SOLARWIND

Definitely stay away from anything without a pure sinewave! As Plonkster said, NO! to try to synchronise with any generator that doesn't have a constant speed with or without load. Anyway, if you grid tie with a diesel generator, your inverter should never be capable to generate more power than the diesel gen does, because it will "see" the generator as a synchronous motor and would attempt to push power into it. This may seem like a good idea to save fuel, but with a diesel engine it won't. A diesel engine has its optimum efficiency when it does the work by itself (the work it was designed to do). Any power input from the outside (inverter feeding in), will just result in heating of the windings of the generator and is counterproductive.

A very simple way to get the same result, would be to install a simple mains operated relay and use the N.C. contact on it. Then use inverter power in series with this contact to supply your remote indicator or whatever.

A clear, hand drawn single line diagram is all that is needed with your application. It must show the change-over switch and clearly show how it safely chooses between your inverter output and the utility mains supply. According to SANS10142-1 the change-over switch must be an approved type with a centre-off position and this fact should be confirmed as a comment on the test report section of the CoC for the installation.

Rather then let the relay connect neutral to neutral instead of to earth, because as you've already said, and that is my point also, you should not connect the neutral to earth other than in the main panel.

The bonding relay is then something that switches the neutral only, which is not allowed.

"This earthed neutral bar shall be the only point at which the neutral of the installation is earthed." That sums it up and means that the neutral of the mains supply DB complies and must be used as the common after the earthing point (where they are combined and then run as separate wires, each with its own function).

Can you please quote that section of SANS 10142-1 that says it is not legal? It is strange that it would be legal to connect the neutral to earth a second time, seeing that it is already connected to earth either in the main panel or at the supply transformer assuming a TN-S or a TNC-S system of earthing at the supply of the utility.I use the existing utility neutral with the inverter neutral without problems.No need to feed the inverter from the mains via a RCD. Treat the ac supply to the inverter as a dedicated circuit of the mains supply DB and add your RCD on the inverter output in the inverter AC panel.

Agreed, no reason to earth it Also no need for additional earth spikes when there is a power earth available. All metal work not carrying current under normal conditions, should be bonded to it and nowhere else.

The only connections to the battery, should be the inverter. Earthing means electrically connecting the utility Neutral to the battery. If the inverter is not transformer-isolated, it means the ac and dc gets connected to a common point.

I was using an IMEON 3.6 with 2 strings on one MPPT. The one string consisted of 9 x 310 Wp in series This array was North-facing. The other string had 9 x 170 Wp modules, also connected in series and this was West-facing. The trick here was simple diode-isolation between the two strings and it worked like a charm, seeing that the two arrays never peaked at the same time, so the slight difference in voltage did not matter. The negatives where tied together and connected together and to the negative terminal on the PV input of the inverter. The two positives I connected to two diodes (positives to anode of each diode and the two diodes where on a heat-sink with their cathodes (K) common to the heat-sink itself). This common point was taken to the positive input on the inverter. That's it! I don't think a heat-sink was necessary and smaller diodes with sufficient voltage and current ratings will probably do, but hey! I had this piece of hardware lying around, so I used it! A good source of such two diodes is found inside some switched-mode power supplies, where two diodes are already combined in one package with three leads. (A-K-A) (They are used as rectifiers where the transformer has a centre-tap). Most of them are Schottky diodes with a very low forward volt-drop.

True, IF there are 100's or 1000's of grid-tied inverters in a specific area, and IF the ESKOM supply to the WHOLE area is ISOLATED WITHOUT EARTHING AS A PRECAUTION, THEN and only THEN will there be a local "grid" which could be live. I agree, there should be safety regulations in place to be 100% safe and I agree that they should rather be strict on the Certificate of Compliance by a duly Authorised person and that the CoC makes provision in the Test Report section thereof that the signatory thereof certifies the safety of the system as a whole. It is ESKOM or the Municipality that should brush up on safety and KNOW that there is nowadays always the possibility of reverse power on the system.THEY are the ones that should make their equipment safe before touching it. (This is the reason for EXISTING safety rules which state that they should TEST, ISOLATE AND EARTH. - NOTHING NEW).

That box is always connected to the area distribution transformer of 50 kVA or much more in some instances. The transformer in turn, is part of the grid, even on its primary side, so theoretically power can be fed back through the transformer (at 11 000 V in most cases). This transformer is thus connected (via a sub station or wires) to various other transformers in the area. At the time of a power failure from the utility side, your 1 kVA/5 kVA or what else, could theoretically be trying to feed the whole area's consumers, which is a dead short as "seen" by a small inverter, so it WILL trip. If there is more than one consumer with inverters running, the sum of their ratings are still way less than the kVA rating of the supply authority. with a grid tie inverter, your grid tie may "see" another grid tie as the "grid" and stay on briefly (20 ms?), then "sees" the overload and die and so will each and everyone of the other inverters in the area.This scenario will take place virtually immediately following a power failure from the utility. By the time the repair team arrives, everything will be off.

This is a feeble excuse as it is impossible for a small inverter to power a whole neighborhood! They will always be safe, because the solar systems will trip out the moment the city power goes off! The main reason is interference with private owners and to know where and how much they are losing out on revenue.Safety is just a nice excuse.

Replace the element of the urn with a 3-phase element. Problem solved.