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Questions about electrics/inverter setup


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Hi all,

 

I’d greatly appreciate an experience eye cast over the design and electrics of a Goodwe ES 5048 inverter setup I’m planning that includes solar and Pylontech batteries to make sure I’m not doing anything stupid.

 

Firstly, some key challenges and pertinent info:

  • The existing DB board is a cheapy, annoying single row job and is nearly full as it is. I am able to make some space for the Goodwe energy meter by removing a lights timer I have in the board, replacing it with a suitable day/night sensor instead. So I am limited by how many devices I can add to this board without adding a surface mount box which I’d like to avoid if possible. This is located in the garage. If necessary, I could move some load breakers, such as the geyser for example to the new surface mount DB by the inverter.

  • I am not totally decided as to the inverter location so some input here would be appreciated. The garage is not the most spacious around the edges and I don’t like the fact I have to put the Pylon’s on the floor where it’s likely to get in the way. Also as garages are, it gets a bit dusty and cob-webby over time, and as it has a metal door facing east, it gets pretty toasty in there in the mornings in summer. Maybe I’m being a bit OCD about this, but this doesn’t seem like the ideal place for the Pylon’s.

  • I have an alternate location in a fairly large built-in cupboard inside the house. The cupboard would be easy to amend with a vent and a quiet 10cm ceiling extractor to assist with airflow. It is however, about 25m away from the distribution board by the way of cable run.

  • To keep things simple I’d prefer to simply attach all the existing loads directly to the inverter output. I believe my energy consumption would allow for that (typically 200-230kWh/month, peak according to efergy meter has been 9kW once in the last 5 months). If I really ran into problems, I could move the stove/geyser from the inverter output.

  • I have 255V coming out of my wall sockets which is just a “feature” of my complex’s feed transformer. I believe the Goodwe can handle up to 270V.

     

Thus, based on the Goodwe manual and other research I have the following basic electrical layout in mind (see Word art below). I haven’t included details such as the fuses and other components on the solar/battery side. My main questions would be:

  • Is my plan sound? If I understand the specs in the Goodwe manual, which isn’t all that clear on the matter, it appears it can supply up to ~9.2kVA from mains as pass-through power if required. Not sure if inverter backup power can be added to this total if necessary. I understand that if power fails I’m limited to the Goodwe’s backup output of 4.6kW but I think that would be easy enough to self-manage around.

  • The wiring from the main DB to the inverter would require 16mm^2 cable in both directions if I am correct. Not cheap, but I’d rather put in the full size cable than down-rate the breakers.

  • How large does the earth wire need to be that runs between the DBs?
  • Is putting the inverter in a cupboard a dumb idea or should I just leave it in the garage?

InverterWiring.png

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One of my main concerns has to do with temperature rating. If I look at the Pylontech batteries, they are rated for operation over 0-50C during charging which should be fine. However, the design life and cycle life are both specified at 25C.  Given I've measure the temperature in my garage at 35C+ in the peak of summer with a hot car in it, my feeling is this is not a good place for these electronics - what have other people's experiences been? Or should I perhaps consider a large extractor in the ceiling in my garage to deal with this?

Also the Goodwe temp derating starts at 45C - how quickly/easily does the inverter get near this temperature when under normal operation or high load?

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2 hours ago, AlexTZA said:

Also the Goodwe temp derating starts at 45C - how quickly/easily does the inverter get near this temperature when under normal operation or high load?

I did not know that it starts derating at such a low temperature. Under full load (4.4kWp PV) my Goodwe ES 5048 reports about 50C in a 28C garage.

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Hi Alex

 

Personnaly  I would not implement it the way you have drawn it.

 

 

In your DB you need to split the Board into Non-essential loads and Essential loads

You only want your essential loads on the Inverter backup output and limit this to 4600 VA.

So remove your Geyser, pool pump and geyser from the essential loads.

With the Hybrid Goodwe you will still be able to power these non-essential loads from your solar panels if excess solar is available ( but not when the grid is not available)

Edited by Jaws
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Hi Jaws. 

The backfeed from the inverter is something I had not considered, but now that you mention it, it explains quite a few things. I presume the power meter that comes with the Goodwe is used by the inverter to regulate the backfeed so that the inverter can supply the non essential load without feeding back into grid, or at least for very short durations when the load changes dramatically. Is that the gist of it? 

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13 hours ago, AlexTZA said:

Hi Jaws. 

The backfeed from the inverter is something I had not considered, but now that you mention it, it explains quite a few things. I presume the power meter that comes with the Goodwe is used by the inverter to regulate the backfeed so that the inverter can supply the non essential load without feeding back into grid, or at least for very short durations when the load changes dramatically. Is that the gist of it? 

That is it yes, excess solar goes to non-essentials but the CT makes sure nothing goes back to the grid.

The only draw back is that when the grid is off then you cant power the non-essential loads even if you have excess solar power.

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Quote

The only draw back is that when the grid is off then you cant power the non-essential loads even if you have excess solar power.

And maybe just for clarity then, what are the advantages of the split load layout, or are they not advantages rather than requirements?

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1 hour ago, AlexTZA said:

And maybe just for clarity then, what are the advantages of the split load layout, or are they not advantages rather than requirements?

It's merely to avoid the pain of a large non-essential load switching on in the middle of a load-shedding slot and plunging the house in darkness because the inverter was overloaded 🙂

It can also reduce cable requirements, eg in my house I have the essential side sized to only 25A, which means I don't need super-thick wiring for the full 60A back and forth to the inverter.

The other way people deal with this is to use contactors that disconnect the non-essential loads when the grid goes out (power the contactor coil from the grid side). Nowadays people also use Wi-Fi IoT switches (eg Sonoff).

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12 hours ago, Jaws said:

The only draw back is that when the grid is off then you cant power the non-essential loads even if you have excess solar power.

If I may.... Is it possible (or even legal) to have a changeover switch after the inverter to feed the non-essentials from battery if need be (emergency or absolute necessity)?

Edited by TheoG
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9 hours ago, TheoG said:

If I may.... Is it possible (or even legal) to have a changeover switch after the inverter to feed the non-essentials from battery if need be (emergency or absolute necessity)?

Nice idea - something like this:

Invertercabling2.png

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1 hour ago, AlexTZA said:

Nice idea - something like this

I can not figure out how your circuit would look like. Where would you put the transfer switch in my wiring diagram? It would be nice to have an option to sometimes switch the non essential loads to the back up (UPS) circuit during load shedding. Wife does not understand why after having spend soooooo much money on our PV system she can not cook during load shedding 🤣.

electrical diagram forum.pdf

 

 

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Nice diagram - did you create it? I see there are single pole breakers on the live between your DB boards - I was under the impression based on the Goodwe manual those had to be double pole?

Regarding the position of the transfer switch, I'm not exactly an expert but something like below seems like it should work, if you can understand my hack of your picture? The transfer switch has inverter output and AC mains as inputs and normal loads as output. This would also allow for the interesting case of the grid powering the backup loads and the inverter powering the non-essentials loads :)

 

Invertercabling3.png

Edited by AlexTZA
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On 2019/03/28 at 2:56 PM, AlexTZA said:

Nice diagram - did you create it?

thank. yes i did. i used profiCad. 

 

On 2019/03/28 at 2:56 PM, AlexTZA said:

I see there are single pole breakers on the live between your DB boards - I was under the impression based on the Goodwe manual those had to be double pole?

not sure about the legal requirement. I am going through the SSEG registration process at the moment. Any non compliance will obviously be fixed.

I pretty much followed the Goodwe diagram. The one i have only has a breaker in the life wire.

On 2019/03/28 at 2:56 PM, AlexTZA said:

Regarding the position of the transfer switch, I'm not exactly an expert but something like below seems like it should work

thanks for the proposal. I am sure it could work. It would however require another 63A change over switch and major rewiring. My DB board is so full already and i hate working with 16mm2 wires ;). I think it would be easier for me to rather educate my wife 🤣

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