RCD - How safe?

[PabloP]

Good to see that you survived the belt.

I believe that reading between the lines that the cause was a mix of things.
- The Xu1 doesn't have an earth wire, else it would have tripped
- There is a fault or weakness in the double insulation properties of the XU1
- In this case you became the earth path from water that leaked into the Xu1 internals.

As a couple of others have said -
Tathradj - I also am not a person that likes double insulated gear especially when aged
19.3 - RCDs do not protect against all weaknesses, as ably demonstrated in this case
One from me - even having the earth lead will not protect against all weaknesses.

I am not an electrician, but am qualified to do test & tag and do many hundreds each year, and I have had similar jolts from gear with an earth connection. Immerson pump in one case running from a non earthed generator (current standard does not require or advise that they be earthed), as I believe it is less of a risk to not earth the generator.

I would definitely put that Xu1 in the bin, and perhaps stay away from them, as we have had many cases of early mortality, as they are only meant for very short term activities and overheat easily. People often don't read the duty cycle info on the doco, even if it is supplied.

Rob P.

 

[Nightjar]

Our earth system is a copper rod belted into the ground at the front tap so that catches the drips- or whenever we use the hose.

Jaros, MB, You will find most homes have the earthing rod near a tap. Some homes you will find the earth wires actually clamped to the galvanised or copper water pipes. Jaros as you mention the ground is usually damp which improves the earth.
The RCD should still function with poor earthing but the chance of electrocution and fire is increased. Push your RCD button MB, missing a bit of the cricket is a better alternative. Offer a beer or three to one of the mining company electricians, feel sure they would gladly check out your system?

 

[mbasko]

The RCD definitely should have tripped and I don't think pressing it's test button is going to prove anything but I'll give it a go

Your right - probably won't prove anything but it's an easy to do check & quickly eliminates/proves one possible problem. The trip mechanism can fail hence the test button although they reckon household RCD's should last without issue for at least 10 years.

 

[Swinging & digging]

Our earth system is a copper rod belted into the ground at the front tap so that catches the drips- or whenever we use the hose.

Jaros, MB, You will find most homes have the earthing rod near a tap. Some homes you will find the earth wires actually clamped to the galvanised or copper water pipes. Jaros as you mention the ground is usually damp which improves the earth.
The RCD should still function with poor earthing but the chance of electrocution and fire is increased. Push your RCD button MB, missing a bit of the cricket is a better alternative. Offer a beer or three to one of the mining company electricians, feel sure they would gladly check out your system?

According to AUS / NZ 3000 Electrical wiring rules. All metal conductive pipes are connected to the earthing system in an electrical installation. The earth electrode is connected to the earth bar in the switch board. The connection to the conductive water pipes is connected to the earth bar in switchboard as well. It is a requirement upon completion for this to be tested by a licence electrician.

Around two years ago a young teenage girl in a rental property in Perth received an electric shock from touching a tap, she suffered significant injuries from the accident. Most likely the incoming neutral to the property was disconnected or had a very high resistance connection. This makes the return current path through the earthing system. The tenants had reported getting tingles off the taps to the Housing commission and an electrician? Had visited the premises but not found a fault?

 

[Moneybox]

Well I checked it out.......

1. Yes I have an earth stake by the tap in damp ground.

2. I pressed the test button on each of the four RCD's and each triggered as expected.

3. Using the same extension lead, I set up a couple of lamps (couldn't find a regular globe), one an LED lead light and the other a QI bed lamp.

I clamped one pin of the plug to the SS cabinet that is standing on the same concrete slab. Then I plugged in a 240v cable with both active and neutral cables bared. You never know which one is active because it could have been wired either way but I flashed each wire onto the exposed pin without any response from either lamp. Perhaps my SS cabinet failed to make good contact with the concrete slab?

4. I tossed the exposed wires into the plastic wheel barrow and they flashed.

Mrs M said "Do that again for the camera" as she usually does. So after checking that the cricket was still showing on the TV I flashed it again :fire: , and again :fire: until the active and neutral wires welded together and started to smoke.

5. I quickly disconnected the plug to save my wiring from a meltdown. After the excitement Mrs M returned to the house and I heard the gasp.. 8.( . The test cricket was on TV and it had eventually gone off. The RDC did trigger in the end but the current that flowed through those wires could have easily fried :fire: my delicate anatomy :awful: by the time that happened.

6. I think I should add "DON'T TRY THIS AT HOME". :lol:

If this place was wired with our old system of fuse wires the first flash would have blown the fuse. Isn't modern technology great... :/

 

[Nightjar]

MB, There is obviously a serious/dangerous fault with your house wiring, certainly wouldn't shrug it off.

 

[Moneybox]

MB, There is obviously a serious/dangerous fault with your house wiring, certainly wouldn't shrug it off.

Perhaps, but looking at the link Simmo supplied, flashing the active and neutral wires didn't trigger the RCD because the current never went to earth. It only triggered the RCD because of current overload so high that somebody could easily have been electrocuted. I need to go back to my first test with the globe sending a trickle of current to ground. That should trigger the RCD but for some reason I never completed the circuit. We accidentally flashed the wires and brought the test to an end. I'll take another look later on with a conformed ground point.

If I don't get back to you, well you can draw your own conclusion... :8

 

[Swinging & digging]

An RCD will trip for an earth leakage current, not for a balance between active and neutral, example if your appliance draws 4.0 amps this current will be present in the circuit in both active & neutral conductors. If you have a fault that allows some current to go to earth the RCD detects the out of balance condition, say you have 4.0 amps in the active and 3.2 amps in the neutral, 0.8 amps flowing to ground.

Some RCDs are both Circuit Breakers & RCDs providing overload and earth leakage fault protection.
Labelled RCBO, check your switchboard, you will notice the power points will be either protected by
20A or 16A rating, and 30mA for your earth leakage. The presence of a test switch is also a clue
as to wether you have RCD protection.

Depending on the age of your house will dictate what equipment you have, there are still ceramic fuse
holders with fuse wire in service and houses with no RCD protection, mine was built in 1986 and had
the old style fuses until upgraded 6 months ago.

 

[Moneybox]

I might just add my opinion on Test & Tag.

This is one of the major industry rip-offs of the modern era. It serves absolutely no purpose other than milking and funds from businesses Australia wide. If I'm going to slice my lead through with the circular saw or grinder that tag won't do much to save me.

 

[Greenhornet_au]

RCD

or

ELCB

There is a difference on how they function, they are different devices.

Your RCD could have let you down.

I suggest that maybe your liquid method of keeping the dust down was not so smart, grinders have fans that suck air over the poles and commutator
to keep things cool.
The fan likely sucked in some water spray from the work surface which then allowed a path for 240V to pass to the normally double insulated metal surfaces.
Water on the carbon brush holders and internal casing would do that, contact with a conductive surface, and then an earthed surface would provide another bridge.

An RCD may not work in these circumstances, it is possible the load on Active and Neutral could be balanced enough, even with your 'barrow and wire' test.
Particularly if the wiring of the RCD was not correct in the switchboard to begin with.(test button would not show that fault)
Different brands of RCD described different methods to wire them - crap idea.

Testing of an RCD or ELCB or even Circuit Breakers is important on a regular basis, contacts internally can become 'surface welded' together,
once every few months would be good. - Mine have never been done by me in many years

Because it is double insulated DOES NOT mean it is safe to use in water !! Rather the opposite !!

Count yourself lucky, really lucky.

Your grinder is probably fine, just let it dry our properly, have it checked if you want to.
Generally all these double insulated devices have to be tested and compliant to standards before allowing them to be sold in Australia.
That is not done for Ebay electrical product imports - a huge problem.

Your "barrow test" really worries me, there is enough current there to melt your wiring inside your house walls !!
Get it all checked properly, and get a certificate of compliance from the sparky, you are going to need it for your household insurance in future.



Cutting dry you can use a fan to blow away the dust if you have no vac that can suck it up, or crack it off with a bolster chisel and hammer.

 

[Swinging & digging]

I might just add my opinion on Test & Tag.

This is one of the major industry rip-offs of the modern era. It serves absolutely no purpose other than milking and funds from businesses Australia wide. If I'm going to slice my lead through with the circular saw or grinder that tag won't do much to save me.

Test and Tag was mainly brought in due to a number of incidents with extension leads on construction sites.
Your lead can be perfect and pass all the tests and inspections, but destroyed by smoko like when a fork lift
truck drives over it, or it gets jammed by a closing door.

Many insurance companies have asked the government to implement testing of all household appliances?
That would cost an absolute fortune.

 

[Moneybox]

RCD

or

ELCB

There is a difference on how they function, they are different devices.

Your RCD could have let you down.

I suggest that maybe your liquid method of keeping the dust down was not so smart, grinders have fans that suck air over the poles and commutator
to keep things cool.
The fan likely sucked in some water spray from the work surface which then allowed a path for 240V to pass to the normally double insulated metal surfaces.
Water on the carbon brush holders and internal casing would do that, contact with a conductive surface, and then an earthed surface would provide another bridge.

An RCD may not work in these circumstances, it is possible the load on Active and Neutral could be balanced enough, even with your 'barrow and wire' test.
Particularly if the wiring of the RCD was not correct in the switchboard to begin with.(test button would not show that fault)
Different brands of RCD described different methods to wire them - crap idea.

Testing of an RCD or ELCB or even Circuit Breakers is important on a regular basis, contacts internally can become 'surface welded' together,
once every few months would be good. - Mine have never been done by me in many years

Because it is double insulated DOES NOT mean it is safe to use in water !! Rather the opposite !!

Count yourself lucky, really lucky.

Your grinder is probably fine, just let it dry our properly, have it checked if you want to.
Generally all these double insulated devices have to be tested and compliant to standards before allowing them to be sold in Australia.
That is not done for Ebay electrical product imports - a huge problem.

Your "barrow test" really worries me, there is enough current there to melt your wiring inside your house walls !!
Get it all checked properly, and get a certificate of compliance from the sparky, you are going to need it for your household insurance in future.



Cutting dry you can use a fan to blow away the dust if you have no vac that can suck it up, or crack it off with a bolster chisel and hammer.

Having trust in the RCD is what let me down. I expected it to trip before I got a decent shock from it.

I know I shouldn't mix power and water but once again I was thinking that I had that level of protection.

The grinder is working as well as it always did. I even used it yesterday but made sure I was standing on dry rubber soles and holding on to the plastic housing. It spent this morning baking in 40+ degrees of sunlight. Most likely suffering now from a meltdown :|

I can understand why the short circuit didn't trip the RCD, the current didn't go to ground. Yesterday was different, I created the connection to earth so it should have tripped.

We had the electrical circuitry checked out before we bought the place in November last year. The problem is you never know who's doing the checking and how much they care. I simply don't trust tradesmen or just about anybody you pay for service. Too many people are just out for the money and not doing a job that they can be proud of.

 

[Moneybox]

I might just add my opinion on Test & Tag.

This is one of the major industry rip-offs of the modern era. It serves absolutely no purpose other than milking and funds from businesses Australia wide. If I'm going to slice my lead through with the circular saw or grinder that tag won't do much to save me.

Test and Tag was mainly brought in due to a number of incidents with extension leads on construction sites.
Your lead can be perfect and pass all the tests and inspections, but destroyed by smoko like when a fork lift
truck drives over it, or it gets jammed by a closing door.

Many insurance companies have asked the government to implement testing of all household appliances?
That would cost an absolute fortune.

Exactly my point. If you're going to damage an electrical device or lead then the tag makes no difference. It's superfluous and a waste of time and money for anybody apart from the persons doing the tagging.

 

[Moneybox]

I've been busy today mixing concrete but I might get a chance in the morning to have a go at shorting a trickle current to earth. I just want to see these things trip out when they are meant to even though they obviously don't give the protection I thought they were meant to.

 

[Tathradj]

Had a smart arse electrician test a store once.
Mega tested all the UPS's.
Scratch 14 UPS's as it stuffed them.
They had a red label under them,
"Do Not Test. "
3 of them were rack mount 2kva pure sine wave jobbies.

Explanation of a UPS.

UPS is a device that sits between the wall outlet and a computer.
It has batteries in it so that if the power goes off or goes too high
or low, The circuitry switch's the mains off and runs on battery power
until the power is restored to normal.
If the power does not restore before the battery (s) discharge to a
pre determined level, The monitoring software shuts down the computer
gracefully saving a tedious rebuild or a loss of trade.

They are all wired with earth reference and they will trip if there is excessive earth leakage.

Megga Testing uses a high amount of voltage that is measured to find out if there is any
leakage within a device or lead.
"Fly back" circuits as in a UPS will be destroyed if tested in this way.
A proper UPS is a very safe device to use.

I might just add my opinion on Test & Tag.

This is one of the major industry rip-offs of the modern era. It serves absolutely no purpose other than milking and funds from businesses Australia wide. If I'm going to slice my lead through with the circular saw or grinder that tag won't do much to save me.

 

[PabloP]

I am not sure that I fully agree with you MB, the testing can and does find many very serious issues that could have severe consequences if not found and corrected. I am involved with almost 2000 tests each year (all as a volunteer for a charity, so no-one is being ripped off) and while most items are ok, on average we will find issues with between 5% & 10% of gear each year. Some of the issues are of a minor nature and most are found by physical inspection rather than electrical testing, but some are found by the electrical testing.

The Test & Tag Standards are intended to reduce the potential for a range of conditions that are known to introduce or increase the risk to the user. They don't and and can't eliminate the risks or manage the poor practices that may be being used (stupidity in some cases), but they do help, and so while it is not work that I like doing, it is work that I will do as it helps to protect the users of our equipment (not eliminate the risks). Understanding the reasons for the Standards and seeing some of the issues found, does help in appreciating the value of the Test & Tag work.

Some industries have implemented more strict practices in their interpretation of the Standards. Unions may have had some influence in that area, but then they can be higher risk industries.

Rob P.

 

[Moneybox]

I am not sure that I fully agree with you MB, the testing can and does find many very serious issues that could have severe consequences if not found and corrected. I am involved with almost 2000 tests each year (all as a volunteer for a charity, so no-one is being ripped off) and while most items are ok, on average we will find issues with between 5% & 10% of gear each year. Some of the issues are of a minor nature and most are found by physical inspection rather than electrical testing, but some are found by the electrical testing.

The Test & Tag Standards are intended to reduce the potential for a range of conditions that are known to introduce or increase the risk to the user. They don't and and can't eliminate the risks or manage the poor practices that may be being used (stupidity in some cases), but they do help, and so while it is not work that I like doing, it is work that I will do as it helps to protect the users of our equipment (not eliminate the risks). Understanding the reasons for the Standards and seeing some of the issues found, does help in appreciating the value of the Test & Tag work.

Some industries have implemented more strict practices in their interpretation of the Standards. Unions may have had some influence in that area, but then they can be higher risk industries.

Rob P.

Rob, they may be a big difference here with what you are doing compared to some turkey just tagging equipment and leads for a job. We used to take on a certain line of work because that was what we were good at or what we enjoyed doing. Too many people, and many of them tradesman, are just doing a job for the sake of having a job and the outcome is rarely good. Then I suppose these people may need somebody to hold their hand when it comes to looking after the gear as well. Never mind, it's a practice I don't agree with.

 

[Moneybox]

Can you imagine me calling an electrician to Cue from the nearest town Meekatharra just 115km away and asking to have my home electrics checked out. I might get lucky and actually get onto somebody who cares enough to tag my job on to somebody else's but the best chance is that we'd both be charged 3 hours travel for a job that could likely be knocked off in under an hour. Even that mightn't be too bad if you actually got a decent tradesman but I know the odds

 

[Nightjar]

Can you imagine me calling an electrician to Cue from the nearest town Meekatharra just 115km away and asking to have my home electrics checked out. I might get lucky and actually get onto somebody who cares enough to tag my job on to somebody else's but the best chance is that we'd both be charged 3 hours travel for a job that could likely be knocked off in under an hour. Even that mightn't be too bad if you actually got a decent tradesman but I know the odds

MB,Can see where you coming from BUT, calling the authorities to say your lovely lady is laying unresponsive. or the reverse her calling...............
Your call mate!

 

[Simmo]

Can you imagine me calling an electrician to Cue from the nearest town Meekatharra just 115km away and asking to have my home electrics checked out. I might get lucky and actually get onto somebody who cares enough to tag my job on to somebody else's but the best chance is that we'd both be charged 3 hours travel for a job that could likely be knocked off in under an hour. Even that mightn't be too bad if you actually got a decent tradesman but I know the odds

Nah man!!!! Pure Wrong!!!

31 compressions to 2 breaths mate... for an hour an a bit...

I'd turn the frikkin power off and get nekkid, light a fire, cook a damper, grab a red wine and wait for that dickhead tradesman!!