Sophon

From what I understand, if panels are connected in series and one panel is underperforming (partially shaded, lower quality, slightly faulty) then every panel in the string will as a result be similarly underperforming. That would be one reason why it could make sense to split your panels into strings, even if your inverter can support more in series. But I could have misunderstood the above.

Thanks, that's a relief. The Jinyuan panels from Global are rated at 8.94A so two strings should just sneak in under the limit anyway, if the inverter has a maximum input current of 18A. I still can't see this stat mentioned anywhere though.

OK, so in addition to the PV input voltage having to be in the inverters MPPT range, the current also has to be below the inverters maximum input. Where do you see what that limit is, In the specs for the inverter I linked to above I can see no mention of this?

So in my set-up 4/6 sq.mm. cables. 4 sq.mm. will probably do as the inverter will be located right under the panels, so the longest cable run will be around 6 m. Breaker 25A or 32A? An inverter such as this one from Lazada: with these specs: would fit nicely with my approx. 229V input voltage, but it would be right on the limit if I arranged by twelve panels in series (which i am not going to do). Still a ways to go, but I feel like I am getting a grasp on how this is going to work, and am almost certain that I will end up going for it.

I'm sure that the above is correct, but can someone help me understand how you arrive at 10A? Taking this panel from Global as an example: Wired up in two strings of six panels, I make it a total of 6x38.2V = 229V. As the maximum the inverter will support is 5kW, that would make a theoretical maximum current of 5kW/229V = 21.8A. In reality a bit less than that, as the panels at the rated 340W would only produce about 4.1kW. Where am I going wrong?

With what BritManToo wrote about the battery cables needing to be able to handle 100A, the Taxnele one in the link would be undersized (only goes up to 63A). But I found this other Taxnele DC breaker, that can handle bigger currents: And this one is actually described as a "battery switch". Would you go for the 100A or the 125A version (same price).

All the solar equipment (panels, battery, inverter) will be very close together, the 50 m run is AC from the inverter to the house and we already have buried 16 sq.mm. cable in place for that.

Will do. What kind of cable size will I need for connecting the AC and DC surge suppressors?

A couple of general questions, not directly solar related. I used a Schneider consumer unit when building the house, so I am not familiar with DIN boxes. Would a "double decker| box such as this one make connecting everything easier? In my head it seems like it would. The above box (unlike my Schneider) doesn't come with an earth bus bar. So would you buy and mount a normal bus bar such as these?: Or would you use something like this, that can be easily mounted on the DIN rail?

Thanks, I will watch that.

Thank for the info, that will come in handy. I have some 16 sq.mm. cable left over from the house construction, so I guess I could use that.

Thank you. One thing I am a little hazy about, are the actual connections on the DC side. From your picture it looks like there are special plugs for plugging into the inverter, rather than the "shove the cable into a hole and tighten a screw" that I am used to on the AC side. The same is probably true for the battery connections, and I have already seen that it's the case when connecting the solar panels. I am also not clear on what cable sizes I need for a 5 kW system, one of the sellers of inverters on Lazada quoted 4 sq.mm. but is that enough for a sustained energy flow of up to 5 kW? FWIW the finished cables that Global sell does seem to be mostly 4 sq.mm. And, as I have not presently any surge suppressors, what kind of cable sizes do they require? They need to be able to divert large amounts of energy, but obviously only for a very short time. Hopefully, these are things that will become clear with further research.

Thank you again Crossy. I will let you get back to enjoying your week-end.

This is where I feel completely lost, i.e. when trying to figure out if equipment meets my requirements or not. How do I know if these two examples of DC MCB's can be used for my battery storage, what is it in the description that gives it away? There are wiring diagrams on the MCB's themselves, but I don't know enough to understand them. Example 1: There are a couple of questions about polarity in the Q&A, but the translation makes them incomprehensible: Example 2:

Thanks. Stupid question alert! I assume that I can use the same ground bus bar for both the AC and DC (surge suppressors) side?

Hi again Crossy. In my reply to using a changeover switch for changing between essential/non-essential load in a hybrid on-grid system, you suggested maybe using one to bypass the inverter also in a hybrid off-grid system. Did you mean something like this: Any glaring mistakes in my diagram? I haven't yet added surge protection on the DC side, as I don't really know where it would be needed?

So that means that I can wire up an AC MCB either way, but what about the MCB for the battery storage? Does that mean that there are special MCB's specifically for the battery storage?

Stupid question. Are normal MCB's directional? In most wiring diagrammes I have seen they have input at the top of the MCB and output at the bottom like e.g. this one: Sometimes it would make for easier wiring to have the input on bottom, and when talking about the MCB for battery storage the energy can flow either way depending on the circumstances. I would have thought that MCB's are bi-directional, and can be wired up either way, but as we have already established my electrical knowledge is limited.

Yeah, I was aware of that. It seems that DC breakers and wiring in general is a little more expensive than AC equipment, but it will not be a major cost so not that important.

Sounds good that I can use a local ground rod, that will make my life easier. I will have string inverter(s). With 12 panels, I believe I would connect them as two strings each with six panels in series, and the two strings then connected in parallel? I am sorry, you lost me with the "and don't forget the D side", is "D" a specific type of arrestor or what did you mean by that?

I have snipped your post to highlight the relevant (to this post) part. Yeah, it's always difficult weighing up options when you are not sure what the future brings. I could do as you suggest, and buy two 5 kW hybrid off-grid inverters, so that i know they would be compatible. The down-side being that I may in reality only need one, so having wasted the cost of the second one. Alternatively, I could buy just one and hope that I can find a compatible unit (or the same model if not to much time has passed), if it turns out that one unit is insufficient. Of course, the risk being that I can not find a compatible unit, and have to buy two new ones, wasting the investment in the original one. The second option do have the benefit of giving me added flexibility. Assuming the first 5 kW hybrid Off-grid inverter lasts me a year or two, and during that time I decide that I need to change to a hybrid on-grid inverter, I would have wasted less money than if going for two inverters right away. Of course, since splitting my load is a deal-breaker the latter option of switching to on-grid would only work, if I can find an acceptable solution to the essential/non-essential load connections. Have you seen my question about connecting both output ports from a hybrid on-grid inverter to a manual switch-over switch, such as is normally used to switch between grid and generator? Could that work? It would give me the option to: Have the switch default on "essential load", and manually switch to "non-essential when I need more than the inverter can handle (when charging EV via wall charger), or have the switch default on "non-essential load", and manually switch to "essential" when power goes out. If i can find an acceptable option to the load problem with an hybrid on-grid inverter, I think that I will probably initially go with a cheap Chinese hybrid off-grid inverter like the model BritManToo uses. That way I can learn from my own real life experience, without having wasted too much on equipment that it may turn out doesn't deliver what I need. Thank you for your patience in answering my questions. I know some of them must sound basic (or even down-right stupid) to you.

From reading posts in the electrical forum over the years, I have learned that having more than one ground can in certain situations be extremely dangerous. As mentioned, my solar panels will be ground mounted close to where the incoming supply enters our land, which is about 50 m (as the crow flies) from the house and where the existing ground rod connected to the consumer unit is located. At the moment I don't have a supply isolation breaker (other than the main RCBO in the C.U), nor do I have any surge protection, so the only way to cut the supply is to have PEA pull the cable from the meter. This is an oversight I now plan to fix, so I will put an incoming breaker where the PEA cable is today crimped onto my cable running to the house and after that I will add a MOV (I think it's called?) surge protection unit. These will be in a small box on the pole we had erected to receive our incoming supply from the PEA pole, which is on the other side of the soi. the new box will be here, where the workers plugged in their equipment during the construction of the house (looks safe, doesn't it?). The panels will be located a few meters away from this pole, and the inverter and battery etc. will be under the panels protected from the elements with some walls (but semi open for ventilation). The Inverter, as well as the surge protection I plan to add, will both need to be grounded, and as the existing ground rod is 50 m away it would not be very practical to run cables to it if it can be avoided. So would adding a second ground rod next to the panel location create a dangerous situation? I have also read about people using the house roof construction as a UFER ground, so would the 6 m x 4 m metal structure with six concrete footers I will build be a suitable ground and would you connect the inverter/surge protection to the structure as well as the second ground rod? All that is, of course, assuming that the answer to my first question is, that a second ground rod 50 m from the existing one will be OK.

Thanks for your comments and suggestions Crossy. Our incoming supply goes from the PEA pole to a pole at the corner of our land (where the solar panels would be located). It then goes underground for 50+ meters and enters the house through the wall downstairs: From there it goes through the floor of the living space upstairs into a cavity wall of one of the upstairs bathrooms into the ceiling space. Making that whole in the wire mesh reinforced concrete floor was a major task even back when the cavity wall was not there yet. It then comes down to the consumer unit embedded in the AAC wall: Splitting the load into essential and non-essential, would require me to run a second buried cable to the house (in itself an added cost of THB 20k+). I would also have to drill extra holes in the downstairs wall, the floor between downstairs and upstairs, embed the extra cables and a second C.U. in the wall . After that I would have to have the wall upstairs and the ceiling downstairs re-plastered and the downstairs wall re-tiled. That is in addition to the actual re-wiring work, which would require me to extend at least some of the existing cables. Having to split the load would be an absolute deal-breaker for me. I have some questions about grounding that I would like your input on, but I think I will post those in a separate post.

With what I have so far learned, i am thinking that the hybrid on-grid system is probably not worth the extra cost, so I am now leaning towards going for a 5 kW hybrid off-grid inverter. If it turns out to be insufficient, especially if i later install a 7 kW wall charger for the EV, I can add a second inverter (I know not all inverter models can do this). Still a little confused though, as Crossy states this about the hybrid off-grid system in his pinned topic: But I am pretty sure that I have read a post from Crossy in a separate topic, where he mentions a model of hybrid off-grid inverter that is able to top up from the grid to deliver more than the inverters rated capacity (and BritManToo saying that his Chinese model can do the same). So some hybrid off-grid inverters do have the ability to top up from the grid???

I looked up the website of the company that are doing the project down at our local river, and found these prices (seems to be without battery storage) Quite pricy.