spurs

[johnphillips]

If a junction box is installed in the ring circuit(power) and a FSU run from this (5A in this case), can another FSU be wired in to this junction box? or must another box be wired into the ring? This is not a spur from a spur but just two FSU supplies running into one box.

thanks John

 

[Pensdown]

Yes, you can do that if you wish but make sure the JB is accessible and to keep with convention the cable feeding the FCU's should be 2.5 T&E.

If you're using the new colours you should also label your consumer unit to say that. You can get stickers when you buy you cable etc.

 

[johnphillips]

Yes, you can do that if you wish but make sure the JB is accessible and to keep with convention the cable feeding the FCU's should be 2.5 T&E.

If you're using the new colours you should also label your consumer unit to say that. You can get stickers when you buy you cable etc.

Thanks for that Pensdown, I am still confused, the condensed IEE comments are that only one spur may be wired from a socket in a ring why is this different from a JB, also on the blurb on a 30A JB from a well known DIY retailer it says "WARNING" only one socket or spur may be wired into this junction box! it gives a small diagram illustrating one socket/spur wired from the ring ! any ideas ?

 

[didthathurt]

The well known DIY retailer is covering itself against a single cable powering multiple unfused spurs being run from the JB. If you are wiring 2 seperate spurs into the JB, you could argue that there is an infinitessimally small length of the ring main connecting the 2. What you are proposing will not exceed the max load of the 30Amp JB because the fuses in the FSU's will limit the current drawn by each of the spurs. I would see no problem in doing as you propose with the normal accessibility and Part P caveats.

 

[Paul Barker]

My only additional thought, and I am sure you have this covered, is that a socket on a ring can only supply one spur because sockets are designed to take a maximum of 3 cables.

Now if you say that a 30 amp JB is designed for four I will believe you because I know no better, if not then OP will have to use a higher rating JB to accomodate the extra.

 

[securespark]

Why not extend the ring?

You are fitting two new cables, which would be the same if you extended the ring.

 

[Steve]

Why not extend the ring?

You are fitting two new cables, which would be the same if you extended the ring.

Perhaps one cable is going up, the other down?

 

[Taylortwocities]

Ooh great, could I then get a nice big Henley block, pop it on my ring circuit and patch in 10 spurs off the one junction? I don't think so....

TTC

 

[plugwash]

good question, as always you have to think about ring balance but two JBs close together is not signifianctly different from one JB with multiple spurs and the latter is neater and less prone to failure (every connection is a potential point of failure so minimise the number)

lots of load concentrated close together on a ring and not near the center is a bad thing regardless of if that load comes from a load of spurs in one JB, a load of spurs coming off multiple sources close togehter a load of sockets close together running lots of equipment.

 

[johnphillips]

Why not extend the ring?

You are fitting two new cables, which would be the same if you extended the ring.

No, this is impractical since the two FSU's are in completly different areas.
The only way of doing it this way would be to wire the FSU's into the ring and run the spurs out from these, since the ring is in the loft and one of the FSU's is switched this is again impractical.