10a switch protection with 16a breaker

[tomodo]

Hi everyone , ive been reading up on it and is it true that you can have a bank of 10a switches supplied by a 16a circuit breaker as long as each switch is only designed to be taking 10a or less? Surely if a fault was to occur then the switch would burn out before the breaker tripped? Any regulations to back this up? cheers.

 

[amlu]

switch is not taking any amps on its own, there will be a load connected to it, and if there will be too much of a load (like constant 13A) it may heat up and fail . there is a breaking capacity as well, it may break 10A, but when there is more then it may start arcing and burn out.
use a 20A switch.

 

[tomodo]

that does make more sense. but the klik system that hager sells works on the same principle they reckon you can have a 16a mcb supplying a row of 6a lighting points with no addictional protection as long as you design the loads so that each point does not exceed 6a

 

[davesparks]

Do you mean the Klik plug in ceiling roses?
They are a bit different to switches, the load is limited by the fact it is only connected to one light fitting, and that light fitting will have an internal fuse if it's on a 16A circuit

 

[tomodo]

Yes thats correct. I understand it cant be overloaded but if a fault was to occur after the klik ceiling rose but before the light (i.e the cable running from the klik to the light) wont the 6a rated cable be damaged before the 16a mbc trips? Surely it would make more sense to have a 6a fuse in each ceiling rose? thanks for the replys

 

[davesparks]

Yes thats correct. I understand it cant be overloaded but if a fault was to occur after the klik ceiling rose but before the light (i.e the cable running from the klik to the light) wont the 6a rated cable be damaged before the 16a mbc trips? Surely it would make more sense to have a 6a fuse in each ceiling rose? thanks for the replys

Is the flex on one of those only rated at 6A then?

It is not very relevant anyway as you are considering fault protection rather than overload protection,

 

[tomodo]

Well they say to use 0.5mm to 1mm flex. Sorry i don't understand what you mean surely you need to provide fault protection aswell?

 

[Knobhead]

switch is not taking any amps on its own, there will be a load connected to it, and if there will be too much of a load (like constant 13A) it may heat up and fail . there is a breaking capacity as well, it may break 10A, but when there is more then it may start arcing and burn out.
use a 20A switch.

that does make more sense. but the klik system that hager sells works on the same principle they reckon you can have a 16a mcb supplying a row of 6a lighting points with no addictional protection as long as you design the loads so that each point does not exceed 6a

I’m glad it makes sense to you. Other than "use a 20A switch" it’s complete and utter nonsense to me.

 

[tomodo]

Lol why hes only saying if you put 13a on a 10a switch it will cause it to fail

 

[JensenDrake2]

[h=3]Transformer Protection Switches, PKZM0-T[/h]DIN rail mounted, mechanically reset protection devices.
Transformer short circuit and overload protection
The short circuit release is set to 20 x I[SUB]u[/SUB], so even transformers that have high inrush currents have protection
Rotary handle for ease of trip indication after a fault has occurred
Rated operational voltage 690V
Trip-fault indication
Phase failure sensitive
93 x 45 x 76mm (H x W x D)

[h=3]Note[/h]PKZMO accessories can be used allowing additional functions.

 

[Knobhead]

So at 10.5A the switch spontaneously combusts? Believe it or not they are designed to carry and break a moderate over load.

 

[tomodo]

I would advise not to do that still though, it doesnt make for good practice

 

[Farmelectrics]

Use 20amp rated switches job done

 

[D Skelton]

If the 10A switch is only switching a couple of amps, it could be on a 1000A breaker!

It's not the circuit protection that governs the rating of a switch, it's the load being switched.

 

[tomodo]

Cheers d skel is there any sort of regulation to back that up that you know of?

 

[D Skelton]

I can't remember the exact reg, but section 433 is where you need to be looking.

 

[Lucien Nunes]

Suppose the load is a fixed one of 3A. If you are going to get any more current flowing through the switch than 3A it's going to be because of a fault and in that case it won't be 13A but probably more like 3000A. Then, it's down to the adiabatic properties i.e. how much damage the huge fault current does before the MCB opens. This is a different consideration to the thermal current rating i.e. how much it heats up over time with a certain steady load.

Manufacturers aren't stupid - they make switches and accessories that can withstand the impulse to clear the protective device let-through, so that you can use reasonable sizes of circuit.

 

[Deleted member 26818]

It is quite possible for the 10A switch to be damaged due to overcurrent conditions, either due to a fault, or because it is underrated.
Usually the contacts will weld themselves together, and the switch will require dismantling to release the contacts before it will operate again.

 

[davesparks]

Well they say to use 0.5mm to 1mm flex. Sorry i don't understand what you mean surely you need to provide fault protection aswell?

Yes you need fault protection, it's overload protection that you do not need when the load is fixed