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3-Phase DB Board Rewiring in Prep for Solar Installation


d3nominat0r
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@NigelL I just have a question regarding the termination of the 2 unused phases in your DB Board. Mostly the incoming feeds come through a single 3P Isolator and 3P Breaker that are single throw switches. Do you leave them just unwired post the 3P breaker although they are active?

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I still have the "other" 2 phases connected to some "high-power" loads (air-con, some plugs etc.) that do not get used very often. In summer I was only using about 10kWh per week from Eskom. Now that we are heading into winter, this has increased to about 20kWh/week 🙂

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4 hours ago, NigelL said:

I still have the "other" 2 phases connected to some "high-power" loads (air-con, some plugs etc.) that do not get used very often. In summer I was only using about 10kWh per week from Eskom. Now that we are heading into winter, this has increased to about 20kWh/week 🙂

Thanks, I was thinking of doing the following. Does it make sense? I added the CG Energy Meter into the board as well to feedback to the non-essential loads in case of excess PV. This is a 3 x 18 (54 slots) DB Board.

 

Current Circuit Board-New DB (Alt).png

Edited by d3nominat0r
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This looks good, but a couple of comments.

  • Phase 2 will probably need its own Earth Leakage.
  • Keep in mind that you will need a separate Neutral Bar for each Earth Leakage unit, and another "common" Neutral Bar. These all take up space in the DB so plan accordingly. I ended going for a 4 x 18 Board - with one row just used for Neutral Bars.
  • I only wired a small number of plugs to the "Essential" loads circuit so that one does not risk tripping the Inverter, with high-power devices, during a mains outage. e.g TV, Internet, Security system, Fridge etc.

 

Edited by NigelL
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4 hours ago, d3nominat0r said:

Thanks, I was thinking of doing the following. Does it make sense? I added the CG Energy Meter into the board as well to feedback to the non-essential loads in case of excess PV. This is a 3 x 18 (54 slots) DB Board.

 

Current Circuit Board-New DB (Alt).png

I did the same (3x18db). Note Sans require a mains isolator for the low and high amp parts. This will also serve as the overload for the amperage necessary. For my 4kw inverter it was a 20a overload. Plugs must be 16a and lights 10a.You can buy a rcd which is also an isolator but it is very expensive.

The only plugs you can really dedicate to the inverter are the ones for the computers, router and tv. The other ones will feed things like heaters which must stay on the high amp side.

I also protected the supply to the inverter with its own isolator and 40a overload. That way I can isolate it from the house if work needs to be done on that side.

I also put in a bypass to the low amp side from the mains (via the inverter bypass switch) son the inverter can be bypassed when necessary. I also isolate the inverter this way when there is a highveld storm.

I put my control circuit in the middle slot. It makes the wiring easier. Here I also installed surge protection - which I will never leave out. R400 is much more affordable than repairing surge (aka lightning) damage.

My bypass switches are seperate on the outside. They are the +R1k items. My mains bypass also includes the generator. When I isolate now in heavy thunderstorms I just switch it to the middle. I use the inverter bypass when my borehole pump is running as it takes too much power from the inverter.

i see you have a 3 phase supply. That should make it even more complex 🙂

Edited by Johandup
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2 hours ago, NigelL said:

Keep in mind that you will need a separate Neutral Bar for each Earth Leakage unit, and another "common" Neutral Bar. These all take up space in the DB so plan accordingly. I ended going for a 4 x 18 Board - with one row just used for Neutral Bars.

Interesting, I thought all phases share the same neutral. Why is this?

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6 minutes ago, d3nominat0r said:

Interesting, I thought all phases share the same neutral. Why is this?

The inverter needs its own neutral bar. You will have an interesting time sorting it all out. Inverters give the most interesting errors when the neutrals are mixed up. It also indicates house wiring problems which must be sorted before thing will run properly.

Btw, Id and mark all cables (I used heatshrink) before stripping and replacing the db.

Edited by Johandup
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2 hours ago, Johandup said:

I did the same (3x18db). Note Sans require a mains isolator for the low and high amp parts. This will also serve as the overload for the amperage necessary. For my 4kw inverter it was a 20a overload. Plugs must be 16a and lights 10a.You can buy a rcd which is also an isolator but it is very expensive.

Just to double check, I have a 25A CB for the Inverter before the changeover switch and then there is an Earth Leakage Unit. I will be adding an 2P Isolator on the Inverter Sub-DB. Not sure if this meets the requirement?

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29 minutes ago, d3nominat0r said:

Just to double check, I have a 25A CB for the Inverter before the changeover switch and then there is an Earth Leakage Unit. I will be adding an 2P Isolator on the Inverter Sub-DB. Not sure if this meets the requirement?

The isolator must be after your changeover ( aka bypass) switches as it cannot isolate two sources being 2P. The bypass switch is isolated when you put it in the middle - depending on what you buy.

I don’t see the use of a surge protector in your inverter circuit. Rather put a N+L one in your mains just after the mains 2P isolator.

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9 hours ago, Johandup said:

The isolator must be after your changeover ( aka bypass) switches as it cannot isolate two sources being 2P. The bypass switch is isolated when you put it in the middle - depending on what you buy.

I don’t see the use of a surge protector in your inverter circuit. Rather put a N+L one in your mains just after the mains 2P isolator.

Got it, thanks @Johandup. Just want to check on the main supply side, I currently have a 3P Isolator and 3P CB, which I copied from the existing board. In my mind the 3P CB is not required as I am adding a Earth Leakage unit to each phase which was is not there in the 2/3 of the phases as they had no plug circuits. Can I remove the 3P CB?

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1 minute ago, d3nominat0r said:

Can I remove the 3P CB?

Nope, you will need it when you need to isolate the 3 phase supply.

My view is you cannot have too many isolators - I was shocked because of this only last week.

Not pleasant. 😞

Btw, it is not nice working on a cluttered db. My ideal one is one that pivots from the one side and also feeds all the cables in from the one side. Redoing mine was back breaking. Did it myself.

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13 hours ago, d3nominat0r said:

Interesting, I thought all phases share the same neutral. Why is this?

The incoming phases all are referenced to a common neutral, however each Earth Leakage device requires its own separate neutral bar for all devices connected "down stream" of the E/L unit.  As Johan mentioned, one can have an "interesting time sorting it all out". Especially if one has an older house where the electrics have been extended by multiple parties over the years.

The real fun starts when you have two circuits, that need to be separated, and they have a shared neutral wire in some well-hidden junction box.

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1 hour ago, NigelL said:

The real fun starts when you have two circuits

so true. It took me days to trace all the neutral. It would have taken the sparky who did the installation in my house only seconds to label the neutrals. I will also request a wiring diagram if I ever have electrical work done again.

Edited by Fuenkli
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8 minutes ago, d3nominat0r said:

What would you say is the best pragmatic way of tracing the live/neutral pairs? Pure testing for continuity might not work due to loaded/unloaded circuits.

Before stripping test each and every circuit by switching on / off at the db.

Make a diagram of the complete house circuits (plugs, lights, stove, geyser etc). I numbered all the db circuit breakers on this diagram. When you redo the wiring this will become your go to information.

Mark them as you test them by switching on and off. I plugged a desk

amp into the plugs. Switch all the lights on as they share circuits.

Once you start stripping mark all the wires - I did it with heat sink tubes which you can write on with a permanent marker.

Where you find more than one wire in a connection you need to test it again. Problems raise their head when plugs etc share a neutral. This is what would make the inverter trip.

Don’t expect to be successful the first time. This is a job best left for an early Saturday.

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On 2019/05/07 at 2:15 PM, d3nominat0r said:

What would you say is the best pragmatic way of tracing the live/neutral pairs? Pure testing for continuity might not work due to loaded/unloaded circuits.

What I found useful was to connect a small transformer-type power supply to the circuit. These usually have a DC resistance that can easily be identified using a multimeter. This should be noticeably different to other normal loads.

One then connects the multimeter between live (trip switch is off!!!) and neutral bar. Then disconnect the neutrals until the resistance suddenly increases.

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On 2019/05/07 at 2:15 PM, d3nominat0r said:

What would you say is the best pragmatic way of tracing the live/neutral pairs? Pure testing for continuity might not work due to loaded/unloaded circuits.

The way I've used in the past -- and I must warn you it is somewhat cowboy/dangerous -- is to disconnect the neutrals from the neutral bar (so they are hanging mid air). You then turn on the breaker on the live side, and with a multimeter you measure between the neutral bar and the neutral wires until you find the one that is hot. That one goes with the breaker you turned on.

It  works because any loads on that circuit will pass a bit of current. With the neutral disconnected, the loose neutral wire is now connected to live via a resistor (the loads on the circuit). It might even make sense to plug in a lamp or something to make sure you have something to pass the current.

It is dangerous because you have a bunch of black wires hanging in mid air and one of them is live. In practice I find that you are rarely seeking a needle in a haystack. Sometimes you can figure it out from the general flow of the wiring, or even the gauge of the wire (light circuits might have thinner wires and the black and red will have the same size), so usually you only have two or three "unsure" wires to figure out using this method.

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  • 1 year later...
On 2019/05/03 at 1:27 PM, ___ said:

If there is an energy sensor/meter involved, such as in a Victron system you might have a Carlo Gavazzi modbus meter used for grid-limiting, that would go in the main DB, right before the branch-off that goes to the sub-DB where your inverter is connected.

You might be thinking of an old photo of mine. I installed that with my previous Multi to make it NRS097-2-1 compliant (because the Multi didn't comply on its own). I ended up replacing the inverter with one that doesn't require external anti-islanding (and Cape Town would not accept the combo anyway), so it is no longer in there. Not required.

This is an interesting point, I am hearing that the CoCT has rejected some applications with non compliant Inverters, like for instance a Victron Quattro (1 relay), even though it has an anti Islanding device with it (Ziehl - 2 relays), if this is actually the case, then the Quattro can ONLY be used for "Nearly Off-Grid" configurations and not for "Grid Connected" configurations, which would mean a 3 phase 30kVA installation would need 6 * MultiPlus II 5kVA instead of 3 * Quattro 10kVA and a Ziehl 

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