Axpert invertors

[[email protected]]

That is true COMPUTEK. lol the concern on this forum that I have is with all due respect is that all the disagreeing cause major confusion. I am quite well knowledges in how electrical systems work. I actually have NTC6 in industrial electronics light current. But the person I would like to hear from is Savage as he installs these units and I have seen pictures of these units ac output neutral being bonded to earth

Let's see what everybody else has to say

By the way I said bond earth to neutral on inverter output not input. Input bond would trip the EL. I saw a picture on one of these posts that shows the same inverter I have with an earth neutral bonded. Now let's get back to what was discussed.

The axpert inverter I have us not internally bonded. I have tested that. The issue I have is when running off batteries the inverter isolates itself from the ac input which says to me that there is no more earth ie floating. If there is any electrical fault where live shorts to chassis of appliance and you are touching it you are going to get shocked as now you are the shortest route to ground.


So this image is a picture from this thread showing bonding on the inverter
https://www.dropbox.com/s/lqjazf65gveu93x/photo%202015-08-12%2C%203%2036%2050%20pm.jpg?dl=0

 

[greg_SA]

Does anyone have photos of the internals of the Axpert Inverters? Photos of the PCBs, etc?

 

[Getafixx]

Interesting how the bonding topic surfaced again now, with some new opinions as well. This thread has become quite long so it's quite a read but there is a lot of info about this a number of pages back.

Anyway, to recap, my Axpert output most definitely floats when running from batteries. (When running from Eskom is is just directly connected to the supply with the relays so then it does not float.) In one of my tests the Live - Earth voltage was about 170V and the Neutral - Earth was about 60V. In another test the numbers were about 210V and 20V. So it most certainly does not use a center-tap transformer and the fact that it truly floats (because of the different floating voltages) tells me that you can bond it at the output.

And you can never have the inverter with N/E bonded output running from E/L because when in bypass mode the E/L will trip. Therefore you should add an extra E/L at the inverter output for the safety of your family who can do who knows what at the plugs. I know, I have boys

 

[[email protected]]

Thanks Getafix.

You answered my question. This is what I assumed. Just one others question is that the inverter earth output has to be grounded so if any short circuit occurs it will be drained to the ground earth ie earth spike.

 

[[email protected]]

Thanks Getafix.

You answered my question. This is what I assumed. Just one others question is that the inverter earth output has to be grounded so if any short circuit occurs it will be drained to the ground earth ie earth spike.

 

[greg_SA]

Regarding the above neutral-earth tie on the output of the inverter...

I understand that it is the best way to go for the Axpert... but when in Bypass mode (running from Eskom), then there are actualyl two earth-neutral ties. There is the standard earth-neutral tie at your incoming Eskom supply to your house, and another earth-neutral tie at the output of the inverter.

So, the neutral currents from the loads connected to your Inverter will flow in both the neutral and earth conductors (between the inverter and DB). So your earth conductor will actually be used as part of the power supply, and not purely for earth leakage currents.

Not sure if that is an issue, but it doesn't seem right. It is also the reason that you can't have an E/L supplying the inverter input.

Technically, you want a earth-neutral bonding relay, that only connects the inverter neutral to earth when the inverter is running from the batteries, and opens the earth-neutral connection when in bypass mode (using Eskom power). I'd like to try this myself, with an external relay - connect the coil to the inverter input (live and neutral) to sense when Eskom power is available, then connect the NO (normally open) terminal to the inverter output neutral, and the C (common) to the inverter earth. Just haven't got round to it yet...

Many inverters have this built in - it is called a bonding relay or ground relay. Many of the Victron inverters have this.

 

[Dimpie (JIGSAW)]

Regarding the above neutral-earth tie on the output of the inverter...

I understand that it is the best way to go for the Axpert... but when in Bypass mode (running from Eskom), then there are actualyl two earth-neutral ties. There is the standard earth-neutral tie at your incoming Eskom supply to your house, and another earth-neutral tie at the output of the inverter.

So, the neutral currents from the loads connected to your Inverter will flow in both the neutral and earth conductors (between the inverter and DB). So your earth conductor will actually be used as part of the power supply, and not purely for earth leakage currents.

Not sure if that is an issue, but it doesn't seem right. It is also the reason that you can't have an E/L supplying the inverter input.

Technically, you want a earth-neutral bonding relay, that only connects the inverter neutral to earth when the inverter is running from the batteries, and opens the earth-neutral connection when in bypass mode (using Eskom power). I'd like to try this myself, with an external relay - connect the coil to the inverter input (live and neutral) to sense when Eskom power is available, then connect the NO (normally open) terminal to the inverter output neutral, and the C (common) to the inverter earth. Just haven't got round to it yet...

Many inverters have this built in - it is called a bonding relay or ground relay. Many of the Victron inverters have this.

When you remove dedicated plugs from the main DB, they are no longer connected to ANY bonding that happens on the (Esksdom) side, so no, there isn't 2x ties That's how i understand it in any event

 

[Gnome]

So, the neutral currents from the loads connected to your Inverter will flow in both the neutral and earth conductors (between the inverter and DB). So your earth conductor will actually be used as part of the power supply, and not purely for earth leakage currents.

Not sure if that is an issue, but it doesn't seem right. It is also the reason that you can't have an E/L supplying the inverter input.

It is 100% definitely not complaint or safe. Hence bonding at the output is not safe. The earth conductor should not be carrying current. Earth wire is rated for a fault, not current carrying. Twin & Earth and Surfix is the perfect example of this. They commonly have a steel earth wire instead of a copper wire (probably to prevent galvanic corrosion in installations with aluminium)

The fact that the EL trips is an obvious sign of a non-complaint install.



SANS actually shows the UPS output should be fed from EL.

Personally I would fix it by: Opening the unit, Wire a wire from the Inverter neutral (not Utility or Common terminals) at the relays (bottom right in the pics) to your ground. When the inverter switches to inverter power the neutral and ground are bonded. Otherwise the neutral of the inverter isn't even connected.

 

[greg_SA]

When you remove dedicated plugs from the main DB, they are no longer connected to ANY bonding that happens on the (Esksdom) side, so no, there isn't 2x ties That's how i understand it in any event

If they are powered in bypass mode, they are effectively connected to the Eskom supply, which has a neutral-to-earth bond. The inverter isn't a double conversion system - the inverter's input is connected directly to the output in bypass mode.

 

[greg_SA]

It is 100% definitely not complaint or safe. Hence bonding at the output is not safe. The earth conductor should not be carrying current. Earth wire is rated for a fault, not current carrying. Twin & Earth and Surfix is the perfect example of this. They commonly have a steel earth wire instead of a copper wire (probably to prevent galvanic corrosion in installations with aluminium)

The fact that the EL trips is an obvious sign of a non-complaint install.

SANS actually shows the UPS output should be fed from EL.

Personally I would fix it by: Opening the unit, Wire a wire from the Inverter neutral (not Utility or Common terminals) at the relays (bottom right in the pics) to your ground. When the inverter switches to inverter power the neutral and ground are bonded. Otherwise the neutral of the inverter isn't even connected.

Cool, so you agree I'm aware of those SANS diagrams - I really wish they showed more detail.

My plan is to fit the grounding relay inside the area where all the connections are done on the Axpert (under the little cover at the bottom).

 

[Gnome]

Cool, so you agree I'm aware of those SANS diagrams - I really wish they showed more detail.

My plan is to fit the grounding relay inside the area where all the connections are done on the Axpert (under the little cover at the bottom).

Does sound like we are saying the same thing

As I said tho, have you considered just connecting the neutral internally (at inverter output at the relays) with a piece of general purpose house wire to your ground. The ground terminal is right there by the relays (bottom right)

You probably have this solution mapped out already but you can do the following:
230v SPDP relay. Communica sell them for like R50. Coil is 230v, connect the coil to Eskom power. Common to house earth. Normally closed to inverter neutral. When Eskom power goes out the NC will connect earth to neutral.

I personally used that very same relay in my own backup power solution (to turn on my inverter). It has super fast switch over time.

 

[greg_SA]

Does sound like we are saying the same thing

As I said tho, have you considered just connecting the neutral internally (at inverter output at the relays) with a piece of general purpose house wire to your ground. The ground terminal is right there by the relays (bottom right)

You probably have this solution mapped out already but you can do the following:
230v SPDP relay. Communica sell them for like R50. Coil is 230v, connect the coil to Eskom power. Common to house earth. Normally closed to inverter neutral. When Eskom power goes out the NC will connect earth to neutral.

I personally used that very same relay in my own backup power solution (to turn on my inverter). It has super fast switch over time.

I don' think that photo you attached is of the Axpert PCB? The filename seems unusual.

I found this in a service manual for a 4/5kVA Axpert...



So permanently grounding the Inverter Output neutral isn't really an option, as that neutral isn't isolated in bypass mode (only the live is).

 

[Gnome]

I don' think that photo you attached is of the Axpert PCB? The filename seems unusual.

It is the PIP 4048 which is another brand the Axpert is being sold under. Quite of a lot of good info about this inverter when searching PIP 4048.

What I found interesting is that this inverter is actually really high quality. They use Jamicon caps in the PIP version which are pretty decent and the construction of the boards are really good.

I'm very impressed with this product!

Many people have tested it extensively and it seems the only weak point on the inverter is the MPPT charger which doesn't hold up well. Inverter wise it is super reliable and high quality.

So permanently grounding the Inverter Output neutral isn't really an option, as that neutral isn't isolated in bypass mode (only the live is).

Ah ok, makes sense that it is possible. Since the neutral wouldn't be energized or even active unless the inverter section turns on, so connecting it is inconsequential.

Guess ground relay it is then.

 

[[email protected]]

Just something I wanted to mention about my installation is that all my lights and selected plugs will be isolated from eskom permanently. In other words they will be completely off grid. This is why I asked about the bonding N/E inverter output.

 

[JohnHay]

Ok, you guys have mostly convinced me that permanently connecting the neutral output and earth might not be the best option.

I still have reservations about the relay and powering it from grid mains. It should work ok, if you use your Axpert only as a UPS.

But what happens if you have PV and in the day the Axpert will supply your load from that even though there is grid available? Or in my case, I actually have an Infinisolar and have more options. I have set it to prefer battery before grid, so in the evening it will run from batteries even though grid is available. The other thing that can happen is if it run from PV or Batteries and that is not enough, it can add from the grid, so a mixed output and I doubt if the neutral is then just straight through.

Hmmm It looks like I will have to test a few of these modes. In the beginning I just tested when it was running from grid and then when the grid is not available.

 

[Gnome]

Just something I wanted to mention about my installation is that all my lights and selected plugs will be isolated from eskom permanently. In other words they will be completely off grid. This is why I asked about the bonding N/E inverter output.

If you will never run from Eskom power then you can bond neutral and ground at the inverter output. But then you should absolutely not connect your house live & neutral to your inverter.

SANS however still requires that:
1) Your Inverter ground is connected to your house ground (even if it is not connected to Eskom)
2) Your solar panel metal parts are grounded to your house ground

It is called equipotential bonding. I suggest you watch this video: https://www.youtube.com/watch?v=-kjM9VWKHnk

That video goes over the procedure for US installs to meet code in the US but the safety aspect is very relevant to SA. SANS also talks about this but that video gives very good examples.

Notice also that aluminium should not be grounded directly using copper wire or vice versa. Either use steel or a steel connector.

Connect the earth wire from your Eskom supply to the Axpert and the DB you use for your Axpert. Connect the solar panel ground wires internally to your DB you use for the Axpert.

Connect your ground spike to your main distribution board.

Note that wire size for you ground matters. This can go a long way to helping you: http://www.ameu.co.za/Portals/16/Documents/Legislation/SANS10142-1Amdt8.pdf

Even among expert low voltage installers some parts of the SANS documents are open to interpretation (found a lot of this online). So if in doubt, I generally Google or look at what people do in the US and UK. Generally whichever they do that is safer is probably the way to go.

Keeping in mind, the whole point of grounding is only so that if any circuit with elevated potential touches a metal surface it will go to ground and trigger a fault. Else the metal will stay at elevated potential until someone touches it and death.

 

[Gnome]

Ok, you guys have mostly convinced me that permanently connecting the neutral output and earth might not be the best option.

I still have reservations about the relay and powering it from grid mains. It should work ok, if you use your Axpert only as a UPS.

But what happens if you have PV and in the day the Axpert will supply your load from that even though there is grid available? Or in my case, I actually have an Infinisolar and have more options. I have set it to prefer battery before grid, so in the evening it will run from batteries even though grid is available. The other thing that can happen is if it run from PV or Batteries and that is not enough, it can add from the grid, so a mixed output and I doubt if the neutral is then just straight through.

Hmmm It looks like I will have to test a few of these modes. In the beginning I just tested when it was running from grid and then when the grid is not available.

I'm looking at this: http://www.voltronicpower.com/oCart2/files/manual/AxpertMKS-MKS+ 1-5KVA_manual.pdf
And this: http://g02.a.alicdn.com/kf/HTB1jrs9...er-PIP4048MS-solar-power-inverter-charger.jpg

I'm wondering if you can use the ground relay and that dry contact to signal when to bond ground and neutral.

So far it doesn't look like it will always work. (Dry Contact Signal section, doesn't seem to be present on the KS version but KMS version does have it)

I've gone ahead and bought an Axpert, when it arrives I'll do more testing

 

[Username:]

I'm looking at this: http://www.voltronicpower.com/oCart2/files/manual/AxpertMKS-MKS+ 1-5KVA_manual.pdf
And this: http://g02.a.alicdn.com/kf/HTB1jrs9...er-PIP4048MS-solar-power-inverter-charger.jpg

I'm wondering if you can use the ground relay and that dry contact to signal when to bond ground and neutral.

So far it doesn't look like it will always work. (Dry Contact Signal section, doesn't seem to be present on the KS version but KMS version does have it)

I've gone ahead and bought an Axpert, when it arrives I'll do more testing

I've look into this today. You are in the right path with your thinking.

 

[scottwday]

I'm wondering if you can use the ground relay and that dry contact to signal when to bond ground and neutral.

According to the manual the dry contact only closes once the battery voltage is low and there's no utility power.

And the warning voltage isn't adjustable AFAIK

 

[Gnome]

According to the manual the dry contact only closes once the battery voltage is low and there's no utility power.

Yeah I'm unsure if low voltage means that it will stop the inverter output. That don't say. If it does, then it is not a problem because the ground no longer need be connected.

Looking at this also: http://forums.aeva.asn.au/uploads/293/HS_MS_MSX_RS232_Protocol_20140822_after_current_upgrade.pdf

That is the RS232 commands you can send to the Inverter. Pretty much everything is adjustable.

EDIT: Ouch, seems to be complicated

Will be interesting to play with however

EDIT2: Service manual for interested parties