What size Fuses do I require?

[GMES]

Not sure I agree with that.

New members do not open up their profiles so we are all guessing ................

This is not a DIY superstore site...........

If you don't feel comfortable answering then don't answer, we would never expect anyone to answer something they're not comfortable with.
I also know it's not a diy superstore and the op isn't a bank holiday shopper , he's a trainee on a proper college course.

 

[telectrix]

What wouldn't achieve discrimination with the 20A device.

16 A fuses may not achieve discrimination with a 20A MCCB, IMO.

 

[westward10]

16 A fuses may not achieve discrimination with a 20A MCCB, IMO.

Got you Tel just reread #1.

 

[Octopus]

If you don't feel comfortable answering then don't answer, we would never expect anyone to answer something they're not comfortable with.
I also know it's not a diy superstore and the op isn't a bank holiday shopper , he's a trainee on a proper college course.

Then he should be enrolled in the training section .................. like many others .................

 

[GMES]

Then he should be enrolled in the training section .................. like many others .................

See #11

 

[westward10]

Then he should be enrolled in the training section .................. like many others .................

When his thread was approved it was not clear that he was a trainee, a later post indicated he was so I believe things are in motion to put this in place.

 

[Flanders]

To the OP I believe if you look in GN1 it gives a suggested maximum overcurrent protective device of 20A. I believe this is due to the fact a radial of more than one 16A socket can be employed, after this 32A, 63A etc... are suggested to be single point radials with a 8protective device used to match their rating. If however the circuit supplies one 16A socket I see no reason to use anything above a 16A protective device.

If you protected two 16 amp sockets with a 20amp mcb whats is to stop one of the sockets being overloaded ? as 16 amp plugs do not come with fuses in them , or have i miss understood?

 

[westward10]

If you protected two 16 amp sockets with a 20amp mcb whats is to stop one of the sockets being overloaded ? as 16 amp plugs do not come with fuses in them , or have i miss understood?

Although not quoted in BS7671 I believe this is what GN1 states, not real it for a good while though.

 

[Flanders]

Although not quoted in BS7671 I believe this is what GN1 states, not real it for a good while though.

I would have to disagree with GN1 then , as designing the circuit this way you could plug a 20 amp load into the 16 amp socket , now to be fare the 16amp socket could probably take the extra 4 amps , but they are not designed for this and over time would overheat.

 

[Octopus]

Discrimation aside a 16A socket should be protected by a 16A OCPD

 

[westward10]

I agree for a single point socket 16A. But it is suggested 20A can be used although I admit these things in GN1 are not necessarily Regulations.

 

[7029 dave]

Hi,

I have a three phase switch fuse supplying a 16A socket. In the specification provided it states the following:

Design Current - 16A
Main Protective Device 20A

The circuit is fed from a C20 MCCB at the distribution board.

What size of fuses should I be putting in the switch fuse?

16A or 20A?

Thank you.

Op no mention of cable size, ccc is a main factor.

 

[Wilko]

...20A is due to the fact a radial of more than one 16A socket can be employed ... however if the circuit supplies one 16A socket I see no reason to use anything above a 16A protective device.

Agree.
Apologies for my dumb question but why are there additional fuses being spec'd here? Local isolation yes, but it's already got a C20 at the board so shouldn't the question be "do I keep the C20 or go to C16?"