ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Ring circuits?Spur unit? RCD Device?

My French electrician says that for new build or remodels, a British ring-main circuit is (and as far as he's concerned always has been) forbidden. They use radial spurs from the consumer unit with suitable breakers or cartidge fuses. Fused cord-caps (plugs) don't exist, but of course many modern appliances have fuses or overload protection built-in.
On 2.5mm2 wire you can have up to 8 outlets on a 20A breaker or 5 outlets on a 16A breaker. Washing machines, dishwashers driers etc. must be on individual spurs, 2.5mm2 with a 20A breaker each. Cooker/range on 6mm2 and a 32A breaker. Electric radiators, up to 3.5kw total on each radial spur, 2.5mm2 with 20A breaker. Radial lighting spurs 1.5mm2 with a 10A breaker can drive up to 6 lampholders each. There are no inspectors, but to work as an electrician you must register as such and the chambre des metiers needs proof of qualifications or you can't get a registration number. There is rigid demarkation between trades, 'sparks' does not plumb and plasterers don't wire stuff. If a client employs an unregistered 'craftsman' [ie hack] he can now be fined up to $30,000,[E30,000] and of course his fire insurance is void. The authorities are cracking down hard on the cheats, prison sentences are being imposed and they reckon every Gendarmerie now has a 'tax evasion' man. DIY is exempt, of course. Nervertheless hacks still abound and the black econmomy thrives, because social security and tax charges on a small one-person business adds at least E30 an hour to the bill. A couple of years ago there was a massive boom in the black economy when we changed from francs to the euro, as all the mattresses stuffed with tax-dodged cash had to be cut open and spent before e-day! Banks were duty bound to tell the taxmen of conversions above E500. Eventually as the deadline approached, even the crooked builders wouldn't touch francs with a stick.

Alan

[This message has been edited by Alan Belson (edited 01-06-2006).]

Thanks to all that provided all the information!
I was not aware that British wiring was so complex at one time with all the different ratings of power outlets and such. (The now BS 1363 outlet and matching plug looks far more robust than the "junk" we use over here!!) I do think North American standards are poor as compared to European and australian standards... 240V for small appliances? Must be nice! Plug in a 1500W heater to your typical 15 A branch here and yer maxed out (80% rule) Don't even think of plugging in the vacuum!

As for that ring circuit... I was always under the impression that the circuit conductors were capable of carrying the full current rating of the fuse or breaker protecting it.... Now I see where it could be dangerous if a group of heavy loads was plugged into a ring circuit close to the end...
To operate safely the loads would have to be spread out OR connected at the midpoint of the ring I think I read correct?

Wow, I learned more than one new thing today!
Thanks again!

A.D

The common arrangement in Ireland is a little different.

While the ring circuit is perfectly legal, it's just not very common. Electricians, for whatever reasons, have just never liked it.

We usually use 20A radial circuits feeding BS1363 socket outlets. (in older installations 16A radials protected by diazed fuses)

I guess you could call it a hybrid of UK and Northern European wiring practices.

---

Ireland used German-style Diazed/Neozed fuses & panels for a very long time. I guess the ring circuit idea just never caught on.

People just expect to be able to isolate a room / group of rooms at the panel without knocking out the whole floor.

Also, radials suit the more sprawling type homes that you tend to get once outside the urban areas here.

Yep -- We had just as much variety as North American parallel and tandem blades, T-slots, etc. As far as domestic is concerned, there were 2, 5, and 15A connector ratings, and at one time each was available in both 2-pin non-grounding and 3-pin grounding versions. To add to the complexity, the pin spacings were different between the 2- and 3-pin versions, so that a 2-pin plug would not fit a 3-pin socket of the same rating!

The 2-pin version of 15A fell out of use, but that still left five different configurations (the un-modernized house my family bought to fix up when I was a kid in 1970 still had a few of those pre-WWII 2-pin 15A sockets).

By the way, I think most people would probably agree that the 5 and 15A ratings are probably quite conservative. The 5A plugs have pins which are similar to those on European 16A plugs.

As for BS546 15A, who was it at ECN a while ago who referred to them as "Hefty enough to brain a rhino?" They really were huge, and looked quite capable of carrying at least four times the rated current.

Although the ring was introduced in the very late 1940s, of course the older BS546 connectors were still in fairly widespread use for many years after. In fact BS546 is still favored in theatre work today for the rigging, mainly because if BS1363 was used it could be very hard to get at a blown fuse.

Today, the 2-pin variant of 5A lives on as the standard connector just for electric shavers. Shaver outlets fed via a 1:1 isolation xfmr are the only sockets permitted in bathrooms under IEE Regs.


Any long-term ECN members remember the discussion with Dspark a few years ago?

That's one of the things I dislike about the ring. Although the IEE considers it unlikely, the system is not foolproof and it is possible to overload the cable without exceeding the rating of the OCPD. If you connect a couple of 3kW loads near to one end, then the short side of the ring can have its rating exceeded. The IEE Regs. were amended on this point a while ago, but it's still a concern in my mind.

Another problem is that if one conductor goes open for any reason, every outlet on the ring still has power. In fact you can have one break on the phase and another on the neutral, and everything still has power, but the cable could end up being severely overloaded. I've seen it happen.



[This message has been edited by pauluk (edited 01-10-2006).]

A similar radial arrangement is also recognized by the IEE Regs., with limits as to the floor area served.

They also recognize a 30A radial arrangement, but obvisouly in this case a larger cable is needed -- Usually 4 sq. mm.


On some of the older installations it was more a case of knocking out almost the whole house here!

The original ring specification for domestic wiring allowed one 30A ring to serve an unlimited number of outlets over a maximum floor area of 1000 sq. ft. (the change to metric didn't alter that by much -- it's now 100 sq. m. or 1076 sq. ft.).

Given that a very large proportion of British homes were/are less than 1000 sq. ft., it was very common in the past to find one ring circuit feeding all sockets (with the exception of the one on the cooker panel).

You can still find places which were wired in the 1950s through 1970s which have the typical four branch circuits for the whole house:

#1. 30A for cooker (range).
#2. 30A ring for all sockets.
#3. 15A for water heater
#4. 5A for lights.

It gradually became more common to install two rings, but in my opinion the often-found system of one ring for each floor is far from being the best arrangement. Given that most homes now have central-heating, the upstairs ring often ends up feeding nothing more than a few radios, TVs, electric blankets, and bedside lights, while the downstairs ring still runs all the heavy appliances.

It's still common for the washing machine, dishwasher, dryer, etc. to be connected to the ring rather than being on a dedicated circuit.

*shrug* my typical arrangement for 100 square metres is: 2 10 or 13A circuits, each feeding sockets and lights in half of the rooms, dedicated 16A circuit for each dishwasher and washing machine. Not much different - actually noticeably less power.

One side note: unlike US GFIs RCDs are purely electromechanical devices.

Here there are _no_ limits of floor area or number of outlets a circuit can feed. No 80% rule either... sometimes resulting in severely overloaded circuits. Example: at school the sockets are on 10A circuits. We often plug in a 1200W kettle and a 2000W kettle simultanously (don't ask me why, that's due to some erm internal problems), totalling 3200W. At a measured voltage around 220V (our school is traditionally low, record being 355V phase-to-phase voltage instead of 400 nominal) that equals to 14.5 A... the fuse takes that quite happily for two pots of tea. (even though circuit breakers were already standard in 1978-1980 when the school was built we still are on Diazed fuses).

Here the recomendations are:

1) Lighting and outlets are on seperate circuits.
2) Radial circuits serve no more than 10 points (applies to both lighting and socket outlet circuits)
3) Radials should only serve up to 2 rooms max.
4) Ring circuits, if used, same 100sq meter rule as UK applies.

5) Circuits should be planned according to predicted load... e.g. the kitchen should usually get more than one radial..
Dishwashers, washing machines, dryers etc need particular attention.

Overloading will just blow the 16A diazed/neozed/minzed fuse or trip the 16/20A breaker anyway. Not really a fire hazzard as overloading a ring at one end might be.


Also:
The Department of Environment has directed that lighting wall switches should not be higher than 1200mm or lower than 900mm. This is to allow easier access for disabled people.

Sockets are generally located at about 800-900 mm for similar reasons. (shouldn't have to stoop over and should be accessable from a wheelchair)

only applies to new installations and is not a wiring regulation. It's a building regulation / accessability regulation.

[This message has been edited by djk (edited 01-11-2006).]

pauluk wrote:


A fully electric dryer over here draws about 30A 240V on its own! (I metered my old one at 22A/27A)

Do UK dryers draw less?? (I noticed that your range circuits are not 50A as ours are.. Are we just power hungry here?? )

Randy

Yes, the average UK clothes dryer is 2400 to 3000 watt, supplied by a standard 13 amp plug or fused connection unit from the same circuit as other appliances. The size of laundry loads tends to be lower to compensate too though.

Our dryer is on a dedicated (16 amp) circuit, simply because it was simpler to run the outlet that way

With regard to the stove/cooker/range circuits, I think the overall loading is similar, 4 burners and an oven, but the regulations here allow for diversity within an appliance such as a stove, meaning that although the theoretical draw might be 40-45 amps, the actual continuous load isn't going to exceed 30 amps, and of course we're not subject to the 80% rule for loading. This means a 30 or 32 amp circuit is acceptable for the purpose. Larger stoves (and other appliances such as electric showers especially, being basically a high power instantanious water heater) can require a 45 or 50 amp circuit, this is far more common for the showers than stoves. I think American ovens may be higher loading due to larger size however.

Edit to waffle on about the stoves and showers

[This message has been edited by chipmunk (edited 01-11-2006).]

For that matter, US ranges generally require a minimum 40A circuit.

We do have a derating factor, of course. Any range rated 12kW or less is assigned a demand of 8kW.

Taking a trip to the local big box store, I see most ranges are between 10.5-12kW. That's for 4 surface elements and electric oven. "Dual-fuel" ranges are also available--gas cooktop with electric convection oven (though nothing like the options they have in France, 3 electric surface elements and 1 gas burner). Cases such as these may warrant a 30A circuit.

The typical electric range may have either a 40A or 50A circuit. In either case, a 50A receptacle is used. (NEMA 10-50 before 1996, NEMA 14-50 after.)

[This message has been edited by yaktx (edited 01-11-2006).]