In House Electrics, Where Do I Go From Here?

[eraymos]

Just install a dual RCD Distribution Board, as is the standard in the UK, and make sure you have a earth at any outlet that will have a possibility of having something plugged in that has a metal casing, and any wet areas.

Is it something like this that you are talking about?

[Forkinhades]

Yep, that's the one

[Forkinhades]

Also, in the UK, the recommendations are such that, in any room, after one rcd has tripped, you will either have a light or socket that still works. Easy enough to design

[Artisi]

Agreed mostly, but will point out that earthing WILL protect a person from direct contact if the value of the earth has a low enough impedance, (which is very difficult to get here in thailand)

Also would like to point out that I have installed a dual RCD DB in my house here in Thailand, so every circuit is protected by an RCD, and when I did the changeover, I found that I had 3 'borrowed' neutrals. Now while this is not considered a problem when everything is up and working, it WILL become a problem for you budding DIY enthusiasts. For when you isolate a circuit that has a borrowed neutral, (for upgrades repairs etc etc) although the 'live' cable is dead, the neutral will become live, and there is a very high risk of shock, but if you had a DUAL RCD DB, installed, then when you touch the 'live' borrowed neutral, the RCD will trip and protect you, but if you split 2 neutrals and hold one in each hand, then you ARE dead! even an RCD will not protect you!

I would appreciate a bit of expansion on the detail in your second paragraph - just want to make sure that my understanding of what you have said is in actual fact correct. Especially "borrowed"neutrals and dual RCD DB .

Thanks

[Crossy]

I would appreciate a bit of expansion on the detail in your second paragraph - just want to make sure that my understanding of what you have said is in actual fact correct. Especially "borrowed"neutrals and dual RCD DB .

A dual-RCD (or 17th edition) board is a bit like the split-service board shown here http://www.crossy.co.uk/wiring/Consumer.html except that both sides of the board are RCD protected rather than just one.

A 'borrowed' neutral, refers to when a circuit has been wired using a live and then using the neutral from another circuit because it was convenient, this often happens when you have 2-way (3-way to our US cousins) light switching, it's easier to borrow a neutral than to wire it properly. The issue is that although you've isolated the circuit you're working on, it's possible for that neutral to become hot and bite.

[Forkinhades]

If you are doing a new install, and feel confident enough to do the wiring, or can oversee the wiring, then a borrowed neutral should not happen. This is another reason why the electrics should be tested and certified here in Thailand!

Although having said that, you would NOT normally test for a borrowed neutral in the UK, but here in Thailand I would test for it, quite easy to find if you have an earthed system, if not the testing procedure becomes a little more time consuming, and a dual rcd board will in general pick any problems up, as it will keep tripping the RCD's.

Like I said before its only dangerous if you are working on the circuits, not after the install has been completed. In the UK it is considered very bad practice to 'borrow' neutrals.

I know of two people here in Thailand that got shocked when they was changing outside lights, they isolated the circuit, tested the cable with a neon screwdriver (an absolute NO NO for me, must use proper test equipment), neon stayed off, so they proceeded to work on the circuit, and both got thrown across the garden!! with the borrowed neutral! that became live

Edited April 6, 2010 by Forkinhades

[bankruatsteve]

"Borrowed" neutrals are not allowed in US code, I doubt any other code. That's a no-no.

Edited April 6, 2010 by bankruatsteve

[Forkinhades]

Pretty sure it is in BS7671, not sure of the reg number though

[Crossy]

Pretty sure it is in BS7671, not sure of the reg number though

Try rule 314-01-04 of BS7671 16th Edition (don't have a 17th).

For those not sure how a borrowed neutral can become live have a look here Book1_Borrowed_Neutral.pdf

[Forkinhades]

Very good reading indeed!

Just goes to illustrate why qualified Electrcians have to spend 3 - 5 years training, on site, and at college!

Now all you DIY ers, still fancy doing your own electrical work!

[bankruatsteve]

Just to have discussion - maybe new thread? Anyway...

Why do some of you think RCD circuit protection is "good"?

To me (and with consideration to underlying physics and psychics), ground wire protection is good enough for most applications. I can go along with GFI protection at point of contact (in socket) like in wet areas (bathrooms, outdoors) - but otherwise I just don't get it.

My reason (opinion): chance for electrocution or even more than a tickle in properly wired (with grounded) circuits seems like it is so low that it just isn't worth that expense.

Can you convince me otherwise?

[powderpuff]

Yes absolutely. Have done so in the past & will do so in future.

Wiring up a 2 way is dead simple.

The only neutral goes to the fixture.

I can do a drawing if anyone is interested.

[Forkinhades]

Just to have discussion - maybe new thread? Anyway...

Why do some of you think RCD circuit protection is "good"?

To me (and with consideration to underlying physics and psychics), ground wire protection is good enough for most applications. I can go along with GFI protection at point of contact (in socket) like in wet areas (bathrooms, outdoors) - but otherwise I just don't get it.

My reason (opinion): chance for electrocution or even more than a tickle in properly wired (with grounded) circuits seems like it is so low that it just isn't worth that expense.

Can you convince me otherwise?

The problem is getting a good earth, in Thailand most installations are TT (in the UK these installations HAVE to be protected by an RCD) ie have no earth. So an earth rod is then installed to provide an earth, and you will be lucky to get reading below 5 ohms. What this means under fault conditions the MCB (circuit breaker) will NOT trip in time to prevent electric shock. A typical 32 Amp MCB type C (which is mostly used in Thailand) will require a fault current of 320 Amps to trip instantly. Now using ohms law V=I x R it tells us that the earth impedance needs to be below 0.75 ohms ( not even taking into consideration the resistance of the live conductor of the circuit) in order to trip the MCB. Whereas with an RCD, you only need 1667 ohms for the device to trip in time.

Sorry but you did ask

RCD will prevent electric shock!!

Edited April 6, 2010 by Forkinhades

[Forkinhades]

Yes absolutely. Have done so in the past & will do so in future.

Wiring up a 2 way is dead simple.

The only neutral goes to the fixture.

I can do a drawing if anyone is interested.

In Thailand they take the neutral to the switches as well, and we talking about undertaking working on existing thai circuits, that could possibly have a borrowed neutral.

[Forkinhades]

Yes absolutely. Have done so in the past & will do so in future.

Wiring up a 2 way is dead simple.

The only neutral goes to the fixture.

I can do a drawing if anyone is interested.

In Thailand they take the neutral to the switches as well, and we talking about undertaking working on existing thai circuits, that could possibly have a borrowed neutral.

[bankruatsteve]

My argument or shall I say discussion isn't what RCD's are designed to do, it's whether they are really that necessary for "protection". BTW: your math is OK but I don't see relevance. (?)

''

[Forkinhades]

My argument or shall I say discussion isn't what RCD's are designed to do, it's whether they are really that necessary for "protection". BTW: your math is OK but I don't see relevance. (?)

''

The relevance is that the MCB will NOT trip (under fault conditions) if you do not have a good enough earth, or will take too long to trip causing death by electric shock. An MCB/RCD are required to trip within 40 milliseconds (BS7671 2008)

Also the UK 17th Edition wiring regulations states that all circuits within a bathroom require earthing AND RCD protection. Thailand also states (IET code) that all water heaters must be protected by an RCD

[bankruatsteve]

Again, I'm not disputing the quantitative protection of RCD (and the like), it's just the idea of whole circuit "protection" (from what?). And I did read post #34 (or whatever). OK - I guess my point is that I can't find statistics to say that serious injury or death from properly wired installations is even a minor concern. Whatever - I think I'll stop here. Cheers.

[powderpuff]

Yes absolutely. Have done so in the past & will do so in future.

Wiring up a 2 way is dead simple.

The only neutral goes to the fixture.

I can do a drawing if anyone is interested.

In Thailand they take the neutral to the switches as well, and we talking about undertaking working on existing thai circuits, that could possibly have a borrowed neutral.

No they don't.

I did offer to make a drawing.

[Forkinhades]

Sorry but I must point out, you state properly wired, indeed you wont find any instances of people being electrocuted by properly wired installations, but I must stress that although you can see an earth at a socket, that does not suggest that the earth is good enough to prevent electric shock. Any electrical installation needs to be tested, and on regular basis. One of the tests is to see whether the earth is stable enough to prevent electric shock.

[Forkinhades]

Yes absolutely. Have done so in the past & will do so in future.

Wiring up a 2 way is dead simple.

The only neutral goes to the fixture.

I can do a drawing if anyone is interested.

In Thailand they take the neutral to the switches as well, and we talking about undertaking working on existing thai circuits, that could possibly have a borrowed neutral.

No they don't.

I did offer to make a drawing.

Are you for real ?, In all the electrical installations I have witnessed in Thailand, they have taken the neutrals to the switches. The question is not how to show a wiring diagram of a 2 way switch, of which you think I need to know?...........jeesh, its about the dangers

[eraymos]

A dual-RCD (or 17th edition) board is a bit like the split-service board shown here http://www.crossy.co.uk/wiring/Consumer.html except that both sides of the board are RCD protected rather than just one.

So what is the verdict on a dual-RCD 17th edition? Should I think about ordering one??? The ones I have seen on the web are from the U.K with names that are unknown to me. I wonder how big of a problem it would be if something needs to be switched out. Is it something that could be made using Crossy's split-service board???

[Forkinhades]

Go for crossy idea, its quite easy to do.

At the end of the day we are talking about safety not only from electrical shock, but fire as well. For me I have a little baby running about the place, sticking his fingers everywhere, so for me a RCD Board would be the minimum, preferably a dual rcd board.

Edited April 7, 2010 by Forkinhades

[david96]

I would appreciate a bit of expansion on the detail in your second paragraph - just want to make sure that my understanding of what you have said is in actual fact correct. Especially "borrowed"neutrals and dual RCD DB .

A dual-RCD (or 17th edition) board is a bit like the split-service board shown here http://www.crossy.co.uk/wiring/Consumer.html except that both sides of the board are RCD protected rather than just one.

A 'borrowed' neutral, refers to when a circuit has been wired using a live and then using the neutral from another circuit because it was convenient, this often happens when you have 2-way (3-way to our US cousins) light switching, it's easier to borrow a neutral than to wire it properly. The issue is that although you've isolated the circuit you're working on, it's possible for that neutral to become hot and bite.

With the MEN system, only the active conductors are switched, and with 2 way switching or 3 way with a intermediate switch the same applies. However if double pole switching is carried out both the active and neutral conductors will be switched. If one has a "borrowed" neutral from another circuits this would fail the correct connections test and the circuit would not comply.

[david96]

Earthing will not protect a person from electric shock by direct contact, direct contact means that the person receives a shock from contact with an energised bare terminal, bare conductor or busbar. The victim may also suffer burns if arcing occurs.

However, an RCD will give protection in some cases where the point of direct contact is on the load side of the RCD/RCBO.

To minimise this risk terminals are shrouded or recessed.

Most electrical fatalities occur by indirect contact eg failure of a PE conductor and no RCD protection along with failure of insulation of the electrical equipment.

[david96]

My argument or shall I say discussion isn't what RCD's are designed to do, it's whether they are really that necessary for "protection". BTW: your math is OK but I don't see relevance. (?)

''

The reason for using RCDs on final sub circuits with socket outlets is that a standard Curve C

MCB must trip at 7.5 times rated current within 0.4secs. However, portable and hand held electrical equipment may be run off a socket outlet and may be connected by a 1.0sqmm flex lead. The impedance of the circuit may have increased to a value that will prevent the MCB operating within 0.4secs. if an earth fault occurs.

The electrical equipment may become damaged while in service and the PE conductor may become defective. In the case of an earth fault the person in contact with the faulty equipment may receive a severe or fatal electric shock.

An RCD/RCBO will automatically disconnect in less that 0.3 sec generally .02 secs at 30ma.

An RCD operates at a very low value of current and operates faster than a current operated MCB.

RCDs have been proven to save lives and property damage. If you save a life by installing RCDs it will not become a statistic.

[Crossy]

Just to have discussion - maybe new thread? Anyway...

Why do some of you think RCD circuit protection is "good"?

To me (and with consideration to underlying physics and psychics), ground wire protection is good enough for most applications. I can go along with GFI protection at point of contact (in socket) like in wet areas (bathrooms, outdoors) - but otherwise I just don't get it.

My reason (opinion): chance for electrocution or even more than a tickle in properly wired (with grounded) circuits seems like it is so low that it just isn't worth that expense.

Can you convince me otherwise?

The big issue (in the UK at least), is some bright spark bashing a nail through a cable buried in the wall and just contacting with the live core. There are numerous cases of things attached to said nails (or screws) becoming live and causing death. ALL cables buried less than 50mm deep (unless in metal conduit) must have RCD protection at the CU under the latest UK regs.

[david96]

Just to have discussion - maybe new thread? Anyway...

Why do some of you think RCD circuit protection is "good"?

To me (and with consideration to underlying physics and psychics), ground wire protection is good enough for most applications. I can go along with GFI protection at point of contact (in socket) like in wet areas (bathrooms, outdoors) - but otherwise I just don't get it.

My reason (opinion): chance for electrocution or even more than a tickle in properly wired (with grounded) circuits seems like it is so low that it just isn't worth that expense.

Can you convince me otherwise?

The big issue (in the UK at least), is some bright spark bashing a nail through a cable buried in the wall and just contacting with the live core. There are numerous cases of things attached to said nails (or screws) becoming live and causing death. ALL cables buried less than 50mm deep (unless in metal conduit) must have RCD protection at the CU under the latest UK regs.

There has been several fatalities in Australia due to nails/screws damaging cables and energising building materials. Installing RCDs to protect cabling in high risk environments will enable compliance with AS3000/2007.

Edited April 7, 2010 by david96

[eraymos]

Back to my original question, WHERE DO I GO FROM HERE?

What type of consumer unit (name brand?) and what type/how many circuit breakers (Amps, RCD, etc, etc) would you recommend for the following? We have found out earlier that the MD will be in the ball park of 64A (thanks Elkangorito)

Kitchen - 4 x DGPO. 1 x SGPO (range hood plus exhaust fan). 1 x combination light/fan. 1 x oven. 1 x cooktop.

Bathroom - 2 x lights. 1 x exhaust fan. 1 x SGPO.

Laundry - 1 x hot water heater. 1 x DGPO. 1 x light.

Master bedroom - 4 x DGPO. 1 x combination light/fan.

Bathroom - 1 x light. 1 x exhaust fan. 1 x SGPO.

Bedroom -4 x DGPO. 1 x light.

Carport - 2 x DGPO. 1 x light.

Living room - 4 x DGPO. 6 x lights.

Hallway - 2 x SGPO. 1 x light.

Sunroom - 2 x DGPO. 1 x light. (fan)

Foyer - 1 x DGPO. 1 x light.

Bedroom -4 x DGPO. 1 x light.

Bedroom - 4 x DGPO. 1 x light.

Outdoor - 2 x DGPO. 6 x lights. 1x SGPO (pump)

[david96]

Back to my original question, WHERE DO I GO FROM HERE?

What type of consumer unit (name brand?) and what type/how many circuit breakers (Amps, RCD, etc, etc) would you recommend for the following? We have found out earlier that the MD will be in the ball park of 64A (thanks Elkangorito)

Kitchen - 4 x DGPO. 1 x SGPO (range hood plus exhaust fan). 1 x combination light/fan. 1 x oven. 1 x cooktop.

Bathroom - 2 x lights. 1 x exhaust fan. 1 x SGPO.

Laundry - 1 x hot water heater. 1 x DGPO. 1 x light.

Master bedroom - 4 x DGPO. 1 x combination light/fan.

Bathroom - 1 x light. 1 x exhaust fan. 1 x SGPO.

Bedroom -4 x DGPO. 1 x light.

Carport - 2 x DGPO. 1 x light.

Living room - 4 x DGPO. 6 x lights.

Hallway - 2 x SGPO. 1 x light.

Sunroom - 2 x DGPO. 1 x light. (fan)

Foyer - 1 x DGPO. 1 x light.

Bedroom -4 x DGPO. 1 x light.

Bedroom - 4 x DGPO. 1 x light.

Outdoor - 2 x DGPO. 6 x lights. 1x SGPO (pump)

You can use this as a guide. Based on a MEN Electrical Installation.

1 x 63A MCB as a main switch.

2 x 10A lighting circuits. 1.0sqmm

6 x 20A power, socket outlets. 2.5sqmm (two circuits to run through kitchen area) approx 12 to 14 socket outlets( points) per circuit. A double socket outlet is 2 points.

1 x 20A hot water system. 2.5sqmm

1 x 20A cooktop. 2.5 sqmm ( more than 5000W less than 8000W)

1 x 20A oven. 2.5 sqmm. (more than 5000 W less than 8000W)

All socket outlets on RCBOs.

DIN MCBs and RCBOs 6kA fault current rating minimum.

Merlin Gerin, Clipsal, Schneider, Hager,

Polycarbonate enclosures supplied with neutral link, earth bar.

Sheet metal enclosures are also available.

One module size on the switchboard is equal to 1 pole.

A 24 pole enclosures should suffice for an installation connected as MEN.

One has supplied this information based on AS3000/2007

You should consider RCD protection on lighting circuits.

Fans points are connected on to the same circuits as the lights.

RCDs are available in one module width ( Schneider, Terasaki. etc.)

If you install a MCB as a main switch the max demand is limited to the rating of the MCB.