Morning all.

Noob here, so please excuse my possibly "stupid" questions.

I recently shelled out for 2x Pylon's (with 9U 4-rack cabinet - may expand capacity to 4x Plyon's in the future) and an Axpert 5k MKS, currently to run as a standalone UPS until I've saved some more for a few solar panels and integration into the main DB.

On reading the manuals/guides/info on the Pylon's, it refers to the "The battery system must be well grounded and the resistance must be less than 1 ohm.", and the diagram in the manual shows the following in terms of earthing the batteries when installed in a cabinet:

There is no other reference or detail on how these must be grounded - judging by the diagram, I only need to connect each battery earth terminal to the cabinet chassis. The cabinet is free standing in the garage on the adjustable legs that came with it. My question is: is it that simple? So each battery earth terminal connects to the same battery chassis point with the supplied earth cable (10AWG) and no other ground connections are needed?

If the cabinet itself must be grounded, how is this done? I've seen grounding kits for 9U cabinets, but these just seem to be a couple of 30cm earth wires with screws...

- All the battery grounding terminals must be connected to the standing rails.
- Standing rails, cabinet's skelet, back and front doors and side panels have to be connected to the standing rails too.
- The grounding cable from the cabinet's skelet to the building's grounding point must be installed.

DO NOT ground positive, nor negative pole of the battery. Such a practice ends with a cloud of smoke usually.

 

 

18 minutes ago, Youda said:

- All the battery grounding terminals must be connected to the standing rails.
- Standing rails, cabinet's skelet, back and front doors and side panels have to be connected to the standing rails too.
- The grounding cable from the cabinet's skelet to the building's grounding point must be installed.

DO NOT ground positive, nor negative pole of the battery. Such a practice ends with a cloud of smoke usually.

 

 

Many thanks Youda.

I assume the standing rails are the cabinet rails the batteries bolt onto in the front?

In a residential house, what would the building grounding point usually be?

Yes - the rails with the square holes in them.

Well, just connect it to the main distribution board, where all the breakers are located. There's a good grounding in it for sure.

3 minutes ago, Youda said:

Yes - the rails with the square holes in them.

Well, just connect it to the main distribution board, where all the breakers are located. There's a good grounding in it for sure.

Great, many thanks!

Just another question, more for my comfort, does it matter what wire gauge is used for the grounding connection to the main board earthing point - I'm going to the local electrical shop shortly to get the ground cable, but see they only seem to have the 4mm (12AWG) and 2.5mm (14AWG) earth cable - the one that comes with the batteries is a 6mm (10AWG) - does this make any difference for the earthing or would the 4mm be sufficient?

If I need the 6mm, I'll have to find it elsewhere...

thicker cables will have less resistance so I would try and get thicker if possible. 

Thanks SilverNodashi, will do

When it comes to cables, bigger is always better. But in this case 2.5mm2 would be suffiecent.

To understand why you first need to understand why we earth equipment. And earth conductor provides a low impedance path for fault current to flow back to the source. The path back to the source`s impedance has to be low because the fault current needs to be sufficiently large enough for the overcurrent device on that circuit  to pick up the fault and interrupt it. So in most cases the conservative approach would be to size the earth conductor the same as a phase conductor.

But there in your case there is no source, or lets rather say you are not earthing the batteries to protect you from a battery voltage shock. Rather what you are doing is, is that you are bonding the batteries and cabinet to earth. All extraneous  metal must be equipotential bonded to earth.   Bonding ensures that two metal bodies that  are bonded will be at the same electrical potential. That means there will not be an  electricity building up on one piece of equipment or between two different pieces of equipment. No current flow can take place between two metal  bodies because they have the same potential.

Also if somehow (and extremely unlikely in this case) a live AC wire gets into contact with the metals case, or metal battery case you won’t get shocked if you should touch it, as  the metal will be a the same potential as your body standing on the ground.

 

 

The 6 mm2 minimum requirement comes form :

 

 

1 hour ago, Jaws said:

When it comes to cables, bigger is always better. But in this case 2.5mm2 would be suffiecent.

Agreed. It sort-off depends on what you're bonding it for. If it is to protect against ground faults, then the cable you use for bonding must be able to carry the full fault current, so you're going to end up with a cable not much thinner than the main battery cables. But if it is for other reasons, such as noise/EMI and so forth, it can be thinner. I seem to remember that the Pylons ship with green-and-yellow cables:

To me that looks about like a 4mm^2 but I can't say for sure.

Thanks @Jaws and @plonkster, makes sense.

Couldn't find the 6mm^2 anywhere today, so went with the 4mm^2-  should be more than fine for bonding the batteries and cabinet to the DB earth point. The ones that came with the Pylons have 10AWG printed on them, which seems to be 6mm^2 equivalent.

1 hour ago, HowardB said:

10AWG printed on them, which seems to be 6mm^2 equivalent

AWG, for the metrically impaired. There is no sane way to relate to it.

🙂

On 2019/03/13 at 10:29 AM, HowardB said:

with 9U 4-rack cabinet

I'm heading in a similar direction to you. Did your feet on that cabinet bolt thru properly ? Was the 1st thing i started with & went OMG what trash have i brought here, Rest of it seemed to go together okay tho.

5 hours ago, plonkster said:

AWG, for the metrically impaired.

Impaired? I find not knowing imperial units is liberating!

Quote

There is no sane way to relate to it.

Oh, there is. I remember that 8 AWG is about 8 mm² (it's actually 8.37, per the Wikipedia page). As the gauge goes up by 3, the cross sectional area goes down by very close to a factor of two. Not exactly two, of course, because <sarcasm=10>American units are designed to be familiar and easy to use</sarcasm>, so it all relates to the familiar 39th root of 92 (I'm not kidding about that part). So 10 gauge is about 2^(2/3) = 1.59 smaller, so that's about 8 / 1.59 = 5.04 mm². The Wikipedia page shows 5.26 mm². If I used 8.37 instead of 8, it would have been correct to three decimal places. (Add 10% divided by 2 for more accuracy when starting with 8 mm²). But I seem to find it hard to remember 8.37.

Less accurately, 10 AWG is about a factor of 10 in area.

Other AWGs to remember are 0 AWG is just over 50 mm², and 17 AWG (never seen, but good for calculating) is just over 1.0 mm². Just have Windows calculator (or equivalent) running at all times.

So using the factor of 10 rule of thumb, with 0 AWG just over 50 mm², 10 AWG is just over 5 mm².

Anyway, there you go, it's very relateable! 🤨

[ Edit: added the factor of 10 rule of thumb. ]

Edited March 15, 20196 yr by Coulomb

8 hours ago, 2una said:

I'm heading in a similar direction to you. Did your feet on that cabinet bolt thru properly ? Was the 1st thing i started with & went OMG what trash have i brought here, Rest of it seemed to go together okay tho.

@2una, to be honest, I didn't use the feet that came with the cabinet as they looked too flimsy; when I test fitted them initially, they didn't seem to go through the chassis holes at all (holes way too small), so I drilled them out ever so slightly (think it was 9.5mm) - the bolts still gripped the chassis holes as they went through. Also wondered what I'd bought, but it did go together quite well in the end.

I also wanted to be able to move the cabinet when needed, so I got some 75mm solid rolling castor wheels from Gelmar - the ones with the 10mm bolt holes - I think the feet that came with the cabinet were also 10mm, but I had to also get some slightly longer bolts to attach the castors. I also added a heavy duty 3mm-thick washer and spring washer on the inside under the nut, just to be sure! Probably overkill though  

The front two wheels have the "brake" and the back two are just normal rolling types - sits very solidly

6 hours ago, Coulomb said:

Impaired? I find not knowing imperial units is liberating!

Oh, there is. I remember that 8 AWG is about 8 mm² (it's actually 8.37, per the Wikipedia page). As the gauge goes up by 3, the cross sectional area goes down by very close to a factor of two. Not exactly two, of course, because <sarcasm=10>American units are designed to be familiar and easy to use</sarcasm>, so it all relates to the familiar 39th root of 92 (I'm not kidding about that part). So 10 gauge is about 2^(2/3) = 1.59 smaller, so that's about 8 / 1.59 = 5.04 mm². The Wikipedia page shows 5.26 mm². If I used 8.37 instead of 8, it would have been correct to three decimal places. (Add 10% divided by 2 for more accuracy when starting with 8 mm²). But I seem to find it hard to remember 8.37.

Less accurately, 10 AWG is about a factor of 10 in area.

Other AWGs to remember are 0 AWG is just over 50 mm², and 17 AWG (never seen, but good for calculating) is just over 1.0 mm². Just have Windows calculator (or equivalent) running at all times.

So using the factor of 10 rule of thumb, with 0 AWG just over 50 mm², 10 AWG is just over 5 mm².

Anyway, there you go, it's very relateable! 🤨

[ Edit: added the factor of 10 rule of thumb. ]

Ha ha - information overload early on a Saturday!  

Good to know though.

Edited March 16, 20196 yr by HowardB

Reminds my of the time South Africa replaced the imperial system with metrical system . Handbooks in inches and measure equipment in mm . Did me a lot of good . Still use it sometimes very handy .

8 hours ago, Coulomb said:

Oh, there is. I remember that 8 AWG is about 8 mm² (it's actually 8.37, per the Wikipedia page). As the gauge goes up by 3, the cross sectional area goes down by very close to a factor of two. Not exactly two, of course, because <sarcasm=10>American units are designed to be familiar and easy to use</sarcasm>, so it all relates to the familiar 39th root of 92 (I'm not kidding about that part). So 10 gauge is about 2^(2/3) = 1.59 smaller, so that's about 8 / 1.59 = 5.04 mm². The Wikipedia page shows 5.26 mm². If I used 8.37 instead of 8, it would have been correct to three decimal places. (Add 10% divided by 2 for more accuracy when starting with 8 mm²). But I seem to find it hard to remember 8.37.

When I said there is no way to relate to it... I meant there is no EASY way to relate to it. You know, like one liter weighs one kilogram, one calorie heats one gram of water by one degree Celsius, and so on... oh hang on... the SI unit for energy is Joule. Grrrr.

🙂

I have two Pylontech UB3000 batteries with brackets. May I connect the earth lug on one to the earth lug on my Goodwe GW5048D-ES inverter. The inverter in earthed to the DB.

On 2019/04/06 at 10:48 AM, Derek said:

I have two Pylontech UB3000 batteries with brackets. May I connect the earth lug on one to the earth lug on my Goodwe GW5048D-ES inverter. The inverter in earthed to the DB.

I don't see why it can't. I understand that each battery must be earthed to the cabinet or to a common earth terminal. If it all goes to the DB lug, then should be fine. 

Mine runs from each battery to the battery cabinet common earth then to the DB earth. 

Thanks