How do you earth solar PV batteries in attic? Is it necessary?

brendandonlon · 18-02-2023 12:22PM #1

Hi all - just adding additional batteries to my setup, and I've realised the original (single) battery wasn't earthed.

Now that I've added two more batteries, I'm wondering if I need to earth them all... And given that they're in the attic, how? Or is it not really necessary?

the_amazing_raisin · 18-02-2023 02:28PM

Your inverter is probably earthed and is nearby, maybe you can wire the battery back to that earth wire?

SD_DRACULA · 18-02-2023 05:38PM

That's exactly how I have mine done.

The Solis hybrid 6G has an earth point on the heat sink on the right side.

brendandonlon · 19-02-2023 03:51PM

Thanks to @the_amazing_raisin and @SD_DRACULA for that tip - I’ve found the earthing / grounding point on the solis inverter (screw on lower right in pic below) - but I thought that was to earth the inverter itself (see second pic)… I’m now wondering is the inverter earthed at all?!

Deagol · 19-02-2023 03:55PM

Battery system is all DC, not sure what point to earthing would be?

Jonathan · 19-02-2023 04:04PM

https://www.boards.ie/discussion/comment/120261577#Comment_120261577

Inverter is ordinarily earthed through the T&E back to the CU and the house earthing.

https://www.boards.ie/discussion/comment/120261598#Comment_120261598

Additional earthing required if using EPS socket. You can lose house earth if TNCS supply is broken.

brendandonlon · 19-02-2023 04:21PM

Thanks @Jonathan - final, and probably most stupid question; I presume I have to turn everything off (AC connection, inverter, batteries themselves) to add the earth / ground wires to the batteries? Or given that they’re DC can I just whack them on? 🙈⚡️

Jonathan · 19-02-2023 04:42PM

https://www.boards.ie/discussion/comment/120261704#Comment_120261704

Better safe than sorry.

SD_DRACULA · 19-02-2023 06:20PM

https://www.boards.ie/discussion/comment/120261644#Comment_120261644

Pretty sure they didn't wire the EPS socket to that earth point on the inverter, just 3 wires from socket to the backup port on the inverter I guess.

Is that a thing that's needed?

https://www.boards.ie/discussion/comment/120261704#Comment_120261704

I didn't, just connected the batteries when they were off then powered them on and no issues but I'd probably take the safer approach now.

Jonathan · 19-02-2023 06:51PM

https://www.boards.ie/discussion/comment/120262194#Comment_120262194

If your earthing is a TNCS arrangement (generally used by ESBN here in Ireland), you don't have an earth rod, but rather use the neutral on the incoming supply.

In a power cut, the inverter closes a relay and bonds the EPS neutral/earth, providing a path to ground for any faults. The problem arises if there is fault which causes the ESBN cable to be cut and you end up with no earth.

If you are using EPS for anything other than (double isolated) fans (in my case), you should probably consider adding an extra earth rod (changing to a TT arrangement).

graememk · 19-02-2023 07:17PM

https://www.boards.ie/discussion/comment/120262321#Comment_120262321

A lot houses (in the country anyway) it's a tncs with an earth rod too. Although no idea of what's that called.

SD_DRACULA · 19-02-2023 07:59PM

https://www.boards.ie/discussion/comment/120262436#Comment_120262436

If it's the thing in the ground under a green plastic cap buried in the concrete then the house has it (assuming it has a rod inside)

Jonathan · 19-02-2023 10:25PM

https://www.boards.ie/discussion/comment/120262436#Comment_120262436

Where is the earth rod connected to? At service head in Cabinet or to the MET in the CU? Are you served by a 50kVA pole-mounted trafo?

https://www.boards.ie/discussion/comment/120262593#Comment_120262593

Are you sure you're not referring to gas bonding? My gas supply is bonded just before the meter cabinet.

Deagol · 19-02-2023 10:36PM

All houses in Ireland have or should have an earth rod.

https://www.myenergi.com/ie/pen-protection/

graememk · 19-02-2023 10:54PM

https://www.boards.ie/discussion/comment/120263272#Comment_120263272

Consumer unit. Recently had it replaced when upgraded the consumer unit, took a turn sledging it into the ground 😂

At the esb head there is the neutral earth bond (all in 16mm2 now)

Found the old one too, just buried under the tar, when digging to bring a new cable to the yard.

Not sure the size of the transformer, will look next time I'm in the neighbours field. But it serves 6 houses.

Jonathan · 20-02-2023 12:04AM

TIL: TNCS means different things in Ireland and the UK.

As @Deagol points out, Ireland requires an earth rod connected as @graememk describes above. However, the UK allows you to rely solely on the DNO's supply for earthing (no earth rod required).

Page 5 outlines the Irish situation.

graememk · 20-02-2023 12:19AM

https://www.boards.ie/discussion/comment/120263525#Comment_120263525

Yeah I've noticed a few differences too,

UK has had double pole isolators for a long time, that's only a very recent thing here.

But on the other side, they don't have a customer owned main fuse or MCB, (that's usually in the consumer unit) just seem to use the DNO one.

__Alex · 29-08-2023 12:55PM

Hi,

I'm adding a Pylontech US5000 battery to my PV system.

I can see my Solis inverter is grounded (see picture below).

In the end, did you guys reuse the same wire?

Thanks!

SD_DRACULA · 16-09-2023 08:28AM

Well the inverter is already grounded via the AC grid cable that connects to it, not sure it needs to be grounded from the AC switch as well.

graememk · 16-09-2023 08:32AM

https://www.boards.ie/discussion/comment/121117280#Comment_121117280

It's meant to be grounded in addition to the cable connection incase the main grounding fails.

SD_DRACULA · 16-09-2023 02:36PM

https://www.boards.ie/discussion/comment/121117297#Comment_121117297

Good to know. Might not hurt to do the same then.

But this cable also comes from the same CU so if it fails won't it fail there too?

graememk · 16-09-2023 04:39PM

https://www.boards.ie/discussion/comment/121118694#Comment_121118694

Now.. don't be poking holes in things 😂

Although of all the places that could be damaged it's the connection from isolator to inverter is the most likely.

ELCAT2009 · 22-03-2024 10:48PM

@brendandonlon did you connect your batteries to the screw on the Inverter? Did you power off batteries and Inverter to do it? I'm in the exact same scenario as your original post so would love to know how you got on!

Thanks 🙂

brendandonlon · 18-04-2024 04:02PM

https://www.boards.ie/discussion/comment/121929035#Comment_121929035

Sorry for belated reply - boards.ie notifications were landing in the Spam folder!

In the end, I did absolutely nothing. I asked this question in multiple places, and got lots of helpful responses that were evenly split down the middle as to whether it was necessary to do in the first place, or even possible to do for an attic install.

We don't have any visible earth rod anywhere around the front / side / back of the house, and the fuse board is two stories and half a house away. So even if I earthed the batteries to the inverter, the inverter itself has nowhere nearby to be earthed to.

Our entire installation was inspected and signed off by the SEAI, as we were an early-stage "one stop shop" customer. And the only thing the inspector asked for in the attic was to put a larger fireproof board underneath the battery cabinet.

And from a quick search of https://www.seai.ie/publications/SPV-Code-of-Practice.pdf it looks like there's nothing in the code that covers a need to earth / ground batteries of the type covered by the scheme.

ELCAT2009 · 22-04-2024 10:36AM

Thanks for reply. I went ahead anyway and earthed my batteries to the cabinet and then earth the cabinet to the inverter. Hopefully never needed!

How do you earth solar PV batteries in attic? Is it necessary?

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