EPS

We want to install an Emergency Power Supply, and I'm told Givenergy may have one coming out soon - any details known?

Lorraine There's an EPS output on both the AC and Hybrid inverters already, limited to 3kW.it's that what you're looking for?

Lorraine Do you already have any PV/Givenergy inverters? Their inverters already include an EPS output which if you plan to be able to use it before any installation work is carried out, can be integrated relatively simply. There are a number of scenarios which can be catered for. Ideally, you would have a separate consumer unit with the circuits you want to supply during a power cut (lighting, boiler supply, broadband/comms maybe?), but if not other manumatic solutions can be implemented. Anything supplied by the EPS circuit will be fed from within the inverter, meaning that it is always live until a grid disconnection occurs. At that point, the inverter disconnects itself from the main consumer unit, dropping the EPS output. However, after a short period (20 milliSeconds?) it reconnects in "island" mode and the circuits already plugged in/connected are fed from the inverter's DC supply of PV and battery.

If you just want to be able to keep power on during a power cut, the EPS could work for you. It switches off briefly at the start of the power cut, and I'm assuming it also disconnects briefly at the end of the power cut while the inverter synchronises itself to the grid again. If you're looking for an Uninterruptible Power Supply (UPS) for a computer/server etc, then this will not provide that uninterruptible supply; you would have to use a separate UPS.

stevelewis Tim

We have PV, a Givenergy inverter and battery. We're not looking for UPS, just to be able to use the PV and battery during a power outage. We're getting a quote for a whole property EPS as it seems that currently we'd have nothing during a power cut even if the sun's shining and the battery is full.

The EPS output limited to 3kW, plus whatever solar generation there is at the time is all we're looking for - enough that with planned outages we can start with a full battery, and with unexpected ones at least we can use whatever solar there is.

I'm very new to all this and not at all technical, so trying to make sure we get it right.

Lorraine Your EPS output will have to be protected to ensure that it doesn't try to drive a load that exceeds its capability. Having the whole property supplied via a changeover switch (manual or automatic) is feasible but I think very difficult to manage. Normally, a supply cable is protected by a fuse or more likely, an overcurrent circuit breaker (RCBO or MCB). The problem you will face, I think, is that the EPS (to changeover switch) cable should be sized for full battery and maximum concurrent PV output current, so maybe a 6mm2 Twin & Earth cable. The cable can then be protected with a 32A RCBO/MCB and everything's hunky dory. The problem comes when there is no PV and the inverter can only supply the 3kW (12A) maximum from battery. In that scenario, the 32A RCBO/MCB still protects the cable and supply to the changeover switch but the inverter will either shutdown (hopefully) or potentially become damaged in attempting to supply more than 12A when the kettle and oven (or other loads combined to exceed 3kW) are switched on at the same time. The same thing could happen if the sun is shining brightly while you have the oven and iron going; if the sun disappears behind a cloud when oven and iron both cut in, the inverter may not be able to supply the load.

We have 2x5kW inverters but as far as I'm aware, the EPS outputs cannot be connected together to provide more than the 2.5kW ours are capable of, as they both have to operate in "island" mode. That means we could feed one consumer unit with up to 12A from one inverter EPS and a separate consumer unit with different circuits on with up to another 12A from the other EPS. We had our consumer unit replaced just before our PV install. Had I known then what I know now, I would have replaced one large consumer unit with three smaller ones: one for upstairs lighting and broadband router (fed from one EPS); one for downstairs lighting, boiler and a socket to plug a (10A) kettle into (fed from the other EPS); and everything else on the other one.

As it happens, we've just got a double switched socket next to the broadband router. If we have a power cut, I'll plug the router in and an extension lead to the boiler. We've always used torches during a power cut, so that doesn't change.

SImilar to @Tim we went for the simplest (and cheapest) option of a double RCD protected socket connected to teh EPS output of the inverter. Per method one here https://kb.givenergy.cloud/assets/EPS%20Configuration%20v2.pdf#viewer.action=download
It has not been called upon and long may it be so. Fingers crossed it all works in the event of an outage

locked

That's what we have too. If we need to add somethin to it, in the unlikely event of a power cut and we have batter reserve, then we can always get an extension lead and plug another device, not already permanently plugged into the EPS sockets (Router, Network switch, fish tank). I will soon put a UPS inline here, as the long awaiting UPS feature is yet to be issued out

I think people are getting advised incorrectly at the moment as I'm seeing numerous posts like this thinking that solar will run the whole house if there was a power fail, where in theory the maximum you could probably use is a kettle.
If people want full house power back up you far better install a decent standby generator with a auto change over. 😄

DeanoC75 and solar will only work if its the Hybrid GivEnergy Inverter?

If the solar has its own grid tied inverter (e.g. legacy FIT scheme), it'll shut down when the grid disappears?

TX200 that's correct with the GivEnergy AC inverter. Some other inverter manufacturers, such as Victron, can control local ac generation during mains failure by varying the local frequency, the GE kit doesn't do this.

locked
What have you done about the TT earth?

DeanoC75
To be fair, a kettle uses a lot of juice. I've got my laptop on, HTPC on, a Pi on, my router, all my POE hotspots, the fridge doing its thing and I'm only using 400w right now.

I think most just want power when it goes out for 10 minutes, not for days because of a disaster.

dbt85 I use the 'kettle' as a perspective power use item, as if the inverters are limited to around the 3kw mark, this could be the same draw as a kettle or there abouts.

Most people would use the EPS to keep low wattage items in use and TBH you could probably use a computer based UPS from the EPS fed socket to the equipment and that would take up the delay in switchover.

I'm just seeing a few posts on FB and other areas where it's looking like 'some' installers are selling the GE system (and others) that it has a full house battery back up system so it will run everything like normal until grid power is back up and running and I just think that it opens it up to people been disappointed thinking that it will as the system will not 'do what they want it to do'

dbt85 re TT earth - 4 foot rod in the ground

DeanoC75 I'm just seeing a few posts on FB and other areas where it's looking like 'some' installers are selling the GE system (and others) that it has a full house battery back up system so it will run everything like normal until grid power is back up and running and I just think that it opens it up to people been disappointed thinking that it will as the system will not 'do what they want it to do'

Ah yeah that's just a lie. Even a Powerwall can't promise that depending on your circumstances. One electric shower and its gameover.

locked
As in, you have one anyway and so when the grid goes down you don't lose your earth, or you put a rod in just for that socket (which seems extreme)?

My house is also TT earthed but the properties that our inverters are in I'm not sure about. They were redevelopments 8 years ago so I guess they'll have done it "properly", unlike our house which is 200 years old.

dbt85 I installed the rod when adding the EPS double socket. It is a little overkill but only cost a few quid and was easy to install.

locked Ahh ok.

Ours wouldn't be terrible to do but given the use case I have for them it would all need to be done officially and I don't actually want the power when the inverter is off anyway. I may just run an extension from an existing socket for my needs (inverter cooling).

Thought I would tag along on this existing thread rather than creating a new one.

Can anyone confirm whether the electrician who fits the EPS socket etc has to be GivEnergy approved or can I get an sparky to do it? The assumption would be that it is done to GE specs, just wanted to know whether they have had to sit through the Powerpoint presentation or not.

Many thanks!

Ra when we had our solar and batteries installed I asked about the EPS and if the installer needed to do it, I was told no and we had another electrician that was doing our extension wire it in after speaking with the GE installer.

dcsh thanks David. I emailed GivEnergy about this and then have said that whoever does it needs to be GivEnergy approved. I need to contact my installer at some point to get this sorted but I know like everyone else he is rushed off his feet so will probably struggle.

Ra you could get the EPS output wired to a 13A double pole fused outlet. Your regular sparky would then be able to do whatever you want from there.

locked
PLUS isolate the incoming grid earth from the consumer unit, inverter and battery earths and connect them to the new earth rod instead.

Ra
Agreed. My GivEnergy approved installer did a great job last month of converting to TT earthing and wiring up all my house circuits to the EPS output through a socking big EPS/Grid changeover switch. I just have to ensure my home demand will not be exceeding the max discharge of my batteries (2.6kW rate) before throwing the switch…..!

Toogie can you tell me the type of EPS / grid changeover switch you have, please. Thinking of doing something similar myself (by an approved / recognised electrician)

jhayman4 search Google for givenergy EPS kB

TX200

Hi TX200 - i have seen these docs and thinking of install along the lines outlined on page 4 or 5 - was wondering if anyone had any experience of specific items of kit (ie the change over switch)

jhayman4
Salzer 3 way switch

jhayman4
Salzer 3 way c/o switch

Looking at a double socket EPS (method 1) for our GE hybrid inverter + battery. The installers didn't have time to do this when the system was installed and are a bit busy at the moment. The GE doc says a TT earth is needed for the EPS and our local electrician has been round to quote for TT earth point and providing the EPS socket. Our property has TNCS earth and the electrician asked if the whole property has to go over to the TT earth or is it just for the EPS side of the inverter? The GE document doesn't really say.

alan_johnston My understanding is that it's just the EPS that has to have separate earthing rather then the whole property, to protect the circuit should the grid connection be lost.

This isn't a field of expertise that I can claim any competence in so I would be interested to hear from anyone who can answer the question whether there is any problem with connecting a TNCS-connected (or any other scheme) consumer unit to a separate earth rod, thereby "improving" the earthing arrangements in the premises?

alan_johnston
Anything that has EPS power has to have TT earth as when in islanding (EPS mode) anything that has power will have lost any network earth as the grid supply cable will be "disconnected".
Anything not on EPS will not be getting any power so I cannot see why it would need a TT earth, and in any event it will still be connected to whatever earth is already there.
I would have thought though that if you create a TT earth for the EPS, then connecting that to your existing CU is a very minor task (bit more earth cable), unless of course the routing is really difficult.

The EPS v2 manual describes earthing for each of the 4 scenarios and for Method 1 (socket) it says "Socket will require TT earthing method". It does not say anything about any part of the system.
The other methods describe more comprehensive earthing.

Regards
Steve

Tim
I think adding more earthing is a good thing.
The problem with anyone without external ground floor space is that creating any sort of TT earth is really difficult.

https://axis-india.com/tt-it-tn-earthing-systems/#:~:text=The%20IEC%2060364%20standard%20has,%2C%20IT%2C%20and%20TN%20systems.

I am by no means an Electrician but the "earthing" situation is about ensuring that everything connected to the "circuit" has the same Equipotential.

Your inverter is already equipotentialy bonded to the incoming Earth of your consumer unit which is in itself connected to the earth of your house (which will be bonded to your gas, water, radiators, taps etc etc).

Adding an additional Earth Rod should therefore be completely unnecessary.

https://electrical-engineering-portal.com/purpose-of-equipotential-bonding

dragon2905 inverter is already equipotentialy bonded to the incoming Earth of your consumer unit

The difficulty with this point is that when the premises becomes disconnected from the grid, the premises earth bonding can also be disconnected. That doesn’t usually matter because there is no mains power. However, with an EPS supply there needs to be an earth bond that cannot be disconnected and can always be relied on.

The EPS circuit(s) only have one earth. My take is that the EPS circuit is always uses the TT (local) earth, even when the mains is 'on' and the EPS circuit is fed from the mains. So, if only the EPS circuit(s) are on a local (TT) earth and the non-EPS circuits are on 'mains' earth, potentially you would have say the lights and the sockets in a room on different earths, which wouldn't be good as the two 'earths' would be unlikely to be at exactly the same potential.

Consider the case where your network router is on an EPS circuit (so you don't lose internet on mains failure), and you have a wired ethernet network around the house with some connected devices not on the EPS circuit. You would likely have some earth current, ie 'leakage', between devices, and apart from being 'not good' it may well trip the earth leakage breakers.

Consider also whether you could touch both a locally earthed device (eg a freezer) and a mains earthed device (washing machine?), ie they are less than arms reach apart. That would not be good.

I would conclude that the whole house has to be either mains earthed or the whole house has to be locally earthed in order to be properly equipotentially bonded, but then I am a civil engineer not an electrical engineer.

It saddens me that a supposedly qualified electrician has to ask his customer what to do. I would have hoped that the electrician would have known the wiring regs back to front.

Baychattan I was told by GivEnergy via email that any electrician (regardless of experience/qualifications) has to have gone through their training to fit an EPS otherwise it wouldn't be covered under warranty.

Baychattan you would have say the lights and the sockets in a room on different earths

And that was my point above regarding connecting the TT earth to the grid-supplied earth. My gut feeling is that they should all be bonded together but (being unfamiliar with the different earthing schemes) I don't have enough current competence to know whether doing this could cause problems in certain circumstances, hence asking if there is anybody familiar enough with the current wiring regs (or DNO regs if different) who can authoritatively advise.

The electrician turning up to do the job should be competent to do what he's been trained to do but sometimes customers want something a little out of the ordinary and (IMO) it's unfair to expect them to know all the answers. As an ex-member of the IET and someone who worked in the power industry I know enough to know that I don't have competence to answer this question, but am hoping there is someone out there who does know.

Baychattan
The GivEnergy document says that for method 1 'Socket will require TT earthing method'. Compare this other methods where it says the whole property will require TT earthing method.
The EPS circuit has grid power when the grid is up.
The electrician was of the opinion that the whole house would have to be switched to TT earth otherwise the EPS socket could have a different earth to the rest of the system when the grid is up.

Tim Does the EPS socket have an RCD & MCB and it’s own earth rod independent of network supply earth