Just a few ideas of some things I'd like to see change in current British wiring practice. All very much my personal opinion, of course. In no particular order:
1. Let's specify dedicated branches for washers, dryers, and dishwashers. With a typical 3kW loading for each, I feel that piling them all onto ring circuits (often all on one!) is not the best approach. The regs. have always specified a dedicated 15A branch for a 3kW water heater. People often expect to be able to use washers, dryers, etc. simultaneously these days, so it's time they followed suit.
2. Let's abandon the ring circuit altogether. Any reasons given for its adoption in the late 1940s are no longer valid, if indeed they ever were, due to changing patterns of usage.
With the heavy stuff moved onto dedicated branches, wiring several radial circuits of 20A for general-purpose outlets would be fine. It would also make for easier servicing than in homes where receptacles are all on one or two circuits. And it would eliminate the possibility of overloaded cables due to an open ring (whether by fault or incompetent DIY).
3. We should abandon the "no sockets in the bathroom" stance. Let's allow a suitably placed receptacle, protected by a GFI of 30mA or less.
People WANT to use blow-dryers etc. in there, and will find a way to do so. They can't run them on the low-VA isolated shaver socket, so they'll run an extension cord to a hall or bedroom, which may well have no GFI protection whatsoever. Better to provide a suitably protected outlet in the first place.
4. We should introduce U.S.-style clamps for terminating our equivalent of Romex at fixture boxes. The current technique of using a conduit knock-out just fitted with a rubber grommet doesn't provide enough protection against straining the internal connections.
5. The color code should be straightened out (or to be more precise, it should never have been messed up in 1970). We know what to expect of course, but it's quite illogical for blue in a fixed cable to be a phase and blue in a flexible cord to be neutral, for example. (Er, or was this system wired prior to 1970, in which case blue in a cord is hot after all!).
6. We really should use deeper boxes in many places. The prevalence of brick walls here is a big factor, but the common 1/2-inch for a switch and 1-inch for sockets just doesn't leave room for extra cables to be added later. (And frankly, is barely adequate for the originals.) I'd like to see 1 and 1-1/2 inch minimum respectively (or 25 and 38 mm as they insist on calling them now).
8. While we're on that subject, can we please tell the dictatorial EU bureaucrats to take a running jump and change all the metric specifications back to units that 99% of Brits are comfortable with.
From my perspective here in the States it would make sense if you had Immersion Detection Protection devices for your hair dryers like we have. This would alleviate the dangers inherent in plugging them into sockets in other rooms..'tho your suggestion of 30mA trip levels sounds like an electrocution waiting to happen. 'Ring circuits' seem like a ripe candidate for being phased out. With all the interest and fears about stray electromagnetic fields (which ring circuits produce when one conductor opens and gets back fed from the other end) I would think that there would be an outcry against ring circuits..at leats for the ones using plastic covered wiring..Mineral Insulated cable would shield the magnetic fields, I would think. Here, we require a dedicated circuit if an appliance takes up 50% or more of the circuit ampacity..so your idea of dedicated circuits seems appropriate. I'm wondering 'tho about all the old masonry buildings which would look pretty cobled up if there were stipulations for lots of separate radial circuits..is that workable?
#133050 - 12/27/0106:37 PMRe: Would like to see...
Well, I certainly concede that a 30mA GFI outlet at 240V to ground could still pose quite an electrocution risk. I picked on 30mA because that's the lowest GFI breaker that's easily obtainable in a wide range here; in fact many houses in rural areas now have a whole-house GFI of 30mA.
But 10mA types up to at least 20A are available, and would undoubtedly be a better choice. And whatever GFI is used, it would at least be better than extension cord hair-dryers run from a non-GFI outlet.
I never came across one of the new blow-dryers while I was out there (it's nearly 6 yrs. since I came back). How exactly do the "immersion detectors" work?
If you applied the 50% rule PER APPLIANCE, then our washers and dryers would still pass, as the ring is a 30A circuit, giving 7200W maximum. But with two 3kW appliances running simultaneously that only leaves 1200W, and in too many homes that 30A ring is also feeding all the kitchen sockets where kettles, toasters, etc. are likely to be in use. And in remodeled kitchens, I have seen washer, dryer, and dishwasher all on the same ring.
You'll see that in the IEE Regs. a ring can feed up to 100 sq. meters (originally 1000 sq. ft.) of floor area. In many older houses there's only one 30A ring for all sockets (except the one sometimes fitted to the cooker panel).
Even where two rings are provided, as is common now, in a 2-story house they are often wired one for each floor, which to my mind is not the way to get a reasonable distribution of load.
Some guides recognize the problem, but then go on to suggest that with the increased load in a modern home it may be a good idea to install a separate ring for the kitchen-area outlets. That seems to me to be missing the point that it's the kitchen area which is carrying the bulk of the load and needs to be divided onto separate circuits.
I hadn't thought about increased EM fields from a broken ring conductor, but I think the possibility of overheated wiring should be of greater concern.
There was a lot of fuss about HV lines a few years ago, but the protests seem to be directed toward cell-phone towers these days (sometimes by people who spend all day on their own cell-phone and who have obviously never heard of the inverse-square law!).
The prevalance of brick and masonry walls does make cabling awkward at times. Where a timber floor is used (e.g. many pre-WWII homes) the ring cables are generally run in the crawl space and brought up to each socket behind the skirting-board (baseboard) and set into the wall. (In earlier times it was actually very common to just screw surface boxes to the board and take the cables straight down trough the floorboards.)
Where the floor is solid concrete, the ring has to be run in the attic and cables dropped down the walls to each outlet, or channeled horizontally along the wall. With two cables to each outlet, it's a lot of work anyway, so I'm not sure that changing to radial circuits would make it any harder in that respect.
#133051 - 12/28/0105:15 PMRe: Would like to see...
To be honest, I'm not sure how the various professional bodies and IEE committees get things changed. It's something I've never really looked into that closely. I'll have a look at the IEE website later.
Regarding the circuit arrangements for radial branches, there's nothing to stop anyone installing dedicated branches for anything, and I've often changed a washer/dryer etc. outlet during other work. In some cases it can be done quite easily from the attic or crawl space without having to tear up walls.
The rules about what outlets are permitted on radials have changed quite a bit over the years, but the current specs. are here:
Paul, from what I have gathered, the immersion detectors respond to conductive liquids modifying the impedance between a sensor probe and an electrode. It will trip the H & N open when the appliance is dropped in water. Its supposed to limit leakage to 6 mA..just like a gfci, but its not to be relied upon to prevent a momentary tingle. But it still sounds safer than the 30mA device that you mentioned. As for the controversy about stray EMF from power systems, our IEEE published findings that pretty much aleviate fears of the power line and building wiring EMF having any deleterious effect on humans..as you probably are aware (you appear to be a really smart guy!). The energy of power wiring is negligible compared to the normal thermal energy in the human body. But, electromagnetic interference can still be a problem and so I would not be too keen about an open in a ring circuit. You can check Mike Holt's web site for further elaboration.
Sparky, if you are reading this I have a question for you: where can I download a copy of the latest ROP's and ROC's?
#133054 - 12/30/0102:56 PMRe: Would like to see...
Interesting on the immersion detection. Does it have a breaker fitted at the plug or in the cord, or does it just short the line and rely on the house breaker to open the circuit?
I don't remember hearing about the American IEEE's conclusion on EM fields, although I recall several groups here recommending that there is no need for further action as "no direct link has been proven," or words to that effect. (Probably worded to avoid being torn apart by lawyers if any link should be found in the future; you can't publicly announce that grass is green these days without a disclaimer!)
Some domestic lighting circuits here were wired with single cables taking different routes, so stronger fields are likely there. As someone who works with sensitive audio and RF equipment, I'd certainly agree that anything which helps keep EM interference to a minimum is welcome.
By the way, this is another reason I don't like rings. The ground wire is run as a ring as well, which can give rise to some awkward loop problems.
#133055 - 12/31/0103:31 PMRe: Would like to see...
Yeah, we have our share of old "knob and tube" wiring that is single conductor routed, and is likely to be a source of EMI--especially if dimmer switches or paddle fan speed controls are used. The IEEE has a panel that oversees the health concerns of EM fields, but I don't recall the title of the volume..it has been about 5 years since I last looked at it in a university library. By the way, I looked over some of your earlier entries re. UK wiring and I realize NOW why you are concerned about the wiring overheating..I never realized before that the wire is undersized..that it needs both ends of the ring to safely handle the current load. Its probably a good thing that your buildings are made of masonry or stone! One redeeming fact 'tho is that the receptacles don't necessitate an actual break in the wiring..decreasing the likelihood of a faulty connection or open circuit from one end of the ring. My understanding is that the immersion detectors are part of the plug..a big ole clunky plug..with a reset button like a gfci. The receptacles in bathrooms are also gfci protected..so its a race to see which one trips out first. I have seen somewhere..I think it was in a '99 code handbook..that manufacturers have a choice as to whether to use an actual immersion detector, or a gfci, or..this isn't a sharp memory..an appliance leakage current interrupter. Perhaps that choice has been recinded by now..you will have to dig for info about it from someone who is really on top of the subject..I'm just slightly familiar with it. I'll leep my eyes peeled next time I go to the store and see if there are any IDCI's attached to the plugs of cords of blow dryers, curling irons, foot massage units, etc., and I'll let you know what I find. Bye for now. P.S. I appreciate your perspective on this site. I only wish I had access to your info 10 years ago..before my trips to England..I could have learned a lot more on my trips! I am a bit amazed by your familiarity with our wiring methods and electrical code. What's-a-mattah, don't you have a life?
[This message has been edited by Elzappr (edited 12-31-2001).]
#133056 - 12/31/0110:42 PMRe: Would like to see...
Yes, the ring is fused at 30A (or 32A with the latest C/Bs) and the cable is rated at only two-thirds or so of that (depending upon derating factors for insulation etc.).
Originally rings were wired with 7/.029 cable, which works out as 0.0045 sq. in. CSA. The change to metric 2.5 sq. mm reduced the CSA to 0.0039 sq. in. I make that just fractionally larger than your #14.
The cable can be looped into a box and stripped to go into the outlet terminals without breaking into the conductors, but in practice it's not all that common to see it done that way.
As for my interest in American wiring, I guess it's just a combination of technical curiosity and a love of the U.S.A. in general. I first read a few U.S. electronics journals when I was young, and of course there were odd references to 120V, a "peculiar" color code, and those "funny-looking plugs."
First time I ever visited the U.S. I found a bookstore and bought a couple of wiring books. Great stuff and full of useful information even though I'd picked up some other odds and ends before then. I've learned a lot more history and background on here as well, of course.
I guess the same "accusation" could be thrown at you: After all, how many American tourists go home with a copy of the IEE Wiring Regulations?
Oh yeah: About 3 years ago I found a U.S. "Teach Yourself Wiring" type book in a public library in the Republic of Ireland. I have no idea why they had it on the shelves, as they follow U.K. practice. I only hope it did't confuse anyone too much!
[This message has been edited by pauluk (edited 12-31-2001).]
#133057 - 01/02/0211:37 PMRe: Would like to see...
Hi Paul..Happy New Year! Yup..I'm a bit too technically curious..but I only did it for my apprentice students! Hey, I took a look at the hair dryers and hydro-massagers..and they have ALCI's on their cord ends..not "immersion detectors"..but I don't know how the ALCI's work, perhaps they are immersion detectors in disguise. Instructions say that you have to unplug the unit before resetting the ALCI. 'Don't know if you HAVE TO or if its just a recommendation. So, what part of the States are you interested in?