Here's a typical modern residential panel using MCBs (plastic see-thru lid raised):



And here's the bit you really want to see :


Note that we never bond neutral to ground in these panels, hence the separate bars. (Yes, I know it must look funny to you to see all those black wires connected like that! )




[This message has been edited by pauluk (edited 07-16-2002).]

The individual conductors of the feeder/source look unusual by typical US practice. Even though it is assumed to be grounded-240V service, that looks like a 2-pole main breaker. Aside from being 2 pole, is an integral “panelboard main breaker” required even with the fused pullout ahead of the meter? The load cables out of the tops of the branch breakers are unexpected. {Black versus white neutrals seem more logical.}

Oddly, the red and black pair into the main breaker look coincidentally and perfectly normal, but at this end that would signify the two ungrounded poles—each 120V-to-ground.

There will always be more than one way to skin a cat.

Two more…what is the interrupting rating of the panelboard {ehh, sorry—consumer unit?} and breakers? Are nonmetallic enclosures the norm? They are fairly limited west of the pond. Seems they would be safer to work on while energized.

Paul—thanks for taking and posting the pictures. One thing about digicams—isn’t it nice not to have to send film out for processing?


 


[This message has been edited by Bjarney (edited 07-17-2002).]

Yes, this is a normal residential 2-wire 240V service tapped from a 240/415V wye system in the street.

Single-phase boards here always have a double-pole main switch which opens both hot and neutral conductors (although 3-ph panels just have a bolted neutral and a 3-pole switch). The main isolator is required despite the presence of the main fuse pull-out, because the latter is sealed by the power company (it's illegal to break the seal).

Note that the main on this panel is just a switch, not a circuit-breaker. These modern DIN-rail panels have interchangeable units, and if this were on a service where grounding is only to a local rod, then a main GFI would be substituted for the switch. Again, such a GFI provides only ground-fault protection, not over-current protection. On older style panels, where a main GFI was needed it was fitted as a separate unit and the main panel would still have a D.P. switch.

In general, having a switch open the neutral is far more common here than in North America. For example, the isolation switch on the "cooker control unit" I posted elsewhere also breaks both sides of the circuit, and isolation switches for fixed room heaters are also double-pole. Even some receptacles now have D.P. switches incorporated.

All-insulated enclosures are pretty much the norm for residential work. In fact, where the house ground is just to a local rod (i.e. many rural areas), the enclosure has to be non-metallic, otherwise a short on the supply side of the main GFI could leave the enclosure energized. (Where the GFI is separate to the distribution panel, the panel can be metal-cased, but the GFI enclosure has to be insulated.)

These C/Bs are GE types rated at 6000A breaking capacity. C/Bs are allowed to have an interrupt rating less than the PSCC (prospective short-circuit current) so long as a protective device upstream is suitably rated. The PoCo-owned cartridge fuse satisfies this requirement.


This has become the standard layout on these panels now, with the ht busbar running along the bottom.


Just what people are used to I guess. Over in Continental Europe they don't associate black with neutral.

Glad you're finding them interesting. Digicams also make it so easy to destroy all evidence of your not-so-successful shots!

(Good to see your name over on Telecom Digest, by the way!)



[This message has been edited by pauluk (edited 07-18-2002).]

This panel looks exactly like what we use in Austria, except for three points: We commonly have double pole breakers fusing the neutral as well. Single poles are allowed but double poles are generally considered safer. 2nd: On every type of service we have a main GFI protecting all circuits. 3rd: Those comb arrangements aren't common here. I've seen one recently, to be exact three combs balancing the load on all three phases. Pretty nice to have these uninsulated combs 1 cm away from a makeshift metallic panel cover! U-shaped jumper wires are more common and in this case would have been safer.

I think connecting the feed to each breaker with a wire link must be another common European trait, as it's done in France as well. It's rare in the U.K. though, except in the case of some small DIN-rail enclosures where there are perhaps just one or two C/Bs.

There's nothing in our rules to prevent the use of a double-pole C/B opening both hot and neutral, but it's not usually done that way (I don't remember ever seeing such an installation). GFIs are a different matter, as they always open both sides of the circuit.

I can see a practical advantage of using D.P. breakers where there is a main GFI. If you turn off a C/B to work on one branch circuit here, although it's safe to touch the neutral is still connected through that GFI. If you accidentally short the neutral to ground (e.g. while cutting a cable) it's possible to trip out the main GFI. (Really annoying if you're working in an attic and your floodlight goes out!) No big deal really, but it means having to open up the panel and disconnect the branch neutral instead of just flicking the C/B off.

By the way, many new installations here do have a main GFI even when not actually required.

Here is a Wylex brand "Standard Range" distribution panel. This one is the metal-clad version, but insulated versions were more common in residential applications:


The separate front cover unscrews to reveal the fuses. In this case I've put just one fuse in and left the other positions either with just the terminal covers or bare so you can get a better idea.

Each circuit position is fitted with a plastic cover which (a) insures that the energized busbar is covered and (b) by the size of the slots prevents the insertion of a higher-rated fuse carrier. The covers and fuses are color coded according to the system I mentioned elsewhere:


And here's the panel (blush!) naked, so to speak:


Note again the double-pole switch which opens hot and neutral.

These Wylex "Standard Range" units remain quite popular, partly because the basic design has not changed in over 40 years (*). It is still possible to obtain replacements for old installations, and in fact Wylex still manufactures this range of panels.

Another reason for their popularity is that the same units can take rewireable fuse carriers, cartridge fuses, or circuit breakers. Upgrading an old installation which has rewireable fuses just requires the replacement of the individual covers and the fuse itself -- No need to even remove the main front cover.

The rewireable fuse was at one time the most common in domestic systems. The prongs are different sizes/spacing to prevent the insertion of, say, a 30A carrier into a position fitted with a 15A cover, but of course there is nothing to stop somebody fitting the wrong size fusewire (very common!), or worse yet a straightened out paperclip! (A favorite trick ) :


Cartridge fuse carriers offer better protection, as a larger cartridge fuse won't physically fit into a smaller carrier (I do sometimes see blown fuses bridged with a piece of wire though <Sigh!> ):


Circuit breakers for this panel are also a plug-in type, using the same back covers as for cartridge fuses. You just have to replace or cut out the center of the front "fuse" cover when C/Bs are employed.

(*) Compare with the old 1966 ad posted here . (The ad is for a one-way "switch-fuse", but multi-branch panels were similar.) You can't get them in brown now, though, and the plastic cases on the new ones are thinner.



[This message has been edited by pauluk (edited 07-27-2002).]

Here's what you find in a typical house where extra circuits have been added over the years:



Anyone like to have a go at following this maze of wiring before I explain the details?

Paul,
I've been going through a few OLD threads and seems there are a few more people at ECN from the UK, these days, I wondered if they would care to comment on these photo's?.
Regarding your fuse carriers in the UK, do yours have little apertures on the front for testing a fuse while it is still in the fuse base?.
Also, with respect to that bottom pic, is there no requirement in the UK to rip out the old stuff and start again, when adding new circuits?.(with respect to the multiple consumer units)
Over here, a new, larger swithboard would have to be installed, during any upgrade or substantial increase in loading.
That is a real mess!.

Good idea to revive some old threads from time to time so that our newer members see them.

This installation had night-storage heaters, so there had to be at least two distribution panels. The top unit is the main panel feeding most of the regular circuits in the house. The small two-way consumer unit below and to the left of the main panel was an addition for a couple of extra circuits.

It wasn't at all unusual in older properties to find extra panels like this added when the need arose rather than a replacement unit big enough to take all circuits. Around here, they're typically added to run an electric shower.

The remaining panel below and slightly to the right of the main panel is energized only during the nighttime to charge the heaters.

The unit to the right of the meter is a PoCo-owned radio-teleswitch which switches the meter to its low tariff and simultaneously closes a contactor to apply power to the heating panel (usually Midnight-7am winter, 1am-8am summer).

On the fuse carriers, we don't have apertures on the front for testing with a voltmeter. The Wylex cartridge fuse carriers pictured above have a small hole in the front centered over where the fuse goes to enable you to see (a) that a fuse is actually fitted, and (b) the rating of that fuse (which you can tell by the color of the body).


[This message has been edited by pauluk (edited 08-23-2003).]

Paul,
What I meant with respect to the small aperture available for testing fuse-links, is actually shown on the front piece of the fuse carrier in pic No.6, as the little white plugs on the front of the fuse carriers.
But, in a situation like this, these plugs are quite useless.
It's only with Fault-finding 63A+, including 100, 200, 400, 600 and 1000A Mains that I have come to realise that these plugs are only effective where the fuse heating is kept to a minimum, otherwise the plugs turn to one solid mass and trying to get the tip of your Duspol through one of these is futile.
In a Domestic Switch-board, I normally open up the panel and test from the reverse side.
Just saves a lot of time!.

Paul,
Sorry, but I never had a close read of your comments in your above post.
Am I assuming that a system of different boards for different Rates applies, in the UK?.
I see that the Consumer unit above the Service Fuse has a large cable exitting it, would this be for a Shower?.
Over here, we would normally supply a Night-store heater or Hot water cylinder from the same board, but it is normally fed from the Meterboard(outside, usually) via the Ripple Relay+ Pilot Wire.
As a rule, an MCB, is fitted to the left side of the Main Switch or a Multi- DIN Rail Board is fitted and all of the Night Rate equipment has it's own Rail.
This just keeps everything tidy and makes Fault-finding easier.

I've never known the little plugs on the fuse carriers as anything other than a way to cover up the live fixing bolts and identify the fuse carrier rating (in the picture above, white=5A).

Yes, on many installations it's quite normal to have a separate distribution panel for the nigh storage heaters. In the photo above, power from the service fuse and neutral block goes straight into the meter. You can also see some smaller cables from the blocks which feed power to the radio-teleswitch, purely for its control side (via the fuse which is located below the meter). The thin cable running from the switch to the meter is the control line causes a solenoid in the meter to mechanically transfer the drive from the normal-rate dials to the night-rate dials.

From the meter, the cables go into the bottom of the main RCD, and from there into the large black junction box at the upper right of the picture. Two pairs of cables go straight from that box to the main panel and the smaller additional panel. (And yes, the cable emerging from that panel did go to a shower, as I recall.)

From the junction box, there is also a neutral taken directly to the night-heater panel, but the live side is run via the contactor terminals on the radio-teleswitch.

It's not too clear in the photo, but if you look to the right of the main unit, behind the cables going into the black junction box, you might just be able to make out that there's an earthing block there linking the earth on the panels and providing bonding and connection to the local ground rod. (This is a TT installation, so there's no earth-neutral bond at the house.)

This is a typical arrangement which applies power for heating only at night, but which also switches the meter so that everything in the house benefits from the low night rate.

There were older schemes which had a second meter fitted and a timeclock to feed the heating panel. It was only the heaters which benefited from the cheap rate, as the main panel remained on the standard-tariff meter all the time. Many people still talk about "white meter" rates, as this was the color of the low-rate meter used on these dual-meter setups.

New installations with DIN-rail mounted breakers can indeed use a split bus arrangement and put the night-heater circuits in the same panel.

Paul,

That's completely unlike anything used here for night rate heating "NightSaver".

Over here on very old installations you'd have 2 seperate meters with the heaters connected to the night rate one via a big electromechanical timer that flips them on at midnight. Each heater would be on it's own 16 / 20 amp diazed fuse on a seperate panel. (If the heating system was sufficiently large it was a seperate 63 amp supply)

(The really old timers were quite noisy, ticked all the time.. but were always located in a garage or in the meter cabinate )

On newer installations a split bus would be used on the night rate heaters including a DIN rail mounted timer arrangement. Each heater would have appropriate radial MCB (16/20 amp).

The meter either includes an electromechanical timer that trips it to the night rate dial or else is fully digital and just automatically goes into night mode after midnight. in this case the whole house gets night rate not just the heaters.

In the newer setup's the water heating system would also be timed (seperately) to power up and heat over night. In older systems they would have gone as far as having a day and night immerision element in one tank! (It was cheaper than interlocks and timers)

The dual-meter system with a mechanical timeclock sounds very much like the old white-meter system that was used here. I don't think any PoCo still offers it as an option, but there might be a few still in use somewhere.

The storage heaters here also use individual radial circuits, one per heater, rated 15/16 or 20A.

Water heating arrangments vary somewhat. In setups such as the one pictured above and where there is only a single element, it's quite common to install an individual timer for the immersion heater which can be adjusted by the homeowner as required, and also allows for manual boost during the day.

Dual-element systems used to be quite popular, sometimes with the main (lower) element wired to the night meter circuits and the smaller (upper) element on a manual switch with power available all day.

A common sight at one time was a twin switch, one marked ON/OFF and the other SINK/BATH, which transferred power between the upper and lower elements.

While we're on the subject of water cylinders and immersion heaters, the cupboard into which the cylinder is built here is generally called an airing cupboard.

I noticed that in Ireland you seem to use the term hot press. Any idea how this originated?

Pretty simple really:

Press = cupboard over here. (Kitchen cabinates are usually called presses)

and in the case of an airing cupboard it's hot inside.. hence it's a "hot press"

They are around quite a while, pre-dating electrically heated immersion heaters, old ranges often heated water cylinders that would have been located in a "hotpress" in the kitchen.

Also, our wiring regs have pushed away from mounting the controls in the cupboard itself, due to a risk of over heating, they are now supposed to be flush mounted on the wall outside.

We never had a white meter we just had 2 big massive black siemens meters and a timer that was almost the same size, also siemens, sitting in the middle.. (all sealed by the ESB). The distribution board (consumer unit) would have been much bigger though. Big old diazed unit with maybe 10 fuses.

At least DIN rails & electronnics etc have made things a little neater

The system was and still is called "NightSaver" and had a terribly corny song to advertise it... something along the lines of "sparkling clean dishes and clean dry clothes, night saver's the answer and here's how it goes.." (shudder)

There are also "GoldShield homes". This is an ESB programme to build homes with integrated electric heating (storage for background, local boost heating, under-floor heating, electric showers, electric water heating (often done in a super-insulated tank more like those found in other EU countries than in the UK) and extremely high levels of insulation. The larger homes are sometimes supplied with 380V power for the heating systems.

It was popular but it's not as flexible as gas fired radiator systems and I don't think the ESB is currently encouraging people to opt to use vast amounts of power, at least until the network capacity catches up with the recent explosion in consumption.

I hope you didnt connect that consumer unit Paul,,,,,,,, rather untidy..

you will be giving them bad ideas on how we do things over here in the UK

Nope, not my work! That's just how it was when I arrived.

DJK,
Thanks for that. I didn't realize that press=cupboard. Hot press makes perfect sense now I know that!