Smallest possible cable for a 4w LED load.

[Energetic]

Hi All, This is a bit niche but i've been asked to refurb an antique lamp to dimmable led and i'm after a very tiny cable that will take 230v but only run a single 4W LED. There are 5 of these on the lamp that come back to a connector then off in 0.75 flex.

Also after an inline dimmer for the whole thing....



Thanks

 

[Pat H]

Are you sure the LED is dimmable?
4W at 230V is less than 0.02 A so its not the current that will be the issue. But you need to ensure its insulation is safe for 230V and its robust enough for the intend use.

 

[Barry White]

I would not use below 0.5mm flex. Below this the mechanical strength is weak.

 

[Wilko]

Hi - just been thinking about thin cables, ADS and the 6A MCB. There will be a limit to how thin the conductor can be for ADS to work without damage to the wiring if a fault occurred. From the Wylex data sheet to hand (for the let thru I2t) and the adiabatic eqn (k=143 from Table 54.2) then a 0.5mm copper conductor looks ok for PSSC of up to 2.5KA which would cover most situations. Otherwise we might need the dreaded 3A fan fuse

 

[Lucien Nunes]

From the OP's reference to an inline dimmer I infer this is a portable appliance - please can you confirm? In this case, you might be in hot water with 0.5mm² internally and 0.75 to the plug, as the ACOP suggests a 13A fuse would be acceptable for the flex, but the 0.5 would not be protected. Perhaps it would be permissible to attach a label stating that a 3A fuse is required? It wouldn't wash on a new appliance because it would not be permissible in EU.

You might hide a fuseholder inside where the junction is, but many inline dimmers have a fuse, so if this is permanently attached to the fitting this might well be sufficient to protect the smaller internal cables.

 

[Energetic]

Thanks for the replies and apologies for the confusion caused by my poor description. Please see photo, it is a thing of rare and terrifying ugliness...

It currently has a round pin 2A plug so was planning to put it on a 2A fuse on a normal plug but with 5 x 4W LED it could go lower still. I will supply a box of fuses with it for avoidance of confustion should it blow. It's for a family friend with no electrical knowledge so i suspect she'd call me rather than try to change it anyway.

 

[westward10]

How will you provide cord restraint at the fitting.

 

[Energetic]

That's not really what the thread is about mate.

 

[westward10]

Well I was interested because I can't see how you will provide it.

 

[Energetic]

Well I was interested because I can't see how you will provide it.

Currently the flex comes through the base and is cable tied. it's a one off commission for a specific situation, it's solid metal and seriously heavy and will be out of the way of any traffic including the flex .

 

[westward10]

Cable tie is not appropriate one off job or not, the fitting is not designed for a trailing cord.

 

[Energetic]

Cable tie is not appropriate one off job or not, the fitting is not designed for a trailing cord.

Thanks for your input.

 

[HandySparks]

Can't quite work it out. Is this thing going to be fixed to the wall or stood on a table?

 

[Energetic]

OK so like I said it's a bit niche the back story is that it's a free standing victorian candle lamp that been previously converted to electric.... so I'm told... it's been in the family years and they want to update it.

If anyone wants to tell me that it's not genuine victorian etc I'm not interested.

It will be going in a windowsill behind some furniture and away from fiddling. the likelihood is that it's probably only going to be used a handful of times per year. it will be plugged into a socket via a fused plug and will be 30mA rcd protected.

 

[westward10]

Not something I would be doing.

 

[Energetic]

Not something I would be doing.

Not asking you to...

 

[westward10]

I know I am harping on here but I cannot see a method for doing that in a compliant manner whether it is used once, twice a year or whether an rcd is involved.

 

[Energetic]

I'm not trying to comply with anything, I'm not manufacturing these, I'm not selling them either.

 

[The Ghost]

Small point but its 1a total load. And LED have high draw current. And why dont you just use the existing cable as a matter of interest?

 

[HandySparks]

Small point but its 1a total load. And LED have high draw current. And why dont you just use the existing cable as a matter of interest?

Eh? Neglecting power factor, it's less than 0.02A per lamp. I guess the new wire (if required) will be partly on the outside of the fitting and accessible, so having the required insulation properties and robustness will be the defining factors.