SELV

[altec]

Two issues i was wondering about:
What does SELV stand for?
Is it possible to get plastic surface box with a 20mm conduit knockout like the steel ones? If you were to drill a 20mm hole in a standard box, how exactly would you go about it?

Thanks,
Declan.

 

[sonofwan]

not a lecky so cannot claim it's for sure but a quick google came up with:
Safety Extra Low Voltage

 

[AdamW]

Would these do the trick?

If I HAD to drill a hole into a standard box I would put masking tape over where I wanted to drill, then drill from the outside in with a 20mm flat wood bit.

There is a real risk of shattering bits off the box though. Cheaper and better to go for a conduit box. I believe I have even seen them in DIY-sheds.

 

[ban-all-sheds]

If I HAD to drill a hole into a standard box I would put masking tape over where I wanted to drill, then drill from the outside in with a 20mm flat wood bit.

A hole saw would be a MUCH better tool to use, and would present no risk of shattering like a flat wood bit would.

 

[plugwash]

iirc selv stands for seperated extra low voltage

 

[ban-all-sheds]

Altec - you might be interested to know that "low voltage" does NOT mean 12V.

ELV, Extra Low Voltage means up to 50V AC or 120V DC, but in practice 99.999999999999% of ELV products on the market are 12V lighting systems.

People often erroneously refer to these as "low voltage", but in the context of the Wiring Regulations, and the various Acts of Parliament relating to electrical things, Low Voltage means up to 1000V AC or 1500V DC between conductors and up to 600V AC or 900V DC between any conductor and earth.

So everybody in the UK has an extensive Low Voltage system supplying their entire house. They may also have some ELV lighting.

 

[altec]

thanks very much for the very helpful replys.
Declan