Advice on proper circuit breakers

[xtrnuno41]

14 hours ago, sometimewoodworker said:

A little pedantic but it isn't fuse but a Circuit Breaker, a fuse is a wire that melts.

 

If a type B, C, D, K, or Z MCB is better or even if it should be used is dependent on the type of load it is used on and the earth fault loop impedance of the circuit, unfortunately it seems that few if any domestic electrical installers (most are not electricians) know how to check that, or even if they know how they do not check.

 

The difference between the various letters is the amounts of short term startup over current they will allow ranging from 2x to 20x the rated current 

ok, i agree, fuse in definition melts. But its easier to say so.

Ofcourse the CB characteristic depends on the load. A normal domestic house installation can do with a B16A.

 

Only if you have really heavy devices running and where the start current is high , it could be worth while.

But even then you can use a higher CB, like a  B20. All depends as well on time of high start current.

There are not many devices in household which exceeds the B16, so there for the B16 is more safe then a C20.

A C characteristic can have 5-10 In while a B characteristic is 3-5 In. With a CB the circuit is protected for high power and so fire and wiring. Asia uses the C20 everywhere, i might think as they might be cheaper.

 

However a differential switch or earth leakage detector should be a must nowadays, which can really safe lives.

[Artisi]

15 minutes ago, xtrnuno41 said:

ok, i agree, fuse in definition melts. But its easier to say so.

Ofcourse the CB characteristic depends on the load. A normal domestic house installation can do with a B16A.

 

Only if you have really heavy devices running and where the start current is high , it could be worth while.

But even then you can use a higher CB, like a  B20. All depends as well on time of high start current.

There are not many devices in household which exceeds the B16, so there for the B16 is more safe then a C20.

A C characteristic can have 5-10 In while a B characteristic is 3-5 In. With a CB the circuit is protected for high power and so fire and wiring. Asia uses the C20 everywhere, i might think as they might be cheaper.

 

However a differential switch or earth leakage detector should be a must nowadays, which can really safe lives.

as far as I know earth leakage protection is now part of the Thai wiring code - mandatory - but who cares, Thai   electricity is different.

[sometimewoodworker]

27 minutes ago, xtrnuno41 said:

Only if you have really heavy devices running and where the start current is high , it could be worth while.

But even then you can use a higher CB, like a  B20. All depends as well on time of high start current.

There are not many devices in household which exceeds the B16, so there for the B16 is more safe then a C20.

A C characteristic can have 5-10 In while a B characteristic is 3-5 In. With a CB the circuit is protected for high power and so fire and wiring. Asia uses the C20 everywhere, i might think as they might be cheaper.

 

However a differential switch or earth leakage detector should be a must nowadays, which can really safe lives.

The RCBO/RCD whole house protection has been required since October 2016 as well as earthing.

 

 

The circuit breaker is there to protect the wiring not the appliances and the type is generally to prevent nuisance trips as well as sort circuit protection and overload protection.

 

If you have a significant number of old fluorescent fittings they may well exceed the 3x~5x over current limits of a type B MCB, so that would be a common use case for a type C MCB, a welder would probably also require a type C or even type D. 

 

I agree that type B should be used far more often than type C, but a type B is not safer than a type C or type D. A short circuit can reach 100s of Amps or 1,000s of Amps and they will all trip fast enough to protect the wiring if correctly sized.

 

But as to the MCB's in use I have 10A, 16A, 20A, and 32A on my final circuits, regrettably some could well be more appropriate as type B

[xtrnuno41]

23 hours ago, Artisi said:

as far as I know earth leakage protection is now part of the Thai wiring code - mandatory - but who cares, Thai   electricity is different.

You should care as it saves YOUR live when doing something stupid, can happen.

Your heart can have 30mA, although depending on your own physical health, and then you even feel it.

I know, did stupid, can happen, just a simple touch, but happily protected by this system !!

I just saw pics of an installation of a HOSPITAL and then even they didnt use earth leakage detectors !!

It was horrifying to see. Just newly built !! 

[Artisi]

25 minutes ago, xtrnuno41 said:

You should care as it saves YOUR live when doing something stupid, can happen.

Your heart can have 30mA, although depending on your own physical health, and then you even feel it.

I know, did stupid, can happen, just a simple touch, but happily protected by this system !!

I just saw pics of an installation of a HOSPITAL and then even they didnt use earth leakage detectors !!

It was horrifying to see. Just newly built !! 

 

25 minutes ago, xtrnuno41 said:

You should care as it saves YOUR live when doing something stupid, can happen.

Your heart can have 30mA, although depending on your own physical health, and then you even feel it.

I know, did stupid, can happen, just a simple touch, but happily protected by this system !!

I just saw pics of an installation of a HOSPITAL and then even they didnt use earth leakage detectors !!

It was horrifying to see. Just newly built !! 

did you miss the irony?

[Artisi]

28 minutes ago, xtrnuno41 said:

You should care as it saves YOUR live when doing something stupid, can happen.

Your heart can have 30mA, although depending on your own physical health, and then you even feel it.

I know, did stupid, can happen, just a simple touch, but happily protected by this system !!

I just saw pics of an installation of a HOSPITAL and then even they didnt use earth leakage detectors !!

It was horrifying to see. Just newly built !! 

Just confirms my comment, no one cares.  

[bankruatsteve]

59 minutes ago, xtrnuno41 said:

You should care as it saves YOUR live when doing something stupid, can happen.

Your heart can have 30mA, although depending on your own physical health, and then you even feel it.

I know, did stupid, can happen, just a simple touch, but happily protected by this system !!

I just saw pics of an installation of a HOSPITAL and then even they didnt use earth leakage detectors !!

It was horrifying to see. Just newly built !! 

An RCD (normally set to trip at 30ma) can be life saving because it will stop the flow of electricity almost instantaneously.  The normal shock/tingle that one gets from non-grounded equipment is usually well below 30ma.  IE: RCD will not prevent those.  If you did receive a 30 ma zap, even briefly, it will be extremely painful and with possible injury.  Most tasers used by police have 50K volts potential which result in less than 1ma of current - but that's enough to immobilize in a few seconds.  

 

Hospitals may not use earth leakage detectors because some circuits are not relative to ground as zero potential.

[Crossy]

2 hours ago, bankruatsteve said:

Hospitals may not use earth leakage detectors because some circuits are not relative to ground as zero potential.

Hospital equipment is designed to minimise the risk of shock. Also, the life threatening situation of an unwanted trip potentially outweighs the shock risk.

 

 

 

[Wirejerker]

There is a bit of misconception here that a rcd or RCBO limits the shock to 30 mA. That’s not the case, the 30 mA is the threshold current that it will trip. To be in spec an rcd with 30 mA test current should trip within 300 ms and test current of 150 mA trip within 40ms. You are not safe with an RCD orRCBO ...just safer. You can’t protect stupid.


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[DineshR]

Hello,

 

I thought I would update all of you that had provided guidance earlier, on where I am on changing out my existing breakers to the RCBO's.

 

1. My electrician was able to source the RCBO's for 1085 a piece. Same price for all amp versions.

 

2. The electrician was here yesterday and was able to change out the breakers for all the water heaters and the oven with no problems. A part of the house that included lights and plug points was also switched out to the new RCBO.

 

However, he was not able to complete the work in the rest of the house (an additional 9 breakers) for the remaining lights and plug points. Apparently, the neutrals for many of the lights and plug points were all connected together up in the roof and he needs to come back next week to separate them out so that the RCBO's will work properly. This was also complicated by the fact that many of the exterior lights were also connected to electronic timers next to the main circuit breaker box. He will need to rewire that to ensure the proper separation of the neutrals. He will be back next week to complete the work. He does understand the need to properly match the live and neutral pairs to ensure proper functioning of the RCBO.

 

This has taken longer than I expected but in the end it's worth it to have the peace of mind w.r.t. electrical safety in the house.

 

Thanks again for all your assistance. Without the knowledge I gained from this forum thread it would have been difficult to get this done properly.

[Crossy]

3 hours ago, DineshR said:

Apparently, the neutrals for many of the lights and plug points were all connected together up in the roof and he needs to come back next week to separate them out so that the RCBO's will work properly.

The fact that he isolated this fact and knew the implications means you need to keep his phone number ?

 

A rare beast indeed.

 

[Artisi]

28 minutes ago, Crossy said:

The fact that he isolated this fact and knew the implications means you need to keep his phone number ?

 

A rare beast indeed.

 

Few and far between.