Is Offgrid Island mode really TNS.... Lets find out and go deep on some testing! 

Here is everything you wanted to experiment with on the EESS course, but didn't get to have a go :-) Really useful Thanks

Very interesting look at testing/demo.

Great video Mark. Very informative. Thanks for taking the time. Really helpful for others in the industry. 👍🏻

Brilliant content thanks very much for sharing this ! , Bruno is doing a marvelous job love him 🤩 Great to see that Polar include the N/E bond relay for island mode , is there anything in the regs which states that any EPS/UPS downstream overcurrent protection device should be of a lower value than the maximum inverter output current ? EG if the inverter is rated at 16A maximum we shouldn't be using 32A Mcb's to protect EPS/ups ring final circuits . Currently It looks like we're more reliant on the internal electronics for current protection rather than any MCB's which rely on a high PFC for quick disconnection . Thanks again this is all very helpful

Mark fantastic video. Mark in any island mode hybrid inverter or generator, I was under understanding that we can join a tncs system to earth rods. New homes have dual connections. If you have any pen fault devices connected, say an ev charger, it will not work in any island mode unless it's connected to the earth rod because of the change over to the island. Earth can never be put on a switch like a change over. This subject is very interesting.

Excellent mark fills in some of the gaps in knowledge between the 2 operating modes. I do agree that some grey areas might still exist particularly when using less common battery & inverter systems and the floating non referenced earth they might output on island mode & whether the RCD/RCBO will operated under all Enviromental conditions:) and any generated reference point from the electronics of the inverter.

Thanks for taking the time to make the video it's very interesting.

Great video Mark, Looks like a great piece of test kit there for measuring EFLI when in island mode. I am just wondering have you obtained the inverter impedance when using calculation of ZS in island mode instead of measuring it? Verifying EFLI in island mode I find really challenging when using calculation as manufacturers can't provide me impedance values for the inverter. I have never fully trusted the values from my test instruments as they seem inconsistent. Hence I have always ensured I have my consumer unit in island mode protected by an RCD, similar to your video.

Great video. I was confused with the earthing arrangements when I did my last solar course. I did not see the point in referencing the installation to the mass of earth in off grid mode as that’s not where the electricity came from (In terms of the transformer).? Electricity always wants to go home. So why the need for an earth rod? Some inverters are almost like a shave point/centre tapped transformer or site transformer so the rod would not do anything in off grid unless there was one at the generating set and one somewhere else? I get the TN-S link that is now becoming a thing within these inverters to give ADS, however just don’t get the fact that the regs/manufactures instructions say that a earth rod is still required? Is the earth rod just to give reference so RCD’s will still trip if people come in contact with the lines? And if that’s the case why don’t shaver sockets have reference?

Does the inverter provide your short circuit protection. It will current limit and cut off supply, in most case a short circuit will never achieve the current required for the mcb to trip ie x5 for type b, so short circuit discrimination is not provided in island mode. The overload discrimination on an all in one is worth some thought ie 32amp ring main an over load of 40amp can the inverter supply this amount of current for long enough to trip mcb ??

I thought you had to disconnect the DNO earth all together as are you not providing a path back to the install with earth points close to each other? Ive gone fully TT and got the DNO to mark the connection as such. Water and Gas have been changed to plastic and DNO earth not connected. I've only got one point to earth now, day after installing TT i got 2.15 Ohms but i went OTT with the TT install

Mind blowing topic - which I will watch this vid, probably a few times in a few days when I get the chance (weekend) I just wonder if the relay switching will tick every single box 101% when things like Garo's PME/PEN EV devices can fail or falsely trip etc... Also. if you have 6 to 10 earth rods, ConduDisc etc... for Island/TT/Off-Grid setup side of things, do you really need to disconnect the main DNO earthing arrangement during island/off-grid, when the all metal gas/water mains are also earthed (proper earthed, not plastic pipes to property) Example: you are on a genuine TNS system, with additional earth rods etc, metal gas/water bonding, then operate a "mostly off-grid" setup, but with grid connection to sync & charge battery overnight from grid on poor solar days/winter... Would you really need to disconnect/reconnect the DNO earth if/when in Island/100% Off-Grid mode & not grid sync'd/supply/top-up batteries ??? This subject seems to be a "Yes you should, but there are exceptions when no you don't" Along with the but it is all still linked with gas/water bonding side of things, when you're a stones throw away from sub-station and then there is always the very slight but still possible risk of said earthing relay failing & be stuck open/closed with running on TT or DNO/TT/Sup Earthing arrangement anyway Surely, (Don't call me Shirley), there must be some sort of method that simplifies & satisfies the safety of owner/dno engineers that main earthing & TT arrangement can co-exist for all instances of grid/island/off-grid operation modes/setups TL-DR, mind blowing topic, cheers for delving into this side of stuff for Island/Off-Grid setups

hi you disconnect earth from the grid but the earth rods are still connect yes??