Now that we have some more international members, I thought it might be an idea to raise this topic once again.
Any of you who have read through some of my earlier posts will know that I'm not a fan of the British-style ring circuit.
How does anyone else feel about it? It would be interesting to compare opinions from those who are used to working with it (U.K. members, of course!) with those who are only looking at it from a theoretical point of view.
Do you like the concept? Do those of you who have to work with rings in practice like them, or would you rather see Britain move back toward radial circuits?
Belgian, Ring circuits are used to supply 13A (BS1363) sockets & certain fixed appliances (up to 3Kw) via 13A fused connection units. A ring circuit starts at a 30/32A MCB in the consumer unit, loops in & out of each socket / fused connection unit in the circuit & back to the same 30/32A MCB. Minimum cable size is 2.5 sq mm Cu/PVC. A ring circuit may supply an unlimited number of sockets, in a maximum floor area of 100 sq M, providing that the known or estimated load does not exceed the value of the MCB.
Radial socket circuits start at the MCB, loop in & out of each socket in the circuit & terminate at the furthest socket in the circuit. (The same as Belgian practice I assume.) Radial circuits may also serve an unlimited number of sockets, in a given floor area, providing that the known or estimated load does not exceed the value of the MCB. 20A Radial: Min. cable size = 2.5 sq mm Cu/PVC. Max floor area served = 50 sq M. 30 or 32A Radial: Min. cable size = 4 sq mm Cu/PVC. Max floor area served = 75 sq M.
Most UK residential wiring is carried out in PVC insulated & PVC sheathed "twin & earth" cable, similar to US "Romex" cable. The cable is usually run in building voids, under floors, above ceilings & within timber stud partitions without any conduit tubing. When run under plaster in solid walls (frequently encountered in England!) it should be protected by capping or conduit. This conduit usually only runs from the socket up to the ceiling or down to the floor, depending on wiring & construction methods. Rewiring or adding extra points at a later date can be a major pain in the a***!
I have a copy of Legrand's International Wiring Guide, which illustrates the basics of the 4 main wiring standards; US, UK, French & German. I will attempt to e-mail it to Paul (hopefully sometime this week) for him to post, as I think it may help us understand each other's systems.
Re: Ring circuits again!#133979 10/14/0208:43 AM10/14/0208:43 AM
In Austria we use only radial circuits, usually 1.5 sq. mm fused 10/13 or sometimes 16A (different values for fuses/breakers), lights and sockets usually mixed. Walls are typically brick, directly plastered (We don't bother with horsehair, bonding agent,... and whatever I've heard about US plastering, our plaster is lime with sand and usually (not necessarily) cement, older plaster is just plain mud mixed with water, sandbox style) sometimes 2" or 3" gypsum mixed with lumps of steel dross (hope I got this right out of the dictionary, it's some remnant of the steel production), supplied in panels 30x60 cm for interior walls. Plaster and lathe was commonly used for ceilings, for finished attic walls and in rural wood structures, always with straw mats nailed onto the lathes for better keying. Wiring is run within the walls, either NM direct buried or THHN in PVC flex conduit. Junction boxes theoretically have to be located above each switch and receptacle (both to avoid too many bends with conduit, and to be able to guess where the wiring runs without having a map.) I hope I can find room wiring schematics and post them. Ceilings contain only the wires to the light fixtures. For adding outlets or anything else it's usually inavoidable to get a sledge hammer and a good chisel, or better a rotary drill hammer with a flat chisel bit. (Myself I use a Bosch hammer for roughly $159.90, 159.90 Euro, Hilti hammers are also very common). Personally I prefer ripping up walls over fishing in cavity walls, you can see what you're doing. Wires within wall/ceiling vavities MUST be in conduit. In the 1970ies and 80ies the use of drywall with standardized aluminium profile studs (Knauf has almost a monopoly on them, Rigips, a brand name, has become synonymous for plasterboard). These studs have KOs for conduit I think every 50 cm. However, exterior walls are still typically brickwork.
Re: Ring circuits again!#133980 10/14/0209:12 AM10/14/0209:12 AM
You guys all have one thing in common: you have the wires in the walls. Here, the cables are often surface mounted. It's not very common on new buildings, but when cables are added or a building rewired all of the wiring end up on the surface of the wall. I suppose Swedish sparkies don't like fishing
Re: Ring circuits again!#133981 10/14/0210:57 AM10/14/0210:57 AM
Are the surface-mounted wires placed in raceways or are they just stapled directly to the wall? Doesn't that expose the wires to potential damage?
Here, when people do surface mount wiring, they either put individual wires in raceways or conduit attached to the wall.
Conduit is used IN walls, not ON walls.
You see: cables are in danger when they are in the wall. Someone might put a nail in them, drill into them or something like that.
Surface mounted, they are perfectly safe. In fact, one of the popular cable types is only approved for visible surface mount. The reason for this is simple: to give the cable a nicer apperance they have cut down on the insulation and up until two years ago the metal shield was ungrounded. Then the European harmonization forced them to add a thin ground wire to the shield. You're not allowed to use it as equipment ground, it's only there to ground the shield. (The electric safety authorities ensure that it is safe to ground it: There is a thin layer of plastic around the shield which prevents anyone from touching it.)
The rest of the world seem to do everything backwards! I learn that Americans put the cable on the wall and then staple it. We do it the other way round: First hammer in the staples, then put the cable in the staples! (You use pliers to fold the staples around the cable)
[This message has been edited by C-H (edited 10-14-2002).]
Re: Ring circuits again!#133983 10/14/0201:57 PM10/14/0201:57 PM
>A ring circuit starts at a 30/32A MCB in the consumer unit, loops in & out of each socket / fused connection unit in the circuit & back to the same 30/32A MCB. Minimum cable size is 2.5 sq mm Cu/PVC.
Why does it go back to the same 30/32A MCB? Is this yo have better ground-fault protection (since it's a TN system)? What type of curve do you have to use in breakers (B/C)? The cable is 2.5mm2 and you use a 30/32A breaker? How is this wire protected for over Ampering?(sorry for my English)
>I have a copy of Legrand's International Wiring Guide, which illustrates the basics of the 4 main wiring standards; US, UK, French & German.
I would appreciate if you could email to me, too: firstname.lastname@example.org
Re: Ring circuits again!#133984 10/14/0202:17 PM10/14/0202:17 PM
The cable is 2.5mm2 and you use a 30/32A breaker? How is this wire protected for over Ampering?
The idea is that, since you have two cables you can double the fuse. 16A coming from one side of the ring and 16A coming from the other.
Therefore 2.5mm2 is sufficient. If the load is not connected at the middle of the ring or if it is not evenly distributed along the ring, there will be an unbalance in the load: You might have 20A on one side and 12A on the other.
If for some reason the ring is broken or the load is connected very close to the breaker, there is nothing to protect the 2.5mm2 cable. It could carry the full 32A. Would you like to have a system like this? Personally, I find it scary.
What type of curve do you have to use in breakers (B/C)?
I leave it to the Brits to answer this, but what do you use in Belgium? Please tell me you use type B for sockets! Do you use 20A or 16A for them, BTW?
Re: Ring circuits again!#133985 10/14/0202:25 PM10/14/0202:25 PM
>Is this yo have better ground-fault >protection (since it's a TN system)?
This is in fact one of the advantages of the ring main. It offers a high integrity earth. If for some reason the earth wire comes loose or break along the way, there is backup wire on the other side. Therefore, the risk of finding yourself with a live socket without earth is minimal.
I really like the idea of a ring system, but I don't like overfusing it. Your opinions on a ring main with 20A fuses? It would allow long runs with 2.5 mm2 cable and offer high intergrity earth, without any risk of fire. This should be of special interest to Americans, since cuircuits in 120V wiring are limited by voltage drop much more often than our 230V ones. (Forget the NEC for a moment - think free! )
[This message has been edited by C-H (edited 10-14-2002).]