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Question of the Day: If you were buying a TV today, which brand would you choose?
Axpert invertors
- Thread starter Draganchor
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Getafixx
Active Member
No, it's direct.
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Getafixx
Active Member
Only if the earth-neutral bond is there when you are on eskom power. That is why we use a relay to only make the bond when running in battery mode. At that point there is no current flowing to/from the Eskom transformer.
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OK, understood. So, if you are making the N-E bond on the inverter output, by means of the relay, while running in battery mode and you do have an E/L unit installed in-between the inverter output and the load supplied by the inverter, are you allowed to connect the inverter input to either before or after the main E/L unit? I know in your installation it is before, but is connecting it after the E/L also fine? Which one is the better/preferred option. What I'm after is the best way of connecting the inverter/ups both legally and safe.
Gnome, any comment?
Thanks guys!
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[email protected]
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OK, understood. So, if you are making the N-E bond on the inverter output, by means of the relay, while running in battery mode and you do have a E/L unit installed in-between the inverter output and the load supplied by the inverter, are you allowed to connect the inverter input to either before of after the main E/L unit? I know in your installation it is before, but is connecting it after the E/L also fine? Which one is the better/preferred option. What I'm after is the best way of connecting the inverter/ups both legally and safe.
Gnome, any comment?
Thanks guys!
Hi All
So here is what I found whilst testing
The following test where done in bypass mode. The panels are connected and the batteries too.
1) The inverter DB panel earth is definitely connected to the Mains DB panel. The chassis of both DB's are also earthed to the mains DB.
2) The neutral is bonded to the earth via the Main DB Panel as the it measures 0 VAC
The following test where done in Battery mode. The panels are connected and the batteries too.
1) The inverter ac out put neutral is floating at about 100 VAC between earth. I believe this is caused by replicating load shedding by turning of the mains breaker to the input of the inverter as you are basically disconnecting neutral completely. This I will only be able to confirm with true load shedding as then the mains neutral will still be connected to the DB outside my yard where I believe it is bonded to earth. I have a sneaky feeling that this will allow the inverter neutral to be bonded via the main DB. But this is an assumption.
2) The Mains earth and the inverter output earth are still connected in some or other way through the inverter.
Okay so I cannot simulate load shedding because if you turn off the main double poll breaker you then are actually disconnecting the mains neutral from the inverter. So I have to wait for true load shedding so the neutral to mains is still connected.
So because of my testing I believe it is possible that if you are running in battery mode and load shedding occurs the neutral of the inverter out put will automatically be bonded to the earth via the Main DB panel. As said I cannot confirm this until I experience true load shedding.
As soon as we have load shedding I will be able to confirm
Dimpie (JIGSAW)
Honorary Master
Interesting
greg_SA
Expert Member
In Battery Mode, during load scheduling, with your mains switch still ON, the Axpert will isolate the input neutral via its "safety relay" - see the image here: http://mybroadband.co.za/vb/showthr...-invertors?p=15835316&viewfull=1#post15835316
So the inverter's output neutral is only connected to the inverter.
So IMHO, the result of your test will be the same as turning the mains switch OFF - floating neutral on the inverter output.
Agreed, if that diagram is a block diagram of the Axpert's in question. That is why you have to bond N-E via the relay.
greg_SA
Expert Member
It is from a service manual for the Axpert (google: Axpert MKS-4000/KS-5000 Service manual)
OK, understood. So, if you are making the N-E bond on the inverter output, by means of the relay, while running in battery mode and you do have a E/L unit installed in-between the inverter output and the load supplied by the inverter, are you allowed to connect the inverter input to either before of after the main E/L unit? I know in your installation it is before, but is connecting it after the E/L also fine? Which one is the better/preferred option. What I'm after is the best way of connecting the inverter/ups both legally and safe.
Gnome, any comment?
Thanks guys!
The power going from your DB board to inverter can be VIA EL or without an EL. (The main EL used for your home)
The power coming from your inverter should go through another EL.
After an EL you can have many devices connected, so long as their neutral and live somehow end up being the neutral and live that goes VIA the EL.
You shouldn't create another path for that neutral or live to "skip" the EL.
Putting your Eskom -> Inveter power on the main EL might cause nuisance tripping for various reasons.
This is how I connected my Inverter:
Main switch -> 25 amp circuit breaker & Eskom EL
So my Eskom EL is in parallel with the 25 amp breaker (my inverter is not on EL)
My output circuit breaker going to my Inverter is 25amp circuit breaker
My circuit breaker coming from the inverter is double poll 20amp circuit breaker with a EL
I'm using 4mm twin & earth
From there my main switch (Eskom) goes to an EL which is wired to various things in the home. (Stove, Geyser, 3 Plugs breakers)
The alternate power goes to various things (lights and two plugs).
At no point do I bond my Inverter and Eskom Neutral (they have seperate neutral connector strips).
At no point do I bond my Neutrals and Earth
At no point do I have a Live wire from my Inverter and Eskom to connect to the same circuit breaker (they are completely separate)
Additionally, right at the inverter I have:
A small DB box
Eskom power from panel running through a double poll isolator
Inverter power coming from Inverter running through double poll isolator (then goes to main panel).
Inverter output in parallel to isolator going to a surge protector. (DIN mount)
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greg_SA
Expert Member
OK, understood. So, if you are making the N-E bond on the inverter output, by means of the relay, while running in battery mode and you do have a E/L unit installed in-between the inverter output and the load supplied by the inverter, are you allowed to connect the inverter input to either before of after the main E/L unit? I know in your installation it is before, but is connecting it after the E/L also fine? Which one is the better/preferred option. What I'm after is the best way of connecting the inverter/ups both legally and safe.
Gnome, any comment?
Thanks guys!
Regarding the connection of the inverters input... It depends on the timing between the E/L device and the bonding relay.
If you are in Battery Mode, the relay is closed, causing the earth-neutral bond. When Eskom comes back ON, then the relay will open to remove the bond, but only after a finite (short) time. During that finite time, the E/L feeding the inverter input might see unbalanced neutral/live current, if the inverter draws power while the the additional bond is still in place. That will cause the E/L to trip.
If the inverter only draws power after the relays is open, then it should be fine.
Hope that makes sense?
Getafixx
Active Member
I agree with the rest that it will be the same during loadshedding. And to confirm I initially had my inverter connected with a single pole breaker and neutral hard wired. When i tripped the breaker and batteries kicked in the output neutral floated.
That is indeed why I have mine before the Eskom EL.
Given that my inverter has its own EL you don't need another.
Slight caveat however: If there is a earth neutral fault, it will fail silently
But going via the Eskom EL has an additional problem:
If you have a ground fault and both EL device are rated for 30mA (or less), it is luck of the draw which will trip.
Not only is it super annoying, it can actually mean that your Eskom EL will trip, switch to Inverter, then trip the inverter EL also. (Assuming you were running on Eskom power and the Eskom EL tripped first).
Point being, don't put the inverter input power via your EL
(unless it is rated for a higher sensitivity, eg. 50mA, 100mA, etc.)TLDR: Agree with greg_SA, don't put your Inverter *input* on EL (definitely put the inverter output on EL however)
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Check.
Check.
Check.
Have had my APC 3000VA UPS connected after main E/L and running like that for more than 5 years and my infini connected the same and running for about 4 months without having any nuisance tripping though.
This is a bit confusing – how I understand this:
Eskom Main Switch supplies main EL and single pole CB feeding the inverter?
Double pole isolator/trip/ EL combination on output of inverter?
Here you refer to the main EL again.
Right?Fine, incoming isolator labelled as Main (sub DB) – fed from Main DB. Check.
Here you could have used a single pole breaker “feeding to the main DB”? Then on the Main DB, coming from the inverter, you’ll have to add another SP+N labelled something like “feed from inverter” and add a panel lamp to it to indicate that there is power coming from the inverter.
Optional extra.
What happened to the relay to sort out the Earth?
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Yep, that happened a few times when I worked on circuits fed by the inverter and Neutral and Earth accidentally touched - Both EL devices tripped. (My inverter is connected after main EL)
APC ups use center tapped transformer (at least my SUA1500i does). So they don't even tie the neutral and ground.
Hence there shouldn't be any tripping
This is my current circuit:
Eskom -> Main Switch -> Single pole 25 amp breaker -> Isolator (Sub board) -> Inverter input
Eskom -> Main Switch -> (Eskom) EL -> Stove, Geyser, Plugs
Notice that your parallel from the main switch to the first EL.
Inverter -> Isolator (Sub board) -> Double Pole Breaker + EL (Main board, labelled alternate power) -> Lights, plugs
I can take a picture tonight if you want
I think a diagram would make this simpler but can do this tonight. Bit hard to explain in words.
My inverter is not near my main DB, so right at the inverter I have a sub-panel with only an isolator
Then a wire runs to my main DB. There I have a combined Earth Leakage and 20 amp breaker. That breaker is labelled alternate supply.
It sits right next to my main Eskom circuit breaker.
So my two power feeds both have switches sitting next to each other.
One says Main Switch, the other says Alternate Power.
Makes it clear that both can be energized and that any power to the rest of the panel will originate from those two.
Haha yes.Here you refer to the main EL again.
My Eskom power is on one EL which is my Main/Utility/Eskom EL.
My Inverter is on its own combined circuit breaker EL.
It is legal to have separate EL devices (in the UK it is actually required for various reasons).
Yep
The isolator is right at the inverter to turn off the inverter power. It isn't a circuit breaker. It is simply to isolate.
Again because my Inverter is in another room and about 4 meters away from my main DB.
The isolator should be double poll (for single phase).
Yep
Still waiting on it, but I'll probably just put it in the Inverter enclosure.
The SANS document says you should bond earth & neutral at the generator terminal.
I'm also not sure about the SANS requirements about putting such a relay in the sub-db, even if I have a DIN mount.
In my case my 3 phase Utility/Eskom EL trips first. It has higher sensitivity it seems.
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greg_SA
Expert Member
This will work if you don't have an earth-neutral bond at the output of the inverter. But without the bond, and E/L on the output of the inverter won't actually trip during an earth fault.
OK, so your installation is not 100% complete and obviously not CoC'd.
Anyone have a CoC'd installation including the N-E bonding relay? Or some other approved installation similar to this?
