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Sunsynk, and the earth neutral bond, again!


Elroc

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Sorry for raising this topic again, I see it's a frequent and well worked through one on this forum across a plethora of threads, but I'd like to try and summarize what I've learned and check if my understanding is correct.

Context:

I recently had my entire system installed - Sunsynk 5.5 kw inverter, 2x Shoto 5.2kWh batteries, 12x 545w Solar panels. Without the earth neutral relay bond I must add, something my installer seems to not be aware of - more on this later. As an engineer myself I like to understand how/why things work so I can fix it or understand why it doesn't work, and this led me down this rabbit hole.

My understanding - please correct if I'm wrong:

1) In the majority of South Africa installations, Neutral is bonded to Earth coming from Eskom at some point prior to entering my house, likely at the meter box, or the transformer. Regardless of this bonding, for the purposes of wiring inside the house, Earth, Neutral and Live are to be treated as distinct lines. I'm not aware of a grid related earth spike on my property, and I only have an earth wire coming from the meter box on the opposite side of the road. 

2) SANS regulations require that in a UPS installation, such as my Sunsynk inverter, split neutrals be used. I.e. The neutral on the non essential (LOAD) side of the inverter shall NOT be connected to the neutral on the essential (LOAD) side of the inverter. I'm sure there is more motivation than just SANS, but for the purpose of my current understanding this is sufficient motivation. Also, both GRID and LOAD side needs their own earth leakage breaker.

3) Within my house wiring earth should be common across the board - I.e all earth (PE) lines can join on the same bar in my main DB. This is in relation to the AC circuitry of course. Panels have their own unique earth spike.

4) When Eskom is on, and the inverter is running in 'normal' mode, the LOAD and GRID live and neutral lines are connected internally in the inverter. This allows the inverter to blend power from multiple sources. 

5) When Eskom goes down, we effectively lose the earth/neutral bond on their side, and we're left with Live and Neutral with no reference to ground, and what people see elevated voltage output on the inverter load output.

6) Because of 5) we need to create that earth/neutral bond in-house dynamically when Eskom power goes out to prevent the elevated voltage, and other funnies. This is where the bonding relay and the Sunsynk islanding mode signal comes into play.

7) Why can't we bond earth and neutral permanently on the inverter load output and take out the need for the bonding relay?

7.1 ) It's not allowed by SANS to have another earth/neutral bond in the home? [citation needed].

7.2 ) Because of the earth neutral bond existing on Eskom side, if we do ANOTHER earth/neutral bond on the house side while Eskom is live, it effectively connects the split neutrals from 2) above via ground. This is a problem because it risks negating/messing with the earth leakage breaker functionality? I'm still fuzzy on why though.

-------

Theory 101 complete, now to my localized issues:

My installation concern:

My installer has connected the Neutral port on the LOAD side of the inverter to both Neutral for the essential loads, AND to my common earth. He's not connected the Earth (PE) port on the LOAD side of the inverter to anything. When I queried him on this he said without this setup (bonding earth and neutral on the load side) the inverter LOAD output voltage floats high (110v), and "all the Deyes and Sunsynks do this and the engineers have not been able to explain why". If my understanding is correct 5) above would explain what they are seeing, right?

Symptoms in-house:

I have the following problems in-house, that I suspect may be linked to this installation approach, some more than others:

1) When everything is 'on', Eskom, etc, my oven clock light has a weird flicker. Some of the LCD display segments blink on and off intermittently. Setting the clock on the oven takes 'longer' (Normally when you adjust the time, pressing and holding on the + button makes the minutes spin by faster and faster, this isn't happening anymore). The oven is on the non-essential (GRID) side of my setup, and if I disconnect my 'AC TO INVERTER' breaker, the oven returns to normal operation, i.e. Eskom is still on, but the AC link into the GRID port of the inverter is severed. I suspect this might be due to the now not-split neutrals as described in 7.2 )

2) I have 2 aircon units (8000 and 12000 BTU), both on the essential (LOAD) side of the inverter. When either one is on, I hear a buzzing sound on the earth leakage breaker for the essential loads. I've replaced the breaker once already, and the buzzing is reduced but it's still not gone. I'm not convinced this relates to the earth/neutral bond situation, but rather caused by cheap RCD. Going to be replacing them. My essential side RCD doesn't even trip (reliably) when I press the test button on it. 

3) Elevated base power draw, and inaccurate load measurements on my house since the installation. My base load at night when only a bare minimum of lights are active is reporting 400 to 600w, and it 'feels' too high. I'm used to around 300w only. Also when something like my geyser element turns on, the inverter reports its load as adding 4kW to the grid draw, and I was under the impression I had at MOST a 3kW element in the geyser. 

4) Bad house wiring (not my solar installers fault). It would seem the original house wiring took shortcuts and had a few plugs and light circuits on the same neutral line. This proved a headache when splitting the DB during the solar installation and it's not in an ideal state. Some lights are causing RCD trips, even though they have removed the light circuits from the RCD's.

Next steps:

Unless I'm completely daft in my understanding, I'm going to get a earth/neutral relay bond installed on the inverter load side, and see if any of the above issues subside. I'm also going to get an electrician to rewire my house side and fix the joined lights/plugs.

If anybody has read this far through my ramblings they deserve a medal. If you have anything to add or correct to my understanding of the whole sunsynk/earth/neutral/bond/relay topic, please feel free to do so. 

 

Edited by Elroc
Added words for clarity. Additions in italic.
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1 hour ago, Elroc said:

My understanding - please correct if I'm wrong:

1. Every man woman and child for him/her/itself... you should not and can not rely on earth bonding on the commercial power side, your house/shack/palace should have its own earth spike(s) and be bonded to neutral before your ground fault trip switch. (Relying on the earth-neutral link from the commercial side can have some shocking consequences and surprises, yes, pun intended)

2. Its generally frowned upon to connect the input of the inverter to its output, ask the manufacturer what they think of this idea, SANS is probably not the only relevant thing here...

3. if you have 2 electrical distribution boards, one for the pre-inverter side and one for the post-inverter side, then the items connected to the pre-inverter side should be earthed there on the pre-inverter side and the items wired to the post inverter side should be earthed at the post inverter side. --- The two earths are separate and not joined

4. Let's say yes... but what you wrote sounds a lot simpler, than I think it is, but hey, I'm an idiot, it may be just as you say... but... I doubt it...

5. Since the earth neutral bond should be at your home/shack/palaces main DB, I disagree, the earth neutral bond is still there before the ground fault trip switch and effectively on the input side of the inverter

6. Yes, but I'm not sure this is quite right, why should the Sunsynk's output be tied to ground when commercial power is there, unless, internally it switched (via a relay or othwerwise) neutral in to neutral out whilst commercial power is there, refer back to point 4 above...

7. see point 2 above...
7.1 not sure, but, the earth leakage/ground fault switch is there to try and prevent home electrocutions, the switch senses the current in both the live as well as the neutral conductors, if there is an imbalance of more than whathever rating is on your earth leakage/ground fault switch, it should trip and presto, potential electrocution prevented... 30mA in the case of the one in the main DB here...
7.2 Yebo yes, I'm assuming the neutral out is not DC coupled to the neutral in, during operation, but the output of the inverter, whilst commercial input power is there, has the neutral out linked somehow, once commercial power is gone, this seems to not be the case anymore. The output side earth thus not being linked in any way shape or form to the neutral, once commercial power is gone, should still allow the earth leakage/ground fault switch to operate, but since this is based on mA and not Voltage and since the Voltage on Neutral could be a few hundred Volts above ground and Live, possibly 220-odd Volt above this, many less mA could be required to expire the average human.

1 hour ago, Elroc said:

Next steps:

Unless I'm completely daft in my understanding, I'm going to get a earth/neutral relay bond installed on the inverter load side,

The neutral-neutral bond between input and output should be severed, this should never have been put in place...

On the output side of the inverter, before the earth leakage/ground fault switch you should have the relay linking earth and neutral, controlled by the inverter, based on commercial power being available or not... short when no commercial power, open circuit once commercial power is back on...

As for 2 above, maybe someone with a circuit diagram/service manual on these units can explain how the output voltage is clamped to earth, whilst commercial power is available and why it cannot continue to be so, once eskom empties its bowels without removing its clothing...

 

Edited by Kalahari Meerkat
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1 hour ago, Kalahari Meerkat said:

1. Every man woman and child for him/her/itself... you should not and can not rely on earth bonding on the commercial power side, your house/shack/palace should have its own earth spike(s) and be bonded to neutral before your ground fault trip switch. (Relying on the earth-neutral link from the commercial side can have some shocking consequences and surprises, yes, pun intended)

This might be something else for me to look into. I'm not aware that I have a spike installed, and for sure my earth and neutral in my main DB is NOT bonded. From what I read in another post I'm basing my understanding on the assumption that we use TNS-C type grid connection. A friend of mine has a similar setup in a much older house with an earth spike and earth neutral bond in the main DB making him have a lot less of these types of troubles.

1 hour ago, Kalahari Meerkat said:

3. if you have 2 electrical distribution boards, one for the pre-inverter side and one for the post-inverter side, then the items connected to the pre-inverter side should be earthed there on the pre-inverter side and the items wired to the post inverter side should be earthed at the post inverter side. --- The two earths are separate and not joined

Assuming one DOES set up an earth spike, does the spike then connect to both these earths? Or should they each have their own spike? My current install has a single DB, with the splitting done inside. Though I'm contemplating having that redone as well. 

 

3 hours ago, Elroc said:

4) When Eskom is on, and the inverter is running in 'normal' mode, the LOAD and GRID live and neutral lines are connected internally in the inverter. This allows the inverter to blend power from multiple sources. 

1 hour ago, Kalahari Meerkat said:

4. Let's say yes... but what you wrote sounds a lot simpler, than I think it is, but hey, I'm an idiot, it may be just as you say... but... I doubt it...

I based it on this circuit diagram from Sunsynk. It might be that ONLY Neutral is bonded at this point, but it's handled by internal relays in the inverter:

image.png.f509ad333e318372e2d59b2a22627932.png

3 hours ago, Elroc said:

6) Because of 5) we need to create that earth/neutral bond in-house now to prevent the elevated voltage, and other funnies. This is where the bonding relay and the Sunsynk islanding mode signal comes into play.

2 hours ago, Kalahari Meerkat said:

6. Yes, but I'm not sure this is quite right, why should the Sunsynk's output be tied to ground when commercial power is there, unless, internally it switched (via a relay or othwerwise) neutral in to neutral out whilst commercial power is there, refer back to point 4 above...

Sorry I wasn't clear, I agree, Sunsynk output neutral should not be tied to ground while commercial power is available. But where I'm (currently) dependent on the commercial power earth and not my own earth spike, when commercial power goes down, the inverter output has no reliable earth reference and leads to elevated voltage (across E-N). To rectify this the inverter output earth and neutral should be tied together, ONLY when commercial power goes down. (And in case you (I) don't have an earth spike), and hence the earth neutral bonding relay. It seems Sunsynk doesn't have one internally, and they advise an external relay triggered by a signal they send from their inverter when commercial power goes down. 

 

2 hours ago, Kalahari Meerkat said:

The neutral-neutral bond between input and output should be severed, this should never have been put in place...

There isn't one (on purpose), but because my earth bar is common all over, and because the installer has a permanent earth/neutral bond on the inverter output side, then yes there is an unwanted neutral/neutral bond, and I concur it should not be there. 

Thanks, I appreciate the input - I'm updating my original wording here and there for future clarity sake, but leaving the original in my quotes here. 

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31 minutes ago, Elroc said:

Assuming one DOES set up an earth spike, does the spike then connect to both these earths? Or should they each have their own spike? My current install has a single DB, with the splitting done inside. Though I'm contemplating having that redone as well.

Depending on the distance between the spike and the 2 DBs, if they are next to each other then yes, use the same earth spike for both, depending on conductivity at your location you may want more than 1 spike all connecting to the DB(s).

35 minutes ago, Elroc said:

when commercial power goes down, the inverter output has no reliable earth reference and leads to elevated voltage (across E-N)

yes, but the why is not clear, when commercial power disappears, surely they don't come and pull the cable and roll it up neatly, thus your earth-neutral should still be there, the transformer feeding you has no input power, but the output side should still be there, thus measuring between earth and neutral on the input side of the inverter should show no Voltage and low resistance between earth and neutral, whether power is being fed or not, so the unreliable earth reference is why? since its ok when commercial power is on, this is the inverters doing and the question is why the flock is Sunsynk/Deye doing what they are doing? The less glamorous Axpert type inverters seem to have the earth neutral bond on the output side included by way of an internal relay, once the commercial power disappears, since these cost a boatload less money than the Deye/Sunsynk inverters, it would be good if someone from Sunsynk can explain why they did not do the same. (Maybe there is a really good reason, just I can't think of one.) The amount of power flowing between neutral and earth should be negligible, so should not require 100A+ sized contacts to be activated on the output side, once the commercial power disappears...

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1 hour ago, Kalahari Meerkat said:

yes, but the why is not clear, when commercial power disappears, surely they don't come and pull the cable and roll it up neatly, thus your earth-neutral should still be there, the transformer feeding you has no input power, but the output side should still be there, thus measuring between earth and neutral on the input side of the inverter should show no Voltage and low resistance between earth and neutral, whether power is being fed or not, so the unreliable earth reference is why? since its ok when commercial power is on, this is the inverters doing and the question is why the flock is Sunsynk/Deye doing what they are doing?

Good point, and I've been wondering the same, allow me to hazard a guess:

Based on this diagram I shameless stole from this informative post: 

Assuming we use the TNC-S configuration, and being completely reliant on municipal Earth; (ignore L2 and L3 for our basic single phase layout) 

image.png.34f617c498311d6246956b112ed0e2cd.png

On the inverter input (Grid connection), when Eskom is down, the inverter internal AC relay disconnects for islanding purposes - you can't push power back to the grid if the grid's not there, you might blow the poor electrician working on the wires to bits. From the wiring diagram for Sunsynk, this disconnects L and N, and by implication the existing E/N Bond on the municipal side. If on the inverter output (Load) side we don't have (add) a E/N Bond, your Earth in your home wiring is not actually earthed or tethered to anything. To use a VERY BAD analogy, there is no string (E/N Bond) to keep your baloon (N voltage) tied to the ground.

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59 minutes ago, Elroc said:

the inverter internal AC relay disconnects for islanding purposes

OK, maybe that is what's going on, but, I would have thought it would make sense to disconnect live, by all means, but keep the earth & neutral connected, there should be no hazard under those conditions, again, wtf do I know, maybe there is a reason that I can't think of...

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15 hours ago, Antonio de Sa said:

@Elroc  you say one pushes power back to the grid? basically what you are saying is that when there is load shedding my inverter is feeding my all neighborhood, or whoever is connected to the phase that feeds my house.

Quite the contrary. Under no circumstances are you allowed to push power back to the grid when the grid is not active, for a wide range of reasons, e.g. the grid might be off to allow someone to work on the wires, so you would be putting wires that someone assumes is 'dead' to live. Or, in your scenario, for a second or two your inverter/generator/hamster wheel might try to power you neighborhood before spectacularly catching fire/exploding/falling of his wheel from being overloaded. Also (and this is where my understanding gets fuzzy), if you WERE able to power you neighborhood in the absence of the grid because your inverter was built by Chuck Norris; once the grid comes back online I believe your generator and Eskom generated power would be out of sync/phase, and 'bad things will happen'[Citation needed]

To accomplish this any power generating device connected to a live grid (such as your inverter) must either have built in islanding functionality, or be islanded using external circuitry to avoid it being able to push back (energize) the grid side when the grid is offline. This is why on you hybrid inverters that can supplement power to your non-essential (grid) side, once the grid is off, you can't power your non-essential devices at all. 

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14 minutes ago, Elroc said:

Quite the contrary. Under no circumstances are you allowed to push power back to the grid when the grid is not active, for a wide range of reasons, e.g. the grid might be off to allow someone to work on the wires, so you would be putting wires that someone assumes is 'dead' to live. Or, in your scenario, for a second or two your inverter/generator/hamster wheel might try to power you neighborhood before spectacularly catching fire/exploding/falling of his wheel from being overloaded. Also (and this is where my understanding gets fuzzy), if you WERE able to power you neighborhood in the absence of the grid because your inverter was built by Chuck Norris; once the grid comes back online I believe your generator and Eskom generated power would be out of sync/phase, and 'bad things will happen'[Citation needed]

To accomplish this any power generating device connected to a live grid (such as your inverter) must either have built in islanding functionality, or be islanded using external circuitry to avoid it being able to push back (energize) the grid side when the grid is offline. This is why on you hybrid inverters that can supplement power to your non-essential (grid) side, once the grid is off, you can't power your non-essential devices at all. 

@Elroc   100% correct, now explain to me one thing, my entire house during load shedding gets its power from my inverters, I don't have a split DB. I know for sure that I'm not pushing power to the grid because I can see my consumption remains the same. So, the only explanation is that during load shedding my prepaid meter disconnects my house from the grid.

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6 minutes ago, Antonio de Sa said:

@Elroc   100% correct, now explain to me one thing, my entire house during load shedding gets its power from my inverters, I don't have a split DB. I know for sure that I'm not pushing power to the grid because I can see my consumption remains the same. So, the only explanation is that during load shedding my prepaid meter disconnects my house from the grid.

Hard to say without knowing your exact setup and type of inverter, but if I check your post history you mention you have 2x Growatt SPF5000ES inverters, so all the below is just assumptions on my side based on this.

From a quick scan on the inverter datasheet, it is an off-grid solar inverter and cannot push power back to the grid, only take power from it. If the grid goes out the inverter then simply powers your house from your batteries and PV panels. And then when the grid goes down, it's down and you don't need to worry about powering your neighborhood :) This also means that you can't push power back to the grid even when the grid is live.

The complexity with the Sunsynk/Deye (and I believe Axpert?) models are that they are "hybrid", and have the option of pushing back excess power to the grid OR, simply supplementing load to devices on the grid (non-essential) side when surplus power is available. In my setup we've left the oven and the geyser on the 'non essential' (grid) side of the inverter. I only have a 5kW inverter, and having either of these draw power from the inverter, on the essential (load) side, would quickly cause the inverter to overload. If however, on a sunny day, if the wife were to be cooking a roast in the oven, and my batteries are full and my house side load is for example just 1kW, I could supplement the power the oven is drawing from my panels or batteries up to 4kW. On condition that the grid is on. If Eskom were to hit load shedding, my oven and geyser are still without power. 

(Disclaimer: I'm no expert, or electrician. At best I'm a computer engineer with a deep urge to understand anything that doesn't behave to my liking, often causing loss of sleep as I try to get to the bottom of things not in my field of expertise. I can confidently tell you lots of things about accounting, SARS tax laws as they relate to home office claims, retrenchment processes, legal principles around body corporates and common property, ADHD, and most recently electrical wiring, inverters and the like. It's very likely anything I tell you is total BS, so don't believe a word I say - always check your actual subject matter experts first :) )

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37 minutes ago, Elroc said:

Hard to say without knowing your exact setup and type of inverter, but if I check your post history you mention you have 2x Growatt SPF5000ES inverters, so all the below is just assumptions on my side based on this.

Correct, yes, I have 2 X 5000Es Growatt inverters.

From a quick scan on the inverter datasheet, it is an off-grid solar inverter and cannot push power back to the grid, only take power from it. If the grid goes out the inverter then simply powers your house from your batteries and PV panels. And then when the grid goes down, it's down and you don't need to worry about powering your neighborhood :) This also means that you can't push power back to the grid even when the grid is live.

I know I cannot feed to the grid, the Growatt inverters have no means of synchronizing my inverters output to the grid frequency.

My question is and as you correctly say during load shedding, I supply my entire DB via my inverters from either my PV, batteries or blending from both. My DB still connected to the grid via the incomer main circuit breaker. What stops my system from feeding the grid? this really puzzles my understanding of electrical circuitry. I'm considering installing a contactor with a timer to switch of the grid completely and energizing it via the timer in about 2 minutes after the grid is restored thus also avoiding possible voltage spikes.

The complexity with the Sunsynk/Deye (and I believe Axpert?) models are that they are "hybrid", and have the option of pushing back excess power to the grid OR, simply supplementing load to devices on the grid (non-essential) side when surplus power is available. In my setup we've left the oven and the geyser on the 'non essential' (grid) side of the inverter. I only have a 5kW inverter, and having either of these draw power from the inverter, on the essential (load) side, would quickly cause the inverter to overload. If however, on a sunny day, if the wife were to be cooking a roast in the oven, and my batteries are full and my house side load is for example just 1kW, I could supplement the power the oven is drawing from my panels or batteries up to 4kW. On condition that the grid is on. If Eskom were to hit load shedding, my oven and geyser are still without power. 

(Disclaimer: I'm no expert, or electrician. At best I'm a computer engineer with a deep urge to understand anything that doesn't behave to my liking, often causing loss of sleep as I try to get to the bottom of things not in my field of expertise. I can confidently tell you lots of things about accounting, SARS tax laws as they relate to home office claims, retrenchment processes, legal principles around body corporates and common property, ADHD, and most recently electrical wiring, inverters and the like. It's very likely anything I tell you is total BS, so don't believe a word I say - always check your actual subject matter experts first :) )

 

Edited by Antonio de Sa
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  • 3 months later...

At the end of load shedding when Eskom power returns my 8kw Deye remains in battery mode for 60 seconds.

This effectively protects your entire electrical installation from any voltage or frequency abnormalities during stabilization of the grid.

It does surely however mean that during those 60 seconds we have neutral to ground bonded at the pole and on the load side assuming there is a bonding relay in place.

Thankyou for the excellent discussion on Neutral to Ground bonding on the load side of the inverter.

Please comment on the protection provided by a normal EL relay connected at the inverter load output point when there is no bond between Neutral and ground.

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6 minutes ago, Stuart Donkin said:

Please comment on the protection provided by a normal EL relay connected at the inverter load output point when there is no bond between Neutral and ground.

Not much to comment on. There is no return path or protection when the grid is off.

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I am finding this Earth/Neutral discussion at the moment is very confusing as both sides seem to have valid points and am not 100% sure what is correct.

I have seen the Sunsynk video on the earth/neutral bonding via a relay when the grid goes down and understand these are the UK regulations. 

I have also been told that the SANS requirement is to have a permanent bond in place as having a relay to do the bonding can, in the event of a relay failure, result in an unbonded earth/neutral which is dangerous. 

I have been told that it is also dangerous to have a permanent bond in place because of other safety issues (not sure exactly what they are and I am not an electrician by any stretch of the imagination so don't know)

Is anyone able to tell me categorically what the situation actually is? 

Does this vary according to provincial electrical regulations (have heard that the regulations differ slightly based on your location)?

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If a quality Contactor in the case of a ATS240 setup is present in the Sunsynk hardware or in the case of its omission then a Quality relay used then I don't see that as a point of failure or weakness. These Inverters have numerous relays built in already carrying out various switching. That E/N relay is actually doing not much work to tie the Earth & Neutral. 

Contactors have industrial reliability & relays much the same.

Once again without trying to be a stickler for rules & regulations. The Inverter needs a means to maintain safe operation when islanding. Use a Relay or a Contactor of make the permanent bond. Much better than not addressing the serious issue that lurks beneath & remaining ignorant. 

Personally I opt for the Finder relay. Gives me more options NO & NC all in one. 

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2 hours ago, frivan said:

Not much to comment on. There is no return path or protection when the grid is off.

If I have a faulty device ( on the unbonded load ) side where the live or neutral has erroneously connected to the grounded frame and I touch that frame whilst standing on say wet ground how will current flow through me as there will be no potential difference between me and ground?

If I am foolish enough to directly touch the floating live or neutral please explain the current path that would result in my demise without the earth leakage device tripping as it is my understanding  that the toroidal transformer within the EL relay will detect an imbalance and trip.

I would really appreciate some clarity on this as I cannot fathom out what happens when you touch an unreferenced floating potential.

Do you simply jump to that potential?

All of the above assuming grid off and unbonded inverter in operation.

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11 hours ago, Stuart Donkin said:

If I have a faulty device ( on the unbonded load ) side where the live or neutral has erroneously connected to the grounded frame and I touch that frame whilst standing on say wet ground how will current flow through me as there will be no potential difference between me and ground?

There shouldn't be much current flowing if all is well in the electrical system. If there is a big network, there may be some capacitive current flowing. The problem is that if the earth leakage doesn't work, you won't know if the live or neutral is "down to earth". You will then create a phase fault/become the load if you come in contact with the live or neutral.

11 hours ago, Stuart Donkin said:

Do you simply jump to that potential?

Yes... but note that domestic a.c. supply is a potential alternating 50 times per second between -325V and +325V.

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  • 1 month later...

Came across this post and wanted to point out to @Kalahari Meerkat that you cannot assume the earth bond from the municipal side is always available even if power is off- cable theft is a reality in many areas.

This is also the reason why you should not permanently bond your earth to neutral as you could unwittingly become the earth point for your entire neighborhood when the "permanent" bond at the municipal connection is stolen upstream.

 

Edited by Thatdamnjoe
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5 minutes ago, Thatdamnjoe said:

Came across this post and wanted to point out to @Kalahari Meerkat that you cannot assume the earth bond from the municipal side is always available even if power is off- cable theft is a reality in many areas.

This is also the reason why you should not permanently bond your earth to neutral as you could unwittingly become the earth point for your entire neighborhood when the "permanent" bond at the municipal connection is stolen upstream.

 

This is two huge pure truths in a compact and concise statement.  👍

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On 2023/06/19 at 9:17 AM, BritishRacingGreen said:

This is two huge pure truths in a compact and concise statement.  👍

IMHO have an independent “Islanding Earth Spike” for the “Load” and “Aux” that is connected to an Earth Neutral Bond Relay. This relay should be engaged when the inverter is in islanding mode and disengaged when the power utility (Eskom) is providing a buzz.

If you want to bond Earth and Neutral from the Power Utility then I suggest to use a separate Utility Earth Spike that is spiked into the terra-firma a few meters away from the Islanding Earth Spike. The further apart the better and even at different heights.

Feel free to comment as you see fit.

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  • 9 months later...
On 2023/06/21 at 11:53 PM, Cryptic Proton Generator said:

IMHO have an independent “Islanding Earth Spike” for the “Load” and “Aux” that is connected to an Earth Neutral Bond Relay. This relay should be engaged when the inverter is in islanding mode and disengaged when the power utility (Eskom) is providing a buzz.

If you want to bond Earth and Neutral from the Power Utility then I suggest to use a separate Utility Earth Spike that is spiked into the terra-firma a few meters away from the Islanding Earth Spike. The further apart the better and even at different heights.

Feel free to comment as you see fit.

https://ecasa.co.za/technical/neutral-earth-bonding-clarified/   Here are the clear regulations. A bonding relay is required in islanding mode. The Neutral output from the inverter is pulled down to earth through the relay to an earth spike. People who say that the relay can fail forget that the eskom earth cable can be stolen or disconnected for some reason. The earth bond installation at your inverter must be according to regulations that is the installers responsibility. The Eskom earth is eskom's responsibility. 

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9 hours ago, TonyH said:

https://ecasa.co.za/technical/neutral-earth-bonding-clarified/   Here are the clear regulations. A bonding relay is required in islanding mode. The Neutral output from the inverter is pulled down to earth through the relay to an earth spike. People who say that the relay can fail forget that the eskom earth cable can be stolen or disconnected for some reason. The earth bond installation at your inverter must be according to regulations that is the installers responsibility. The Eskom earth is eskom's responsibility. 

Bryan Cranston Mic Drop GIF

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A interesting observation is that one points out that the relay for bonding can fail but we never see comments on the reliability of numerous relays in smart switches or those inside the inverter. Due to the mostly lowish current in the bonding relay if of the correct spec it could be one of the lowest risk relays on the whole PV system and should be very reliable. Easy enough to detect if it should fail. 

I like the relays with a LED to show when the coil is energized. 

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  • 3 weeks later...
On 2023/06/19 at 9:09 AM, Thatdamnjoe said:

Came across this post and wanted to point out to @Kalahari Meerkat that you cannot assume the earth bond from the municipal side is always available even if power is off- cable theft is a reality in many areas.

This is also the reason why you should not permanently bond your earth to neutral as you could unwittingly become the earth point for your entire neighborhood when the "permanent" bond at the municipal connection is stolen upstream.

 

I Really want to understand this statement thoroughly. I have drawn up a little "Scenario sketch" to illustrate my (possibly wrong) understanding:

If you have PV installed you most likely have an Earth-rod installed as well. Your installer permanently bonded your Inverter Output Neutral to Earth.
Your minisub neutral bar gets stolen during loadshedding. The return path to the transformer-neutral of all the homes on that minisub takes place the moment your inverter synchronizes to mains and connects output Neutral to Eskom Neutral. Effectively connecting the neighborhood Eskom neutral THROUGH YOUR LITTLE EARTH BRIDGE to earth. Earth carries the current of all homes back to the Eskom Neutral. Your main breaker will trip, but there might be a possibly-large explosion inside your inverter.

Am I missing something?

Scenario A.png

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