PaulUK

Could you please take the time to explain ring circuits to me?

Are the conductors protected at their ampacity or at some higher value because there are two paths to each power point?

Are your receptacle outlets provided with individual overcurrent protection.

Is the conductor continuous or is it spliced?
--
Tom

Hello Tom:

Your wish is my command....

A ring circuit is fed from a 30A fuse or C/B, but lower ampacity cable is used. The original ring specification used a cable known as 7/.029 (i.e. 7 strands each 0.029" diameter), which was rated at 20A maximum.

The equivalent size used since the change to metric cables is 2.5 sq. mm, which is just fractionally larger than your #14.

To be considered a ring circuit by the IEE Regs., the two live condutors from each cable must both be terminated into the fuse or C/B way at the panel, and both neutrals must similarly be connected directly to the neutral busbar.

Almost all domestic wiring is with "Twin & earth" (like Romex), and in this case the earth (ground) wires are also wired in a ring.

Cables may be run with or without splices. The IEE recommends not cutting into the wire if possible, but of course this is often just not practical. They specify that when spliced the joint must be made in such a way as to ensure the integrity of the ring. It's one of those rather vague phrases; after all, I like ALL my splices to ensure the integrity of the connection!

The most common is for cut wires to be twisted and clamped together in the terminal at each socket (recptacle).

In domestic wiring, each ring can serve any number of outlets within a floor area of, originally 1000 sq. ft, now 100 sq. metres (1076 sq. ft.).

The sockets and plugs are rated 13A maximum, chosen to allow for a load of up to 3kW (everything is 240V remember).

Each plug is fitted with a ceramic-bodied fuse, 1" long by 0.25" diameter. Several ratings are available, but 3, 5 and 13A are the most common nowadays. There are no two-prong versions of these plugs, by the way, so even a small lamp with no ground still has a 3-prong plug.

Besides sockets, it is also possible to use a "fused spur unit" on a ring. This is basically just a device to hard-wire some fixed appliance into the ring. It takes the same type of fuse as the 13A plug, and is available in switched or unswitched versions.

It's also possible to wire one or more "spurs" off a ring. A spur is simply a single cable running from the ring to a socket or fued spur unit. The spur may be tapped into the ring either at a socket or by using a junction box. The latter are designed in such a way that the ring cable can be stripped and laid into the terminals without cutting the conductors.

The ring circuit (introduced late 1940s) has been the most common arrangement for domestic 13A outlets, but other configurations are used as well.

P.S. Take a look at "Hello from the U.K." in the General area. I talked about rings there.

Excellent post, Paul!!! I printed the thread for reference!

Scott SET

Why, thank you, Sir. We aim to please!

Paul,
i guess someone's gotta ask sometime here, why a ring???

>why a ring???
That was covered in another thread, perhaps the one Scott found.

I've never been able to find a definitive explanation, but here are a few relevant points.

I guess the first thing to bear in mind is that the typical British home in the late 1940s was quite different to today. Central heating was rare, and most people had open coal/wood fires, gas fires, and portable electric heaters.

Up to then, there were outlets of three different ratings used: 2, 5, and 15A, with non-interchangable plugs. A 15A socket to run a large electric heater was often fitted next to a fireplace and wired back to its own 15A fuse. It was rare to have more than one such outlet in each main room, and sometimes none upstairs in the bedrooms.

Other "general purpose" outlets were 5A, and wired on various 5 or 15A branches. (The IEE Regs. still recognize these circuits with up to three 5A outlets permitted on a 15A branch.) Wiring was what the IEE now calls "radial" circuits - like American wiring.

The 2A outlets were intended mainly for plug-in table lamps etc. and were often wired on 5A branches with fixed lights.

To add to the confusion, both 2-pin ungrounded and 3-pin grounded versions of the 5A outlet were very common. Unlike American receptacles, however, the spacing of the hot & neutral is slightly different, so a 2-pin plug won't fit a 3-pin socket. 2A sockets also came in 2 and 3-pin types, although lighting circuits were rarely run with a ground wire at that time. 15A only came in 3-pin grounded versions by then, but a lot of 2-pin 15A sockets installed in the 1920s/1930s were still around (the old house I moved to as a kid in 1970 still had some!).

The mix of sockets meant that a plethora of adapters were often used. A typical type plugged into a 3-pin 5A outlet and provided a 3-pin 5A socket on the front plus a 2-pin 5A outlet on each side. Another type allowed 5A plugs to be connected to a 15A socket, but many different combinations were available.

It was this "electrical lottery" of plugs apparently, which led to the search for a universal connector and the design of the 13-amp plug with its built-in fuse.

That's the background. OK,back to those big 2 and 3kW portable heaters.....

I've heard it said that the IEE wanted to work out a simple circuit arrangement which would allow two 3kW heaters to be run simultaneously and still leave capacity for smaller appliances. The design was to be such that the heaters weren't restricted to just one or two outlets as before, but could use any sockets in the house.

Whether that's true or not, I'm not sure, but as a 30A circuit provides 7200 watts, it's certainly a possibility. And a massive 30A fuse at the panel, of course, necessitated the adoption of fuses in the plugs.

OK, that still doesn't answer "Why a ring?" From the practical standpoint, it allows the use of smaller cable; e.g. the IEE Regs. permit a 30A radial circuit, but this means the use of (in modern sizing) a 4 sq. mm cable - about 20% larger than #12 AWG.

I've also seen various claims (and counter-claims!) that in the design of homes being built at the time, the ring resulted in the use of the least material - important in post-WWII Britain with shortages and rationing.

I've never actually sat down & tried to work this out. It might prove interesting.

Other than those arguments, I've never been able to find out why for sure. I guess it seemed like a good idea at the time, and we've had rings ever since.

Oh boy, 2 a.m. already! Must've been talking too long!

What problems, if any, would the parallel paths of diffent lenghths cause?

Does this have the tendancy to naturally balance itself (as resistance rises with temp)?

Why does the NEC consider small parallel conductors bad (even at equal lenghts and with the same "path")?

Very interesting questions, Virgil. You've actually made me sit own with a pen & paper mand try out various scenarios.

As an example: Assume a ring with a total loop length of 120 ft. feeding standard twin (duplex) outlets. If both sockets of a twin were loaded to the full 13A, this would place a 26A load on the circuit. If this happened to be the first socket of the ring located, say, just 12 ft. from the panel, the long leg would be carrying just 2.6A while the short side would get 23.4 amps!

An extreme case, perhaps, and unlikely to happen, but it's possible, and of course is one reason why the cable used for a ring has to be rated more than half of the 30A protective device.

As for temperature stabilizing effects, I don't have the appropriate data to hand to work out what the changes in resistance would be. Obviously the short leg would heat up more than the long one, and in increasing its resistance would slightly affect the currents in favor of balance. I don't think the overall proportions would change by much though. Even doubling the resistance in the short leg would still leave it carrying over 21A of the load.

By the way, if you want to experiment with ring calculations, the IEE Wiring Tables specify that the voltage drop for 2-core 2.5 sq. mm cable (used for rings) is 18mV per amp per metre. So for a single conductor, the resistance is 0.009 ohm per metre, or approx.0.0082 ohm per yard.

Paul,
what are the majority of homes in England constructed of????

Sparky:

The majority of houses are brick. There's usually a double brick outer wall with a cavity of about 3 to 4 in. between for insulation. Many older houses only have a single layer wall.

Internal partitions these days are usually timber frames with sheets of plasterboard; older properties had lath & plaster walls & ceilings. Some load-bearing internal walls are brick or block as well.

The roof is usually slates or tiles. American-style shingles are practically unknown.

This is what our real estate agents call "conventional" construction. There are some timber-framed houses, but they're rare compared to the U.S.A.

There are also one or two other styles, such as some very old houes built from stone and the pre-fabricated homes of reinforced concrete sections that were built quickly after WWII to provide emergency housing.

From the practical point of view, I think timber is by far the easiest to work with. Work on the old stone places is the worst.

Off Topic cont'd:

Have you worked with much Hebel Aerated Concrete Block ?

High insulation values (R-11 to 35) and you can shape and drill it with a 1" Spadebit and a 12V Drill! Neat Stuff... Getting more popular among the "hippies" around here, I've heard it's fairly popular in Europe.



[This message has been edited by sparky66wv (edited 09-23-2001).]

Paul,
is the fact that your homes are so solid the rationale behind the 'ring'? , is sounds hard to 'fish' wires thru what your describing.

Virgil,
if you find a link that can create some sort of viable building blocks out of manure, i'll cut you in for 50%

Virgil:

I don't recognize the name "Hebel," but aerated blocks are becoming more common in new construction now. One trade name here is "Thermalite" - Very light weight and easy to drill.

Steve:
Yes, running new cables can sometimes be very frustrating in homes here. Fitting outlet boxes etc. onto walls can also be tricky and involves a lot of hard work to chisel out a recess in the brickwork. Old brick & mortar can often crumble easily; I wish I had a penny for every time I've drilled and plugged a wall, then tightened the box to it only to have it fall out 10 seconds later!

I much prefer timber walls. I sure do love mobile homes.....!!


I understand they actually use such building blocks in some poor African countries. Maybe they collect the material from our Houses of Parliament..... (ouch!)

Paul,
how would you know if there is a break in the 'ring'

oh, about the manure crack, i just have more of it <animal> than i really need...... i'd be happy to oblidge any African relief effort

The possibility of a break going undetected is one of the downsides to the ring arrangement. In fact, if you think about it, there could be one break in the live and one in the neutral, but all outlets would still be energized with the possibility of a cable overload.

The IEE test prcoedures specify a continuity test between the two ends of each conductor before final termination into the fuseway/busbars. It's good practice to disconnect the wires and repeat these tests after any work on an existing ring.

hmmm,
very interesting! if you were to add a room on a home, would you "T" off of a ring, or make the ring bigger ?

It depends on how many outlets need to be added, in combination with the practical considerations of taping into existng wiring, running new cables with minimal damage etc.

A single-cable spur from the ring can feed only one outlet. Spurs use the same size cable as for the ring itself, so any more and there would be the possibility of the spur cable being overloaded. (A faulty appliance can't overload it because of the fuse in the plug - Max. 13A).

So, if there are only couple of new sockets in the extension and ring wiring near to each one, then it's often easiest to wire them as spurs. Otherwise, it's a case of breaking into the existing ring so that the new wiring becomes part of the ring. Sometimes a combination works the easiest. The Regs. also specify that the total number of spurs must no exceed the number of outlets wired directly on the ring itself.

Quite often, and particularly if there is a spare way at the main panel, it may be easier to wire a small extension as a new circuit. The IEE allows a radial arrangement using a single cable fused at 20A, subject to floor area limits for the circuit.

They also allow a 30A radial branch, but this means using a larger cable and is rarely seen in residential wiring.

Would there be any problem with attaching a new ring in a figure-8 arrangment rather than breaking the existing ring at any point?

That is, is it forbidden to have more than two paths to any outlet/junction?

This isn't permitted by the Regs. If the new wiring were tapped onto the existing ring near its mid-point, there wouldn't be a problem.

If the tap-point of the "figure 8" was close to one end of the ring, however, the short leg would carry the bulk of any heavy load connected to the new outlets with the possibility of an overload.

It's sometimes easiest to make the physical layout almost a "figure 8" while keeping it a single ring electrically.

e.g. Cut into the existing ring and terminate each end into one of two adjacent junction boxes. Then bring the two ends of the new wiring into each box. This also makes it easy to run the new wiring then shut off power just long enough to make the two j-box connections.

>If the tap-point of the "figure 8" was close to one end of the ring, however, the short leg would carry the bulk of any heavy load connected to the new outlets

I don't understand how this is any different from a longer ring. To me, they appear electrically similar. If anything, the figure eight would produce a better balance.

Can you provide any rough numbers to back up this assertion?

Yes, if the new ring was spliced in a figure-8 form to the exact mid-point of the old ring, then obviously the total load on the new ring would always be evenly distributed around the two halves of the old ring.

The problem arises if the new ring were joined onto the old ring close to one end. Go back to the example I used before: Existing ring of 120 ft. with a outlet placed 12 ft. from one end of it.

Now assume that a new ring feeding several outlets in the extension is tapped into the existing ring at that outlet in a figure-8 form (albeit a very lop-sided figure-8!).

OK, if the new ring is feeding just a TV, table lamp, etc. there's not going to be any problem. But if the new outlets are a kitchen or utility area, they could have a heavy combined load. Let's say that 6kW is connected to the new ring, giving a current of 25A.

Obviously that 25A will divide around the new ring, but as far as the old ring is concerned, it represents a 25A load at a point just 12 ft. from on end. Now suppose that the existing outlet at that 12-ft. point is feeding a 1200W load, bringing the circuit total up to the maximum of 7200W or 30A.

We now have a 30A load divided between a 12-ft. cable and a 108-ft. cable. The result is just 3A in the long leg and 27A in the short leg, which is greater than the cable rating. Obviously if the tap point was less than 10% from the end of the ring, the imbalance would be even greater.

I'll concede that in most situations an overload is unlikely, but it is possibl.

This perhaps highlights a general point about designing a ring which is seldom mentioned in text books: For best current dstribution, design the heaviest loads either into the mid-section of the ring -OR- put heavy loads likely to be on simultaneously at opposite ends of the ring to balance the current as much as possible.

Bearing in mind that in many kitcens the ring feeds a 3kW washer, 3kW dishwasher, etc. this can be quite significant. I would still rather run separate, dedicated branches for such loads.

>Yes, if the new ring was spliced in a figure-8 form to the exact mid-point of the old ring, then obviously the total load on the new ring would always be evenly distributed around the two halves of the old ring.
But that was never a criterion.

>The problem arises if the new ring were joined onto the old ring close to one end.
This remains to be demonstrated.

>Existing ring of 120 ft. with a outlet placed 12 ft. from one end of it.
Now assume that a new ring feeding several outlets in the extension is tapped into the existing ring at that outlet

This is really no difference at all whether the new ring is spliced into the old ring and it remains closed or if the old ring is widened into a new longer ring.


>Let's say that 6kW is connected to the new ring, giving a current of 25A.
Obviously that 25A will divide around the new ring,
"Divide" in some sense. Naturally this doesn't mean a perfect split.

>as far as the old ring is concerned, it represents a 25A load at a point just 12 ft. from on end.
Which is perfectly acceptable, right?
I mean there is no problem to the ring is 25 A were loaded at that point, right?

>Now suppose that the existing outlet at that 12-ft. point is feeding a 1200W load, bringing the circuit total up to the maximum of 7200W or 30A.
Okay.

>We now have a 30A load divided between a 12-ft. cable and a 108-ft. cable.
True.

>The result is just 3A in the long leg and 27A in the short leg, which is greater than the cable rating.
Simply amazing.

I challenge your calculation as being bogus numbers that you made up from merely the relative lengths.

Obviously any wire carrying the 27 A would heat up, its resistance would rise, and the current would favor the cooler but somewhat longer path. This would tend to equalize current in both directions. I don't have an equation for this. But the result will be much, much better than 27:3.

>Obviously if the tap point was less than 10% from the end of the ring, the imbalance would be even greater.
It is not obvious to me.

>I'll concede that in most situations an overload is unlikely, but it is possible.
I imagine that if you put a 30 A load on a 25 A cable, overloading just might be possible.

>For best current distribution, design the heaviest loads either into the mid-section of the ring
That sounds silly to me.

> -OR- put heavy loads likely to be on simultaneously at opposite ends of the ring to balance the current as much as possible.
Again, this is silly.
If the ring can withstand a heavy load at each end, then why can't it withstand a heavy load at one end when the load at the other end is not operating?

(What you are saying could make sense for an American 240 V system in terms of minimizing current on the GC.)

>I would still rather run separate, dedicated branches for such loads.
I also would if the ring is not of sufficient ampacity to haul the current.

Regardless, I don't see how interconnecting reasonably short rings can place an overload at a point on a given ring if the total load or the second ring would be permitted at an outlet on the first ring.

Not exactly true. Connecting the new wiring so that it becomes part of the existing ring will increase the overall resistance of that ring. The extra load on the new wiring will then be farther along the ring than if it were joined figure-8.

>>as far as the old ring is concerned, it represents a 25A load at a point just 12 ft. from on end.
>Which is perfectly acceptable, right?
I mean there is no problem to the ring is 25 A were loaded at that point, right?

You're getting close to the crux of the matter now. At this loading the short leg of the ring would be carrying 22.5A (starting cold & accepting that the resistances will change slightly as the cable warms up).

The cable ratings per current (1992) IEE Regs. are:
Clipped direct (i.e. surface run), 27A
In wall in trunking, 23A
Buried in thermal insulation, 18.5A

So even this far, it could be borderline. And to be frank, I think the 27A surface rating allowed these days is too high anyway. (This wire is about 20% greater CSA than your #14.)

The IEE in general figures that it's unlikely for two 3kW loads to be plugged into the same twin socket.

OK, now look at a secondary ring spliced figure-8 at the same point on the old ring. As this new ring will be feeding outlets spaced apart, and maybe even in different rooms, it's considered far more likely that two heavy loads (e.g. 3kW each) could be connected simultaneously.
As far as the old ring is concerned, this is equivalent to two 3kW loads at the same outlet at that 12-ft. point, which we've already seen is borderline at best. And that's before we've allowed for the extra 1200W available which could easily be on the original outlet.

I'll admit that a similar situation could arise with a "legal" system. Example: The same original ring with a spur at the 12-ft. outlet to another single socket. Any combination of 2 x 3kW plus 1 x 1.2kW on these three sockets would give the same result of putting the whole 7.2kW load at the 10% point on the ring. Again, the IEE considers it unlikely that this would happen, though of course it is possible.

>I challenge your calculation as being bogus numbers that you made up from merely the relative lengths.

Do you agree that the proportions are correct when starting with cold cables?

>Obviously any wire carrying the 27 A would heat up, its resistance would rise, and the current would favor the cooler but somewhat longer path. This would tend to equalize current in both directions.

True. Perhaps the argument comes to just how much the temperature rise would affect the balance. Does anyone have a temperature coefficient formula for Cu conductors to calculate this?

>>Obviously if the tap point was less than 10% from the end of the ring, the imbalance would be even greater.
>It is not obvious to me.
How so? The resistance in the short leg would be reduced and that in the long leg increased by the same amount.
The initial imbalance would have to be greater, so are we just back to how much the heating effect would change this?

>If the ring can withstand a heavy load at each end, then why can't it withstand a heavy load at one end when the load at the other end is not operating?

Maybe I phrased my point about this rather badly. Bearing in mind the above points about the short "home legs," what I meant was that if one heavy (3kW) load has to be connected close to one end, a second similar load would be better on the opposite side of the ring rather than very close to the first.

Best OVERALL balance around the ring is achieved with the load distributed as evenly as possible around it.

>Regardless, I don't see how interconnecting reasonably short rings can place an overload at a point on a given ring if the total load or the second ring would be permitted at an outlet on the first ring.

I hope I've shown that an overload is theoretically possible with a "legal" system. A secondary ring with several outlets just makes it more likely to occur if the point of contact between the rings is at one end of the primary ring.

I agree though, that if the secondary ring feeds just a few sockets in low-load ares, it is extremely unlikely.

>Connecting the new wiring so that it becomes part of the existing ring will increase the overall resistance of that ring. The extra load on the new wiring will then be farther along the ring than if it were joined figure-8.
In the U.S.A. we wouldn't see that as a good thing.

>At this loading the short leg of the ring would be carrying 22.5A
My question was whether a figure-8 was allowed for an extension. If the ring is overloaded at any point, it is overloaded regardless of how the loads are attached.

What I see from this is that a ring really doesn't buy you double the ampacity except for a load at a point that is equidistant from both ends of the ring.

> it's considered far more likely that two heavy loads (e.g. 3kW each) could be connected simultaneously.
What is considered does not alter reality.

>As far as the old ring is concerned, this is equivalent to two 3kW loads at the same outlet at that 12-ft. point, which we've already seen is borderline at best.
The fact continues to be that heavier wire should be used or there should be complete separation.

>I'll admit that a similar situation could arise with a "legal" system.
My point exactly. There is really no new hazard with a figure-8 that wouldn't exist in a larger single ring.

>Do you agree that the proportions are correct when starting with cold cables?
Sure. I'd even agree that they might be worse than you state.

>Does anyone have a temperature coefficient formula for Cu conductors to calculate this?
Sure. But that is a side issue. Nothing will eliminate the overload except sifficiently sized conductors.

>what I meant was that if one heavy (3kW) load has to be connected close to one end, a second similar load would be better on the opposite side of the ring rather than very close to the first.
My point being that the ring is assumed to withstand this. So it should also withstand the load at one end being on while the load at the other end is off. As far as current goes, that's the same as adding a sub-ring close to one end.

>I hope I've shown that an overload is theoretically possible with a "legal" system.
Yes.


[*] What you've shown me is that a ring topology has no safety advantage over a linear topology or the American star topology.


[*] U.K. ring systems may be operating way over conductor ampacity just because of incorrect assumptions about the load distribution; whereas the NEC protects ungrounded conductors based on their so-called actual ampacity.


[*] The system is premised on the idea that more resistance is better. I have never thought of balancing electrical loads by increasing the length of the path back to the source (RF loads are a different story).
Even if I had learned nothing else, your discussion with me got me thinking outside the old box.

Thank you!


[This message has been edited by Dspark (edited 09-29-2001).]

Well, I'm glad it's got everyone thinking about different arrangements.

>>Connecting the new wiring so that it becomes part of the existing ring will increase the overall resistance of that ring.
>In the U.S.A. we wouldn't see that as a good thing.
No arguments from me there. Higher resistance = higher voltage drop = more power loss.

>My question was whether a figure-8 was allowed for an extension.
Whatever the rights or wrongs of it, the short answer according to the IEE is "No."

>What is considered does not alter reality.
Wow, I think we're finding more points to agree on now!

I agree that what the IEE considers "normal" or "reasonable" loads is often in conflict with reality, and the ring system is not completely foolproof. When I say "It's considered that" I'm just passing on what the IEE publications quote as the reasons; I don't necessarily agree with all of them.

>The fact continues to be that heavier wire should be used or there should be complete separation.

For foolproof ring circuits fused at 30A, yes. But the next size up is much bulkier & harder to work, so I'd rather just forget the whole ring concept altogether.

>My point exactly. There is really no new hazard with a figure-8 that wouldn't exist in a larger single ring.

Well, I can still see the IEE's point of view to a degree: That with a sub-ring with several sockets there's more chance of a larger load than a single spur soket.

But, thinking about it, it would be possible to wire a compliant ring with three outlets within the first 12 ft. of ring, each with a spur to a single outlet elsewhere. Given the wrong loading, this could even be worse than a three-outlet sub-ring tapped figure-8 at 12 ft., so I do see your point.

>

[*] U.K. ring systems may be operating way over conductor ampacity just because of incorrect assumptions about the load distribution;

I think that sums the situation up quite well. As I said, it's not foolproof.

If you look back at earlier threads on rings, you'll see I said that personally I don't like them. Thanks for making me think hard about it again and remind myself of one of the reasons why!

Everyone else is remarkably silent on this topic. Or were they just waiting to hold our coats?!

That last one is probably a British expression!

Had you been fond of rings, it might have been a different outcome.

why jump in when you are doing so well?

boy reminds me of US power distrobution... underground cables feeing transformers are set up in loops so to speak... heres an example: Bø ~---TX---TX --TX--TX--~ Bø all transformers can be fed from 2 places when theres an open in one segment.. theres usually one transformer thats a "normally open" so the loop gets fed from one side to the normally open, and the other side from another riser, should a segment fail, they just move the normally open and feed the transformers more on one side, fewer on the other.. power is still on though. we also call transformers fed from one source radial feeds... im interested in british power distrobution, and ive often wanted to work in england as a utility worker, or even a regular electrician.. id do it, if i could find some good food.. lol tell me pauluk, whats the house service? a single leg of 240 to ground or what? how do they meter it, and whats a usual service amprage size?

-m

Merritt:
The big HV distribution stuff is a little out of my league, but I do know that they also use a system similar to that which you described for the feeders to local xfmrs.
Yes - Residential service is normally just a 1-ph 2-w service with neutral and a hot leg at 240V to ground. In all but the odd remote property, residential services are just tapped off one phase of the standard 3-ph 4-w 240/415V wye.
Metering is just a simple 2-w meter although many people have the "Economy 7" tariff with a dual-reading meter for cheaper rates at night.

Most new services for all-electric homes are 100A, although 80A is still being installed for lower demand homes.

Older services are often lower: Many installed up until the late 1970s were 60A, and there are sill a few 40A (and even 30A) services on old houses that haven't been upgraded.


[This message has been edited by pauluk (edited 10-09-2001).]

hmm.. where are the secondary transformers located? when i took a trip to london 2 years ago i didnt see any "pad mounts" or anything... do they use manhole systems or what? also how is power distrobuted in london.. i dont recall seeing any powerlines at all...

-m

This thread is getting kind of long and gone on to other matters, so I think I'd best start up another one for this.

Take a look a "UK Power distribution."