So I’ve discovered something rather concerning. I’ve been trying to trace misterius voltage pulsing trough my house. Fist I’ve noticed some led lights where glowing very dim after being switched off.  

Which sent me on a hunt of what was putting ~24v onto my lights circuit. 

Eventually after checking all light switches, dimmers etc. I’ve ended up discovering that my Axpert is pushing voltage even when switched off and disconnected from batteries, but connected to the mains.

 

For now I’ve disconnected inverter from my house supply and running on main grid only. 

 

Very concerned about this. Below are readings that I’ve collected on inverter in out terminals.

 

With inverter switched off, main grid connected inverter:

In live and neutral 230v 

In neutral and earth 0

Out live and neutral 0 

Out neutral and earth 24V

 

With inverter on , grid batteries pv connected.

In live and neutral 230V

In neutral and earth 0

Out live and neutral 230V

Out neutral and earth 99V

 

Take a look at Annex P.4 starting on page 361 of SANS 10412-1:2017 ed2

I sadly cant share this with you because my scanner has recently croaked and I haven't got around to sorting it out, but in summary you should bond your main E terminal (from earth bar in Main DB) to your inverter N terminal (at the inverter) which will prevent your floating voltage situation. The earth conductor should be a minimum of 50% size of the Live conductors.

This should be done before the inverter output Earth Leakage which I am sure you have installed.

So as an example if you run a 50amp 10mm L/N from the Main DB to your Inverter L/N(in), then you should run at least 6mm from your main E-bar to the inverter body and to the N(out) terminal (looped, not 2 separate wires).

But for Pilotfish solution to work correctly you require a change over switch 

thx @pilotfish & @Jaws

One would expect this to have been done in the inverter already,  but I guess that is why some inverters don't make it to the approved devices list.

18 hours ago, Padwan said:

Out neutral and earth 24V

One thing I discovered that causes this: Surge arrestors and EMI filters (okay that is two, but it is the same class of thing). It is pretty typical for such a filter to have three capacitors in a little triangle arrangement between live, earth and neutral. Of course they are really low-value caps (otherwise they'd pass too much current and cause all sorts of havoc), but they are enough to create a little voltage divider that pulls your earth up to roughly half of supply. So you will easily measure 90V or higher on an unbonded earth.

Those aren't the only culprits. Switch Mode Power supplies often have a capacitor on the input side. Good design dictates that you stick a bleeder resistor across it to bleed off the energy, but not everyone does that. Those appliances can be a lot of fun, unplug them, then stick the exposed 3-pin plug against your leg for a nice jolt as the small filter cap sends a small 350VDC spike through you 🙂

So this mish-mash of caps and filters in your house stores all sorts of small amounts of energy, and pretty soon you have LED lamps glowing for a couple of seconds after switching them off and spurious voltage on earth.

2 hours ago, Padwan said:

One would expect this to have been done in the inverter already

Not all earthing arrangements are TN (Terra-Neutral), so by leaving the bond off the inverter remains agnostic of the earthing system, which is technically a good thing. In some inverters this is configurable, and in some bonding is required (Victron Multigrid and Multiplus-II, their relay test will fail if you don't have bonds in the right places). In yet other inverters (usually cheaper square wave jobbies), bonding cannot be done because it will blow up the inverter. Such inverters cannot be connected to your house wiring, not legally anyway.

14 minutes ago, plonkster said:

In yet other inverters (usually cheaper square wave jobbies), bonding cannot be done because it will blow up the inverter.

That's the second time I've heard that today. How on earth 🤮 does connecting earth to neutral out blow them up?

1 hour ago, Coulomb said:

How on earth 🤮 does connecting earth to neutral out blow them up? 

I got it from an old video I watched long time ago, which I now found again. Basically, the output is V-0-V and they connect the center tap to the case and also to the battery negative. Both sides are "hot". You attempt to bond earth to neutral, you short out the one "leg". Might not blow it up, might just cause overload.

On 2019/02/10 at 12:28 AM, plonkster said:

Both sides are "hot". You attempt to bond earth to neutral, you short out the one "leg".

Ah. On those sorts of inverters, the neutral is the centre tap, not one of the lives. [ Edit: and you want one of the "lives" to become a neutral for normal 240 V usage. ] Strange that they don't leave the centre tap isolated from the battery negative. That's what I was missing, then. Thanks. 

Edited March 4, 20197 yr by Coulomb
Added a clarifying sentence. I was confused.

So this has just got progressively more interesting.

After making a star point in my sub-board to deal with said 94 odd V on the inverters out terminal and everything looked ok.

Last night, however, after attempting to switch over to a grid supply, every time there was AC in on the inverter it tripped the earth leakage on my sub-board. 

So as none of that made any sense, I've decided to experiment some more. Removed a star point from my sub-board and inverter came on, took ac input and did not trip earth leakage.

Next was to measure earth and neutral on the inverter out terminal, and it was giving zero reading. Whilst I was scratching my head and wondering what on havens is going on, [5-10 min] I took another reading and it was back to 94V. So star point back on the sub-board and reading between earth and neutral on out terminal is back to zero.

 So now I'm totally puzzled, does this appear to be a malfunctioning inverter or am I'm missing some profound detail of how this all works and needs to be wired?

 

2 hours ago, Padwan said:

Next was to measure earth and neutral on the inverter out terminal, and it was giving zero reading. Whilst I was scratching my head and wondering what on havens is going on, [5-10 min] I took another reading and it was back to 94V.

I'd say you have one of the Axpert models that has the neutral-out to earth relay (or extra contact, really). This is a normally closed contact, so with the unit switched off, you'll read zero ohms, as you did. And when in battery mode, it's also going to be shorted. But in line (bypass) mode, the assumption is that the incoming neutral will already be earthed, and the earth to inverter-out-neutral is floating.

With that in mind, the whole situation may become a lot less mysterious.

The models with this neutral to earth "virtual relay" seem to be the ones that come with main firmware version 73.00.

From this post:

2 hours ago, Padwan said:

So as none of that made any sense, I've decided to experiment some more. Removed a star point from my sub-board and inverter came on, took ac input and did not trip earth leakage.

I assume that by "st ar point" you mean you bonded earth and neutral on the inverter output. Then when you switched back to the grid, the RCD started tripping.

This is actually perfectly normal, it is exactly what should happen. You added a second bond to the system (there is already one on the grid side). When the grid is disconnected, the bond on the grid side is also disconnected, which is why the earth floats up to 94V. Add a bond, and things now work normally. Bring the grid back, and now there are two bonds in the system, allowing current to partially bypass one of the RCDs and tripping it. Remove the second bond and all is fine again, until you remove the grid and you're back with 94V between T and N.

The trick is to bond earth to neutral automatically when you disconnect the grid. Victron inverters has this built in. Axpert's implement this using the dry contact relay, but you must add an external relay/contactor to actually implement this, and your firmware has to be new enough... basically I have no idea which models actually supported it, I only know the early ones didn't support it at all.

I drew a picture again (cause I'm learning this new "dia" tool). The current flow (not all of it, but enough of it to cause an imbalance), takes the route indicated by the yellow arrows. The grey line shows the bond installed by the supplier (that should be there), and the blue one is the one installed by you (that should be a relay/contactor that is only closed while off-grid). The current at 1 bypasses the RCD at 6.

This is just one example of how it happens.

1 hour ago, plonkster said:

I assume that by "star point" you mean you bonded earth and neutral on the inverter output

Ive 

1 hour ago, Coulomb said:

With that in mind, the whole situation may become a lot less mysterious.

Yes, now it all fits in, and ive confirmed that by measuring in two different states.

When in battery/PV mode there is a reading of 94V on the out terminal, bonding E&N on subboard is than necessary to get 94V off there.

When in grid mode, its 0.1V,  however, have to take E&N bonding away in this case before I can change modes again.

There appears to be a dry contact on the inverter, but its labelled PV input and ohm values don't change from NC / NO when going from grid to battery so I guess that cant be used to connect the relay to control bonding.

Will go over the link above to see if there are any ideas how to deal with this. 

 

 

Edited February 10, 20197 yr by Padwan

1 hour ago, plonkster said:

Axpert's implement this using the dry contact relay, but you must add an external relay/contactor to actually implement this, and your firmware has to be new enough... basically I have no idea which models actually supported it, I only know the early ones didn't support it at all.

This appears in my manual,

how would I test if this dry contact is useful for the purpose of 

1 hour ago, plonkster said:

The trick is to bond earth to neutral automatically when you disconnect the grid.

38 minutes ago, Padwan said:

how to deal with this

It's doing it all for you. Just don't switch the neutral at the AC input; switch only the active.

If your inverter can do the relay via dry contact thing, you have to enable it with setting 38. But I can't see how you'd need this.

8 minutes ago, Coulomb said:

It's doing it all for you. Just don't switch the neutral at the AC input; switch only the active.

Doesn't the Axpert's transfer switch disconnect the neutral? I know one suggestion (not legal according to SANS) is to bridge the neutral from the input to the output, so that only the live/active/hot is switched by the transfer switch. That way the TN bond remains active.

The other way is, as you say, through setting 38. I tried to get the manual... Voltronic wants me to register and then review the application... this is going to be interesting... I used my work email address 🙂

1 minute ago, plonkster said:

Doesn't the Axpert's transfer switch disconnect the neutral?

Yes, but when it does, the other contact connects inverter neutral output to earth. So you get the inverter neutral output earthed either through the incoming neutral, or by relay contact. As you can see from the diagram.

1 minute ago, Coulomb said:

As you can see from the diagram

Aaaah! I have seen that diagram so many times that I have stopped "seeing" it, so I didn't notice that the one contact turned into a double-throw that now bonds earth and neutral. I now also understand a previous comment from you that I initially thought was sarcasm... 🙂

If his inverter has that... well then he shouldn't have to do anything.

1 hour ago, plonkster said:

I tried to get the manual...

@plonksterWould this help ?

Axpert MKS-4000_KS-5000 Service manual. Axpert MKS Charger_ Inverter. Service manual.pdf

 

 

1 hour ago, plonkster said:

If his inverter has that... well then he shouldn't have to do anything

 

How does one verify if this is present or not?

Edited February 10, 20197 yr by Padwan

1 hour ago, plonkster said:

If his inverter has that... well then he shouldn't have to do anything.

how does one validate this, if its present or not?

2 hours ago, Padwan said:

Would this help ?

I was looking more for the user manual instead of the service manual. My idea was to look if it explains the program 38 that @Coulomb speaks about. This setting, if I understand it correctly  (I'm not a fan of these inverters, as everyone knows 😛 ), tells the inverter how to use the relay that is in it. You can use it to start a generator (for example), which is what it is most commonly used for... but in one of the firmware versions they added the ability to use it for bonding.

But, as Coulomb has said (which also came to my attention properly today), Voltronic did add a bonding feature in the hardware of later models. If you had such a model, you should not be having the 94V-between-earth-and-neutral issue. With that relay closed the voltage must be zero between earth and neutral (while the grid is disconnected and the inverter is running on its own).

2 minutes ago, plonkster said:

I was looking more for the user manual instead of the service manual.

According to my manual and LCD display, there is no option 38, it stops at 31. So I guess that is off the table than for my inverter.

5 minutes ago, plonkster said:

But, as Coulomb has said (which also came to my attention properly today), Voltronic did add a bonding feature in the hardware of later models. If you had such a model, you should not be having the 94V-between-earth-and-neutral issue. With that relay closed the voltage must be zero between earth and neutral (while the grid is disconnected and the inverter is running on its own).

Would visual inspection help to identify if this is a model with such a feature?

This Inverter is distributed under the branding of "The Sun Pays" and @Coulomb and I had a lengthy discussion about how this "generic" components and ability to custom branding and serial numbers that are not matching Axpert mainline brand and production, create confusion on whats genuine models and what are clones. Especially in light that those units are actually distributed with his patched firmware in place. 

As much as its fun and gives a great opportunity for learning about this, i'ts starting to feel that i should start making a short list of alternatives that I can use as a primary workhorse and keep Axperts for play and learn.

I see you have Victron, any particular combination or model I could add to that list, and any others I should consider?

I'm CPT based but on Eskom network, if that plays any role in decision making.

If you remove the sticker over the barcode of these inverters there is only a blank space on the original sticker . ???. I was working at a production plant with ISO standards . Never would this go out to customers .

Setting 38 from user manual only later models . Hope this can assist you

1 hour ago, Padwan said:

Would visual inspection help to identify if this is a model with such a feature?

On the inside, you can look up the part numbers of the 4 relays at the bottom, eg bottom right:

If you look up the "Song Chuan 832ha" relay series, you will see that the 4 in this one are all single pole. If one of them are double-pole... then maybe. But then I also wouldn't expext the floating neutral voltage you noticed... so I kinda sorta think you have a model without it.

49 minutes ago, plonkster said:

On the inside, you can look up the part numbers of the 4 relays at the bottom, eg bottom right:

I can only make out three of them in there unless smaller grey one is "the fourth"

 

 

29 minutes ago, Padwan said:

I can only make out three of them in there unless smaller grey one is "the fourth"

I think that's 220nF capacitor. It has "224k" written on it. Those three relays are all single pole.