Discuss Theoretically... cables must be fused down when a lower size cable is connected to a larger sized ca in the Electrical Forum area at ElectriciansForums.net

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I agree it is not likely but assegayer did ask what could cause an overload and this is probably the only way it could happen. Certainly there is no requirement for it to be accounted for in the regulations.
This is exactly why i asked the question, because i always hear people saying in fault conditions but they cant even tell me what fault conditions other then short circuits. thanks
 
The situation i was thinking was if someone wanted a light outside and the house inside is all concrete ceilings and walls etc which do not want to get wrecked. But you had a perfectly good ac unit outside with its dedicated circuit it would be much easier and less hassle to just stab of that. And as mentioned earlier a fcu would jsut not be practical.
 
The situation i was thinking was if someone wanted a light outside and the house inside is all concrete ceilings and walls etc which do not want to get wrecked. But you had a perfectly good ac unit outside with its dedicated circuit it would be much easier and less hassle to just stab of that. And as mentioned earlier a fcu would just not be practical.
Weatherproof FCU exist and you could connect the 6mm² together in the back of the box and have a short say 4mm² spur off to the FCU terminals.
 
@darkwood
@Richardburns

Thank you both for your in depth explanations. So in conclusion if all Zs values are met it could probably be safe and sound

In theory yes, meeting regulations no, the set-up itself would mean you could only really achieve this only with a short 1.5 extention to the lamp, the higher resistance of the 1.5 in comparison to the 6mm against the lower permitted zs allowance often stops you doing this, although the cowboys out their who do do this kind of poor work are not bothered about zs if they even know what it meant.

EDIT... in conclusion that would bring us back to it's likely not to meet zs so the smaller cable would suffer damage in a fault and could negatively effect the properties and di-electric strength of the insulation and sometimes the sheath.
 
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Haven't fully read the thread so don't know if this has been mentioned, but the regs allow a change in cable size without fusing down at the point of size reduction if the circuit ocpd is rated to protect the smallest cable size in the circuit. This could be the easiest way to protect the 1.5mm cable in this situation.
 
@Andy78 ... Yes I brought that up in a recent post although it's an unlikely option when the 6mm is probably running a heavy load to start with but acknowledge we are talking theorectical here.

Ah sorry, that's me skim reading. I thought the situation was a repurposing of a former 6mm sitcom supply.
 
So, if we were to hypothetically say that I had already done this dodgy spur, what sort of hypothetical justifications should I use to hypothetically convince myself I haven't left a firetrap behind?
 
hahaha, mate i understand why we use fuses. But no one can ever give mean answer other then the one there college tutor gave them oh its because in fault conditions, what fecking fault conditions can cause a 1.5mm cable to melt supplying one light.

It's is very unlikely that a fault of this type will occur, but the problem would be defining when this could be allowed to be done and when it would not. If one light is ok then why not two? Or if one 100W light is ok then why not 10x 10W lights?
 
The situation i was thinking was if someone wanted a light outside and the house inside is all concrete ceilings and walls etc which do not want to get wrecked. But you had a perfectly good ac unit outside with its dedicated circuit it would be much easier and less hassle to just stab of that. And as mentioned earlier a fcu would jsut not be practical.

For a start you would no longer have a dedicated circuit for the AC if you extend it to do other things!
 
hahaha, mate i understand why we use fuses. But no one can ever give mean answer other then the one there college tutor gave them oh its because in fault conditions, what fecking fault conditions can cause a 1.5mm cable to melt supplying one light.

Someone pieces the cable with a screw/nail, small rodent crews though cable. A Led bulb or CFC has been fault that causes a short. The fitting it self gets damaged or bulb its head knocked off and shorted, some child/thick adult sticks something into light fitting. to name but a few.
 
The situation i was thinking was if someone wanted a light outside and the house inside is all concrete ceilings and walls etc which do not want to get wrecked. But you had a perfectly good ac unit outside with its dedicated circuit it would be much easier and less hassle to just stab of that. And as mentioned earlier a fcu would jsut not be practical.
What would happen when the A/C unit is switched off for the winter? no supply to the FCU you have connected to it
 
Someone pieces the cable with a screw/nail, small rodent crews though cable. A Led bulb or CFC has been fault that causes a short. The fitting it self gets damaged or bulb its head knocked off and shorted, some child/thick adult sticks something into light fitting. to name but a few.
Blimey Stephen can I get some of the stuff you are on?
 

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