Did you know .....

[sb_89]

Hi , I'm new and thought I would introduce myself with a few generally unusual reg facts, please feel free to add your own - or even tell me mine arn't that uncommon knowledge . here goes .....

Did you know ?

A bare mineral insulated cable, under full load conditions, is permitted to have a sheath temperature of upto 105*C ,enough to cause burns if touched (Table 4G2A BS7671)

The sheath of pvc T&E becomes soft and sticky to the touch , and eventually brittle, if it comes into contact with expanded polystyrene over an extended time ! - i didnt know that until about 5 minutes ago .

Unless in a TN or TT system ( in which case all socket back boxes must be earth in accordance with Reg 411.5.1) - where an accessory has an earthing strap and either one or two eyelets, and the metalic accessory box has two fixed ( non - adjustable ) lugs, there is no requirement to fit an earthing tail (flyer) between the accessory and the accessory box ( ALTHOUGH - still desirable) --- wording taken from NICEIC guide

I'm not responsible for the wording of any of these, all where copied word for word out of various guide to the reg books by the niceic, i just found them and thought they were interesting.

 

[Andy™]

you can omit the earth to the backbox providing 1 of the lugs is fixed, not 2.

last 2 are pretty much common knowledge. first is also well known but not as much. there are also limited cases when you can have it running it 105

 

[SLIPSHOD & SLAPDASH]

Yes i did But welcome anyhow. There has been many a 'discussion' about earthing backboxes. With the polystyrene the pvc eventually hardens and cracks due to the polymers being leeched out

 

[sb_89]

copied word for word from the guide to the regs .... it says if both or 1 .

 

[Barx]

I thought it was one fixed lug too. I personally ALWAYS earth backboxes. All other lads I work with whenever we start a new job it's the first question to leave their mouths trying to get out of it. Then as soon as someone says don't bother I tell them I want it doing anyway. Don't know why they still ask.

 

[SLIPSHOD & SLAPDASH]

copied word for word from the guide to the regs .... it says if both or 1 .

Thats correct. Although rare some really cheap accessories only earthed one of the 'eyelets'( fixing holes) if the fixed lug in the box was not the same as the one earthed on the accessory it would not be correct. Nothing wrong in having more than one fixed lug ( except adjustment issues).

 

[sb_89]

1 or 2 it says here , and add to the list , there must be somethings that you have come across tht are obscure ? unless every1 knows everything already ? lol

 

[Apache]

Hello and welcome.

A bit of advice, go to the BGB and OSG for info. The NICEIC don't write the regs, but having read various things on here you'd believe they thought they did.

 

[sb_89]

no but they do write guides to the regs. I dont solely rely on them , but they are useful and generally correct

 

[SLIPSHOD & SLAPDASH]

Hello and welcome.A bit of advice, go to the BGB and OSG for info. The NICEIC don't write the regs, but having read various things on here you'd believe they thought they did.

Thats correct, but sb 89 did state he was quoting from their 'guide' which always teaches good workmanship as well as the regs.

 

[sb_89]

here's 1 for you , i seen a thread on here where somebody had posted a picture of their very neat DB , but they had tie wrapped the cables inside the board ( browns together, blues together, earths together) does that not derated the cables current carrying capacity,its seems pretty common practice , ive seen a few done like this a few times

 

[SLIPSHOD & SLAPDASH]

If its that close to being de-rated before the cable ties then there's more issues than that to worry about. I cant remember exactly but...... short distances dont matter ? (some rule or guide)

 

[sb_89]

i suppose it doesnt really matter a great deal, maybe a pain when testing , but you can just snip them off lol

 

[Evans Electric]

SB 89 I think most sparks know those things TBH but welcome to the Forum .

Some of the touch tempertures for hand held in the BRB are a bit high if I remember correctly but it'll all be changed next year and we can shell out yet another

 

[Andy™]

here's 1 for you , i seen a thread on here where somebody had posted a picture of their very neat DB , but they had tie wrapped the cables inside the board ( browns together, blues together, earths together) does that not derated the cables current carrying capacity,its seems pretty common practice , ive seen a few done like this a few times

quite a few people cable tie them during install to keep them together, then remove the cable ties once job is finished. the cable kidna hold their position a little better

 

[Evans Electric]

here's 1 for you , i seen a thread on here where somebody had posted a picture of their very neat DB , but they had tie wrapped the cables inside the board ( browns together, blues together, earths together) does that not derated the cables current carrying capacity,its seems pretty common practice , ive seen a few done like this a few times

Don't worry about stuff like that SB ....you'll go mad !!

 

[sb_89]

well evans , tell me something i dont know? it was only ment to be for fun , i thought people could add to the list maybe. BS 7671 is an extensive book, you cant retain everything and there will be somethings covered in it that you will probably never come across for example, i have never came across a VOELCB and i wouldnt of known how to test , id of referred to the book ....

 

[SLIPSHOD & SLAPDASH]

Ask me anything about section 740, i wont know & doupt if i ever will need to.

 

[sprocketflup]

Did you know the conductor names are actually Steve, Mark and for some reason unbeknown to anyone, Billy-joebob?

Still dont know which is which :dunno

---------- Post Auto-Merged at 21:48 ---------- Previous post was made at 21:47 ----------

Ask me anything about section 740, i wont know & doupt if i ever will need to.

Ok, what comes after section 740?

 

[Andy™]

end of the world