Ring Final Circuit - spurs only

[John-SJW]

I read that it is against the regs that a ring final circuit cannot be just a ring with with spurs off it. In short, a ring must have sockets on it which double up as junctions. I find that hard to believe.

 

[davesparks]

Sockets are not for permanently used appliances. They are to be plugged in and out. Permanently wired in appliance need to be hard wired. And that in theory includes a 24/7/365 fridge.

Why not? Sockets are for any appliance regardless of how often it needs to be connected/disconnected.

This is especially true in domestic installations where small appliances, white goods, etc will often be connected/disconnected by untrained or unskilled people.

 

[UNG]

Sockets are not for permanently used appliances. They are to be plugged in and out. Permanently wired in appliance need to be hard wired. And that in theory includes a 24/7/365 fridge.

So why do some manufacturers consider removal of the plug from the socket is safe isolation of the appliance when they need to carry out warranty work. Back to the old you can't cut the plug off without voiding the warranty debate

 

[mart spark]

There is/ was a Collins D.I.Y manual i had from about 2007ish which showed that an RFC could be wired in this way so it is quite possible that there are more than a few homes wired up this way.

 

[mart spark]

I used to believe this too. I don't know if it was included in the 15th or 16th edition, but there's no mention of it in BS7671:2018+Amd2:2022 (at least as far as I can see).From memory this was apart of the 16th Edition OSG at least.

 

[davesparks]

The point is a ring without sockets, either with for e.g., having only jboxes or appliances hard wired on the ring. Why the jbooxes are there or why the appliance are hard wired in is not the point. It is a regs point.

The point of a ring final circuit, the whole reason it was created in the first place, is to supply multiple, general use sockets over a relatively large area as efficiently as possible.
The point of the ring final circuit is to have the flexibility to supply multiple loads which are generally unknown and generally moveable.
The design of the standard ring final circuit is based on certain assumptions, including the assumption that loads will be relatively evenly distributed

If you are installing a dedicated appliance circuit what would be the point of installing a ring circuit? The loads are known at the design stage, a dedicated appliance circuit can be designed to cater for the appliances and has no real need to be a ring.

 

[davesparks]

So why do some manufacturers consider removal of the plug from the socket is safe isolation of the appliance when they need to carry out warranty work

Because it is a safe method of isolation, you can't get more isolated than fully disconnected.

 

[davesparks]

A dedicated ring for only heavy appliances, hard wired in comes to mind. Sockets on a separate ring.

Why would you us a ring for this? Dedicated circuits for heavy appliances are normally better off installed as radials.

 

[John-SJW]

And a very early answer was "yes, but it would be non-standard"

Whatever standard and non-standard are.

 

[nicebutdim]

Read the beginnings of this thread last night and its aim is less than clear.

Initially the OP expressed disbelief that a ring could not exist for the sole purpose of providing a source of power for spurs. This was cleared up by @davesparks who pointed out the rules which apply in terms of the number of allowable spurs and their dependence on the number of sockets in that ring and that a ring can not simply exist as a form of busbar, from which sockets can be spurred.

We then have a suggestion from the OP of a ring serving as a busbar for heavy appliances, which brings us back to the point from previous, similar threads about ring final circuits and how the OP's thinking fails to take other regulatory limitations into account.

While I do think there's merit in the idea of such a busbar, it could never exist in practice (in a domestic installation) if one is to meet all regulatory requirements. In some regards I applaud the OP's inclination to think 'outside the box', but that tendencey to think is severely hampered by an apparent inability to 'see the bigger picture'. Surely anyone familiar with BS7671 would see the numerous problems such a proposal poses and not just the one potential benefit? This isn't the exploitation of a loophole the OP thinks it is, but a potentially huge headache for any homeowner who allows such an experiment in their home. I'm sure the OP would feel assured in their misplaced confidence to sign off such a departure from BS7671, but very much doubt they'd be prepared to bear the costs incurred when remedial work was required to resolve the obious issues likey to arise. This industry evolves through innovation, but sometimes it's better not trying to be clever and to simply work within the confines that a century of experience places upon us.

 

[Pretty Mouth]

I used to believe this too. I don't know if it was included in the 15th or 16th edition, but there's no mention of it in BS7671:2018+Amd2:2022 (at least as far as I can see).

It's in the OSG, H4. Not sure I understand the reasoning behind it though

 

[UNG]

Because it is a safe method of isolation, you can't get more isolated than fully disconnected.

Really that was the point I was making to the post I quoted to see what response SJW would post as a reply

 

[davesparks]

Whatever standard and non-standard are.

In this situation standard refers to the standard circuits described in bs7671 and associated publications. They are best described in the on-site guide I believe.
Standard circuits refers to the 32A ring final, 20A radial and 32A radial circuits described in those publications. Details are given for minimum cable size, maximum length of cable etc etc

Non-standard refers to any other circuit which you will have designed yourself.

 

[nicebutdim]

Sockets are not for permanently used appliances. They are to be plugged in and out. Permanently wired in appliance need to be hard wired. And that in theory includes a 24/7/365 fridge.

Manufacturers have ensured that there's nothing permanent about fridges, nor any other white goods, and a fridge is one appliance that I'd never consider supplying from a ring in any new installation.

This one appliance is very likely to be the greatest source of trouble in your theoretical circuit, despite its relatively low power consumption, and for reasons you've failed to take into account.

 

[John-SJW]

And then, when the homeowner needs a new fridge, he has to get a sparky out to disconnect the old one and reconnect the new one.

Makes perfect sense to use a plug, especially since it will come with a pre fitted one.

Yep. Some fridges use 750 watt. That needs hard wiring.

 

[John-SJW]

Assuming the average ring circuit has 10 sockets on it and you save 3m of cable per socket that's a saving of 30m of cable.
At current prices that could be about £25 saved.

Depending on your preference for joint boxes they could realistically cost you £25.
Then you need to consider the additional time involved.

Other considerations are best practice, it is generally accepted that best practice is to avoid unnecessary joints in cables, every joint being a potential point of failure.

Also you need to consider maintainence and fault finding, it is going to be a lot harder to fault find a ring circuit where you can't readily get to the ring itself.

MF jboxes.