Extend ring main

[Stuprocter]

 

[Stuprocter]

Hi can someone help is this an acceptable way to extend a ring main..disconnect cable from lounge socket fed from above.put into surface mounted junction box and feed through wallround conservatory back to lounge socket and connect to lounge socket

 

[ericmark]

I have used LAP grid switch unit so two 13 amp sockets in a double socket box and used them to split and extend a ring final, however the first job is to test, we are permitted a 5% volt drop and the earth loop impedance for a TN system with a B32 MCB has to be lower than 1.37Ω, in the main it is volt drop which is limiting factor, we are permitted 106 meters of 2.5 mm² cable maximum to stay within the volt drop limits. So with a 657 prospective short circuit current at the incomer (0.35Ω impedance) then looking for better than 244 amp PSCC at mid socket (0.94Ω line - neutral impedance).

You can use a low ohm meter, or a loop impedance meter, or enquiry (i.e. some one has measured it before and entered readings on a minor works, installation, or EICR so you know the reading).

For the DIY guy the FCU is likely best option, as it is unlikely you will exceed the limits, again the LAP grid system this shows a FCU and socket used to make a previous unfused spur into a fused spur and add more sockets.

 

[Simon35]

Hi can someone help is this an acceptable way to extend a ring main..disconnect cable from lounge socket fed from above.put into surface mounted junction box and feed through wallround conservatory back to lounge socket and connect to lounge socket

Its ok, but I would join the cables with connector strip in the back of the lounge socket box, rather than a new box. If there's room of course.

How are you getting past the door, are you aware of permitted zones for cables?

 

[Stuprocter]

Thanks both of you.still not sure the best way to go.dont think length of cable will be a problem as it's only a small terrace 7m long by 6m wide and is on a separate ring to upstairs..am aware of safe zones but not sure untill it's complete whether there is room for trunking at the bottom if not take it over the door and drop down after door.also was thinking of using wago connecters in socket box.

 

[JohnW2]

..am aware of safe zones but not sure untill it's complete whether there is room for trunking at the bottom if not take it over the door and drop down after door.

If the cable is to be 'buried' (i.e. not visible on the surface) it is usually difficult to get a cable around a door (up, across and down) within 'safe zones'.

Kind Regards, John

 

[Stuprocter]

Yes trunking at the bottom would be easier.if not cold run up where light switch is across at safe zone at top and down where socket is

 

[JohnW2]

Yes trunking at the bottom would be easier.if not cold run up where light switch is across at safe zone at top and down where socket is

Strictly speaking, an accessory only creates a 'safe zone' for cables which are 'connected to' it - i.e. a light switch does not create a 'safe zone' for the cable of a sockets circuit.

I suppose that makes some sense - since someone could theoretically, in the future, remove or move the light switch, leaving you socket circuit's cable no longer in a 'safe zone'.

Kind Regards, John

 

[Stuprocter]

Thanks all for your help will wait for completion of conservatory then decide which way to go