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Wiring assistance and validation please


stoic

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Here is a drawing of my existing setup:

Everything above the blue line is currently in place, everything below the blue line is what i want to add. (note, i did not included fuses and additional cutoff switched in the picture)


 

image.thumb.png.2e56c63264c1b04137c43e5719349619.png



I have a whole host of questions though. some for my existing wiring and some for the new wiring.

As you can see, i have 3 phases coming into the property and i am using one of the phases to connect to my inverter, from the inverter it supplies my current house. I would like to change things up a bit as i want to extend power from the inverter to a second house, but i want to still be able to manage each properties' supply manually if need be.

The changeover switches will have three positions, 1-Utility, 2-Inverter and 3-off. This will allow me to independently switch each house to either utility or inverter.

Questions :)

  1. Is it fine to have all the above independent earth rods? 
    • reason i ask is i've heard quite a bit about neutral/earth bonding. and i am still not 100% sure what that means?
  2. Will it be ok to split the utility neutral between the three supplies? one going to inverter, one going to one house, one going to the other
  3. I know your loads should be as well distributed as possible between your three phases, this setup will completely break that rule, is that fine?
  4. will it be possible to feed back only on L2, and not the other three? i will look at something like a fronius. (or what ever the thing is called)
  5. barring existing fuses and breakers on the inverter side, should i look at adding any other safety fetures going to house 1 and house 2?

I will most likely think of more questions but will pop them in the responses :)

 

 

Edited by stoic
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1. You will get a host of answers on this point, but I believe your grid supply earth should be tested and if it is a good earth it should be hard-wired and distributed to all other the places you show an earth spike.

There should not be earth spikes all over the place, this can cause problems.

If you have to use a spike, use sufficient spikes close to one another and measure to make sure its a very good earth and everything gets hard-wired back to there. Additionally you should earth the PV panel frames to your system earth with a transformerless inverter, like a Fronius.

2. Yes, if wire size is same as the live phase. (What I don't like about your drawing is that DC+ & DC- , are the same colours as L# & N).

3 & 4. Yes and No, you can electrically, with the caveat that I have my doubts about getting things approved, but there are enough people on this forum who can quote you the domestic regulations.

5. Yes, if you use a transformerless inverter, then there is a direct connection to the DC side of things from the AC side. So besides you needing earth-leakages, you now need a special AC & DC earth-leakage. A Type B RCD. 

 

 

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4 minutes ago, phil.g00 said:

You will get a host of answers on this point, but I believe your grid supply earth should be tested and if it is a good earth it should be hard-wired and distributed to all other the places you show an earth spike.

thanx, i was not sure about this, so i spiked them all :) , it will be fairly easy to make sure they all use earth from utility. i'll have it tested first thuogh.

 

5 minutes ago, phil.g00 said:

Yes, if wire size is same as the live phase. (What I don't like about your drawing is that DC+ & DC- , are the same colours as L# & N).

this is just my depiction, its actually propper battery type cabling, grey, with colored shrinkwrap around it :) 

8 minutes ago, phil.g00 said:

Yes, if you use a transformerless inverter

using  victron Multiplus II's here, not sure if it is transforemerless or not

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By the way, I wouldn't do things this way if I was planning to use a single phase inverter on a three phase system.

What I would do is take the three phases everywhere, and from the outset I'd be pretty disciplined about what was on each phase.

Along the lines of L1 = the loads I'll do without when load shedding, L2 = the critical loads i want to stay on during load-sheding, L3 the loads I want to turn on to coincide with the noon production peaks so I am not nett exporting.

But this might be quite a daunting task with a large existing setup.

 

Edited by phil.g00
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25 minutes ago, phil.g00 said:

By the way, I wouldn't do things this way if I was planning to use a single phase inverter on a three phase system.

What I would do is take the three phases everywhere, and from the outset I'd be pretty disciplined about what was on each phase.

if only i owned the place from the outset. 

There are 12 db boards in total on the plot... tracking down loads per phase is damn near impossible. The previous owner is an electrician... and you know what they say about the shoe maker's children.

 

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Note that your change-over switch will switch the supply to your houses from L1 (L3 for second house) to the Inverter which is synchronised to L2.  There is typically 400Vac between L1, L2 and L3 so one should not rapidly switch over - otherwise you may damage some equipment (e.g. motors) and burn the changeover switch contacts. You will need to switch to the OFF position for a few seconds before connecting to the opposite position.

Edited by NigelL
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Hi Stoic

There is typically 230Vac between each phase and Neutral, but about 400Vac between any two phases.  Normal household appliances connect between one phase and Neutral (i.e. never between phase 1 and phase 2) - so will not be exposed to 400Vac.

The simplest way to visualise this is by considering the following diagram.  This shows the 3 phases plotted relative to Neutral - Neutral is the "0V" line. Each phase is at most +1.0 or -1.0 relative to the 0V reference. The difference between phase 1 and phase 2 can be much higher - i.e. 1.5 or -1.5.

Image result for 3-phase diagram 220V rms

If one does the maths for sine waves that are 120 Degrees out of phase, it turns out that the voltage between phases is 230Vrms x 1.732 = 398Vrms. 

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This is a shade cheaper:

https://www.alibaba.com/product-detail/RHENES-high-quality-30mA-100mA-300mA_62027700118.html?spm=a2756.order-detail-ta-ta-b.0.0.2c2e2fc2KDWgA4

You only need the type B, where there is a possibility of a DC earth fault. In other words where there isn't galvanic separation between the AC and the DC circuits.

This happens with transformerless grid-tied inverters. Where there isn't a link between the AC and the DC, the normal  30mA RCD will suffice.

However a 30mA Type B would still work in a pure AC circuit as well, it just has a extra measuring element for DC.

As to your set up as shown, I'd go for single phase RCD's, one on each phase. Although I might be inclined to have one per house, after the changeovers, if you are not using L2.

They should be downstream of the supply and upstream of the first instance of power usage.

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8 hours ago, phil.g00 said:

This is a shade cheaper:

https://www.alibaba.com/product-detail/RHENES-high-quality-30mA-100mA-300mA_62027700118.html?spm=a2756.order-detail-ta-ta-b.0.0.2c2e2fc2KDWgA4

You only need the type B, where there is a possibility of a DC earth fault. In other words where there isn't galvanic separation between the AC and the DC circuits.

This happens with transformerless grid-tied inverters. Where there isn't a link between the AC and the DC, the normal  30mA RCD will suffice.

However a 30mA Type B would still work in a pure AC circuit as well, it just has a extra measuring element for DC.

As to your set up as shown, I'd go for single phase RCD's, one on each phase. Although I might be inclined to have one per house, after the changeovers, if you are not using L2.

They should be downstream of the supply and upstream of the first instance of power usage.

each house have their own board with their own 3P RCD. 

considering the fact that i want to run earth from my utility to my dc earth busbar, i take it i will then need a type b, cause that earth will also run to both changeover switches and there is then a possibility that there could be a dc and ac fault on my earth. Would it not make sense to then rather leave the dc earth separate on its own earth rod?

I am seriously starting to think that need to get an electrician that does not cost an arm and a leg to help me out here. I mean, i am cautiously confident in what i am doing, but basic electrical knowledge does not help when one need s to make sure it is 100% safe.

any takers in the Vereeniging area?

 

.. picture of the Earth Leakage that is on both DB Boards: 

image.png.4479e042d75986ce025e11e85e97bfb6.png
 

Edited by stoic
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8 hours ago, stoic said:

each house have their own board with their own 3P RCD.

Why? unless your drawing is inaccurate?

8 hours ago, stoic said:

considering the fact that i want to run earth from my utility to my dc earth busbar, i take it i will then need a type b, cause that earth will also run to both changeover switches and there is then a possibility that there could be a dc and ac fault on my earth. Would it not make sense to then rather leave the dc earth separate on its own earth rod?

No

8 hours ago, stoic said:

I am seriously starting to think that need to get an electrician that does not cost an arm and a leg to help me out here. I mean, i am cautiously confident in what i am doing, but basic electrical knowledge does not help when one need s to make sure it is 100% safe.

Considering you didn't know basic 3 phase principles, this is a good idea.

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