Only the phase and neutral is supplied to this board. The earth is connected to the original utility board for the building. That is to avoid having 2 earths for one building.
The A/C main board for the off grid system has it's own earth for the AC and the equipotential bonding of the DC side.
johotech,
Jul 23, 9:48pm
So you're saying that the 6mm2 with the earth label goes to the other board, which is in the _same_ building?
And the other board has the earth stake, and a MEN link?
comsolve,
Jul 23, 9:53pm
Yes.
Not relevant because that is a utility supply board. The power to this board is supplied from the off grid system. In other words, this is not a sub board off the place where it's earthed.
johotech,
Jul 23, 10:10pm
I don't understand now because the other switchboard has the PV labelling, and it has subcircuits for "this room only" - so it's the main switchboard.
So how can this board with the digital meter on it come from the "off grid system" - but not come from the board with the PV labelling? Isn't it connected to the MCB marked "house"?
comsolve,
Jul 23, 10:15pm
Sorry if I have confused you. The board with meter is supplied P/N from the solar system board, via the MCB marked "house". This solar board also has a light and GPO circuits, via the RCD, for the room it's in. It has it's own earth which serves the AC and the equipotential bonding for the array, DC breaker box, inverter, PV combiner and charge controller.
The P/N supply then goes to the house. That is the 4mm TPS (thickest) cable you see, with the earth wire cable tied. The house also has a utility board. The 6mm tagged earth wire is run to the utility board to connect up with it's earth, so the house only has a single earth stake.
johotech,
Jul 23, 10:23pm
Where does the earth for the solar board come from? The main utility board?
comsolve,
Jul 23, 10:25pm
It has it's own earth as detailed in my previous post before this.
johotech,
Jul 23, 10:29pm
We're having non-electrician translation difficulties ;) "its own earth" is not clear. An earth stake in the ground?
From what you're saying, it seems like there is no earth connection between the solar board and the board with the meter, or the main network (utility) switchboard?
comsolve,
Jul 23, 10:30pm
Yes. A stake in the ground.
No earth between the solar and meter boards.
Meter board is earthed to the utility board.
vivac,
Jul 23, 11:14pm
So there is a phase and nuetral link connecting the two boards but not an earth link connecting the two boards? Do you have an MEN link in the PV board?
johotech,
Jul 23, 11:18pm
And it's all in the same building?
I'm 99% sure that's not right.
There must be a MEN link (neutral to earth link) in the solar switchboard to get the local RCD to operate. Which means that the neutral conductor supplying the "house" board, is also earthed at the solar board end, then there's another MEN link in the "house" board, linking the neutral and earth. Then there's another earth going to the main "utility" switchboard. That switchboard must also have its own earth stake (different from the solar board stake)? Which means there's 2 earth stakes at the building?
Those earthing issues, along with the way the neutral is looped at the meter, and the meter is before the main switch, and the totally incorrect labelling on the solar switchboard main switches, the main earth conductor label on the house board earth conductor when it's not a main earth. other small issues like no fire proofing of the cable penetration at the house board (which an inspector would pick up in 2 seconds) - basically, I would have concerns.
You probably don't know what I meant in the previous post about "the neutral being live", as most people think that neutrals can't be live. But I can tell you, electricians probably get more shocks from neutrals than from actives. In the case of your board, the active is feeding the meter, but there's also a connection through the meter to the neutral - so if that neutral isn't connected to the earth side for some reason, the neutral (and any neutrals or earths in the house connected to it) can achieve a dangerous voltage above actual earth (the ground, or concrete slab for example) - think little girl in Perth getting shocked off a garden tap, type of voltage.
If you had a drawing of all the main connections (neutrals, earth conductors, where earth stakes are connected etc), and how the main connections between the switchboards are done, I could get it checked by someone much more experienced in solar than me.
Only you know how it's been done, and how much of it has actually been inspected. So I'll leave it up to you.
comsolve,
Jul 24, 11:33am
I have had a discussion this morning with a sparky who works professionally in the solar industry. He said what I have is safe, however, as a matter of practice, he would advise me to earth the sub-board back to the solar system earth. He said if the building housing the off grid system and house were physically separated, what I have would be fine. But, by his analysis they are not and therefore the sub board should be earthed back to the point of supply.
comsolve,
Jul 24, 11:39am
You are right that is dangerous. However, the incoming neutral is earthed at the solar distribution board.
comsolve,
Jul 24, 11:52am
My interpretation of the regs was that earth labeling was correct. I will go back and reread this. Can you elaborate on what you mean by "neutral looped at meter"?
johotech,
Jul 24, 5:31pm
It's impossible for me to go through and tell you how to make every part of it compliant with possibly multiple mistakes. That's what your inspector was supposed to do.
As for the neutral on the meter, I suspect you added the meter later and just connected it into the main supply cable, which is wrong. It seems logical, but it's wrong. The neutral from the supply should go to the bar. The neutral to the meter (single) comes off the bar. The supply active should go to the main switch, then to the meter input, then to the RCD.
Then there's the problems with the earthing. There should only be one main switchboard, one earth stake, one main earth conductor and one MEN link, ONLY connected at the main switchboard.
All other switchboards should be supplied with A, N & E from the main switchboard, or cascaded if you have capacity.
You also mentioned about the "house utility board", which you haven't really explained how or if it's connected, other than to say that one earth conductor goes to it. You haven't said if it is actually has power or not. But you have said that you're 100% off grid.
As for the solar sparky, he asked you the same question that I did, about one building or multiple buildings, because the wiring is obviously not correct for a one building situation (and not optimal for multiple buildings either - but that's a different story).
As far as the wiring to the switchboards go, there is no difference between a solar supply or a network supply, once you get past the connection point, mains switches, and metering point if you are grid connected. So you don't actually need a solar expert to sort it out.
And after all that, I suspect that all that great quality circuit protection you have fitted probably won't do very much, other than the RCDs - because your inverter won't have the short circuit current capacity to be able to trip them. So probably the only protection that will work, will be whatever the inverter has internally.
I don't mind helping anyone out, and giving advice. Even for DIY. And you have gone to the trouble of learning enough to do it, and you probably got an inspection of the work that needed to be inspected. But I think you just carried on by yourself after that.
My advice is get an experienced electrician to sort it out. Or your electrical inspector back to go through with you and make a list of what needs to be rectified.
I know you're thinking of the possibility of renting out a room or whatever. But I can tell you that there's a real risk that part of the installation is unsafe.
comsolve,
Jul 24, 5:44pm
The EI has only viewed and ROI'd the system up to and including the A/C board at the solar system. The rest of the work has been done since, so I need to get him back.
I am currently reading through s5 of AS/NZS 3000:2007 to try and determine if I can use the earthing conductor in the 4mm cable to run back to the solar board. Otherwise I will have to pull it apart to run the 6mm through. The standard says the minimum size is 4mm (s.5.3.3.2) so I am trying to work out whether that applies in this instance or whether the 6mm standard applies.
To recap the advice I was given this morning- 1. Earth to the point of supply 2. Add signage to the sub board so it's clear what the point of supply is.
comsolve,
Jul 24, 5:58pm
That consideration was not lost on me at the time of install. On that subject, I will add the inverter is type approved for AU/NZ :-) The inverter's current exceeds the MCB but I will contact HPM and obtain further info on whether the trip time is within the inverter's surge rating.
johotech,
Jul 24, 6:11pm
The earth in the 4mm2 T&E submain to the board with the meter isn't a "main earth conductor" so 5.3.3.2 doesn't apply. It's 5.3.3.1
As for the inverters current, you said maybe 23-24A - but that might not be it's short circuit rating (probably higher). But anyhow, 23-24A would not trip a 20A breaker. At 30A, a 20A breaker might trip in around a minute. @ 25A, it could be 15 minutes or longer.
comsolve,
Jul 24, 6:14pm
Further reading suggests the 4mm stipulation only applies to the connection to the earth stake. This is not an issue as I don't need to change this part (It's already 6mm in accordance with the equipotential bonding requirements of AS/NZS 5033. Further reading suggests for the sub board to main board earth - this needs to be a minimum of 2.5mm to suit the 4mm I have used. (Noting the earth conductor in the 4mm TPS is only 2.5mm)
comsolve,
Jul 24, 6:17pm
Thanks. You got in ahead of me. So by my reading, I can use the 2.5mm earth in the main to sub lead for this. Whew, that will save a lot of work. I conclude this after reading the table 5.1 and caveats 5.3.3.1.1
In regards to the MCB issue - what you have posted is what I am thinking as well. I will promptly make enquiries with the importer of the inverter and HPM if necessary. If it needs to be rated down (16A?) I will certainly do this.
comsolve,
Jul 25, 2:03pm
Update @ Johotech. Have changed the earth so it goes back to the solar board as discussed and removed N/E link from the sub board. Tested RCD.
johotech,
Jul 25, 5:31pm
So you will have made an appointment with the inspector to come and test the whole installation now?
johotech,
Jul 26, 12:40pm
Is that the sound of crickets chirping that I can hear?
vivac,
Oct 17, 5:57am
What could possibly go wrong?
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