Permanent installation of plug-top power supplies

[InMyHO]

With so many low-voltage devices now powered from plug-top power supplies (the ones where the power supply and three-pin mains plug are one unit) there is sometimes a need to use these in permanent installations. For example lights - like the ones used to decorate the plinths of kitchen units or stairways - are often supplied with this type of electrical transformer. What is the correct way of making a permanent installation of this type of power supply? You need a mains socket but often, if it is for lighting, it would need to be wired into the lighting circuit and not the ringmain. So you do not want anyone mistakenly using this as a general socket. If it is hidden away that reduces the chances but is there more to it than that? Low voltage halogen lights would have transformers hidden in walls, ceiling voids or wherever to power the 12v lights. Is it right to add a socket into which the plug-top power supply is permanently connected in a hidden location (like in a wall or ceiling void) and connected to the lighting circuit? Do you need to add a warning label or somehow permanently couple the plug and socket? What are the rules or best practices?

I hope all that makes sesne!

 

[ban-all-sheds]

With so many low-voltage devices now powered from plug-top power supplies...

• //www.diynot.com/wiki/electrics:voltage-bands
  
• With only a top, i.e. no pins, you couldn't plug it in. You can, because it has pins, because it's not just the top.
  
• Sockets on lighting circuits will only cause the circuit breaker to pop if used for too large a load. An important issue though is that until fairly recently it was unusual for lighting circuits to be RCD protected.
  
• A concealed socket contains screwed joints, and so must be accessible, like junction boxes or anything else with screwed joints.
  
• If you put anything in a wall void remember to follow the rules for the cables running to and from it: //www.diynot.com/wiki/electrics:walls
  
  
  

 

[chivers67]

One method is to use smaller plugs and sockets that are suitable for lighting

http://www.tlc-direct.co.uk/Main_Index/Wiring_Accessories_Menu_Index/Plug_Tops_2/index.html

 

[plugwash]

I don't think there are any specific regs regarding putting such sockets on lighting circuits but personally I'd want to see the socket both placed in a location where it was unlikely to be used for "general use" and labeled with it's intended use.

 

[ban-all-sheds]

One method is to use smaller plugs and sockets that are suitable for lighting

http://www.tlc-direct.co.uk/Main_Index/Wiring_Accessories_Menu_Index/Plug_Tops_2/index.html

If the power supply has a trailing plug that can be removed and an FCU used.

If it's a wall-wart then those sockets are useless.

 

[InMyHO]

Thanks Ban-all-Sheds for your helpful post

1. So this is an extra-low voltage and not low voltage problem - got that my mistake.

2. If one does permanently mate one of these plug-top powersupplies with a socket then that socket must be accessible for maintenance because it employs screw fittings - understood.