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Planning for the Inverter


douwgza
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HI all,

 

New to the forum but I have been following the topics on here as well as trying to educate myself as far as possible.  I am getting ready to make the move to purchase an inverter to operate in UPS mode for when loading shedding occurs.  What I have done is to document what my DB looks like today, what I think it should change to in order to get ready for the inverter install and what it should look like with the inverter installed.

 

PLEASE NOTE - I am not going to do this install myself but I'd like to have a better understanding of what will be done and how it is wired to my DB before getting the electrician out so that I can at least understand the concept before I get an expert out to do the quote.  This is mainly to ensure I don't get taken for a ride :)

 

It also so that forum members can have a look and see if there is anything glaringly wrong with my current setup.

 

I am attaching a PDF with the diagrams as I currently understand things to work.  Feel free to let me know if I am way off track here.

 

Thanks in advance!!

Douw

 

GERBER - INVERTER.pdf

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Hi Douw

 

Warning- I am NOT an electrician! I am a farmer. We farmers tend to get a bad rap (rightly so) for dangerous wiring. I am trying to buck the tend.

 

You do not say what size Inverter you are putting in?

 

So as I read your diagram you have 3 phase power and you plan to put your essential circuits on the red phase first and then install an inverter. The 20A breaker (should be near the inverter) on the up side might be a bit small - remember everything you are going to power when the grid is on has to come through that breaker. You also need a breaker/main switch on the output near the inverter (for safety).

 

Others may disagree with me but the neutrals from the circuits you power from your inverter need to come to their own neutral bar which then feeds back to the inverter output. The earth wires from these circuits needs to be separate from the rest of the earth leakages and go through their own Earth leakage/RCCB. these earths need to be fused to your neutral output at the inverter.  Remember when operating in battery mode you are supplying the electricity and not Eskom - stray current needs a pathway back to the inverter not Eskom. Technically everything needs to work from the main neutral/ earthing with Eskom on and circuits powered by the inverter need a earth pathway back to the inverter during load shedding. I have seen an installation that makes use of  contactor to achieve this but a bit of an overkill. The looped neutral and earth wires in the proposed wiring are going to make troubleshooting a nightmare. The input of the inverter could come straight from the mains or the neutral bar and earth on the input side to the earthbar.  

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Hi Douw

 

Warning- I am NOT an electrician! I am a farmer. We farmers tend to get a bad rap (rightly so) for dangerous wiring. I am trying to buck the tend.

 

You do not say what size Inverter you are putting in?

 

So as I read your diagram you have 3 phase power and you plan to put your essential circuits on the red phase first and then install an inverter. The 20A breaker (should be near the inverter) on the up side might be a bit small - remember everything you are going to power when the grid is on has to come through that breaker. You also need a breaker/main switch on the output near the inverter (for safety).

 

Others may disagree with me but the neutrals from the circuits you power from your inverter need to come to their own neutral bar which then feeds back to the inverter output. The earth wires from these circuits needs to be separate from the rest of the earth leakages and go through their own Earth leakage/RCCB. these earths need to be fused to your neutral output at the inverter.  Remember when operating in battery mode you are supplying the electricity and not Eskom - stray current needs a pathway back to the inverter not Eskom. Technically everything needs to work from the main neutral/ earthing with Eskom on and circuits powered by the inverter need a earth pathway back to the inverter during load shedding. I have seen an installation that makes use of  contactor to achieve this but a bit of an overkill. The looped neutral and earth wires in the proposed wiring are going to make troubleshooting a nightmare. The input of the inverter could come straight from the mains or the neutral bar and earth on the input side to the earthbar.  

 

Hi there Chris,

 

Thank you for taking the time to give me such a detailed response - it seems like I am not too far off from understanding what needs to get done :)  But still a bit unclear to me.  I will amend my diagram and update to reflect how I understood your reply.  I havent completly opened my DB so not sure what the neutral and earth bar setup looks like. Will check this weekend but I did think that the Inverter and the plugs attached to it should be on it's own neutral and earth bars.  Did I understand you correctly?  I have also read that it is a good idea to have a bypass switch in-case the inverter fails and has to be removed for repairs.

 

Yes, the house is 3 phase and I am looking at a 5Kva inverter - all the lights are LED, the fridge is brand new Samsung, Microwave is 1000W - but only gets used in the mornings - all 5 TV's in the house are LCD/LED but are never all on at the same time.  I don't have DSTV.  There are two PC's at 200W. So I think a 5Kva should be good.

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Hi I presume that this is how you dB is now and how you plan to get it ready for inverter and then once installation is complete.

 

Is your under floor heating falling away? Perhaps label your circuit breakers A1 A2  B1 B2 C1 C2 and so on in your diagram so that it is easier to follow the changes you are making. In the 2nd diagram give a CB it old label and new position label to follow what is happening. It is all in your head and easy but difficult for others (me :huh: ) to follow.

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Thanks Chris,

 

Is the attached image making things even more crazy?  Yes underfloor heating will be disconnected.  The attached image is how I imagine it will look at the end.  3 phases of which one (RED) is connected to the inverter.

post-993-0-42308900-1438594715_thumb.jpg

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I havent completly opened my DB so not sure what the neutral and earth bar setup looks like. Will check this weekend but I did think that the Inverter and the plugs attached to it should be on it's own neutral and earth bars.  Did I understand you correctly?  I have also read that it is a good idea to have a bypass switch in-case the inverter fails and has to be removed for repairs.

 

Yes, from the inverter output you will have to have a new Neutral bus-bar, isolated from the existing Neutral bus-bar. All the earth wires must be connected together though.

 

As per you explanation a changeover/bypass switch would be handy in case of inverter failure.

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Yes, from the inverter output you will have to have a new Neutral bus-bar, isolated from the existing Neutral bus-bar. All the earth wires must be connected together though.

 

As per you explanation a changeover/bypass switch would be handy in case of inverter failure.

Hi there Superdiy

 

Did you see the attachment to my post prior to yours?  Is that looking right?

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Thanks Chris,

 

Is the attached image making things even more crazy?  Yes underfloor heating will be disconnected.  The attached image is how I imagine it will look at the end.  3 phases of which one (RED) is connected to the inverter.

 

Hi douwgza

 

You have a 100A breaker on the input of the inverter - that should be 50A maximum. (page 7 in the manual)

You have a 60A breaker on the output of the inverter - that should be 25A maximum. (5KVA / 250 V  => 20A output)

 

The bypass / changeover switch should be something which can switch both Neutral and Live with preferably an off position as well. You will connect it in a similar way as with a generator installation where the one side is fed from the utility and the other side from the inverter output - you then route either the utility power or inverter power to the load.

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Hi douwgza

 

You have a 100A breaker on the input of the inverter - that should be 50A maximum. (page 7 in the manual)

You have a 60A breaker on the output of the inverter - that should be 25A maximum. (5KVA / 250 V  => 20A output)

 

The bypass / changeover switch should be something which can switch both Neutral and Live with preferably an off position as well. You will connect it in a similar way as with a generator installation where the one side is fed from the utility and the other side from the inverter output - you then route either the utility power or inverter power to the load.

Thanks!!!

 

As mentioned I dont know about breaker sizes etc and dont intend doing this myself - nervous about this - so I'll get a electrician to do the actual work - but what I am trying to ascertain is whether my picture in concept is accurate - ie components may be different size etc but I have listed all the components and the wires are going to the right place?

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Thanks!!!

 

As mentioned I dont know about breaker sizes etc and dont intend doing this myself - nervous about this - so I'll get a electrician to do the actual work - but what I am trying to ascertain is whether my picture in concept is accurate - ie components may be different size etc but I have listed all the components and the wires are going to the right place?

 

Yes, your diagram makes sense. Just change the changeover / bypass switch wiring. It will be similar to the top section in this diagram: http://3.bp.blogspot.com/-wS0Fw0Vqoog/UiQzXb403BI/AAAAAAAAFGQ/d5flEUPIxjs/s1600/inverter+to+AC+mains+changeover+circuit.png

 

The DPDT Relay would be your switch, just with another off / dummy position on the switch in-between the "AC OUT" connection from the inverter and "To Mains AC" connection. "To Appliances" in the diagram would be the live feeding the breakers and the neutral feeding the new neutral bus-bar.

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Like so....

 

Please see attached?

 

Almost, but the inverter input will not go through the bypass switch. The inverter input neutral will be connected to the current neutral bus-bar and the breaker in the live line to the inverter input will be mounted in the DB and fed from the current red 3-phase line.

post-594-0-17852300-1438599478_thumb.jpg

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Almost, but the inverter input will not go through the bypass switch. The inverter input neutral will be connected to the current neutral bus-bar and the breaker in the live line to the inverter input will be mounted in the DB and fed from the current red 3-phase line.

 

That is unless the inverter is not going to be installed close (1-2 meters) to the DB.  If the inverter is going to be installed further away you will have to install more breakers, at least one SP+N on each side.

 

And something I forgot, you have to have another earth leakage unit on the inverter output between the inverter and the bypass switch.

And an indicator to indicate that there is power in the DB when the inverter is running, but utility power is off - safety requirement.

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Added earth leakage and indicator light.

 

Is this looking right now?

 

Once again thanks for looking at this for me super and chris.  my field of expertise is IT but I am finding this so interesting - always nice to learn new things :)

 

 

post-993-0-74157200-1438602445_thumb.jpg

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Added earth leakage and indicator light.

 

Is this looking right now?

 

Once again thanks for looking at this for me super and chris.  my field of expertise is IT but I am finding this so interesting - always nice to learn new things :)

 

Yes, that is pretty much it. I've added the one I've been working on in the mean time...

post-594-0-11833400-1438603656_thumb.jpg

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Final version - I think I have covered all areas...

 

The Indicator / panel lamp is still not "wired" correctly. It will not be connected "in series" with the live from the changeover switch to the set of red CBs, but rather connected to the live and neutral coming from the changeover switch.

 

Will the "Inverter DB" be close to/next to the current DB?

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Is your Main Switch an ELR ?. 

I prefer diverting the circuits to the inverter DB if adjacent.

 

I agree.

 

PS  If you follow the images in this thread you will notice that the "inverter db" was only added later on - initially the inverter was simply "wired into the main db", but the better choice would be to move all the "inverter circuits" to the "inverter db".

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