Fuse in a spur

[EFLImpudence]

I'm (almost) sure I've seen FCUs (not BS 1363 types) used in other European countries.

OK.

433 etc is not really appropriate, as it is about protecting circuits of the installation, rather than protecting appliances that might be connected to that installation.

Is that not the point, though? 433 is protection against overload.

Some of the small products I was involved with simply didn't have the space inside for a fuse that could break the prospective fault current,

Not sure if that is the sort of thing we are talking about.

so it seems quite reasonable that the manufacturers should limit that prospective fault current by specifying a more robust protective device be fitted in the circuit?

I disagree - that it is reasonable.

 

[EFLImpudence]

Why would you want to use a 13a fuse if a 3a is sufficient?

Not exactly sure what you mean.

Why would you want to use a 3A if the 6A or 16A MCB is sufficient?

 

[stillp]

Is that not the point, though? 433 is protection against overload.

Yes, against overload in the installation. Accessories and appliances are outside the Scope of 7671.

Not sure if that is the sort of thing we are talking about.

Probably not; I was thinking about industrial products.

I disagree - that it is reasonable.

Well, it's reasonable for CUs to be deigned to require a 100A fuse upstream, and BS1363 accessories to require a 32A OCPD upstream, so why not a 3A fuse upstream of something else?

 

[eveares]

Why would you want to use a 3A if the 6A or 16A MCB is sufficient?

Because the lowest rated fuse what is suitable for the connected load will blow quicker than a higher rated fuse what is also suitable for the load. Of course the cable feeding the appliance being suitable for the fuse in the first place.

If I wire an alarm panel using 2.5mm² T&E, does that mean I should use a 13 amp fuse feeding it because 2.5mm² T&E can safely carry greater than 13A?

Or that I wire a 100W motor in 1.5mm² flex I should use a 13 amp fuse, again for the same reason as proposed above?

Anyhow, while the BS1362 fuse in the FCU is primarily designed to protect the cable feeding the appliance, having a second means of over current protection provided by the BS1362 fuse in the FCU (Or the only means for devices lacking any OCP at all) can not be a bad thing under most domestic circumstances.

 

[winston1]

If I wire an alarm panel using 2.5mm² T&E, does that mean I should use a 13 amp fuse feeding it because 2.5mm² T&E can safely carry greater than 13A?

Or that I wire a 100W motor in 1.5mm² flex I should use a 13 amp fuse, again for the same reason as proposed above?

Yes you could in both cases. The alarm panel will have internal oppropiate protection and I hope the motor will as well. And if you were wiring these in many other countries they have a 16 amp protective device.

 

[ban-all-sheds]

Ban
I'm talking gas regs in the UK. What does selling programmers in France or Germany have to do with gas regs in the UK?

A lot less than it has to do with TTC citing a programmer as an example of an ELECTRICAL appliance which supposedly "needs" a 3A fuse and yet is sold in countries where such provision cannot be made.

Maybe we should ask any gas lads here if there are gas regs covering this. I grew up being told all gas appIiances and systems were limited to 3A. Can it be completely fabricated?

Given what many of the gas lads believe about main and supplementary bonding, quite possibly.

 

[ban-all-sheds]

This from another forum:

"Yes, there is. It's part of the gas regs. Gas boilers must be protected by a 3A fuse. Has been the case for many years.

Jolly good.

I'm not saying you are wrong, but I would want to see you quote the actual regulation before I believe that you are right.

 

[EFLImpudence]

Because the lowest rated fuse what is suitable for the connected load will blow quicker than a higher rated fuse what is also suitable for the load. Of course the cable feeding the appliance being suitable for the fuse in the first place.

That is not the criterion. The fuse is to prevent cable damage.

If I wire an alarm panel using 2.5mm² T&E, does that mean I should use a 13 amp fuse feeding it because 2.5mm² T&E can safely carry greater than 13A?

I think you have got a bit mixed up there.

Or that I wire a 100W motor in 1.5mm² flex I should use a 13 amp fuse, again for the same reason as proposed above?

You keep saying "should"; if you are using a plug then 13A will be the maximum available.

A motor will not be the same - but if you were wiring a 100W lamp, would you use a 500mA fuse?

Anyhow, while the BS1362 fuse in the FCU is primarily designed to protect the cable feeding the appliance, having a second means of over current protection provided by the BS1362 fuse in the FCU (...)can not be a bad thing under most domestic circumstances.

Is it a good thing, though? That is, is it of any benefit?

(Or the only means for devices lacking any OCP at all)

If it needs further protection, then the manufacturer should have, and most likely will have, fitted it.

What sort of items have you in mind?

 

[ban-all-sheds]

Why does everyone keep banging on about boilers in other countries? We're talking about regulations in this country.

Dunno.

Why not ask the person who was the first one to start banging on about gas boilers in this topic?

 

[ban-all-sheds]

An overload fries the programmer, it doesn't blow an internal fuse.

I'm surprised that this is considered acceptable in the rest of the world.

 

[ban-all-sheds]

Some of the small products I was involved with simply didn't have the space inside for a fuse that could break the prospective fault current,

Then they were shoddily designed.

so it seems quite reasonable that the manufacturers should limit that prospective fault current by specifying a more robust protective device be fitted in the circuit?

No.

Never.

 

[ban-all-sheds]

Isn't it apparent as Britain is the only place that uses them and "Ib ≤ In ≤ Iz" and 433.

So the rest of the world allows cables to be installed which are known to be inadequate to carry the load expected of them?

Blimey.

 

[ban-all-sheds]

Yes, against overload in the installation. Accessories and appliances are outside the Scope of 7671.

Probably not; I was thinking about industrial products.

Well, it's reasonable for CUs to be deigned to require a 100A fuse upstream, and BS1363 accessories to require a 32A OCPD upstream, so why not a 3A fuse upstream of something else?

Spot the connection?

 

[securespark]

stillp

I don't know of FCUs in Euroland, but there are some 1363 FCUs in Singapore and Malaysia, amongst others.

 

[ban-all-sheds]

Accessories and appliances are outside the Scope of 7671.

113.1