Inverter Earth

[ellal]

I'm expanding a solar power system on an outbuilding, and part of that was to get a bigger inverter.
Wired it up as recommended including earth lug to service earth.
However when doing a check before using and fitting the extra panels, my Martindale socket tester came up with an earth fault notification.
When plugging in the socket tester to the same service circuit it came up fine.
Thought I'd then put the old inverter back in and revert to the old setup and it came up with the same earth fault reading.

I then tested each solar panel individually (I am adding two to the existing one), and each came up with the same fault.
In addition I am adding a second battery, so tested on both and got the same thing.

Reading up on the inverter manual it says that the earth lug is connected to the neutral internally.
So is this why the socket tester thinks it's an earth fault?

I also found online that an earth fault can be caused by water getting into a solar panel.
I can understand if that were the case with the original one, but both new ones?

Any advice would be appreciated.

 

[ericmark]

My inverter only links the earth and neutral when running as an island, then there is a grid connection there is no link. So one needs to carefully read the instructions with your inverter.

 

[ellal]

Instructions said that if used in a car/camper etc the earth lug should be connected to a chassis point.

If in a static position the earth lug should be connected either to an earth rod or preferably to a service earth.

Thus the confusion as to the reading on the socket tester.

 

[Mottie]

You’ll be alright without an earth. <snigger>

 

[jurassic sparkk]

Watch out from a floating earth.

 

[plugwash]

You mention a "service earth" and a "service circuit", those aren't terms we would normally use in the UK. Does this outbuilding have power from the grid?

Can you post a complete diagram of the wiring?

What fault exactly does this "socket tester" show?

 

[ericmark]

My inverter has a number of diagrams like this each dependent on the country used in. It has instructions like

there are loads of other instructions as to how neutral and earths should be connected

the instruction set is full of things like this, and to give advice without reading the instructions could be dangerous, as not all instructions are the same. Both this and this are plug in Martindale testers, the latter may be OK for a gas engineer to use before plugging in a boiler, but the 1.7Ω is not good enough for a ring final the pass mark is 1.38Ω with a TN supply, however with a TT supply we have

NOTE 2:* The resistance of the installation earth electrode should be as low as practicable. A value exceeding 200 ohms may not be stable. Refer to Regulation 542.2.2.

I have not read the instructions that come with the tester, but to explain how it depends on the earthing system used may be missing, to learn how to inspect and test I did a course of 12 weeks at 3 hours a week, and the course was for electricians not for anyone to do, so to explain all the things covered would take some time, if I could remember all that was covered.

This is not a DIY job, and putting an earth rod in the wrong place can be dangerous. I can link to an article about loss of PEN it has become with EV charging points one of the subjects often talked about today it can result in fires and it seems the cases are increasing.

Most solar panels and EV charging points seem to use voltage to detect loss of PEN, although there are other methods, but this is a complex subject, and I am not qualified to really teach about how it should be handled, I only got to level 5 with my studies.

 

[ellal]

You mention a "service earth" and a "service circuit", those aren't terms we would normally use in the UK. Does this outbuilding have power from the grid?

Can you post a complete diagram of the wiring?

What fault exactly does this "socket tester" show?

US based company, so just using the terms in their manual.

Here's the Circuit. Earth lug not included.

And here's the socket tester error

No fault light on the inverter (normal power light), but the socket tester shows an earth fault.

 

[plugwash]

That diagram doesn't show any of the AC wiring, only the DC stuff.

If it's a device designed for the US market it may well have a 120-0-120 output, which would likely cause socket testersto show an earth fault.

 

[ellal]

That diagram doesn't show any of the AC wiring, only the DC stuff.

If it's a device designed for the US market it may well have a 120-0-120 output, which would likely cause socket testersto show an earth fault.

The Inverter is from a US based company (hence the terminology), but 240v output and UK socket.

AC side is meant to be used for battery charging and plug in lighting. Also low powered tools.

 

[ericmark]

Sorry I thought you were using a grid tie system, not stand alone, with small inverters designed to supply a single socket one can use an IT supply as used with shaver sockets, so the supply is not bonded to earth. When using multi items however there can be a fault with more than one item, so you in the main need to bond one leg of the supply to earth.

Reading up on the inverter manual it says that the earth lug is connected to the neutral internally.

This should mean it is internally bonded, but my own inverter has dip switches

these are set according to where and how the inverter is used, there are two configurations just for UK

and since I did not commission the unit, not looked into difference between G99 and G98 other than to do with forms submitted to the DNO.

I have in the past had problems with generating sets in respect to the earth, one was a 110/230 volt one, where earth was 55 volt from neutral, when in 230 volt mode, and another where the 110 volt supply was 0 - 110 instead of 55-0-55 volt. In fact it was 110-0-110 so also had a 220 volt centre tapped output.

The problem with 110-0-110 is we only fuse the line, we have no fuse in the neutral, so using grey imports can cause problems. Both with earths and with frequency, I have an UPS which was given to me with a 60 Hz output. I do have a meter which will measure frequency, but it is not something one tends to do unless using generators.

It seems this is what the tester looks like today and it says warning "Like all other standard socket testers, these units cannot detect common earth and neutral or earth neutral reversal." I have read the data sheet and manual and it does not tell one much.

It seems one needs to get out the proper test gear when they show a fault. I use to have one with the caravan as have found lives reversed in the past, but not used one in years.

A link to the instructions for the inverter may help.