extending a ring circuit to include 2 fans

[joecoe]

Hi

I would like to strip out a double socket on a ring and install a 3 pole isolator and then continue on to feed an additional 4 double sockets on a ring circuit. At the end of the ring can i spur off to supply 2 no. ectract fans at high level. The isolator is just to kill that area - not fussed if it knocks the fans off. Is this ok?
where do i put the isolator more importantly.

 

[securespark]

Why Triple-Pole?????????

 

[joecoe]

sorry spark, double - I take it I must terminate all 4 cables (minus earth) in the isolator.

 

[breezer]

why not extend the ring, and put in a fcu for each fan and make the fcu 's part of the ring?

this is a fcu, other brands of fcu are available

 

[joecoe]

cheers breezer. but how about the isolator?
Will i have to go thru' the isolator at the start of the ring and when it returns to the CU?

 

[ban-all-sheds]

Do these fans have a timer-overrun? If not, then doing as Breezer suggests will give you your isolation switch; the FCU (provided you buy a decent make that has a double pole switch).

3-pole fan isolators are needed when a fan has both a switched and a permanent live feed, to provide a timed overrun feature, as that provides a single point at which the entire fan can be isolated from the supply.

Do not under any circumstances install a switch in a ring that breaks its continuity.

 

[joecoe]

thanks, but my main issue is that I want to knock off a switch/isolator to kill the ring circuit when i leave the room, like if I just tripped the MCB(which i dont want to do).

 

[ban-all-sheds]

thanks, but my main issue is that I want to knock off a switch/isolator to kill the ring circuit when i leave the room, like if I just tripped the MCB(which i dont want to do).

When you say the ring, do you mean the entire existing ring circuit, or just the supply to these 4 sockets and 2 fans?

If it's the latter then put a DP switched FCU into the ring, and run a 2.5mm cable feeding the sockets and the fans from that.

 

[joecoe]

yes the entire existing ring circuit!

 

[ban-all-sheds]

The problem is that MCBs are not designed to be switched on and off all the time, and I'm not sure about the main switches in CUs either.

This product is billed as a "switchfuse", but does anybody know if it is rated for repeated use?

Alternatively, does anybody know if a 3-phase switch, with a switched neutral, i.e. this sort of thing:

would be allowed? With TP+N switching, you could isolate both conductors of both ends of the ring.

You might have more luck arriving at a solution if you tell us what you want to achieve. You say you want to isolate the ring, but why? What is it servicing? What's on it? What is the purpose of isolating it?

 

[joecoe]

basically its a ring circuit serving a small display area, with some cabinets with lighting etc. So at the end of a day it all can be switched off by one isolator rather than walking round and swith each individual point off - suppose its lazy b***ard syndrome!

 

[ban-all-sheds]

Is this a location where members of the public, or any "third party" class of people have access?

 

[joecoe]

yes to above

 

[ban-all-sheds]

Then I think you should read the small print of any public liability insurance you have, and property agreements - you may find that you have to use a qualified electrician, in which case he can sort out the switching that you need....

 

[securespark]

Ban

I thought all switched conn units had dp switches???