The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured Items:

Switch Bit - Interchangeable Flex Bit System
>> Switch Bit -
Interchangeable Flex Bit System

>> 2014 NEC and Related

Recent Posts
Looking for a new truck
by sparkyinak
Yesterday at 09:52 PM
Australia-wall boxes not required
by Owain
Yesterday at 10:44 AM
Burnt meter leads testing receptacle voltage
by mbhydro
08/31/14 07:30 AM
Markings required on Disconnects, OCD,ect
by HotLine1
08/27/14 08:21 PM
Circuit Breaker temperature ratings and the CEC
by twh
08/23/14 11:55 PM
New in the Gallery:
Copper Theft
Shout Box

Top Posters (30 Days)
gfretwell 16
HotLine1 11
Potseal 7
captzap 4
arctic_wire 4
Who's Online
1 registered (Texas_Ranger), 119 Guests and 6 Spiders online.
Key: Admin, Global Mod, Mod
Page 3 of 4 < 1 2 3 4 >
Topic Options
Rate This Topic
#146299 - 11/30/06 04:40 AM Re: GFCI vs. RCD
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Quote:
Seems the term ELCB was still in use when they were installed though.

I'm trying to remember when RCCB came into use as the replacement term for a current-operated ELCB. I don't think it was until the early 1980s.

 Quote:
Does anyone know how this change of terminology happened ?

I'm not sure why the change was ever proposed in the first place. And although RCD might be easier to say than RCCB, that was an even more ridiculous change. Why replace the more descriptive term circuit breaker with the vague device anyway?

Although RCD is now the "official" name, I know that at least a couple of years ago Crabtree was still labeling some units as RCCB.

 Quote:
ElCBO is also so much easier to say than RCCBO.

Just to confuse things even furthe, over here the combination overcurrent/earth-leakage breaker is now generally referred to as an RCBO (only one C).

Top
Test Equipment:

Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement
Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement

#146300 - 11/30/06 04:59 AM Re: GFCI vs. RCD
Wolfgang Offline
Member

Registered: 09/25/05
Posts: 154
Loc: the very West of Germany
The only advantage of the renaming is that the English abbreviations are taught in other countries also. (Theoretically) every German electrician should know the terms RCD (common), MCB (rare) and RCBO (also rare).

Top
#146301 - 11/30/06 09:51 AM Re: GFCI vs. RCD
djk Offline
Member

Registered: 12/26/02
Posts: 1269
Loc: Ireland
I've seen Hager units here multi labled in French, German and English

RCB, FI, Differential

Siemens Ireland seems to have always had its own labeling though. The details on the old RCD are

Siemens - Made in Germany
Current Operated Earth Leakage Circuit Breaker
30mA
60A
Diagram of the circuit and test instructions explaining how to find an earth leakage fault by unplugging all appliances connected to the sockets, resetting the breaker and plugging them back in one by one.
Calling an electrician / having the faulty appliance professionally repaired or disposed of.

Other than that there's a 2 pole RCBO for the shower and 10A RCBO covering lighting in the bathroom and outdoors. (Modern ABB units, much smaller than the old siemens one)

[This message has been edited by djk (edited 11-30-2006).]

Top
#146302 - 11/30/06 10:52 PM Re: GFCI vs. RCD
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8470
Loc: SI,New Zealand
One thing that has to be remembered about a plain vanilla Residual Current Device.
That's all it does, is sense an imbalance between Phase and Neutral in a circuit.
A RCBO, has two functions, it senses like the RCD does, but it has the features of a Circuit Breaker built in to it.
The term RCCB and ELCB mean the same thing.
However, Voltage Operated ELCB's were a different kettle of fish, they were only used where the basics of earthing could not be provided and used to trip if the voltage got above 22VAC, with reference to earth (cold water pipe).
They were used here in places at (usually) the ends of long spur lines, where the ground was so rocky that if you went to sink a rod, the thing would either bend and come up a foot or so away from where you were driving it or on the first hit, would disappear into oblivion below.
They used to be really bad things, trip at night when the soil temperature dropped below a certain value.
Considering that they were sealed by the local Power Company here, the Home-owner was not allowed to reset them.

{Message edited to remove a few typo's}


[This message has been edited by Trumpy (edited 12-01-2006).]
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

Top
#146303 - 12/01/06 06:09 AM Re: GFCI vs. RCD
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8470
Loc: SI,New Zealand
BTW Dave,
I think I must have mis-understood you, in your post about the Isolating Transformer and the RCD.
We have plates here that have both for bathrooms in hotels.
As in a Shaver socket, that would be the Isolating Tranny and anything else would be fed via the RCD.
However, I'm interested to know if a Selective Type RCD would be used up-stream of the 30mA unit in the bathroom?.
Type S being 100mA?.
I know that Aussie uses them, and we should do, but what is common in Ireland and the UK?.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

Top
#146304 - 12/01/06 09:32 AM Re: GFCI vs. RCD
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Quote:
One thing that has to be remembered about a plain vanilla Residual Current Device. That's all it does, is sense an imbalance between Phase and Neutral in a circuit. A RCBO, has two functions, it senses like the RCD does, but it has the features of a Circuit Breaker built in to it.

There's certainly some confusion in the less enlightened DIY circles here as to the difference.

In this regard, the American GFCI fitted to a panel to protect one branch circuit is thus equivalent to the RCBO here (except for the lower trip current).

 Quote:
However, Voltage Operated ELCB's were a different kettle of fish, they were only used where the basics of earthing could not be provided and used to trip if the voltage got above 22VAC, with reference to earth (cold water pipe).

For those across the pond who are having trouble visualizing how these devices worked, have a look at this diagram , which is in the U.K. power systems thread in the reference area.

This shows how the voltage ELCB was wired to provide whole-house protection. Note that the protective grounds from throughout the house are not grounded directly but are instead connected via the operating coil of the ELCB. The rod connected to the other side of the coil to provide an earth reference had to be located outside of any overlapping resistance gradient of other rods/pipes.

 Quote:
Considering that they were sealed by the local Power Company here, the Home-owner was not allowed to reset them.

What was the idea behind that?

The British ELCB was/is part of the homeowner's apparatus, and thus fully accessible for reset (or for testing with the button which deliberately connects the line to the coil through a suitable resistance).

Although obsolete for a good many years, there are still plenty of voltage ELCBs still in service in rural areas.

See this thread for some pictures of a typical old voltage-operated ELCB as used in domestic wiring:

Voltage-Operated Earth-Leakage Circuit-Breaker


[This message has been edited by pauluk (edited 12-01-2006).]

Top
#146305 - 12/05/06 03:27 AM Re: GFCI vs. RCD
Kenbo Offline
Member

Registered: 04/07/06
Posts: 234
Loc: Scotland
Reno

Here is a diagram of the RCDs used here in the UK

Sory it is on this web site (Paul) but it appears to be the best diagram I can see to explain how it actualy works. (I use the same one to explain it to my students)

RCD diagram
_________________________
der Gro├čvater

Top
#146306 - 12/05/06 07:24 AM Re: GFCI vs. RCD
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5016
Loc: Blue Collar Country
Thanks, Kenbo!

Top
#146307 - 12/05/06 09:05 AM Re: GFCI vs. RCD
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Quote:
Sory it is on this web site (Paul)

Well, at least that website is good for something!

Let's go into a little more history, starting with the typical domestic installation of the 1960s. The situation is complicated in the U.K. by the different types of earthing arrangements employed (see link to U.K. power diagrams above).

In areas served by TN-S (installation grounded by a completely separate conductor right back to the transformer) or TN-C-S (grounded to the neutral, American-style), ground-fault protection normally relied upon the regular fuses or MCBs (overcurrent circuit breakers). In rural TT areas (installation grounded only to a local rod) though, the loop impedance could be far too high to blow even a 5A fuse on a lighting circuit, nevermind a 30A fuse on a ring or range circuit. So in houses fed by TT, it was necessary to fit a main ELCB to provide ground-fault protection to the whole installation. This was normally the voltage-operated ELCB described above at that time, but current-operated ELCBs could also be used, often with 300 or even 500mA trip in the earlier days.

Since that time, the voltage ELCB has become obsolete, the current-operated ELCB became the RCCB/RCD and the trip current reduced, first to 100mA and then to 30mA which is the norm today.

Under the current Regs., RCD protection at 30mA is required for any outlet which is likely to be used to feed equipment outdoors (it is also needed on any other circuit in which the loop impedance and operating time of the overcurrent device cannot provide disconnection within the specified time, but that would be rare in a domestic setting).

So, we have some circuits which need RCD protection and some which do not. In TN-S/TN-C-S houses, that gives several options. We could fit an individual RCBO for each branch circuit which requires RCD protection. Unfortunately, even though costs are dropping the RCBO is still relatively pricey here, so for anything more than a couple of circuits it can soon become very expensive.

The alternative, and more common solution to date, has been to use a split-load board. There is a simple main isolator switch (not circuit breaker) for the whole board, then circuits which do not require RCD protection can be put on MCBs straight onto that main bus. The bus also feeds to a sub-main 30mA RCD, then circuits requiring RCD protection are placed on MCBs on that RCD bus. Thus a ground-fault on a circuit still knocks out more than just that one circuit, but not the whole house.

In rural TT areas -- where all circuits need RCD protection simply due to the high loop impedance -- it's still common to find just a single main 30mA RCD which protects the entire system (or a 100mA RCD installations dating back to the 1980s). That's far from ideal though, and it has led to wider use of the split-load board with two RCDs.

This works in a similar way to the split-load board on a TN-S/TN-C-S system, but with a 100mA delayed-trip RCD in place of the main isolator switch to guarantee that a fault on the 30mA bus will trip that sub-RCD and not the main one.

Below is a typical split-load board, main switch on the right, 30mA RCD protecting the left-hand part of the board. For TT use, we'd swap the main on the right for the 100mA delayed RCD.


Top
#146308 - 12/06/06 04:56 PM Re: GFCI vs. RCD
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8470
Loc: SI,New Zealand
Paul,
 Quote:
What was the idea behind that?

This happened (so I'm told by an older Faultsman) because a guy up on a farm tried to bypass the unit one day back in the 60's and nearly burned himself to death after he tried to tie the wrong wires together to re-instate the supply to his house, the pole fuse down the road never tripped because of corrosion.
After that, all of the units sported covers over the entire unit, except for a red neon that showed if the unit had tripped.
Our Deputy Chief Fire Officer also confirmed this story, apparently half the house was lost as well.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

Top
Page 3 of 4 < 1 2 3 4 >



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals