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Bond Neutral and Earth on Growatt SPF 5000TL HVM


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Backstory: My wife came to me today and told me that our washing machine is broken, because it doesn’t want to switch on. Turns out she was correct in that it doesn’t switch on, but also nothing on Eskom’s circuits switched on. Checked the mains, no breakers tripped. Inverter is using battery. No neighbours have power failures. Cool, so CoCT came to fix my cabling running from their kiosk. Really impressed with their response time. Took roughly 3 hours from logging the call to saying goodbye.

On Topic: During this time of no Eskom power, my wife asked me again to come check out something weird: A dimly glowing LED light (our only LED ceiling light) in the guest bedroom...

Since all the lights are on the inverter, does this mean that the inverter mentioned in the topic title doesn’t bond neutral and earth when Eskom is out? After Eskom was fixed, the light stopped dimly glowing. The light would come on normally when Eskom was out, powered by the battery, but switching it off would leave it dimly glowing again.

I understand this isn’t really a desirable feature for an inverter to be missing, but it might just be mine. I am having it replaced anyways with a Victron system on Thursday, but thought to post this here because I know here are some with this Growatt inverter who might want to check whether this is the case for them as well.

I haven’t yet tested whether it would do the same if I manually switch off the main breaker, but can’t imagine why not. I’ll see if I get around to it tomorrow.

Edited by jykenmynie
Left inverter name out of title
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8 hours ago, jykenmynie said:

Since all the lights are on the inverter, does this mean that the inverter mentioned in the topic title doesn’t bond neutral and earth when Eskom is out?

As far as I know the later Voltronics and their rebadged siblings do bond T and N. Just take a multimeter and measure between neutral and earth. You want a voltage that is nice and low, preferably zero or so close that you wonder if the multimeter is just picking up radio noise... 🙂

About LEDs glowing dimly. Even with an unbonded TN I would be very distrustful of a glowing LED. That is no excuse. That would imply it is somehow getting enough power from the earth/neutral potential difference to light up a couple of LEDs (albeit dimly), which means there is a neutral/earth fault and RCDs should be tripping (assuming you have them installed, some people don't put the lights on an RCD).

But start with measuring your neutral to earth (on any plug on the output of the inverter, while the grid is disconnected). Then work from there.

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What would you make of it that the dim glow went away after the power from Eskom was restored? Doesn't that mean my inverter didn’t have a TN bond while Eskom weren’t providing it?

After they’ve installed my Victron system tomorrow I’ll measure the volts between N and T while the grid is disconnected. Not going to bother too much with my stuff now... 😅

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27 minutes ago, jykenmynie said:

Not going to bother too much with my stuff now

I disagree. This will take you all of 5 minutes to test now, and then we have more data about that kind of inverter, plus we know afterwards (if the problem persists, or goes away) whether it might be related. Carpe Diem!

Edited by plonkster
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Haha! I'll try to get a chance a bit later today - My helper is busy with the washing machine, tumble dryer and dishwasher (all on non-essential) so if I turn off now, I might mess up those things.

To test it: Do I just turn off the main breaker and then stick a multimeter into an essential plug socket and test the voltage between neutral and earth? Or would I need to open up the plug socket to test it on the inside? Sorry, I'm not really clued up with these things. I've got a multimeter, but barely knows how to operate it... 😅

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Nevermind, I did it quickly with a very janky setup: A old plug and wire lying around with the wires exposed at the end...

Tested with grid on:

230V between live and neutral and live and ground

0V between neutral and ground

Tested with grid off:

80V between neutral and ground

230V between neutral and live

150V between live and ground.

So yes, it seems that I've got a floating neutral when the grid is down?

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1 hour ago, jykenmynie said:

So yes, it seems that I've got a floating neutral when the grid is down?

Yes, it is floating. 80V is a pretty typical voltage.

Come to think of it, I can think of a mechanism why the LED might be dimly lighting up. Many appliances have surge arrestors between live/earth/neutral, and these devices can often pass up to a milliamp to earth (it is acceptable to have a small standing loss and almost all modern switch mode psu type appliances have it). With 80V between neutral and earth, maybe just enough sneaks via one of those devices (they act like small capacitors so they will pass AC) and this lights up the LEDs dimly.

Edited by plonkster
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19 minutes ago, jykenmynie said:

It would be useful if someone else with this type of inverter can test. Might be possible mine is just broken?

Naaah. As I recall the bonding is done by using a double-throw contact in the relay and simply putting earth on the other side. Older models use a different relay without the extra contact and does not have it. Either you have it or you don't. It is unlikely that the inverter is broken...

This again makes me wonder. How important is this bonding? I know SANS says you must have it for the installation as a whole, but I am not 100% certain what the rules are for backup loads. If neither the Growatt or the Goodwe has it, how suitable are they really for whole-house backup type setups?

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So this goes beyond any knowledge that I have, but as far as I know the Growatt is incapable of pushing back into the grid. However, the Goodwe can do that. Would this neutral feed not find its way on the grid then? I.e. can someone working on the municipality side of your main breaker get shocked on the neutral at your connector box (where the municipality's cables come in and they create the fixed bond between neutral and earth?)

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11 minutes ago, jykenmynie said:

incapable of pushing back into the grid

I'm talking about when it is running in islanded mode. The grid falls away and the TN bond on the grid side is no longer there (and SANS says you're not allowed to rely on it in any case). The Goodwe also doesn't bond TN during a grid outage. The Australian instructions says to bridge neutral across to retain the bond, but that is relying on the upstream bond (which SANS prohibits). I'm not an electrician though, which is why this always ends up in the grey for me.

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15 hours ago, plonkster said:

The Australian instructions says to bridge neutral across to retain the bond, but that is relying on the upstream bond (which SANS prohibits).

We in Australia use MEN (Multiple Earthed Neutral). So we have one neutral to earth bond at the switchboard. That means we don't rely on the neutral to earth connection that is also at the transformer.

In Australia, we're amused by your obsession of disconnecting the neutral (double pole switches and breakers).

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7 hours ago, Coulomb said:

We in Australia use MEN (Multiple Earthed Neutral). So we have one neutral to earth bond at the switchboard. That means we don't rely on the neutral to earth connection that is also at the transformer.

For houses that are wired TN-C-S (with a local earth spike, also sometimes called PME, protective multiple earth), we have the same. Then the neutral is tied to earth at the main switch, and the main switch interrupts only the live connector. My in-laws's place is like that.

Places that are TN-S (earth at the transformer) have double-pole breakers, and in those cases you are not allowed to rely on the transformer-side bond, since 1) it is disconnected if your main breaker is open, but also more importantly, 2) a broken cable would leave the installation unbonded.

So it depends on where you live in many cases. Older neighbourhoods often have a local earth. New places don't. As I understand it TN-S is more expensive (due to the additional cost of the earth cable), but is considered safer.

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3 hours ago, plonkster said:

Places that are TN-S (earth at the transformer) have double-pole breakers, and in those cases you are not allowed to rely on the transformer-side bond, since 1) it is disconnected if your main breaker is open,

The S is for Separate, right? N and PE are separate everywhere?

Surely if you open your main breaker, you don't disconnect earth as well?

The N is for Network source for PE; yet you have to provide you own bond anyway?

Earthing systems other than the one I'm used to here confuse me.

3 hours ago, plonkster said:

2) a broken cable would leave the installation unbonded.

Yes, of course. So you always need your own bond, so the network provided earth is mainly a backup I guess. And perhaps it generally has a better connection to ground than most dwellings can afford.

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5 hours ago, Coulomb said:

The S is for Separate, right? N and PE are separate everywhere?

Yup. Even in a TN-C-S setup it is _C_ombined only up to a point, and from there on N and PE is separate for the rest of the installation.

5 hours ago, Coulomb said:

Surely if you open your main breaker, you don't disconnect earth as well?

Nope, earth remains connected. Only L and N disconnected. Recently an electrician did explain to me that sometime a fault with your neutral can affect someone on the same phase as yourself, so they need to be able to isolate both when fault finding... so not knowing any better, I assume that is why they do it.

5 hours ago, Coulomb said:

yet you have to provide you own bond anyway?

People without inverters don't provide their own bond. It's bonded up at the transformer (assuming TN-S) and no other bonds are allowed. But when the inverter takes over because the grid has failed, THEN you have to provide your own bond. You may not bond it twice, and you may not rely on the upstream bond. It is pretty much written in such a way (to my understanding at least) that you must have a bonding relay in the inverter.

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  • 2 months later...

Earth & Neutral must be earthed downstream DB of the inverter output at either the EL earth to Neutral or on the connection terminal strips of the earth and neutral a link can be done.The Growatt doesn’t have this done at board level and this needs to be done or you have a floating earth at the inverter which causes it to go faulty(Error 09).The Growatt SPF5000ES this can be done in Setting 24.

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  • 4 months later...

Ok I went to a client with a Growatt SPF 5000 and I got the same, 90V on neutral and 140V on lIve.

What I found out is that you need a grounding box to ground the neutral and correct the voltage.

When I installed it I saw the volts were corrected 230V on live only.

Although I bridge the contact of the grounding box because the NO on the inverter does not close when needed even if I change setting 24.

And I think the causes the Inverter not to change over in the morning from Utilities to Solar.

Did anyone else install a grounding box and get it to work correctly?

 

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Hi All. I have installed a grounding box I made myself, basically a 220VAC power relay that is able to handle 60A, to be actuated by the dry contacts of my Growatt spf 5000 to connect neutral and earth when running in island (battery) mode. I have enabled setting 24 and everything seems to work as it should, however the power relay is a tad slower than the internal switchover relay - causing the earth leakage feeding the inverter from Eskom's side to trip when going back to grid as the neutral and earth is still connected at the inverter for a milisecond or 2 longer. Can anyone provide some advice? Is there perhaps a setting to adjust the timing of the dry contacts relative to the internal switchover? Or am I doing something horribly wrong? 

I have started with this whole grounding box addon because when in battery mode, the neutral and earth are no longer connected and I see "earth not connected" fault warnings on my test plugs.

Thanks

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1 hour ago, Johan-Henry said:

Hi All. I have installed a grounding box I made myself, basically a 220VAC power relay that is able to handle 60A, to be actuated by the dry contacts of my Growatt spf 5000 to connect neutral and earth when running in island (battery) mode. I have enabled setting 24 and everything seems to work as it should, however the power relay is a tad slower than the internal switchover relay - causing the earth leakage feeding the inverter from Eskom's side to trip when going back to grid as the neutral and earth is still connected at the inverter for a milisecond or 2 longer. Can anyone provide some advice? Is there perhaps a setting to adjust the timing of the dry contacts relative to the internal switchover? Or am I doing something horribly wrong? 

I have started with this whole grounding box addon because when in battery mode, the neutral and earth are no longer connected and I see "earth not connected" fault warnings on my test plugs.

Thanks

Never mind, looks like I made a mistake taking the inverter main input feed through the earth leakage protection.

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  • 1 month later...

Hi All - this topic is of interest to me as I supervised installation of a solar backup system for my folks here in Kenya.
In January I found some dodgy wiring (neutral & earth bonded sockets) from a previous "technician" when i got zapped touching the switch on a brass coated socket.

Longish story cut short....... there is a return on the neutral circuit whenever the inverter (Growatt SPF5000 TL HMV-P) is in battery mode. As soon as grid cuts in to power the household the return disappears.
I understand this has something to do with setting #24 - what do I need to do (other than enable #24)?

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12 minutes ago, ZorbatheGeek said:

Hi All - this topic is of interest to me as I supervised installation of a solar backup system for my folks here in Kenya.
In January I found some dodgy wiring (neutral & earth bonded sockets) from a previous "technician" when i got zapped touching the switch on a brass coated socket.

Longish story cut short....... there is a return on the neutral circuit whenever the inverter (Growatt SPF5000 TL HMV-P) is in battery mode. As soon as grid cuts in to power the household the return disappears.
I understand this has something to do with setting #24 - what do I need to do (other than enable #24)?

Search “Sunsynk” and you’ll find a similiar problem and the posted solution. 
On the Sunsynk there is a special connection for a relay.

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46 minutes ago, Johandup said:

Search “Sunsynk” and you’ll find a similiar problem and the posted solution. 
On the Sunsynk there is a special connection for a relay.

Thanks Johandup.......Umm I don't see it....... is it also to do with neutral return?

Installer should know this surely?

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On my Infinisolar it stipulated its own seperate neutral.  Not to be shared with the incoming connection. 
It never had a leak from neutral to earth. 
I suppose its  got to do with the design - I know some makes earth their own neutrals. 
Anyhow, the circuit after the inverter must trip its own earth leakage. 

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2 hours ago, Johandup said:

On my Infinisolar it stipulated its own seperate neutral.  Not to be shared with the incoming connection. 
It never had a leak from neutral to earth. 
I suppose its  got to do with the design - I know some makes earth their own neutrals. 
Anyhow, the circuit after the inverter must trip its own earth leakage. 

OK noted Johandup ... more questions in my head now:

  • Are the Infinisolar and Growatt based on the same platform?
  • How do you keep the neutrals separate if the inverter feeds to the main DB eventually? Should the inverter then have its own grounding, separate to the grid supply, and inverter neutral is then bonded to this?
  • But then when the internal changeover switches to grid output will it use both inverter and grid neutral/ground? (any problem with this?)
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