Why didn't the circuit breakers trip when I cut the extension cord??

[Crossy]

7 minutes ago, VocalNeal said:

Because the hedge trimmer was plastic (insulated) there was no way for the current to get to you and through you to the ground.

The danger and cause of many deaths in the UK before RCDs became mandatory, is not actually cutting the cable but picking up the (live) cut end.

 

[giddyup]

1 minute ago, Crossy said:

The danger and cause of many deaths in the UK before RCDs became mandatory, is not actually cutting the cable but picking up the (live) cut end.

 

I was careless, not crazy!

[Fruit Trader]

1 hour ago, MuuKondiao said:

I think you are wrong about that. A short circuit, by definition is a means for the current to go through a shorter route - not through the electrical motor or appliance it was circuiting through - and back to the source or to ground, which could be through the person cutting into the wires.

So, if the live wire was not cut then the current continued through the narrowed pathway, while some pieces of metal -  the sparks - flew elsewhere.

Current could quite easily pass through a short circuit and hedge trimmer motor at the same time. In fact there could be quite a decent shower of sparks while trimmer continues to cut and go unnoticed if conductors are not broken.

 

In this case the hedge trimmer sliced through cable insulation and created a circuit before the final destination (short circuit). The short circuit duration was most likely not of sufficient length to trip the protective device. Sparks would be created as the cable conductors rubbed against the dirty cutting blades but never finding a decent low resistance connection.

 

The real danger comes when tool operator fails to notice insulation damage and later grabs exposed conductors making his body a deadly path to ground.

 

Circuit breakers have trip ratings that define how long the over current value can remain before tripping. Most house breakers in Thailand are C rated to withstand the high starting currents of stuff like pumps and AC motors.

[lopburi3]

15 minutes ago, VocalNeal said:

Yep. Just reset the Safe-T-Cut. There should be no short if the house is unoccupied but...rats.....

Rats normally make direct path hot to neutral rather than ground so breaker trips.  Had that happen a few times.  Safe-T-Cut did not trip.

 

Had a life saving Safe-T-Cut trip when using those nasty plastic extension cord reels - when plastic cut insulation off hot wire where I took hold of it to drape over a chair.  Will not use that type again (similar to below).

[emptypockets]

1 hour ago, bankruatsteve said:

Whew.  There is nothing wrong with the OP's "board".  The advice is to add safety protection for earth faults by putting a RCBO as the main breaker.  AGAIN - RCD detect earth faults NOT shorts.

They actually detect an imbalance between the current flow in the active and neutral to be correct, usually caused by a current flow to earth. Grab both conductors simultaneously and you could very well end up fried.

As an aside, Australia now requires safety switches on all circuits, light and power, below 20 amps (or 25....don't have AS3000 handy) but basically all domestic circuits in a new installation including stoves and HWS where applicable. I recall it was also mandated to retrofit for power circuits in rental properties some years ago. They have also changed the old way of measuring resistance for the earth circuit to impedance measurement.

[emptypockets]

1 hour ago, simon43 said:

 

Well, a reasonable suggestion actually, since flip-flops are typically made of rubber which is a bad conductor of electricity.

 

When I used to work on the live 3 phase electrical systems at my little hotels in Phuket, (I designed/installed the circuits), I always wore my best thick rubber trainers and stood on a rubber car mat, just in case...

They won't help you if you contact 2 phases simultaneously. 380 volts at whatever current will flow from one point of contact to the other. Many years ago (and I mean many) it wasn't uncommon to see the 'boss' check the temperature of 3 phase busbars in MCC's by touching each in turn. Of course rubber boots and a mat were used. Stuff that!!! use an infra red camera these days.

[emptypockets]

44 minutes ago, Arjen said:

Wrong!!!!

 

Earth leakage devices, RCBO's, how ever they are called do not need a earth wire connection to work! They disconnect power when the current difference between N and L is higer then 20, 25 or 30mA, depending on rating. When the decive has no earth connection, you are the earth. It can be a nasty experience, but you will not die from it....

 

You give dangerous and wrong advice!!!

 

I hope people with more knowledge on this subject will confirm this.

 

Arjen.

With the proviso that the switches are in fact the residual current device type i.e current imbalance A-N. Older switches did actually use a current flow to earth for measurement and subsequent tripping.

Don't forget that it is not only the mA parameter that should be considered but also the tripping time (typically less than 0.4sec) and in the case of a combination safety switch and MCB also the kA rating.

 

Perhaps a protected outlet similar to this might be an easy fix until the OP decides his course of action.

[VocalNeal]

1 hour ago, lopburi3 said:

Had a life saving Safe-T-Cut trip

 

From a a purely pragmatic point of view. Good enough for me. The rest of you guys can continue with your Phd theses.

[bankruatsteve]

41 minutes ago, emptypockets said:

They have also changed the old way of measuring resistance for the earth circuit to impedance measurement.

Impedance = resistance in AC circuit.

[brianthainess]

9 hours ago, chingmai331 said:

Hmm.  Interesting.  Maybe i should check my rented house.  don't even know if ground wire is installed.

Well, summer is soon so hot water shower device will be OFF>

Electric showers have a built in R.C.D.. and will not give hot water unless earthed so i'm told. They have a test button.

[lopburi3]

23 minutes ago, brianthainess said:

Electric showers have a built in R.C.D.. and will not give hot water unless earthed so i'm told. They have a test button.

The test is of the ELCD - not that it has a ground attached.  They work without ground - that is why most are now shipped with large red lettering on front advising to install a ground - suspect many are not grounded so always a good idea to check.  The ground should trip breaker for most faults before you do so rather important to have.  Yes it could save a life.

[Crossy]

36 minutes ago, lopburi3 said:

Yes it could save a life.

Could!!!!

 

It is (very) important to understand that the parameters for "safe" electrical exposure, usually stated as 30mA, 30ms, 30V were chosen to be non-lethal to 90(something)% of the population. The very young, old, infirm or sick could well die when shocked with less than this.

 

The use of a decent ground for Class-1 appliances along with an RCD/RCBO will minimise (but not totally eliminate) the chances of death.

 

[xtrnuno41]

You have C characteristic breakers, they can do 1.5-2 X the nominal value , so a C16 runs up from 24 to 32 A and so on for the other ones.

With the shortcut you had, the Amp's stayed under the working point of the breaker, less then 24-32 Amp on the C16 breaker.

If your powerline was on a C 32, then you even have way bigger AMps to run, DOUBLE.

I dont know why people need a C32. Here they are B16 and thats it, you can run your household.  

Also the wiring behind a C32 should be bigger, if not you can have a meltdown in your wiring and have fire.

I see they are for water heaters, dont know which one you have, like 6.5 kW(?) then you need the C32 or better B32, it depends on AMps when starting heater> If heater is, like 3 kW, you can have again the B16.

Maybe they are cheaper en therefor in THailand. Or Thai found it annoying when it shuts down. But save?? NO

More safer is a B characteristic breaker. That one goes from 0-1.5 X nominal value.

 

There arent test knobs on breakers, only on a RBCO. It is very wise to have an RCBO placed in your electrical cabinet.

It measures the difference between in and outgoing Amps and shuts down on 30mA, only have that one. NOT 40 or otherwise.

There are also adjustable electronic devices, however i dont trust them. Its switchable, never knows what happens if switch is corroded or what ever. And then your safety is gone again.

This device prevents high currents through your body if you touch it. Hence you make connection to earth and the power will follow your body to go to ground. If you dont have RCBO it s not limited and higher Amp's can pass your body. Your heart cant have that , only 30 mA and not 32 A.

As you have 8 groups, i think you need several of them. I think for each heater seperate ones. Ok you can also put the 2 on one, saves you money and space. BUT be sure then your RCBO can handle the 64 Amps. Then you need one, i saw them in shop RCBO 65A shutdown value 30 mA. 

You have airco's, they are that big C 20A, higher then 3840 watts or 3.8 kWatt? But ok you can have again the 2 on RCBO 65A shutdown value 30 mA. 

The other 4 groups you can place on another RCBO RCBO 65A shutdown value 30 mA.

Your box is too small, and need to be replaced then by a bigger one.

 

You also could do with just one , replace the main fuse C50 by one which is AND a breaker AND RCBO, you need C50 and shut down value 30mA. However if in one group is a problem then everything will shut down.

But this is already a big improvement and safer for you and besides the cheapest. 

 

Consider yourself lucky it didnt touch you.

[impulse]

12 hours ago, simon43 said:

 

Well, a reasonable suggestion actually, since flip-flops are typically made of rubber which is a bad conductor of electricity.

 

When I used to work on the live 3 phase electrical systems at my little hotels in Phuket, (I designed/installed the circuits), I always wore my best thick rubber trainers and stood on a rubber car mat, just in case...

 

Don't forget to keep one hand in your back pocket, because if you touch the hot wire and the neutral wire at the same time, you don't need a path through ground.  And no MCB, RCBO or (as we call them here) GFI will save your bacon from frying.

 

[emptypockets]

10 hours ago, bankruatsteve said:

Impedance = resistance in AC circuit.

Sort of -yes in most correctly wired domestic installations.

[emptypockets]

So true

[Banana7]

On 2/12/2019 at 9:25 AM, giddyup said:

No test button that I see.

Those 32 amp water heater breakers look too big. If you have 4,000 watt heaters, 20 amps should be sufficient. I use 20A with 4,000 watt heaters and never has it popped. Also, I suspect your AC breakers could be reduced to 16 amps., if they are dedicated circuits to an AC. Need to check the wattage for the ACs. One reason that breakers do not pop on short circuits is that the breaker is too big.

 

[emptypockets]

7 hours ago, xtrnuno41 said:

You have C characteristic breakers, they can do 1.5-2 X the nominal value , so a C16 runs up from 24 to 32 A and so on for the other ones.

With the shortcut you had, the Amp's stayed under the working point of the breaker, less then 24-32 Amp on the C16 breaker.

If your powerline was on a C 32, then you even have way bigger AMps to run, DOUBLE.

I dont know why people need a C32. Here they are B16 and thats it, you can run your household.  

Also the wiring behind a C32 should be bigger, if not you can have a meltdown in your wiring and have fire.

I see they are for water heaters, dont know which one you have, like 6.5 kW(?) then you need the C32 or better B32, it depends on AMps when starting heater> If heater is, like 3 kW, you can have again the B16.

Maybe they are cheaper en therefor in THailand. Or Thai found it annoying when it shuts down. But save?? NO

More safer is a B characteristic breaker. That one goes from 0-1.5 X nominal value.

 

There arent test knobs on breakers, only on a RBCO. It is very wise to have an RCBO placed in your electrical cabinet.

It measures the difference between in and outgoing Amps and shuts down on 30mA, only have that one. NOT 40 or otherwise.

There are also adjustable electronic devices, however i dont trust them. Its switchable, never knows what happens if switch is corroded or what ever. And then your safety is gone again.

This device prevents high currents through your body if you touch it. Hence you make connection to earth and the power will follow your body to go to ground. If you dont have RCBO it s not limited and higher Amp's can pass your body. Your heart cant have that , only 30 mA and not 32 A.

As you have 8 groups, i think you need several of them. I think for each heater seperate ones. Ok you can also put the 2 on one, saves you money and space. BUT be sure then your RCBO can handle the 64 Amps. Then you need one, i saw them in shop RCBO 65A shutdown value 30 mA. 

You have airco's, they are that big C 20A, higher then 3840 watts or 3.8 kWatt? But ok you can have again the 2 on RCBO 65A shutdown value 30 mA. 

The other 4 groups you can place on another RCBO RCBO 65A shutdown value 30 mA.

Your box is too small, and need to be replaced then by a bigger one.

 

You also could do with just one , replace the main fuse C50 by one which is AND a breaker AND RCBO, you need C50 and shut down value 30mA. However if in one group is a problem then everything will shut down.

But this is already a big improvement and safer for you and besides the cheapest. 

 

Consider yourself lucky it didnt touch you.

Can't argue with that!!

[sometimewoodworker]

On 2/14/2019 at 6:54 PM, xtrnuno41 said:

I dont know why people need a C32

Probably because "B" breakers are not easily available.

[giddyup]

Have decided to go with the Schneider circuit breaker. The electrician said that if I buy the unit he will charge me 1000 baht to install, does this seem fair? I know he has to turn off the power at the meter, but after that it's pretty much pull out the old breakers and replace with the Schneider, 1000 baht seems a bit excessive to me.

[bankruatsteve]

1 hour ago, giddyup said:

Have decided to go with the Schneider circuit breaker. The electrician said that if I buy the unit he will charge me 1000 baht to install, does this seem fair? I know he has to turn off the power at the meter, but after that it's pretty much pull out the old breakers and replace with the Schneider, 1000 baht seems a bit excessive to me.

It is - more than a bit.  Is that someone from the PEA?  If not, you should ask there.

[giddyup]

14 minutes ago, bankruatsteve said:

It is - more than a bit.  Is that someone from the PEA?  If not, you should ask there.

Not sure if the PEA actually supplies people to do private jobs.

[bankruatsteve]

1 minute ago, giddyup said:

Not sure if the PEA actually supplies people to do private jobs.

PEA won't "supply" them, but if you go ask, someone will be willing to do it on the side.

[Crossy]

3 minutes ago, giddyup said:

Not sure if the PEA actually supplies people to do private jobs.

They don't, officially. But many of their (mostly highly competent) staff will moonlight.

 

Slightly larger case. We had our four poles from the road to the house installed by chaps driving a PEA truck, wearing PEA uniforms, the poles are stamped "PEA". Of course this was done on a Sunday and a cash payment made  

 

Everyone is in on the act. The PEA inspector who checked our installation noted that the drops between poles were uneven and told them to come back to fix it.

[giddyup]

2 minutes ago, bankruatsteve said:

PEA won't "supply" them, but if you go ask, someone will be willing to do it on the side.

How can I do this with a phone call to the PEA? Will they connect me to an electrician who I can ask?

[giddyup]

3 minutes ago, Crossy said:

They don't, officially. But many of their (mostly highly competent) staff will moonlight.

 

Slightly larger case. We had our four poles from the road to the house installed by chaps driving a PEA truck, wearing PEA uniforms, the poles are stamped "PEA". Of course this was done on a Sunday and a cash payment made 

How did you arrange for them to come?

[bankruatsteve]

1 minute ago, giddyup said:

How can I do this with a phone call to the PEA?

I always went in person, with the wife.  They might not respond to a phone call but I don't know.  For sure most don't want to speak English.

[Crossy]

Just now, giddyup said:

How did you arrange for them to come?

"I" didn't, but Madam visited the local PEA office. Like I noted, even the supervisors were in on the game, nothing surreptitious, just business as usual.

  

[giddyup]

1 minute ago, Crossy said:

"I" didn't, but Madam visited the local PEA office. Like I noted, even the supervisors were in on the game, nothing surreptitious, just business as usual.

  

Pretty  sure the PEA is some distance from where I live so not sure that's going to be practical, but I'll ask around.

[VocalNeal]

2 hours ago, giddyup said:

Have decided to go with the Schneider circuit breaker. The electrician said that if I buy the unit he will charge me 1000 baht to install, does this seem fair? I know he has to turn off the power at the meter, but after that it's pretty much pull out the old breakers and replace with the Schneider, 1000 baht seems a bit excessive to me.

 

WHAT? Minimum wage is 300+  He has to travel to you and provide his own tools etc., and travel back home.  

 

Just say yes and pay the man.

 

Try calling an electric gate company in Bangkok. May of them won't get out of bed for less than 10,000.