Neutral earth bonding on backup systems.

[Justloadit]

""""Depending on the generator, it has an earth terminal connection, it does not have an internal earth bond as per your statement, as an alternative supply, it requires an earth neutral bond for proper operation, which is done at the time of installation, just as with an inverter. There is no fail safe mechanism on the generator either. Not connecting Neutral to earth, will not trigger the ELU when there is an earth fault, and the reason for doing this when the inverter is in islanding mode.""""

excuse me --- what statement??????

and yes, some generators (quite a lot) does have a permanent N/E bond directly on the winding side, built into the gennie.



I have been repairing generators before the dead sea was even sick and i have seen a lot of gennies in my 60 years with a permanent N/E bond INSIDE the gennie.

anyway - i see no use debating this further following this somewhat biased narrative.

good day.

Attachment 8894

Thank you for the photograph.
Interesting I had tested 2 large generators, and none have an earth Neutral bond so with this information, I made my post as you have highlighted "and yes, some generators (quite a lot) does have a permanent N/E bond directly on the winding side, built into the gennie."
So according to your statement, this mean that gennies with out the internal Earth Neutral bond do not comply.

Please note that we are all friends here from a vast number of backgrounds, and if a question is made, it is with intent of getting some information.
Debating is how we learn.

[Justloadit]

In reference to NRS-097-2-1-Published-2024, kindly provide by GCE in post #121, I have copied the following referring to inverters and Earth Netral Bonding

5.4 Neutral to earth bonding when forming an intentional island

5.4.1 To prevent a SSEG neutral connection to the the utility neutral through an earth conductor when the SDU opens, the SSEG shall not have a permanent neutral bonding to earth.
5.4.2 A hybrid system intended to form an intentional island on the load side during utility supply interruption shall open the SDU to prevent unintentional island on the utility side.
5.4.3 Since the SDU opens the neutral on the utility side, the intentional island neutral shall be bonded to earth within 200 ms after the SDU operation using a neutral to earth bonding unit (NEB).
5.4.4 The NEB shall open within a time period of 200 ms before the SDU reconnects the inverter to the utility supply.
5.4.5 The NEB shall consist of an electromechanical switching device rated at the nominal current rating of the inverter.
NRS 097-2-1:2024 12
5.4.6 The total clearance between the inverter neutral and earth conductors when the NEB is switched off, shall be equal the clearance of the SDU in its open state or more.
5.4.7 The NEB shall be an internal inverter component or an external device that is activated by a dedicated control port of the inverter.
5.4.8 The inverter data sheets shall indicate that it contains an internal NEB or a dedicated NEB control port for external devices.
5.4.9 Installation requirement: Inverters equipped with the NEB control port only, shall have external electromechanical NEBs installed that are SANS/IEC 60947-1 and SANS/IEC 60947-4-1 certified.

[Derlyn]

Question.

If one opens the back end of an alternator and finds the neutral and earth are bridged, how does one know when this bridging took place ?

Was it before the unit was sold as new, or was it done by someone like myself afterwards ?

Difficult to answer.

Does it matter ?

I say no. What matters is that it's there and it will ensure that a RCD in working order will do it's job and disconnect the supply should an earth fault occur. That's the important part.

The big problem with alternators is that the suppliers make no distinction between a portable unit and a standby unit. Here I'm referring to the smaller types that are sold at hardware stores to the general public and not the big diesel units used as standby units for whole shopping centres etc.

If one were to ask the salesman whether the unit you are eying to buy is a portable or standby unit, the chances are in the region of 99% that you'll get a blank stare reaction. Should you ask if the unit may be used as a standby unit at home, you will get a resounding "yes" even if it's VOV wound. All he wants to do is make the sale.

It is up to us, as electricians, to educate our clients as to the importance of certain procedures that need to be followed when doing a standby alternator installation. How many times has it not happened when quoting on a job that the prospective client questions why an earth spike at the alternator is necessary when his buddy down the road doesn't have one. I then explain with pen and paper and with the assistance of my reg book, why it's necessary. One or 2 days later I get a call from his buddy to come around and inspect his installation and do what's necessary to make it compliant and reasonably safe.

Anyway, just to end off, I am a toppie with many, I mean many domestic alternator installations under the belt and have yet to see a newly purchased alternator of 8Kw or smaller that has a permanent neutral earth bridge on the output. I've always had to do it myself. Hence my original question.

Have a super week ahead, all.

[Isetech]

I fit a changeover switch and breakers to suit the cable size, socket rating and changeover, I then a socket on the wall and what people plug into the socket is not my concern.

There is a notice above the socket ...

Do not plug in V-O-V generators.

Suitable for a 5 kva or what size the system was designed for a the time.

There is not much more you can do.

[Derlyn]

So this morning I was called out for an inverter tripping on overload intermittantly.

After much testing, I found that when the geyser is on, the output reading on the inverter goes up to over 4Kw even although the geyser is not fed by the inverter.

Whilst getting this reading of 4Kw, I put a clamp meter on the inverter output and it was only supplying 1,5 A (+-340W). The electronics of the inverter was somehow reading the current drawn by the geyser even although it was not supplying the geyser. It was time to call a friend.

The problem dissapeared when the permanent neutral earth bond on the inverter output was removed. As soon as it was replaced, the fault showed up again.

A couple more tests were done and it was found that everything was A ok when the earth neutral on the inverter is ONLY bridged whilst in islanding mode. The current in the earth neutral bridge was 10,5 Amps.

Anyway, thought I,d mention the above in case anyone comes across the same fault one day.

Moral of the story. DO NOT bridge the neutral earth on the inverter output permanently. Use a relay to perform this function when in islanding mode only.

Thanks for the assistance this morning Isetech. Much appreciated. And so we learn.

[GCE]

So this morning I was called out for an inverter tripping on overload intermittantly.

After much testing, I found that when the geyser is on, the output reading on the inverter goes up to over 4Kw even although the geyser is not fed by the inverter.

Whilst getting this reading of 4Kw, I put a clamp meter on the inverter output and it was only supplying 1,5 A (+-340W). The electronics of the inverter was somehow reading the current drawn by the geyser even although it was not supplying the geyser. It was time to call a friend.

The problem dissapeared when the permanent neutral earth bond on the inverter output was removed. As soon as it was replaced, the fault showed up again.

A couple more tests were done and it was found that everything was A ok when the earth neutral on the inverter is ONLY bridged whilst in islanding mode. The current in the earth neutral bridge was 10,5 Amps.

Anyway, thought I,d mention the above in case anyone comes across the same fault one day.

Moral of the story. DO NOT bridge the neutral earth on the inverter output permanently. Use a relay to perform this function when in islanding mode only.

Thanks for the assistance this morning Isetech. Much appreciated. And so we learn.

I would hazard a guess and say you are going to be back there for a mains incoming neutral fault - Could be that there is a loose connection coming into the property and that every now and then it utilizes the inverter neutral due to the bonding

[Derlyn]

You are probably right GCE.

I'll wait for them to phone and tell me that they're getting a tingle on the shower taps.
That's my bad neutral signal.

[Isetech]

or flickering lights.

You are probably right GCE.

I'll wait for them to phone and tell me that they're getting a tingle on the shower taps.
That's my bad neutral signal.

[Isetech]

The more I scratch this neutral/earth bond the more it itches.

Too many things popping up which are neutral/earth bonding related issues.

I hope it is not going to take a person getting electrocuted for the powers that be stand up and sort it out once and for all.

I am willing to step up and join a group of people with a lot of elctrical experience to sit down with a bunch of meters and technical skills and try figure out how to create a safe environment for the public. I can make time on a Saturday morning and my time will be free.

Herholdts has a decent service centre in Durban with all the equipment needed to test and test some more. It would be even better if Sunsynk stepped up and showed their commitment to resolving this issues which negatively effects their equipment, because of the open relay which is not fail safe. They have the capacity to make their units safe in SA.

[Isetech]

What would we be trying to achieve:

1/ To find a way to make the relay fail safe, by using a N/C contact, which would have to be linked to the inverter control and display a fault, and message to the app. This is the only method you can use in eThekwini.

2/ To identify if the permanent bond is dangerous, why there is a high current on the bond and if it poses a danger to the the public and animals or if it is just circulating current within the system. THERE SHOULD NEVER BE A A CURRENT ON AN EARTH WIRE, UNDER NORMAL OPERATING CONDITIONS EVER. If you think I am talking crap, connect an earth leakage unit and tell me what happens.

3/ To identify which earth arrangement requires a permanent bond or a rely, as we are all aware, you cannot by law do a permanent bond on on an inverter with a TN-S system, which is the earthing arrangement in eThekwini. I cannot comment on other parts of the country. This also why it is so important for people to start doing a little research s that they know what system arrangement is applicable for their area.