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Hello,

Does anyone have any resources for what the various options are for EPS? I'd like to read up on it.

My hybrid inverter suggests that it can do some kind of EPS but the manual is a little lacking in the details.

Ideally I would have just a double 13A RCD socket behind a rotary AC isolator and manually switchover - but I am not sure if that is allowed.

The setup you describe is perfectly fine, you just need to sort how the earthing and earth-neutral link work in both on and off grid mode. Easy to solve with a manual changeover switch.

Stinsy wrote: ↑Wed May 11, 2022 7:48 pm The setup you describe is perfectly fine, you just need to sort how the earthing and earth-neutral link work in both on and off grid mode. Easy to solve with a manual changeover switch.

Or just use it for devices which are doubled insulated so don't need (or even have) an earth like a table lamp or telephone charger. etc.

I plan to use it for a freezer which I don't think is a class 2 device.

I've found the IET code of practice for such things and it looks like in my arrangements I cannot rely on the PME earth and there are some other regulations in BS7671 that apply - will talk to the sparky and installer about it who should have more manufactures details.

Swwils wrote: ↑Thu May 12, 2022 9:09 am I plan to use it for a freezer which I don't think is a class 2 device.

I've found the IET code of practice for such things and it looks like in my arrangements I cannot rely on the PME earth and there are some other regulations in BS7671 that apply - will talk to the sparky and installer about it who should have more manufactures details.

I think people here have always said that if you are going to run anything with the mains isolated you have to have a good alternative earth installed.

Swwils wrote: ↑Thu May 12, 2022 9:09 am I plan to use it for a freezer which I don't think is a class 2 device.

I've found the IET code of practice for such things and it looks like in my arrangements I cannot rely on the PME earth and there are some other regulations in BS7671 that apply - will talk to the sparky and installer about it who should have more manufactures details.

Exactly! In the event of a power outage you cannot rely on the supplier's earth-neutral to provide protective earth. You can convert your house from TN-C-S to TT all the time, or you can run TN-C-S on mains power and TT when running in EPS mode. You also need to bridge the earth and neutral at the inverter when in EPS mode but not when running grid power (some inverters contain a contactor that does this for you). Additionally the brand new 18th Edition Amendment 2 (released a few weeks back) has made some changes that (I think) allow you to have your own earth spike in compliment to the supplier's PME earth, in which case you would be able to rely on your house's existing earth in the event of an outage.

Long story short you need to find the sort of electrician who actually understands the fundamentals, the regs and how to apply them to non-standard situations. Most electricians like to spend their days working with bog standard stuff and are unwilling to apply thought or research to something else.

Stinsy wrote: ↑Thu May 12, 2022 9:53 am Additionally the brand new 18th Edition Amendment 2 (released a few weeks back) has made some changes that (I think) allow you to have your own earth spike in compliment to the supplier's PME earth, in which case you would be able to rely on your house's existing earth in the event of an outage.

Excellent, cos that what Nowty Towers uses.

I thought it was historically a no no with the DNO, although personally I could not see any downside to it.

nowty wrote: ↑Thu May 12, 2022 1:47 pm

Stinsy wrote: ↑Thu May 12, 2022 9:53 am Additionally the brand new 18th Edition Amendment 2 (released a few weeks back) has made some changes that (I think) allow you to have your own earth spike in compliment to the supplier's PME earth, in which case you would be able to rely on your house's existing earth in the event of an outage.

Excellent, cos that what Nowty Towers uses.

I thought it was historically a no no with the DNO, although personally I could not see any downside to it.

I'm not an expert on "the regs", but it looks like earth rods have gone from "prohibited" to "required" in TN installations and that applies to all installations, not just us lot (who they now call "prosumers" and "PEIs"). Guidance Note 8 (to be published at the end of the month) will hopefully clarify.

Luckily my spark is very on it.

I am waiting for the guidance note because at the moment it can read either way - are sparks now suddenly going to be putting earth rods in on almost any job(?!).

Swwils wrote: ↑Sat May 14, 2022 3:03 pm Luckily my spark is very on it.
I am waiting for the guidance note because at the moment it can read either way - are sparks now suddenly going to be putting earth rods in on almost any job(?!).

Lucky man! How do we find these people?

More to the point, why isn't/wasn't extra earthing always a desirable thing in any circumstances? Can anyone imagine a situation when it could cause a problem?
When we get such dramatic about-turns it makes me suspect that the experts always knew what was needed, but were stitched up by people on committees who were only there to represent vested interests. The changes in building regs or fire safety approvals which lead up to the awful fire in Grenfell Tower are a case in point.
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