FCU on spur from ring circuit

blueandgreen

Hi, If I run a short (1m approx) spur to feed a new double socket from an existing ring circuit, do I need, according to the regulations, to add an FCU between the ring and the new spur socket?

DublinDilbert

What is the ratting on the MCB? Ring circuits aren't that common in Ireland and often only have a 20a MCB. In England they use one 32a ring for the entire house much more frequently.

If it is a ring circuit and the new socket is only 1m away, why not extend the ring?

I would do everything I can to avoid putting a fused spur on a ring circuit.

kirk.

Ya the rules changed for ET101 so you had to fit the FCU on the ring

The FCU is rated to supply an appliance or a single socket, not so much a double socket which would be rated at 20A

The MCB may be a 20A but they can be uprated by sparks when changing a board or whatever so not good practice to rely on that as protection even though 1M of 2.5 supplying a double socket is not going to cause an issue anyway

JL spark

I had a inspection on a job we took over once ,

kitchen was wired in a ring on a 32amp breaker

I had to add isolaters for appliances,

I installed FCUs off the ring ,

The inspector didn’t like that , so I split the ring into 2 radials and installed 20amp double pole isolaters instead ,

Just to keep him happy and get power on for the client ,

kirk.

That was the system I used when I was a REC ,can't see the issue there

Isolators on radial circuits and FCUs on rings

At this stage with all the advancements in main boards and domestic safety it's hard to see a place for ring final circuits, still plenty of use in commercial and industrial

kirk.

Domestic work is a mix of DIY minor works and RECs so I think fixed wiring should be protected which means no ring final circuits

For example a diyer branching off a 2.5 in attic ,no guarantee he will fuse branch

blueandgreen

thanks everyone

blueandgreen

https://www.boards.ie/discussion/comment/118854455#Comment_118854455

yes, extending the ring probably makes most sense-thanks

kirk.

If Im recalling correctly I don't think there was ever provision for unfused branching to double sockets

I think it was unfused branching or spurring only to a single socket

Et101 did away with that and any branches had to be fused on the ring, to eliminate branches being extended and overloaded etc later

The FCU is only suitable for feeding an appliance directly or a single socket for an appliance

As per the second post anything else should entail extending and maintaining the integrity of the ring

kirk.

https://www.boards.ie/discussion/comment/118855132#Comment_118855132

Thinking back now when the FCU on the ring came in, the switch to radials in the kitchen and utility happened at the same time, it may only have been an advisory

Was still using rings for long bedroom runs

So it was mostly isolators switching inaccessible sockets in kitchen/utility

The small issue with fcus switching inaccessible sockets would be the 2 13amp fuses in series not the greatest design although generally not an issue as they don't blow

That could have been your inspectors issue above or maybe the fcu was switching a double socket which would be bad design dunno