3a fcu from a spur?

[Staylor79]

Is there anyone that can clarify what i can and cant do here?

I am planning to install 2 low voltage wall lights either side of the bed. Both of these have a double socket below. I am happy to spur of of these into a 3a fcu and then up to the lights. My problem is that one of the sockets is on the ring and the other is a spur from the ring. I gather i am able to do the fused spur from the ring main socket however am unclear whether the fcu from the spur is allowed or would even pose a problem. It will be a 3a fuse.

I am however able to incorporate the spur socket back into the ring but would rather not get the floor up. If this is the best option i would do.

Any clarification of how to do this would be gratefully recieved.

 

[securespark]

You could take the FCU off the socket on the ring and feed both lights from it. You don't need one FCU for each light.

Do the fittings have a built-in switch?

 

[Staylor79]

That was one other option i was thinking of... Thanks. Unfortunately the lights dont have switches built in so i would have to take the thinner lighting cable up the other side of the bed to a switch and then on to the light.

Would a 3a fuse in the fcu be enough to power these 2 lights. They use a 25w bulb each. I guess it would be.

Thanks for your speedy reply.

 

[securespark]

Oh yes.

 

[Staylor79]

Thanks for your help.

 

[Taylortwocities]

2 x 25watts = less than ¼amp. SO 3 amp will be big enough!

Actually, the fuse is there to protect the wiring, so at 3amp, the wiring you use will need to be at least 0.75²mm.

 

[JohnW2]

Actually, the fuse is there to protect the wiring, so at 3amp, the wiring you use will need to be at least 0.75²mm.

Did you mean to type 0.5 mm²?

Of course, as you imply, a 1A fuse (and appreciably smaller cable) would actually suffice for the lights.

Kind Regards, John

 

[EFLImpudence]

Table 52.3

 

[JohnW2]

Table 52.3

Interesting - I'd never noticed that it included flexible cables. Thanks.

However, the wiring we're talking about is for 'a specific appliance' (the wall lights), in which case the Table says that the minimum CSA is "as specified in the product standard". What standard/Standard would that be, I wonder, and what minimum CSA does it specify for the appliance in question?

Kind Regards, John

 

[EFLImpudence]

A luminaire is not an appliance.

Would it not be a lighting circuit? - especially if both lights fed by one cable.

 

[JohnW2]

A luminaire is not an appliance.

It appears that you are right, per BS 7671 definition - but it seems a very odd definition. What is so special about luminaires and 'independent motors' (whatever that means) that singles them out as the only exceptions to the definition that any (other) current-using equipment is an appliance?

Would it not be a lighting circuit? - especially if both lights fed by one cable.

That would certainly be logical and, in any event, would presumably be covered by the 'any other application' (0.75 mm² min) category for flex in Table 52.3.

The Table is, in fact, not well written. As above, the section on flexible cables seems to indicate that 0.75 mm² is OK for a lighting circuit ('any other application'), but the first part of the table ("Non-sheathed and sheathed cables", without any mention of whether they are flexible or not) would seemingly require 1 mm².

Kind Regards, John

 

[EFLImpudence]

Would it not be a lighting circuit? - especially if both lights fed by one cable.

That would certainly be logical and, in any event, would presumably be covered by the 'any other application' (0.75 mm² min) category for flex in Table 52.3. The Table is, in fact, not well written.

I shall have to agree with your logical interpretation of yet another badly written example.

As above, the section on flexible cables seems to indicate that 0.75 mm² is OK for a lighting circuit ('any other application'),

Yes.

but the first part of the table ("Non-sheathed and sheathed cables", without any mention of whether they are flexible or not)

Presumably 'not flexible' (by the definitions) because 'flexible' is covered in the lower part of the table.

would seemingly require 1 mm².

Is that only because there is none smaller?

 

[EFLImpudence]

Thinking about more anomalies in the table -

T+E (non-flexible) has 1mm² minimum for lighting and 1.5mm² for power.

However, as written, flexible has minimum 0.75mm² for lighting AND the same for power - albeit impractical.

 

[JohnW2]

I shall have to agree with your logical interpretation of yet another badly written example.

Quite.

but the first part of the table ("Non-sheathed and sheathed cables", without any mention of whether they are flexible or not)

Presumably 'not flexible' (by the definitions) because 'flexible' is covered in the lower part of the table.

Yes, that was 'presumably' their intent - but we should not have to presume or assume. The wording of that first part of the table, taken in isolation, implies that it applies to any cable (flexible or otherwise). As we're agreed, badly written!

would seemingly require 1 mm².

Is that only because there is none smaller?

In the case of T&E, that's probably the reasoning/intent. However, as above, there's nothing which explicitly states that it only applies to T&E. Indeed, there's a 'chicken and egg' issue here. Did manufacturers decide to make their smallest T&E 1 mm² (rather than, say, 0.75 mm²) because of the regs, or did the regs specify 1 mm² because no smaller T&E was available?

Kind Regards, John

 

[JohnW2]

Thinking about more anomalies in the table - T+E (non-flexible) has 1mm² minimum for lighting and 1.5mm² for power. However, as written, flexible has minimum 0.75mm² for lighting AND the same for power - albeit impractical.

Indeed so - but I'm not so sure about 'impractical'. I can think of plenty of situations in which it might be appropriate to have a low current ('dedicated') 'power' circuit protectedby a 5A/6A OPD, if such were allowed, can't you?

Kind Regards, John