Theoretically... cables must be fused down when a lower size cable is connected to a larger sized ca

[assegayer]

Now I completely understand why cables must be fused down when a lower size cable is connected to a larger sized cable. To ensure the cable does not burn out from current that it cannot take.
Yes i know this

Now current doesnt go anywhere it isnt in demand for so if a spur off of say a 6mm for a aircondition unit someone was to take a 1.5mm off that for a light.In my thinking it would work fine as none of the current being pulled by the airconditon unit is going to go down the cable for the light.

Again i know you have to fuse down but im just speaking theoretically

 

[Octopus]

Have you tried getting 2 x 6mm in the average fcu?

 

[assegayer]

Have you tried getting 2 x 6mm in the average fcu?

So what are you implying?
All this talk is just theoretical as 'would it work fine'

 

[D00DY_T00DY]

Have you tried getting 2 x 6mm in the average fcu?

I have theoretically

 

[Andy-1960]

The reason for the fuse is to protect the circuit under fault conditions. If your 6mm cable is protected by a say a 30A fuse that is fine for that cable under fault (short circuit or overload) conditions, but if the fault (overload) was on the 1.5mm cable joined to the 6mm cable, the 1.5mm cable could melt and catch fire before the fuse blows.

 

[assegayer]

The reason for the fuse is to protect the circuit under fault conditions. If your 6mm cable is protected by a say a 30A fuse that is fine for that cable under fault (short circuit or overload) conditions, but if the fault (overload) was on the 1.5mm cable joined to the 6mm cable, the 1.5mm cable could melt and catch fire before the fuse blows.

thats perfectly acceptable but for example its just one 100w light the 1.5mm will never get overloaded

 

[Octopus]

I have theoretically

After a hair cut I suspect....

 

[D00DY_T00DY]

After a hair cut I suspect....

What? Haha

 

[Andy-1960]

thats perfectly acceptable but for example its just one 100w light the 1.5mm will never get overloaded

But it will if there is a fault!!!!

 

[assegayer]

But it will if there is a fault!!!!

but what type of fault could cause it too melt?

 

[Andy-1960]

but what type of fault could cause it too melt?

Ok, you win, we shall just do away with fuses.. life will be much simpler...

 

[Richard Burns]

If you are omitting the overcurrent protection to a section of cable , which is what you are describing here, then that section of cable should be protected from the chance of damage. The load also has to be one that is incapable of overload, of which a light (especially if incandescent) is incapable.
However in your case you would also need to ensure that the 1.5mm² cable can handle the fault current in the case of short circuit.

Partial damage to a cable that generates a high resistance connection to line could happen to create a fault that can cause an overload but not cause the breaker to trip.
In general the easiest way to ensure that a cable will not overload is to provide overload protection.

 

[assegayer]

Ok, you win, we shall just do away with fuses.. life will be much simpler...

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.

 

[Andy-1960]

If you are omitting the overcurrent protection to a section of cable , which is what you are describing here, then that section of cable should be protected from the chance of damage. The load also has to be one that is incapable of overload, of which a light (especially if incandescent) is incapable.
However in your case you would also need to ensure that the 1.5mm² cable can handle the fault current in the case of short circuit.

Partial damage to a cable that generates a high resistance connection to line could happen to create a fault that can cause an overload but not cause the breaker to trip.
In general the easiest way to ensure that a cable will not overload is to provide overload protection.

What he said!

 

[assegayer]

If you are omitting the overcurrent protection to a section of cable , which is what you are describing here, then that section of cable should be protected from the chance of damage. The load also has to be one that is incapable of overload, of which a light (especially if incandescent) is incapable.
However in your case you would also need to ensure that the 1.5mm² cable can handle the fault current in the case of short circuit.

Partial damage to a cable that generates a high resistance connection to line could happen to create a fault that can cause an overload but not cause the breaker to trip.
In general the easiest way to ensure that a cable will not overload is to provide overload protection.

Thank you, that makes sense

If you are omitting the overcurrent protection to a section of cable , which is what you are describing here, then that section of cable should be protected from the chance of damage. The load also has to be one that is incapable of overload, of which a light (especially if incandescent) is incapable.
However in your case you would also need to ensure that the 1.5mm² cable can handle the fault current in the case of short circuit.

Partial damage to a cable that generates a high resistance connection to line could happen to create a fault that can cause an overload but not cause the breaker to trip.
In general the easiest way to ensure that a cable will not overload is to provide overload protection.

Thank you, but in the case of a short circuit wouldnt it only effect the 6mm cable in the situation described and not the 1.5mm stabbed of the 6mm. also dont mcbs detect short circuits whether big or small and trip anyway.