Domestic Electrical Wiring

[Crossy]

Back in BKK from 20/12/06 hopefully for good this time (we shall see). Haven't tried smoking tulips but there's some interesting stuff sold in the 'coffee shops'.

I note we've been unpinned and replaced by a link topic. Certainly reduces the dead space taken by the pinned topics but I'm worried people won't see this thread.

We shall have to see how it goes.

[JimmyGreaves]

Why has this been unpinned. It's an awesome thread and very very relevant to this topic group.

PIN IT!

[elkangorito]

Back in BKK from 20/12/06 hopefully for good this time (we shall see). Haven't tried smoking tulips but there's some interesting stuff sold in the 'coffee shops'.

I note we've been unpinned and replaced by a link topic. Certainly reduces the dead space taken by the pinned topics but I'm worried people won't see this thread.

We shall have to see how it goes.

Is there some rule on this "pinning/unpinning" thing? Would some kind moderator please re-pin us.

Muchas gracias in advance

[Crossy]

I note we've been unpinned and replaced by a link topic. Certainly reduces the dead space taken by the pinned topics but I'm worried people won't see this thread.

Is there some rule on this "pinning/unpinning" thing? Would some kind moderator please re-pin us.

Muchas gracias in advance

Astral's pinned topic contains a link to this thread as well as the house building topics that have also been unpinned. I think the mods/admin are trying to keep the dead space used by pinned topics down.

[astral]

[Astral's pinned topic contains a link to this thread as well as the house building topics that have also been unpinned. I think the mods/admin are trying to keep the dead space used by pinned topics down.

Exactly.

[chownah]

It would be nice if they could get at least a short list of what's available somehow up in the one pinned topic's description or something.

[elkangorito]

It would be nice if they could get at least a short list of what's available somehow up in the one pinned topic's description or something.

Top idea

[astral]

It would be nice if they could get at least a short list of what's available somehow up in the one pinned topic's description or something.

Top idea

Click here.

[chownah]

Astral,

My idea is that when someone looks at the Real Estate, Housing, and etc. page they will see a short list of the types of things that can be easily accessed in the FAQ topic. Often people don't take the time to look at the pinned topics but if right there at the top it said what could be accessed in the FAQ topic then maybe people would see it and open the FAQ topic for access.

Chownah

[stickyb]

This from today's Bangkok Post - note it doesn't say what the standard is.

The Thai Industrial Standards Institute has finally put in place a standard for household appliance plugs and sockets _ starting with refrigerator plugs, on Dec 23. Next in line next year are plug and socket standards for washing machines, electrical appliances (colour TV, DVD, stereo), rice cookers, kettles, fans, irons, electronic pans, electronic stoves and water heaters. ''The standard has finally arrived after 30 years of lobbying, putting Thai products on an international level,'' said Kattiya Kraikan, who chairs the Federation of Thai Industries' electronic and electric appliance group.

''The standard is commonplace even in Malaysia and Singapore.''

Mr Kattiya lauded the institute's move to ensure better consumer safety, saying sub-standard plugs and sockets had led to many deaths caused by electrocution and electric shock.

The institution will clarify the new requirements with appliance, socket and plug producers and the assessment agency on Dec 8

[elkangorito]

This from today's Bangkok Post - note it doesn't say what the standard is.

The Thai Industrial Standards Institute has finally put in place a standard for household appliance plugs and sockets _ starting with refrigerator plugs, on Dec 23. Next in line next year are plug and socket standards for washing machines, electrical appliances (colour TV, DVD, stereo), rice cookers, kettles, fans, irons, electronic pans, electronic stoves and water heaters. ''The standard has finally arrived after 30 years of lobbying, putting Thai products on an international level,'' said Kattiya Kraikan, who chairs the Federation of Thai Industries' electronic and electric appliance group.

''The standard is commonplace even in Malaysia and Singapore.''

Mr Kattiya lauded the institute's move to ensure better consumer safety, saying sub-standard plugs and sockets had led to many deaths caused by electrocution and electric shock.

The institution will clarify the new requirements with appliance, socket and plug producers and the assessment agency on Dec 8

Thanks for the info Sticky. BTW, here's the TISI web address for those interested in finding out how many standards have been recognised (but not necessarily implemented) by Thailand.

http://www.tisi.go.th/

Also, thanks to Astral for changing the topic name in the pinned "useful links".

Just found something interesting on the net....

http://ts.nist.gov/Standards/Global/upload/sukit.ppt

Don't know if it's actually implemented by the MEA or PEA but it's something.

Edited November 28, 2006 by elkangorito

[astral]

This from today's Bangkok Post - note it doesn't say what the standard is.

The Thai Industrial Standards Institute has finally put in place a standard for household appliance plugs and sockets _ starting with refrigerator plugs, on Dec 23. Next in line next year are plug and socket standards for washing machines, electrical appliances (colour TV, DVD, stereo), rice cookers, kettles, fans, irons, electronic pans, electronic stoves and water heaters. ''The standard has finally arrived after 30 years of lobbying, putting Thai products on an international level,'' said Kattiya Kraikan, who chairs the Federation of Thai Industries' electronic and electric appliance group.

''The standard is commonplace even in Malaysia and Singapore.''

Mr Kattiya lauded the institute's move to ensure better consumer safety, saying sub-standard plugs and sockets had led to many deaths caused by electrocution and electric shock.

The institution will clarify the new requirements with appliance, socket and plug producers and the assessment agency on Dec 8

The idea of a "standard plug" is excellent and the one used in Malaysia and Singapore (actually the UK standard) is a very good choice, with fusing at the plug level.

However, there are no compatible sockets installed in Thailand, so my guess is that the Thais will simply cut off the new plug and put on an old, unsafe one.

Still, it is a start in the right direction.

[elkangorito]

This from today's Bangkok Post - note it doesn't say what the standard is.

The Thai Industrial Standards Institute has finally put in place a standard for household appliance plugs and sockets _ starting with refrigerator plugs, on Dec 23. Next in line next year are plug and socket standards for washing machines, electrical appliances (colour TV, DVD, stereo), rice cookers, kettles, fans, irons, electronic pans, electronic stoves and water heaters. ''The standard has finally arrived after 30 years of lobbying, putting Thai products on an international level,'' said Kattiya Kraikan, who chairs the Federation of Thai Industries' electronic and electric appliance group.

''The standard is commonplace even in Malaysia and Singapore.''

Mr Kattiya lauded the institute's move to ensure better consumer safety, saying sub-standard plugs and sockets had led to many deaths caused by electrocution and electric shock.

The institution will clarify the new requirements with appliance, socket and plug producers and the assessment agency on Dec 8

The idea of a "standard plug" is excellent and the one used in Malaysia and Singapore (actually the UK standard) is a very good choice, with fusing at the plug level.

However, there are no compatible sockets installed in Thailand, so my guess is that the Thais will simply cut off the new plug and put on an old, unsafe one.

Still, it is a start in the right direction.

I believe the standard will be more likely to control aspects of plug/socket manufacture technique & also the materials used. It would also indicate a "standard & conventional" polarity of such plug & sockets, as exists in many other coputries.

The concept of using fuses at plug level is considered dangerous, particularly if the prospective fault current is not limited. These fuses are only used as overload devices, which are generally not needed. These fuses do not perform any safety function that I can imagine. Consequently, fault current limitation at the consumers board (breaker box) eliminates the need for such devices. This type of fault current limitation is facilitated by the use of an HRC fuse, either BS88 (10 kA) or BS1361 (<6kA).

My recent calculations, based upon a minimum 150kVA 3 phase distribution transformer @ 4% impedance, indicate that prospective fault currents at the secondaries of the Txers will be no greater than about 5 kA (5000 Amps). Assuming that all Thai houses are supplied using this configuration, fault current limiting devices need not be used as long as 6 kA breakers are used in the home...but then again, I don't trust the Thai electrical system.

What do ya think Crossy?

[chownah]

Appliance chords are often smaller than the rating for the circuit they are plugged into......because of this they do consitiute a fire hazard since they could draw more current than they can handle without tripping the circuit breaker..... installing a fuse sized correctly for an appliance chord at the plug would eliminate this hazard........wouldn't it?

Chownah

[elkangorito]

Appliance chords are often smaller than the rating for the circuit they are plugged into......because of this they do consitiute a fire hazard since they could draw more current than they can handle without tripping the circuit breaker..... installing a fuse sized correctly for an appliance chord at the plug would eliminate this hazard........wouldn't it?

Chownah

In some ways Chownah, you are correct (Appliance chords are often smaller than the rating for the circuit they are plugged into) but this is not a problem.

Let's say your electric iron develops a highly resistive fault to neutral &/or earth. A slightly increased current will be drawn from the supply, large enough to perhaps blow some "plug" fuses you mention. But this current will not be enough to cause damage to the appliance cord since most current ratings for cables are pretty well "de-rated", which allows then to handle a higher than rated current (not recommended). Not only this but it is unusual for a fault of say 8 amps, to develop & remain exactly at 8 amps. That is, most faults exponentially worsen to the point where a large current momentarily flows in the circuit, large enough to trip the circuit breaker quickly. If you check the 'Time Current' curve of a standard 20 Amp thermal magnetic circuit breaker, you will notice that the trip time for a current just over 20 amps is about 300 to 400 seconds. I don't think an electric iron will develop a 16 amp fault that will remain at 16 amps. It is likely that such a fault will quickly worsen (in seconds) & cause the circuit breaker to trip. Besides, fuses in a plug (probably glass) are very slow acting compared to circuit breakers. Also, modern cable insulation is designed to handle high temperatures for very short periods of time (> 100 degrees C). A temperature rating of 70 deg C means that the cable can continuously safely operate at this maximum temperature.

I think the concept of this fuse usage might have been applicable once when there was a guaranteed maximum fault current (say 2 kA) at the consumers board, cable insulation was not to todays standard & circuit breakers were not readily available & expensive. This sounds very much like an old system (now redundant) that has not yet been removed ie is still a "convention".

Attached; a time current curve of a typical 20 amp thermal magnetic circuit breaker.

[Crossy]

I agree with elkangorito, it's more likely to be a manufacturing standard, I too doubt that it would include the introduction of fused plugs a-la UK.

For anyone interested, a brief history lesson re the UK fused plug.

During the rebuilding of the UK's major cites after WW2 there was a major shortage of copper.

The solution introduced was to wire each circuit as a ring of 2.5mm cable, this ring could be safely fused at 30A. With such a rating a single ring could service an entire (small) house reducing the total amount of cable and therefore copper required.

BUT, with 30A available it was quite possible that a fault in, say, a table lamp could draw enough current to set fire to the flex without pulling the 30A fuse.

Thus the introduction of the plug fuse, your table lamp would (should) be fused at 5A, the fault would therefore blow this fuse and protect the flex.

Remember this system was introduced in the days of rubber insulation and a copper shortage. Modern materials doubtless are less likely to start fires etc. But we Brits are even less likely to do away with our beloved fused plugs

[tjo o tjim]

Having RCB protection for all circuits is likely to prevent electrical fires and I do not believe the likelihood of such fires to be very great in cement building construction as found here.

Actually, the RCB isn't going to do much to prevent a fire statistically. The US code now requires the arc-sensing breakers for residential applications; this does a lot to reduce the problem of arcing fires.

[lopburi3]

The US use of RCB is at point of use so no - they would not help much as that is not where the rodent/nail shorts normally occur.

[elkangorito]

Having RCB protection for all circuits is likely to prevent electrical fires and I do not believe the likelihood of such fires to be very great in cement building construction as found here.

Actually, the RCB isn't going to do much to prevent a fire statistically. The US code now requires the arc-sensing breakers for residential applications; this does a lot to reduce the problem of arcing fires.

Obviously, ELCB's were not designed to prevent fires.

The most common causes of electrical fires are;

1. Resistive connections, which can introducing arcing in its' latter stages. Good & CORRECT electrical & thermal insulation will slow this process down. Most electrical insulation will not sustain a flame without an external heat source.

2. Incorrect prospective fault current calculation thereby allowing incorrectly sized cables to be installed OR totally disregarding the prospective fault current & installing "load rated" cables.

This situation is by far the most dangerous. Fault current magnitudes are such that cables will melt, copper will touch copper, sparks will fly & things will burn...VERY QUICKLY. If the protective switchgear is correctly selected, it will not weld closed (worst case) or explode during the fault. If calculations are correct, switchgear should be able to safely interrupt a high magnitude fault in much less than 1 second. Therefore cables should be sized for the fault induced temperature rise, for a maximum period of 1 second.

3. Arcing due to electrical insulation failure or mechanical interference.

1 & 2 directly relate to insulation. What worries me here in Thailand is that I see many appliance & extension leads that are only single insulated (1 layer of insulation). This 1 layer is supposed to act as both electrical & mechanical insulation. If it is damaged, the cables' integrity is compromised & should be discarded. The ultimate & correct solution is to use double insulated cable (electrical & mechanical insulation) rated to at least 600 volts AC & 75 degrees Celsius. These days, circuit breakers are fast enough to protect most cables (temperature rise wise) & overload protection for cables is not required.

[chownah]

I think I understand Elkangoritos explanation of why plug fuses are not of much benefit on appliances....because any overload of the chord would likely trip the circuit breaker in the panel. What about plug fuses on extension chords. Extension chords are usually rated lower than the circuit to which they are connected and it is entirely possible to overload an extension chord without overloading the circuit to which it is connected.

Chownah

[elkangorito]

I think I understand Elkangoritos explanation of why plug fuses are not of much benefit on appliances....because any overload of the chord would likely trip the circuit breaker in the panel. What about plug fuses on extension chords. Extension chords are usually rated lower than the circuit to which they are connected and it is entirely possible to overload an extension chord without overloading the circuit to which it is connected.

Chownah

I can see what you're getting at Chownah but if circuit breakers are used (not rewirable fuses, which are dangerous) & are correctly sized (both overload & fault interrupt capacity), such cords can heat up enough to melt at which point in time, will cause a large fault to occur. The fault will be safely cleared by the CB & the cable will have melted but not be on fire.

Bearing in mind that 70 degrees Celsius is very hot, the current passing through such cords would be well above the current rating of the cord but would not conceivably exceed this temperature.

For example;

A 1.5mm 2 core flexible cord has 16 amps passing through it. Such cords word be normally rated for about 10 amps continuous. In actual fact, the copper can handle about 20 amps but would get a bit warm in such a case but not warm enough to damage CORRECTLY selected insulation (70 degree). If 22 amps were passed through this cord, the circuit breaker would eventually trip.

Conclusion.

Heat generated by an overload condition is usually not enough to damage the cord/cable. IF protected by a correctly sized circuit breaker, a fault may exist but will be cleared.

Heat generated by a high magnitude fault WILL damage the insulation IF an incorrectly sized circuit breaker is used.

Glass wire fuses are dangerous...especially under fault conditions.

This is based on modern insulation ie PVC, Cross linked polymers etc & not rubber, paper etc.

[elkangorito]

As a result of recently being able to get some definitive information about typical distribution transformers & therefore being able to caculate a prospective fault current (based on a transformer no larger than 150kVA), I have updated the "residential wiring" drawing to reflect this info.

This drawing is my minimum recommendation for any domestic electrical installation.

The changes are as follows;

Addition of Note 4 (in red).

Addition of a Fault Current Limiter on the consumer side of the Kilowatt Hour Meter.

Main Circuit Breaker re-labelled to Main Switch.

In summary, having a Fault Current Limiter (FCL) before your consumer board will prevent all manner of disasters. An FCL is not expensive & is generally installed BEFORE the Kilowatt Hour Meter (to protect the Kilowatt Hour Meter) but in Thailand, I don't think that the PEA/MEA would do this.

Please ensure that you use circuit breakers of the same make & model.

Drawing attached below

[elkangorito]

Coming soon.......

The facts about Lighting (and dispelling some myths).

[elkangorito]

Coming soon.......

The facts about Lighting (and dispelling some myths).

Information regarding domestic electric lighting is in the below attachment. Questions welcome.

[astral]

Another myth to dispell is about the "long life" of the low energy lamps.

They do not last 5 years as the manufacturers would have us believe.

[chownah]

As fluorescent tubes get older they emit less light.....do they also consume less power?

Chownah

[elkangorito]

Coming soon.......

The facts about Lighting (and dispelling some myths).

Domestic Lighting, revision 1 attached below

[elkangorito]

Another myth to dispell is about the "long life" of the low energy lamps.

They do not last 5 years as the manufacturers would have us believe.

...but they can last 5 years, subject to a clean electrical supply & if only used at a greatly reduced duty cycle.

I always ignore claims that state 'years' & only recognise 'hours' as being truly representative of a lamps life.

As fluorescent tubes get older they emit less light.....do they also consume less power?

Chownah

Sadly, no they don't.

[astral]

Another myth to dispell is about the "long life" of the low energy lamps.

They do not last 5 years as the manufacturers would have us believe.

...but they can last 5 years, subject to a clean electrical supply & if only used at a greatly reduced duty cycle.

I always ignore claims that state 'years' & only recognise 'hours' as being truly representative of a lamps life.

The clean supply is most probably the key in Thailand.

I have had several failures and I checked against the hours figure, not the years

and the lamps were failing well before they reached the rated life.

[elkangorito]

Another myth to dispell is about the "long life" of the low energy lamps.

They do not last 5 years as the manufacturers would have us believe.

...but they can last 5 years, subject to a clean electrical supply & if only used at a greatly reduced duty cycle.

I always ignore claims that state 'years' & only recognise 'hours' as being truly representative of a lamps life.

The clean supply is most probably the key in Thailand.

I have had several failures and I checked against the hours figure, not the years

and the lamps were failing well before they reached the rated life.

Agreed.

Also, I've found that by sticking to the more expensive brands (Sylvania, Osram, GE, Phillips etc), you get a better lamp & therefore better results. The rule "you get what you pay for" especially applies to lamps.