What size Fuses do I require?

[Gavin Millar]

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.

 

[SparkyChick]

I would say fuses appropriate to protect the cable connecting the switch fuse to the socket.

 

[Pete999]

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.

Don't mean to be funny, are you an Electrician? do you have any electrical experience? sorry for the questioning but your profile reveals nothing.

 

[Gavin Millar]

Don't mean to be funny, are you an Electrician? do you have any electrical experience? sorry for the questioning but your profile reveals nothing.

I am a trainee electrician and it is a question asked today at college to which the discussion never revealed a correct answer, we thought that it would be 16A fuses due to it being a 16A socket.

 

[Squid]

I can't answer your question but I believe there is a trainee section that will be able to help with these types of question and many more that you may have without the snide comments ;o))))))

Good luck in your training, I'd just use Wriggleys chewing gum wrapping to be honest but then you won't pass any exams ;o))))))

 

[telectrix]

I can't answer your question but I believe there is a trainee section that will be able to help with these types of question and many more that you may have without the snide comments ;o))))))

Good luck in your training, I'd just use Wriggleys chewing gum wrapping to be honest but then you won't pass any exams ;o))))))

and of course, you leave the partly chewed gum in there as a flash guard, even though it's more hazardous than asbestos. i can honestly say, i've never got my shoe stuck in discarded asbestos.

 

[Fitzy]

Don't mean to be funny, are you an Electrician? do you have any electrical experience? sorry for the questioning but your profile reveals nothing.

Not being funny either Pete999, but your profile doesn’t show your qualifications either, even outdated ones.....

 

[GMES]

Yeah we are getting a fair few reports about the constant questioning of quals and empty profiles, maybe we could just start answering the questions with a relevant answer.
Cheers
GMES

 

[Pete999]

I am a trainee electrician and it is a question asked today at college to which the discussion never revealed a correct answer, we thought that it would be 16A fuses due to it being a 16A socket.

Thanks Gavin, it makes it easier to answer that's the reason for asking

 

[Pete999]

Not being funny either Pete999, but your profile doesn’t show your qualifications either, even outdated ones.....

Thats because I fell in line, and deleted them I will put them back on tomorrow even the outdated ones if you wish me to.

 

[GMES]

I am a trainee electrician and it is a question asked today at college to which the discussion never revealed a correct answer, we thought that it would be 16A fuses due to it being a 16A socket.

Pm sent Gavin

 

[Pete999]

Yeah we are getting a fair few reports about the constant questioning of quals and empty profiles, maybe we could just start answering the questions with a relevant answer.
Cheers
GMES

Perhaps some discussions among staff members would be a good idea, all on the same page so to speak.

 

[westward10]

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 protective 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.

 

[telectrix]

this question is problematic.one would assume that the 16A circuit would be protected with a OCPD suitable for the cable and load. so 16A or 20A would be appropriate.however,you'd not achieve discrimination with the 20A MCCB. catch 22 here.

 

[telectrix]

Thats because I fell in line, and deleted them I will put them back on tomorrow even the outdated ones if you wish me to.

great thoughts pete,but please translate them from latin for the younger members. .

 

[westward10]

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

 

[GMES]

Perhaps some discussions among staff members would be a good idea, all on the same page so to speak.

Staff do discuss things and I know exactly what you're referring to, which proves we do.
My only point is that we are getting reports by members that it is becoming almost a stock question.
As for incomplete profiles even if was compulsory it would not guarantee that new members would fill them in truthfully.
All we're asking is for you and others to evaluate the question from any given op and answer that question, it can almost put the op or thread on the back foot before it's begun.
That's all we are asking , nothing more nothing less.

 

[Octopus]

Yeah we are getting a fair few reports about the constant questioning of quals and empty profiles, maybe we could just start answering the questions with a relevant answer.
Cheers
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...........

 

[Squid]

great thoughts pete,but please translate them from latin for the younger members. .

Stone slabs are hard to scan Tel....... as they scratch the glass......

 

[Squid]

Are certs still valid for old farts......?

 

[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?"