Spur from cooker circuit

[breezer]

thats as may be but the idea in life is to prevent accidents not cause thm by spuring off a 6mm cable with a 1.5 mm cable

 

[user56565]

no breezer, i have to disagree with you here. i don't see how this would cause an accident. as long as the cable is fused along its length, it is being protected.

it won't carry any more current than it is designed for - the current has to go through the fuse. therefore there is no risk of overheating or fire.

DNOs do this all the time - the main supply cable for a house isn't fused at the point where it leaves the feed cable. it's fused at the end - in the cutout. the cable is still overload protected, and this isn't dangerous!!

 

[breezer]

a cable in a house is more likely to be damaged than an overhead cable.

what also if the end user (not this poster) over loads the 1mm cable. Now tell me its safe

 

[Steve]

56565, put it this way. Where this 1.5mm cable enters the FCU, what if, by some rare chance, a fault occurs before the fuse, that causes 32A to flow along the 1.5mm, which is only designed for about 15-20A? The MCB will not trip. The cable will melt and may create a fire, before the MCB trips. Even less chance if its protected by a rewireable. Therefore, it should be done in 6mm cable, like the rest of the circuit. Then if such a fault occurs, the MCB will trip before the house catches fire, and more current can, theoretically, flow, so it will trip quicker.

(my hashed-up version of what someone else has said on here before, probably not that accurate)

Also, what if someone comes along, to replace the cooker control unit, and sees this 1.5mm cable going off somewhere, what are they to think? They aren't going to realise it goes to the light under the steps are they? It would be much better to wire the FCU into the kitchen ring, possibly label this, and take 1.5mm cable from there.

DNOs do this all the time - the main supply cable for a house isn't fused at the point where it leaves the feed cable. it's fused at the end - in the cutout. the cable is still overload protected, and this isn't dangerous!!

You cant compare this with things the REC do, they protect 10mm2 cables supplying 3 houses with 100A wire fuses at the end of them. How is this not theoretically dangerous?? This cable is overloaded over about 60A, yet it has 300A protection. My take on things anyway, im sure people will disagree

 

[breezer]

user56565 isn't dangerous ? click here

(just been off finding it)
it may take a second or two to downlaod, and for clatity, its a substaion transformer

 

[plugwash]

56565, put it this way. Where this 1.5mm cable enters the FCU, what if, by some rare chance, a fault occurs before the fuse, that causes 32A to flow along the 1.5mm, which is only designed for about 15-20A? The MCB will not trip. The cable will melt and may create a fire, before the MCB trips. Even less chance if its protected by a rewireable. Therefore, it should be done in 6mm cable, like the rest of the circuit. Then if such a fault occurs, the MCB will trip before the house catches fire, and more current can, theoretically, flow, so it will trip quicker.

if a cable fault is drawing 30A then you have far far worse things to worry about than the ability of the cable to safely supply 30A. (30A at mains voltage is a lot of power that power has to go somewhere)

 

[user56565]

haha very funny breezer!

a cable in a house is more likely to be damaged than an overhead cable.

yes but an underground cable doesn't have short circuit protection. if one cut through it, this would be extremely dangerous. an internal cable has short circuit protection, and the installer can ensure that disconnection times can be met without any damage to the cable.

what also if the end user (not this poster) over loads the 1mm cable.

how could they overload it?? the fuse would have blown long before there's any damage to the cable!!

what if, by some rare chance, a fault occurs before the fuse..

what kind of fault are you referring to in particular? i can't think of one that would result in such a situation.

what if someone comes along..

i'd hope the person who changes the unit is reasonably competent. one may not expect the cable there, but by disconnecting they could establish it was the lights. no-one should alter a circuit without knowing what's doing what anyway.

You cant compare this with things the REC do..

but you can! im not sure what particular case you are referring to, so i can't comment. but RECs aren't going to be wiring up the country's electric supplies in such a way that it puts the public at risk!


now guys don't get me wrong, its ideal to fuse before, because this is what's most often done in practice. but where it's not reasonably practical to do so, it's not any less safer to fuse after..

 

[plugwash]

user56565 isn't dangerous ? click here

(just been off finding it)
it may take a second or two to downlaod, and for clatity, its a substaion transformer

http://205.243.100.155/frames/longarc.htm has a higher resoloution version along with some others.

 

[breezer]

haha very funny breezer!

it wasnt meant to be funny, just to show what can happen if you follow your idea

 

[user56565]

you can only say it's dangerous if you can prove/argue why.

and you haven't exactly been able to make any valid arguments against my points!

 

[breezer]

you can only say it's dangerous if you can prove/argue why.

and you haven't exactly been able to make any valid arguments against my points!

stupidity springs to mind (it wasnt me who laughed at a sub station blowing up)

haha very funny breezer!

its like holding a pointed gun to your head, it will go off but when

 

[kevplumb]

you can only say it's dangerous if you can prove/argue why.

and you haven't exactly been able to make any valid arguments against my points!

then why ask

i used to build them things and have watched a few go bong at brush in loughborough

if your not going to listen to advice why ask

 

[user56565]

kevplumb - i don't understand your post. you used to build what things and what went wrong?? and who's asking for what advice and not listening to it??

user56565 isn't dangerous ? click here

(just been off finding it)
it may take a second or two to downlaod, and for clatity, its a substaion transformer

"...click here" suggests that i personally contributed to that particular clip. so your post comes across as a joke.

im here in this forum to contribute and learn, and don't expect to give or receive mild abuse:

stupidity springs to mind (it wasnt me who laughed at a sub station blowing up)

if you can give a sound explanation as to why its unsafe, id accept! however ranting on along the lines of "it's unsafe, its gona blow up, burn the house down" without any sound logic does border on stupidity:

its like holding a pointed gun to your head, it will go off but when

several hundred years ago, people ranted on illogically about the earth being flat, in the centre of the universe etc.. and that view was adopted by establishments. had they been logical, and used reasoning and accepted scientist's (ie galileo) views, society would've likely progressed a lot further.


ill gladly discuss this with someone logical and intelligent (like mapji, or ban-all-sheds). so if one of you is reading this, please comment..

 

[Spark123]

Where a protective device is used for fault current only as in this case, the operating time of the MCB or fuse under both short-circuit and earth fault conditions must not exceed the time given by adiabatic equation t=(k²S²)/I². As in this case no-one but the installer has the information required, I believe it is only safe and practicable to say the cable must be large enough to carry the full load current as defined in table 4D5A of the iee regs.

 

[kevplumb]

i used to build distribution transformers 2.5 mva
then go and witness the short test all three phases connected

that vid (albeit on a smaller scale) could well be happening in your house
if you go down the road you are proposing

so go slag a plumber why not