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wire size for 60A single phase DB board


Fuenkli
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I have a single phase Eskom power supply with a 60A main switch. What is the minimum wire size inside the DB board from the main switch to the RCD's and bus bar's? I thought it should be at least 16mm2 but the neutral bus bar holes are only big enough for a 10mm2 cable.

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28 minutes ago, Fuenkli said:

16mm2

That is the correct size.... I normally remove and Re-Drill the big hole to fit the 16mm. I assume you are using the square (solid) neutral bar.

I like these.

1123815144_Neutral1.PNG.1294d2b35ea133ce2d2d026a220741e7.PNG

Or these with One or two bigger size holes.

848502622_Neutral3.PNG.76a2d0aa3e1aa8de5b2fc68abf1df71f.PNG

But I guess you are using something similar to this

947898408_Neutral2.PNG.11c050496efd049ae7f8b8253d26c203.PNG

These are the ones I drill a bit bigger. 

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2 minutes ago, Jaco de Jongh said:

I assume you are using the square (solid) neutral bar.

yes it is the solid square neutral bar. I will do what you do and enlarge one hole to accept the 16mm2 cable. Strange that they fit neutral bars like this.

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I am after these, for non-DB board connections. Waiting on better prices ... 

Maybe use them for the thick cables, and when it gets close to the DB board, the last few cm, make the cables short and thinner to fit a DB board?

image.png.ea472ac93e3c88170208af2cad8f6b0b.png

image.png.2514fda705051420921bec4e3da97cd0.png

image.png.9ba7b0e3251b177045a6957f2a74efb9.png

image.png.1f7eb1e89271f57df353d7ea1948b44b.png

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31 minutes ago, SilverNodashi said:

10mm2 is rated at ~65A, hence the 10mm busbars and 10mm being the common cable found in most homes. 16mm2 leaves room for some future growth, but as you've seen, it doesn't fit into anything (standard) generally found in a house DB

I am sorry Silver but this is just not true. 

Firstly have a look at the following SANS table, you will see that in instalation method 1 and 2 (Home Installations)  the max rating of a 10mm in a single phase installation is 52Amps

Ampacity.PNG.9d2d6f9dce9c2d90519c8b80a9d4e9fe.PNG

The common busbar available from your electrical supplier is equivalent to 16mm square and all standard breakers (2.5 and 3KA) are designed to take a minimum of 16 mm wire to accommodate the standard wire for a standard 60Amp installation. 80A installations normally call for a 5ka breaker that will allow a 25mm cable and 40Amp connections use 10mm wire.

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36 minutes ago, The Terrible Triplett said:

I am after these

I opted for these. A bit bigger, needs a bigger box, but overall thicker, more space for cables, M8 connections, and way less expensive. And you can actually buy them from an electrical supplier (it's called an earth bar).

596abf3fadba79e284614fb57458818a.jpg

 

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16 minutes ago, Jaco de Jongh said:

I am sorry Silver but this is just not true. 

Firstly have a look at the following SANS table, you will see that in instalation method 1 and 2 (Home Installations)  the max rating of a 10mm in a single phase installation is 52Amps

Ampacity.PNG.9d2d6f9dce9c2d90519c8b80a9d4e9fe.PNG

The common busbar available from your electrical supplier is equivalent to 16mm square and all standard breaker are designed to take a minimum of 16 mm wire to accommodate the standard wire for a standard 60Amp installation. 80A installations normally call for a 5ka breaker that will allow a 25mm cable.  

Just cause it isn't true, doesn't mean installers follow the SANS guidelines to the letter. 10mm2 is cheaper than 16mm2 and get installed more often. I've also seen installations with 1.5mm for plugs and 2.5mm for geysers. With a COC. 

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1 minute ago, SilverNodashi said:

I've also seen installations with 1.5mm for plugs and 2.5mm for geysers.

And here I am spending extra money on 4mm Surfix when I could have used cheaper 2.5mm ...

Truth be told, the 4mm Surfix is still only good for 32A... If I was doing this properly I'd be going up another size. Instead I'm just going to fit a 25A breaker to protect the lot. 5KW is ample for essential loads.

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7 minutes ago, Jaco de Jongh said:

I do hope that on this forum we can teach the Members to follow the correct  standards and not the corrupt installers. ;)

Agreed. But the general public should not be installing their own DB's ;) Registered electrians should. Now, how do we get the "general sparky" to follow standards?

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6 minutes ago, plonkster said:

And here I am spending extra money on 4mm Surfix when I could have used cheaper 2.5mm ...

Truth be told, the 4mm Surfix is still only good for 32A... If I was doing this properly I'd be going up another size. Instead I'm just going to fit a 25A breaker to protect the lot. 5KW is ample for essential loads.

well that's the thing. Do we really need too big wiring / CB's for most devices / appliances? 25A @ 240V = 6KW, which is more than the average blue or grey inverter on this forum ;) 63A is 15Kw. Keeping this in mind helps using the right equipment for the application. 

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7 minutes ago, SilverNodashi said:

But the general public should not be installing their own DB's ;) Registered electrians should.

That has changed a bit. My grandmother can wire her house as long as someone with a COC signs it off. For example , TTT does his own Solar and all the wiring he is comfortable with. Then he gets an electrician to connect to grid and issue the COC and then he calls his Engineer friend to sign the final paper. No one in the loop was worried about who did what, they only want to test and see all is correct. 

 

11 minutes ago, SilverNodashi said:

Now, how do we get the "general sparky" to follow standards?

That is easy, when you see this 10mm wires in a db again, Phone the ECA and direct them to the site. I can guarantee you after a run in with them, he will follow the standards next time round, if there is a next time for him..  

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1 minute ago, SilverNodashi said:

25A @ 240V = 6KW, which is more than the average blue or grey inverter

The transfer switch in the 3kva Multi is capable of 50A, which only really applies in passthru or when running ESS. But I decided to limit it to something lower, because I already decided not to put the whole house through it.

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38 minutes ago, SilverNodashi said:

I've also seen installations with 1.5mm for plugs and 2.5mm for geysers. With a COC. 

You can use any size wire for plugs, so long as your CB is rated for the smallest cable in the circuit. Use 1.5mm wire for plugs is CoC compliant, so long as the CB is 16A or lower

2.5mm for geyser on a 20A CB is fine, but on a geyser your earth wire should be min 2.5mm so you cant supply with Surfix/FTE because the earth wire is not 2.5mm (you can use if you run a separate 2.5mm earth.)

@plonkster I hope that the 25a CB is not directly supplying any plugs or switches that are rated at 16amp without sub CB's because your CB may not exceed the rating of you socket/switch by more than 25% - so max 20amp CB no matter what size cable you use.

Edited by pilotfish
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8 minutes ago, pilotfish said:

I hope that the 25a CB is not directly supplying any plugs or switches that are rated at 16amp without sub CB's because your CB may not exceed the rating of you socket/switch by more than 25% - so max 20amp CB no matter what size cable you use.

Of course not. The 25A breaker is on the input side of the inverter (in fact, it's an RCBO). Then on the output of the inverter there is another main switch, an RCD, and then separate breakers for each circuit.

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10 minutes ago, Jaco de Jongh said:

... being old school I still use conduit and GP wire. 

Not old school. When we built on-top of the existing house (we lived in it, took 7 weeks and the roof was back on - done via email).

All the wires below had to be re-done, replaced with conduit and 3 separate wires inside, 2.5mm I think.

Electrician just made it so as it is easier and better he said. They drilled into the concrete and fixed the conduit to the underside of the concrete slab - looked like a piece of art. 

The electrician - he is young - and his worker even younger. They where brilliant.

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10 hours ago, pilotfish said:

You can use any size wire for plugs, so long as your CB is rated for the smallest cable in the circuit. Use 1.5mm wire for plugs is CoC compliant, so long as the CB is 16A or lower

2.5mm for geyser on a 20A CB is fine, but on a geyser your earth wire should be min 2.5mm so you cant supply with Surfix/FTE because the earth wire is not 2.5mm (you can use if you run a separate 2.5mm earth.)

@plonkster I hope that the 25a CB is not directly supplying any plugs or switches that are rated at 16amp without sub CB's because your CB may not exceed the rating of you socket/switch by more than 25% - so max 20amp CB no matter what size cable you use.

The problem, again, is that sparkies / installers don't adhere to strict standards. 1.5mm is fine if the isolator is 16A - I agree, but how many houses actually have a 16A breaker on the plugs? Most have three or four plugs on the same breaker, and thus use a 20A or even 32A. 

 

On the flip side, it we merely work on standards, then most homes have insufficient cables and breakers for general usage. At least in the kitchen / garage / scullery areas. As example, my dish washer use 3Kw for heating (both on the pre-wash and drying cycle) and if someone uses  the tumble dryer at the same time, the power trips. And the Axpert moans. Luckily it trips at the DB before the Axpert has a stroke. And my wife and the cleaning lady has learned not to use those two on the same day. Same with the kettle and induction plates. Use either of the two, not both. The house is almost 40 years old, with decent wiring and circuit breakers throughout, but there's 3/4 plug per breaker. Maybe, just maybe, one day, when I'm bored, we'll rewire it. But for now it's still within SANS standards. 

 

 

Coming back to the OP, I would also have liked to have a 16mm cable from Eskom. Some time ago I helped someone setup a bitcoin farm. He had 5 PC's, with 7X GPU's on each. All went well till we powered them on at the same time and they decided to install two aircons. Then everything just overloaded the 63A isolator in the street and he had to abandon the idea of running this from home. Or at least on  single phase, and their complex didn't allow to 3 phase. 

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13 minutes ago, SilverNodashi said:

most homes have insufficient cables and breakers for general usage

I agree. My house is brand new (moved in 2 years ago). The Bosch induction Hob alone keeps tripping the 20A CB it is on. I have a big problem with my wife because she thinks it is all because of the  PV system :D

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1 hour ago, Fuenkli said:

induction Hob alone keeps tripping the 20A CB it is on

Stove should be on a larger breaker. Funny story with that one.  The isolator next to my stove broke. It was a cheap plastic thing and because we were concerned about the kids getting burned when they were little, it got turned off every day. So off I went to the hardware store to get a replacement, with the rating in the back of my mind. It was a 60A isolator.

In store I can only find a 50A replacement. So now I am worried... but I buy it anyway and install it. Now I often solve issues like these at night just before falling asleep... staring at the ceiling, it hits me like a train: The breaker in the DB is rated at 40A. You're perfectly fine with a 50A isolator lower down :-)

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6 hours ago, SilverNodashi said:

Some time ago I helped someone setup a bitcoin farm. He had 5 PC's, with 7X GPU's on each.

To ensure proper operation I guess he chose 1500-1600 Watt power supplies for each Rig.. Depending on the GPU model his rigs can reach 1400 watts each x 5 = 7kw. Basicaly halve of his supply capacity. Not at all a game you want to play at home... Our Crypto farm consumes the equivalent  of R60k worth of electricity a month. 

Just for interest sake. Rather call it a Crypto  Farm/Mine. To mine Bitcoin, you need asic miners. GPUs can mine various other coins and some mining pools might even reward you in BTC for mining other coins for them, but Technically GPu's cant mine/farm Bitcoin

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