Whole house Safe-T-Cut or individual RCBOs?

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Whole house Safe-T-Cut or individual RCBOs?

Postby thailazer » Sun Mar 17, 2013 7:02 am

We wired our house with individual RCBO's to help isolate any problems that might occur. Last night a friend called to say his house went dark. Turns out his whole house Safe-T-Cut tripped for some reason. After a reset it was fine, but no clue as to which circuit the problem came from or whether it was just a false trip. I'm glad we have individual RCBO's, and am wondering what the advantages the whole house concept has. The only one I can think of is that you can run all the neutrals to a common bar. (With individual RCBOs, each circuit's neutral has to return to the individual RCBO.) No fun having the whole house go dark!
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby Roger Ramjet » Sun Mar 17, 2013 7:55 am

thailazer,
If there was a problem on a circuit, the tripper switch on that circuit would have tripped. If the main tripper switch went then he has a major problem, with incoming power which should have tripped his incoming breaker and not the board, which should be separate. You can test the Safe-T-Cut boards and individual circuits quite simply by following the instructions (in English) that are supplied. If your mate has a problem turning on one tripper at a time, reducing the RCBO sensitivity each time, so that the suspect circuit can be identified, then he can't read. The Safe-T-Cut people even recommend testing just like that every six months. It's simple, easy and recommended to test for leaks. Sate-T-Cut boards are designed so that if there is a leak that circuit can be individually identified within 10 minutes.
For a person to isolate ever circuit in a house would require every outlet having an RCBO at the outlet and at the board. In my case that would require over 100 RCBO's just for the kitchen and lounge room and as yet I have never seen a house or factory that is wired like that.
How do I know all this? I have three separate Safe-T-Cut boards each with 10 breakers each, I also have a mains breaker before splitting to the separate boards. If there is a fault with the board (which the electrician should have tested) then the Safe-T-Cut people will actually bring you a replacement. I've never heard of that, but I'm sure it could happen.
You do not get false trips, there is always a reason.
Tell your mate to send a photo of the Safe-T-Cut board and post it here, I'd love to see if he has a main's breaker (required by law) next to it. I'd also like to see the setting he has on the RCBO.
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby BKKBILL » Sun Mar 17, 2013 12:50 pm

As I understand it protecting individual circuits not individual outlets with RCBO’s (Residual Current Circuit Breakers with overload) is the best and safest way. As the amount of electrical appliances we have in our home increases, so does the likelihood of Nuisance Tripping. If there are a large number of appliances plugged in to the home at one time and a small amount of current leaks from each, the current adds up to become more substantial. This may mean that the safety switch is continuously on the verge of tripping. If there is the tiniest change in electrical current from PEA as happens often here it can push the switch to its limit causing it to trip. This can become more of a problem in older homes where the electrical wiring is not in good condition. Limiting the amount of appliances plugged in at one time can help minimize this type of tripping but TIT.

Lightning strikes are another cause of a safety switch going off. When lightning strikes your home, power lines or a power station it may cause a power surge which can cause a safety switch to trip. If this occurs, it is best to wait until the storm passes before resetting the switch.

Have been in a number of homes that had whole house Safe-T-Cut protection and most of the time the adjustable setting has been turned to direct leaving an even more dangerous situation as people think they are protected when their not. On asking was told sometimes the unit would trip cutting current to whole house. It’s adjustable so it must be OK right, right, zap.

Except for RR I know of no one who would test individual electrical circuits but doing so probably wouldn't find the problem especially if small leaks as commented on before were occurring on different circuits.

Right you are thailazer no fun sitting in the dark especially when you are the only one on the block doing so. As for the advantages of whole house protection think the only one would be cost. Since RCBO’s that are small enough to replace standard breakers are relatively new and with the small uptick in cost is probably reason more are not being installed.
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby Ians » Sun Mar 17, 2013 1:39 pm

I fitted RCBO to all power circuits with o/load breakers on all other circuits, however, I am considering fitting RCBO on the water heater circuits with already have built in RCBO's and are properly earthed.
1 whole house RCBO although a very safe option can be a nuisance as already pointed out - the cost of a handful of RCBO's is not much in the overall build of a house and well worth the expense for convenience.
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby Roger Ramjet » Sun Mar 17, 2013 1:53 pm

Bill,
There are a few things I disagree with:
BKKBILL wrote:As the amount of electrical appliances we have in our home increases, so does the likelihood of Nuisance Tripping.

Firstly, in this day and age (unless it's from China) most electrical appliances have not only the frequency marked, they also have the wattage used by that appliance at peak running. If the outage had been a nuisance trip then it would have tripped the breaker to that circuit, not the whole board. If it had come from outside (PEA) then the 50 amp or 100 amp breaker before the board should have done the job; if it didn't then it's time to change that breaker.

BKKBILL wrote:Have been in a number of homes that had whole house Safe-T-Cut protection and most of the time the adjustable setting has been turned to direct leaving an even more dangerous situation as people think they are protected when their not. On asking was told sometimes the unit would trip cutting current to whole house. It’s adjustable so it must be OK right, right, zap.

I am astounded that so many homes have Safe-T-Cut boards and the electricians who installed them did not set the adjustable RCBO to green. viewtopic.php?f=3&t=1864&start=1395 I know of no Safe-T-Cut boards that have a "direct" marking on them, they go in colour from red through yellow to green.

BKKBILL wrote:no one who would test individual electrical circuits but doing so probably wouldn't find the problem especially if small leaks as commented on before were occurring on different circuits.

There should be no small leaks on any circuit because then the tripper switch for that circuit would trip and is the whole point of having an RCBO.
There are ten tripper switches on my Safe-T-Cut board and one RCBO, if there is a small leak anywhere the RCBO will do its job and trip that circuit only. If it trips the main two switches, then the problem is from outside.

If Safe-T-Cut boards are so bad for reliability and don't work, perhaps someone could tell me why you get a lifetime 1,000,000 insurance policy for each board that includes fire and electrocution?

Ians,
I agree. I fitted extra breakers next to all my appliances (water heater etc), just to be sure.
If you fit RCBO's then it is your responsibility to test them every three months and if there is a problem; call an electrician.
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby pattayapope » Sun Mar 17, 2013 2:37 pm

I have done the same as thailazer and ians and think this is the best way to go. As I said on a different post you have to make sure you have the correct neutral otherwise it will not work. If you retrofit an existing system I would recomend a safetcut over a regular rccb. I would also agree with bkkbill on his comments, from my experiance most Thai electrcians do not have a clue on circuit design or loads.[*] :roll:
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby BKKBILL » Sun Mar 17, 2013 4:20 pm

A reply to correct some misinformation. Here is a picture of the Safe-T-Cut I was commenting on showing the sensitivity adjustment that can go all the way to direct.

Safe-T-Cut.jpeg


By Goggling “Nuisance Tripping” you will get about 389,000 results. Now I know a few will have nothing to do with Safe-T-Cut but the fact is "NUISANCE TRIPPING" is on the increase not in decline.

i.e.
Sometimes AFCI / GFCI / RCD breakers trip because of events that mimic trip conditions.

Examples:

Voltage drop on a circuit fed by a GFCI Breaker can cause the breaker to trip due to loss in the electrical wiring greater than 6ma.

Cheap surge protector power strips can cause GFCI and AFCI breakers to trip due to the MOV shunting to ground at a low clamping voltage.

Any surge in the electrical system can cause a temporary malfunction of a GFCI (RCD)and AFCI which can be called "NUISANCE TRIPPING".

This from http://www.gofusion.com.au/resources/rc ... etripping/

RCD / Safety Switch Nuisance Tripping

This is a frustrating problem which will probably become slightly more common as we use a greater array of electronic appliances in both our homes and offices.
Firstly, we’d like to give you an overview of how a safety switch works so that you can understand the cause and effect. A safety switch measures the amount of current leakage to earth from the wiring and appliances within your premises. When the leakage reaches the factory-set level, the safety switch operates and switches off the power supply to that circuit or circuits.
If an appliance develops a fault and excess current leaks from this appliance, the safety switch senses this additional leakage and if it exceeds the factory-set level the safety switch operates and the power is disconnected.
In all electrical installations there is some leakage present. This is normal and in most instances very low. The amount of leakage increases with the number of appliances connected. The condition of the wiring in your property will also affect and possibly add to the level of leakage. All appliances leak a very small amount of current and when you have a number of appliances each leaking this small amount, then the accumulative value of all of these appliances are added together to produce a larger value.
If the normal day-to-day leakage is high, due to the amount of electronic equipment and/or the condition of your electrical installation, then the safety switch will be close to tripping most of the time. All it will take is for a very small disturbance and this will cause a safety switch in this situation to trip.

RR you are correct about the 1,000,000 Baht insurance policy but to my knowledge no one electrocuted has personally collected on that but TIT. :mrgreen:

As first said "As I understand it protecting individual circuits not individual outlets with RCBO’s (Residual Current Circuit Breakers with overload) is the best and safest way".
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby BKKBILL » Sun Mar 17, 2013 5:13 pm

Thailazer here is a little more information you could pass on to your friend. Possibly relieve some worry from the tripped Safe-T-Cut.

Problems With RCDs
As far as users are concerned, the single greatest problem with RCDs is nuisance tripping. This problem will either be due to the design of the RCD or due to the installation. Nuisance tripping can be a frustrating problem for the user and there have been cases where RCDs were strapped out, removed from installations completely or replaced with RCDs with a higher rated trip current. All of these types of actions are very dangerous and should be avoided. Where the problem lies with the RCD, it is usually attributable to factors such as voltage spikes, surges, switching transients, noise, inrush currents, etc.

Over recent years, the problem of nuisance tripping attributable to the RCD itself have been addressed by IEC. New tests have been introduced into the product standards to ensure that RCDs have a higher immunity to nuisance tripping. Unfortunately, all RCDs do not comply with the new requirements. To minimise this problem, ensure as far as possible that the RCD has compliance to IEC61008 or EN61008 (RCCBs) or IEC61009 or EN61009 (RCBOs) and also to IEC61543 or EN61543 (EMC requirements for RCDs).

Over recent years we have seen an increasing use of RCDs on the market which are not compliant with relevant product standards but are marked as if they comply. Users should insist that only compliant products are used in their installations.

Sometimes the problem of nuisance tripping is attributable to the installation. IEC recommends that the standing earth leakage current on the installation should not exceed 30% of the rated trip current of the RCD intended to be used on that installation. This means that for a 30mA RCD, the standing leakage current should not exceed 10mA. Given that a 30mA RCD may trip anywhere from 15 - 30mA, a 10mA standing leakage current will virtually prime the RCD to trip. In general, RCDs cannot tell the difference between a standing leakage current and an earth fault current. The sum of these two currents is the residual current seen by the RCD and if this aggregate current is greater than its rated trip current, the RCD will trip.

The problem of standing leakage currents is increasing due mainly to two factors:

a) equipment manufacturers filtering internally generated noise to earth


b) fitting of RFI suppression to provide immunity to mains borne noise.

European Directives on EMC require manufacturers of products, appliances and equipment, etc. to contain within specified limits the levels of RFI type emissions produced by their products. Manufacturers often have to resort to the use of filtering circuits to meet these requirements. The filtering circuits can divert high frequency signals to earth, but can also result in significant levels of leakage current to earth at the standard 50Hz frequency. Under IEC rules, an electrical appliance may allow a standing leakage current of up to 3.5mA/50Hz to flow to earth. Several such appliances coupled with other sources of standing leakage current can give rise to nuisance tripping.
Washing machines, oil or gas burners and even immersion heaters can contribute to nuisance tripping. Temperature and humidity may also be factors in nuisance tripping.

Other factors contributing to nuisance tripping may be poor earth terminations or surge suppressers. Before changing the RCD in response to a nuisance tripping problem, check the installation by measuring the standing leakage current and carrying out an earth loop test. Also try to identify equipment that is likely to contribute to standing or transient leakage currents. Dividing the installation into subcircuits with individual RCD protection is probably the most effective way to minimise nuisance tripping problems.


or for the full pdf.

http://www.westernautomation.com/DemystifyingRCDs.pdf
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby thailazer » Sun Mar 17, 2013 8:04 pm

BKKBill, cost is definitely one of those things I forgot about so thank you for that. All the RCBOs in our panel ended up being a lot more expensive than a whole house RCD unit, but for me it is worth it to aid in trouble-shooting. I checked over the various whole house units when we were building and was not very impressed with their setups. The Square D RCBO's looked to be the cat's meow, and except for an infant failure (which HomePro replaced at no cost), they have been very reliable with no nuisance trips. The construction panel had one in it and I thought we were having nuisance trips until I found a wimpy extension cord in the water by the mixer. It was doing its job protecting the workers.

It appears my buddy's unit was set at 5 mA and tripped due to a current surge as a kitchen hob was turned on. Sounds like it is about eight years old.
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby Ians » Sun Mar 17, 2013 8:40 pm

5 ma is too low, 30 ma is more than OK for a house situation.
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby Roger Ramjet » Sun Mar 17, 2013 10:47 pm

Bill,
That Safe-T-Cut board you show in the photo went out of production nearly ten years ago.
I do think people are mixing up what an RCBO does and what other electrical equipment does.
http://en.wikipedia.org/wiki/Residual-current_device and this http://www.diynot.com/forums/viewtopic.php?t=6852
There is also a lot more information out there with conflicting views by so-called electricians citing various codes, but I'll go back to what I said before: When a company provides a written insurance policy for 1,000,000 in case of electrocution or fire, then I'll buy that company's product without the slightest hesitation. And as I've had absolutely no problem with my three Safe-T-Cut boards I'll also back that product.
And I also stand by my statement about leakage. http://in.answers.yahoo.com/question/in ... 025AAhqh8M Electrical circuits do not leak, they have faults.
http://www.ul.com/global/documents/corp ... uary09.pdf
And if you have an RCBO on the board it will trip the tripper switch at the slightest hint of a fault. Note, the tripper switch for that circuit, not the whole board.
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby thailazer » Mon Mar 18, 2013 11:16 am

A bit off topic and perhaps pedantic as well......."Leakage current" is more generally used in the electronics/RF side of electrical engineering whereas the term "fault" is used on the power transmission side. "leakage current" is generally any current that is unknown that causes Kirchoffs Current Law to appear violated, or it can refer to an undesired current such as reverse (leakage) current in a diode, or leakage current in a capacitor. I can certainly see why many would call an unintended path to ground from the household load line a leakage current. Leakage current was a much more commonly used term in my years as an Electrical Engineer, but I was on the electronics/communications side of things. I only used the term "fault" to get through the power classes in college!

http://en.wikipedia.org/wiki/Leakage_%28electronics%29
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby Davidxxx » Tue Sep 08, 2015 2:37 am

I am struggling to understand why the Thai answer to RCDs and RCBO's is different to the UK.
In the UK a dual RCD system is widely used, the dual RCD is so that if one RCD trips there is still power in the other half of the house and you don't lose all the lights. This seems to work fine, you rarely hear problems with nuisance tripping. It is also cost-effective - MK for example do a Consumer Unit with dual RCDs and 10 MCBs for about £100. It also follows European standards so other makes of components can be used.
I am familiar with these, I have always had MK or Wylex, have never had any problems and they do the job.

I am thinking of using one in my Thai house near Buriram and would like to know if there is any reason why it is not suitable, or is there a good quality equivalent available in Thailand.
The Safe-T-Cut concept of an adjustable RCBO sounds just rubbish or am I missing something.
My plan is to design the electrical wiring system and buy the stuff, get a Thai electrician to lay in the cables and boxes, and I will check the connections and do the basic tests.
Any advice from those who have done it would be appreciated.
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby Roger Ramjet » Tue Sep 08, 2015 5:47 am

Davidxxx wrote:I am thinking of using one in my Thai house near Buriram and would like to know if there is any reason why it is not suitable, or is there a good quality equivalent available in Thailand.

Firstly I would not be worried about the electrical equipment not being suitable. Your first worry is finding someone competent enough to instal it.
As far as your RCD and RCBO's statement about not understanding, if you go back four posts there's detailed posting on the difference.
The reason things are "different" here is because, mostly the Thai "sparky" has no idea what he is doing if it involves anything other than what he has been taught.
Davidxxx wrote:The Safe-T-Cut concept of an adjustable RCBO sounds just rubbish or am I missing something.
My plan is to design the electrical wiring system and buy the stuff, get a Thai electrician to lay in the cables and boxes, and I will check the connections and do the basic tests.
Any advice from those who have done it would be appreciated.

Again if you read the electrical section all the questions have been addressed previously and answered in great detail. This is Thailand not the UK. You can't look up certified electricians in the yellow pages here, it's all a bit pot luck, so good luck.
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Re: Whole house Safe-T-Cut or individual RCBOs?

Postby Sometimewoodworker » Tue Sep 08, 2015 6:03 am

Davidxxx wrote:My plan is to design the electrical wiring system and buy the stuff, get a Thai electrician to lay in the cables and boxes, and I will check the connections and do the basic tests.
Any advice from those who have done it would be appreciated.


Good luck with finding a Thai electrician who is remotely competent. Our local man couldn't wire a 2 way switch because he couldn't understand how it works :roll:
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