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Observations on E/L tripping


MaurizioZA
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I have some observations and empirical conclusions which may be relevant only to my hybrid inverter (Santek HS 4.5kw which should be equivalent to the Infini 3kw plus) or maybe not.

Firstly: I have no real issue with E/L tripping (even if if neutral and ground are not bonded on the inverter output).

I used to have a little of a problem but only until I realized that I was not following the correct bootup procedure for the inverter (start up inverter with DC only and only after all was stable switch on AC grid power to inverter and only then push  ON button on inverter to enable grid if I did not wish to wait 5 minutes). 

However I did notice that whenever I add a circuit breaker under the inverter E/L, the E/L may become unstable and more prone to tripping. In order to resolve the issue I need to reboot the inverter as described above.

This procedure is similar to what described in the Fault Reference Codes section of the inverter manual 

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Now that I have finally identified that the cause of odd trips of E/L under inverter I can state that they were "not completely related to my inverter" but rather due to an actual leakage in one of my circuits (garden lights during or after rain).

[how did I find out that? I bypassed inverter for circuits U/L and my main E/L also tripped. Then I removed one by one circuits until I identified the faulty one].

Clarification of "not completely related to my inverter": the E/L trip could also be resolved in that particular moment simply by rebooting up the inverter following the procedure above.

However if I rebooted the inverter in a dry moment as it rained the E/L under inverter would start tripping again.

My personal feeling (and it is nothing more than a feeling) is that during bootup the inverter registers the potential difference between neutral and earth and only if there is an increase in difference it will trigger the E/L. A fault or even adding a circuit might trigger the event.

While thinking of a way to describe this I came up with the term "dynamic E/L".

I think that it is quite important to get to the bottom of this issue since if my observations are correct it might be possible, unwillingly, to add an unsafe faulty circuit under inverter E/L.

I am also asking myself if then bounding neutral and earth on the inverter output becomes a necessity rather than an option (wouldn't that also neutralize the negative effects of a "dynamic E/L"?).

Maybe others might wish to voice their opinion and experiences on the matter.

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Some years ago I had the strangest problem with an ELB. It would trip randomly, but ONLY if the tumble dryer and the electric fence energizer was plugged into the same circuit. Eventually we used an extension cord to power the tumble dryer from a nearby circuit and this went on a few years, until one night it tripped and nothing would bring it back. At this point I found out that the neutral side of the ELB had gone open circuit. Replaced the ELB and we could finally move the tumble dryer back to a closer plug.

To this day I do not understand what went on there. The Fence energizer, completely encased in plastic, doesn't even have an earth pin...

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In case anyone wonders: I have installed under inverter a brand new E/L just to be sure there is nothing funky with the E/L breaker itself.

I have another two E/L breakers in the cb board (one 3-phase E/L and one single phase for outbuildings ... any [email protected] device connected there does not affect me) which I can use as control in case of doubts.

I have noticed that the outbuilding E/L is extremely sensitive to tripping. I was explained that this is to be expected since the more the trips the more sensitive an E/L becomes ...  until eventually it needs replacing.

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15 hours ago, MaurizioZA said:

I have noticed that the outbuilding E/L is extremely sensitive to tripping. I was explained that this is to be expected since the more the trips the more sensitive an E/L becomes ...  until eventually it needs replacing.

Doesn't make sense, the current imbalance is sensed by electronic components, the only wear and tear can occur with the mechanical tripping components.

Have an electrician Meggar the outbuilding circuits, a combined insulation resistance reading 11Kohm and you will have tripping, each individual circuit should have reading not less than 1Mohm.

Also check the tripping current with an Earth Leakage tester, with all circuits isolated, tripping will occur at 20ma. With circuits on, tripping will occur at a lower current.

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Theories should be based on observations: if observations don't tie up with theory something is not 100% with the theory itself ;)

11 hours ago, Eugene said:

the only wear and tear can occur with the mechanical tripping components.

I have no opinion about E/L electronic components but I tend to agree with the statement above: I suspect that mechanical components might be the main weakness of CBI E/L units (no experience with other brands).

More on observations: most qualified electricians I have come across (except one) whenever have trouble resolving a leakage issue for work they have done will resort to take a circuit out of leakage and have no trouble issuing a CoC.

Wear and tear is a tricky subject: would you define as wear and tear 10-20 trips in 60 days? Or is wear and tear defined by a magnitude of hundreds of trips ?

The previous E/L unit (I still have it somewhere) progressively became more and more sensitive to trips so much so that after a few months since purchase it could not be re-engaged (unless main was switched off as discovered later). This unit was returned to CBI which found it to be in order rejecting the electrician guarantee claim (although with recommendation that e/L should only be re-engaged only with main power off - I see no such warning printed on E/L unit). A few (20?) trips later it  became unable to be re-engaged at all but by then it was out of guarantee :(

Until this unit worked satisfactorily under supply from grid (notwithstanding nuisance that main had to be switched off before it could be re-engaged) it never worked at all under inverter: within one hour it would trip for no apparent reason.

On the other hand a brand new identical unit has worked and is working well under inverter ... at least until an actual leakage event recently triggered it. Once that leakage issue was resolved it has worked well once more.

 

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On 14/03/2016 at 10:04 PM, plonkster said:

To this day I do not understand what went on there. The Fence energizer, completely encased in plastic, doesn't even have an earth pin...

There doesn't need to be current in the earth lead, unless it's a very old type of "earth leakage" detector. In Australia (I don't know about South Africa), "earth leakage" detectors were replaced decades ago by Residual Current Devices, which detect a difference in current between active and neutral. The difference is presumed to be earth leakage, potentially through a human or pet, so more than a certain level (often 30 mA these days) will trip the device. Colloquially, these are sometimes still called "earth leakage" devices. I suspect that this is the case in South Africa as well (it seemed to be confirmed by a very brief Google search).

An electric fence has plenty of opportunity to leak to earth (ground). It should not, of course, if it is operating correctly; there should be isolation in there so that the shock delivered won't be more fatal than was intended :o Perhaps the isolation has been compromised, perhaps by water or dirt that has taken in moisture over the years.

Edited by Coulomb
Added "decades ago"
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You know, after I posted that, that was my thinking too: That all that is needed is a leak to ground. It still does not quite explain why the problem goes away if you put them on separate circuits, seeing as the whole house is on one ELB (two now, the Inverter has its own).

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> It still does not quite explain why the problem goes away if you put them on separate circuits, seeing as the whole house is on one ELB

Indeed. I hate to say it, but the only thing I can think of is that one circuit has active and neutral swapped, and the leakage is only from active to earth. Might be worth checking?

It might be trying to tell you something... :o

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above conversation just reminded me of that strange neutral (blue wire covered by black insulation tape) I had found in the main board. Obviously during house wiring they ran out of black wire and they must have made a "plan". I need to trace it because I have a feeling it might bring to light the reason why I have a couple of plug points intolerant with E/L when some appliances  are plugged in and cooked a notebook power supply while I was moving some circuits from one phase into another.

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1 minute ago, plonkster said:

I have an entire "wing" (the flat on top of the garage) wired with blue wire. It's passed inspection twice...

Also queried this and have been told that blue is acceptable for neutral.

My stove also uses a blue wire for neutral.

Then if you think about it guys the colour of plug wires also use blue for neutral ;)

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Just now, viper_za said:

Also queried this and have been told that blue is acceptable for neutral.

I have live wires that are blue. I saw it when swapping out a dimmer switch... which I had to do because the LED lamps I installed wasn't dimmable. SO I don't know if it has something to do with the two-switches-one-light thing that you do where two wires run between two change-over switches... so that the wires are live but only one of them is live depending on switch position... but there are blue wires in there that carry live current.

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1 minute ago, plonkster said:

I have live wires that are blue. I saw it when swapping out a dimmer switch... which I had to do because the LED lamps I installed wasn't dimmable. SO I don't know if it has something to do with the two-switches-one-light thing that you do where two wires run between two change-over switches... so that the wires are live but only one of them is live depending on switch position... but there are blue wires in there that carry live current.

For this I would say someone needs a slap against the head, but when using it for neutral thinking of the plug wires it makes sense.
Other thing that was mentioned to me was made distinguishing the specific circuit also a little easier

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no idea what present regulations are but in a 3-phase board (phases on red-yellow-blue with neutral black) blue for neutral is misleading (I guess that's why it had been covered with black tape). To me it does not seem right to have some conduits where blue is phase blue and others where blue is neutral.

On the other hand electrician who wired house on output of 3-phase circuit breaker of borehole pump used black-red-red-yellow and then in a box (where armored cable black-red-yellow-blue is connected) one of the reds becomes blue. confusing

Also confusing is yellow or white: all new cables come with yellow but in the old days it was white. And some electrician insist on using white for yellow adding a new colour in board (I replace with yellow once they are gone).

By teh way: JHB CityPower uses yellow and technicians refer to yellow phase.

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  • 3 weeks later...

SANS 10142-1:2003 Edition 1.1 (As amended 2003)  6.3.3.2  The means of identification for an a.c. circuit may be by colours or by numbers, as follows:  a) where colours are used   1) a neutral conductor shall be identified by black only,   2) an earth continuity conductor shall be identified by the bi-colour green/yellow only, or by being bare. Green/yellow insulated conductors shall NOT be used as live conductors under any circumstances,   3) a phase conductor shall be identified by a colour other than    green/yellow, green or black, and  Amdt 1  
 NOTE  Welding cable manufactured to SANS 1576 (SABS 1576) should not be used in circuits above 100 V. Amdt 1   4) the colours may be applied at the ends of the conductor (of a multicore cable) by means of durable colour marking (e.g. insulating sleeves or by electrical insulating tape wound more than once around the conductor), and Amdt 1 B) where numbers are used, "0" shall indicate the neutral conductor.     Amdt 1  
 NOTE  Where the purpose or the function of a conductor is apparent, marking is not required. 

Extract from my 2003 copy, doubt whether it has changed much since I retired.

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Some older installations (prior to SANS 10142) allowed Blue for Neutral in Single Phase installations, hence the amendments. Also, older installations can still have a traditional "Earth Leakage" (with an Earth detection) rather than a "Leak Current" detection. We still refer to both as Earth Leakage.

While "Earth Leakage" systems are still allowed and will pass most CoC if existing (electrician dependent), it is HIGHLY recommended that it be replaced. Traditional "Earth Leakage" systems can be slower to respond to faults. Any new/replacement HAS to be with "Current Leakage" (you can't even buy the older type anymore).

Source: My memory from SANS 10142 Course & Exams in 2014, where these exact questions were asked.

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