculated backwards from the potential load (In) and then decide the size of cable.  The cable ampacity  (Ib) will always be larger than In. The appropriate CP is then chosen. Should the load develop a fault the CP will not trip until the fuse rating is exceeded. You know as well as I a motor can burn out without tripping the CP until it is far too late to save it.

 The CP has not protected the load, that's already shot but it has stopped the cable overloading and burning out possibly causing a fire. CP only operates historically, after the event, it cannot predict failure.

Protect the cables and load protection is secondary.

 

Perhaps you were not aware that the fuses in the 11kV switch (one per phase) are usually 50 amp expulsion fuses inside the breaker and possibly oil insulated*. There will be similar in the 6.6 switch. Siemens or Bussman have online catalogues for such things.

 

*A bit of a generalisation

 

I should say that my experience of mining is limited to drift mines and UK standards but the principle remans the same. If the system is properly designed it will as safe as is reasonably practicable. It will contain faults, not prevent them.

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As far as I'm aware, none of the 11Kv breakers we had U/G had any fuses, except the control circuit fuses in the low voltage protection circuits. I recall opening up one of the 3.3Kv isolator fuses in a Belmos Peebles HV contactor, they were about a foot long and filled with sand.

As far as 6.6Kv CB's we used the brush SF6's, which had three charged gas interupters. (Sulpher Hexafloride gas). None had HV fuses, but all had elaborate control circuits.

Good job it was a blown fuse, those things were EXPENSIVE!!

Most of the mines I worked in were safety lamp mines, so virtually everything was FLP and controls circuits IS.

Even the gypsum mine had FLP equipment, mainly ex NCB as it would have been cheaper than brand new heavy duty industrial.

First Australian colliery I worked at was like going back to the 1930's with most of their gear, slate boards containing the isolaters, contactors and control gear on the mobile transformers, ironically IT worked!! Face machinery was modern though. Second colliery was ultra modern state of the art equipment, although moving 11Kv flexible armoured cables live gave me the willies!!

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Motor burn outs have many reasons, can't say I have seen one due to overload in mining, as there were too many protections from fluid coupling drives to O/L settings, which had to be set to the engineers instructions.

From a few years in the repair trade overhauling electrical machinery, I'd say 90% of winding failures were insulation failing, then water, which is insulation failure anyway, and bearing failure damaging the windings.

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As a poor old house wirer and airport maintenance guy I'm out of my depth here.  :biggrin:

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I wish I could read it, for some reason I find bold type impossible to read? :Shock:

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29 minutes ago, DJ360 said:

Thereafter, each of the main circuit breakers protects sections of the house wiring, such as 'upstairs lighting', (5A) 'downstairs sockets', (13A) etc.. with a separate higher rated feed ( 60A) for ovens.  There are now also as I've mentioned above, assorted Earth Leakage devices which I believe are mostly designed to protect people who decide to grab hold of live wires, or who are exposed to some other wiring fault.

 

You're talking about circuit discrimination  Col although any cooker circuit with a 60amp fuse would have me running for the hills!  It equates to almost 14 kW :( and would need at least a 10mm cable

 

I have read some of the theories and practices in HiFi and quite frankly most of it is technically BS but if it makes someone happy then who am I to argue?

I will make a comment about using a solid link in a plug top though. Unless it's on a properly designed and rated circuit it's  Bloody Stupid!

 

There is a question in the PAT test exam about fuses and the correct answer is 3 or 13 amp. You give any other size and you automatically fail.

 

IEC leads can be confusing.

1. BS1362 itself says that the preferred values for the plug fuse are 3A and 13A
2. BS1363-1 says that you size the plug top fuse off the CABLE SIZE - 0.5 mm is 3 A fuse, except some large inrush appliances where 5A is acceptable. 0.75mm and greater is 13A.

There is a whole argument about them due to the rating of the socket they plug into - it's only 10amp.

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RR, my eye's aren't the best, and I find bold type much easier to read, that's why I select it.

 

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Hey Dave, I've seen some odd things when I was in the repair trade, cast iron frames of AC motors getting hot in the test area, current flowing through eyebolts, but all easily explained when the history of those motors were pulled out the filing cabinet, which should have been done BEFORE the stator was rewound.

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Brew, they have invented something to look at to lower BP. It's called an Aquarium, with fish.

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Nearly spring!! I've noticed bud burst on a few saplings and the Daffs have flower heads forming, soon be an "ocean" of yellow here .

 

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Taking care of that fish tank would raise it again BK.  :biggrin:

 

Re. fuses in 13 amp plugs.  It seems dangerous to me to bypass that fuse in any way, because in my day the whole ring main system was backed up by a thirty amp fuse or breaker.  Not great for lamp cords! 

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We had many Sf6 switches but I think they're banned now. There are various versions of SF6 but many do have fuses, some trip relays but all use one of the worst greenhouse gases on the planet!

 

Burn outs have as you say many reasons which rather proves the point the CP is not protecting or preventing damage to  the load.

 

The sand in a fuse body turns to glass from the heat of the arc after the link ruptures and creates an insulating barrier between the contacts, simple but quite brilliant.

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