Earth leakages at each sub boards only

[rinners]

The electrician set up the board in the garage, pool, cottage each with their own EL at their respective boards/boxes without being on any EL on the main board. Main board has EL, but only for the breakers in that board.

Is this up to the SANS standards? Curious because if someone hit a buried cable with a spade or whatever then it would only trip on overload.

[Jacques Ester]

You cant put 2 E/L in series. The upstream one will trip.

This sounds quite normal. An extra db is fed by a double pole breaker and then each Db has its own E/L.

 

[rinners]

You may have misunderstood, there is only an isolator on main board side of the cable going to the sub boards and E/L at the sub boards.

E/L at the main board is for the house plugs, lights etc. The sub boards for the garage, pool etc are connected before the main board E/L 

[Vaal]

9 hours ago, Jacques Ester said:

You cant put 2 E/L in series. The upstream one will trip.

This sounds quite normal. An extra db is fed by a double pole breaker and then each Db has its own E/L.

 

Jacques, I don't agree with you on this statement. If you have 2 EL's in series you get a whole bunch of nuisance trips. 

To the OP, yes it is legal to have multi EL's as long as it is not in series and everything is protected by a EL. It is actually very nice to have it this way because if I you trip the EL in the garage you don't "upset" the people in the house. To do fault finding, it makes it a lot easier.

[frivan]

10 hours ago, Jacques Ester said:

You cant put 2 E/L in series. The upstream one will trip.

This sounds quite normal. An extra db is fed by a double pole breaker and then each Db has its own E/L.

 

Is the double pole breaker a new requirement? I can't say that I have ever seen this for sub-DBs.

[TaliaB]

15 hours ago, rinners said:

You may have misunderstood, there is only an isolator on main board side of the cable going to the sub boards and E/L at the sub boards.

I think you guys is misunderstanding @rinners concern about the secondary cable protection to his outbuilding. First of all just to clarify: There is 2 types of RCD's (EL) 1. RCD with oveload protection and 2. RCD without overload protection. The secondary cable from the main house db is wired from a isolator not a curcuit breaker so no protection for the cable. Need to install a single pole or double pole curcuit breaker to protect the cable. If the sub db board is fitted with RCD's with overload protection it can be used as a main switch and marked as such. If Rcd does not include overload a 2 pole curcuit breaker must be added before the RCD. @frivan if it is marked or used as MAIN SWITCH it needs to interrupt the L & N should it be Main db or sub db.

[frivan]

1 hour ago, TaliaB said:

if it is marked or used as MAIN SWITCH it needs to interrupt the L & N should it be Main db or sub db.

Double pole breakers for sub-DBs, out buildings and for main switches is not how 99% of households are wired.

[TaliaB]

Just now, frivan said:

Double pole breakers for sub-DBs, out buildings and for main switches is not how 99% of households are wired.

Neutral is considered a live conductor not even looking at the regs let's consider it from a safety point of view what would be the best practice and common sense? to isolate the entire sub db or the live conductor only. 

[frivan]

8 hours ago, TaliaB said:

Neutral is considered a live conductor not even looking at the regs let's consider it from a safety point of view what would be the best practice and common sense? to isolate the entire sub db or the live conductor only. 

If you lick the back of your hand and touch neutral, you won't die. So installing more breakers than is necessary is clearly stupid.

[TaliaB]

33 minutes ago, frivan said:

If you lick the back of your hand and touch neutral, you won't die. 

That is stupid!!!

[Thunderdolt]

So I am confused about E/L in series from the above comments.

Would this be the correct wiring for an essential load diagram incorporating 2 outbuildings , where the 2nd building is fed by a cable from the 1st one?

(I left out a double pole breaker in the line to the 2nd outbuilding because I am to lazy to edit the diagram  but it should be there.)

 

 

Edited May 8, 2023 by Thunderdolt
remove pdf, add jpg

[Jacques Ester]

On 2023/05/06 at 5:02 PM, frivan said:

If you lick the back of your hand and touch neutral, you won't die. So installing more breakers than is necessary is clearly stupid.

Well then you have definitely not been shocked by a neutral. There are a lot of equipment that can create backfeeds. I would always use a double pole breaker to isolate both live and neutral.

[frivan]

2 hours ago, Thunderdolt said:

So I am confused about E/L in series from the above comments.

Would this be the correct wiring for an essential load diagram incorporating 2 outbuildings , where the 2nd building is fed by a cable from the 1st one?

(I left out a double pole breaker in the line to the 2nd outbuilding because I am to lazy to edit the diagram  but it should be there.)

 

 

Wrong. The MCB is supplied from the EL below the inverter. This causes the downstream ELs to be in series with the first. The MCB should be fed from the top of the first EL.

[frivan]

2 hours ago, Jacques Ester said:

Well then you have definitely not been shocked by a neutral. There are a lot of equipment that can create backfeeds. I would always use a double pole breaker to isolate both live and neutral.

I got shocked good and proper with a neutral but that was because I disconnected the neutral supply of a circuit that was actually live. I see little risk in a system where neutrals are connected solidly. I suspect the old engineers had the same view but then again they had electricity 24/7.

[Thunderdolt]

4 hours ago, frivan said:

Wrong. The MCB is supplied from the EL below the inverter. This causes the downstream ELs to be in series with the first. The MCB should be fed from the top of the first EL.

Thanks @frivan. So then is this the way it should be?

[frivan]

20 minutes ago, Thunderdolt said:

 So then is this the way it should be?

Yes, your earth leakages are in parallel and won't trip one another.

[Thunderdolt]

7 hours ago, Superfly said:

Why not just have  have a Change-over at DB1 to individual MCD's which feed their RCB's and individual  circuits  - with 3 main switches you can control what is on the RCB at each DB. (Won't kill the whole  circuit with a single trip) Why 63A? 

Why 63A? Because that's what is there! 

[P1000]

3 minutes ago, Superfly said:

LOL.. OK.. I hope you are using 16mm cable then - overload protection is best though an MCB as I mentioned.

Most RCDs don't have overload protection and HAVE to be used with an MCB.

[Scorp007]

2 minutes ago, Superfly said:

Exactly.. that is why I don't understand why people use an RCD as a Main switch...

Funny that I have never used or advised to use an E/L without overload protection. Seems a false savings drive and 1 space wasted using 3 instead of 2.

I have to be different.

[rinners]

On 2023/05/06 at 7:23 AM, TaliaB said:

I think you guys is misunderstanding @rinners concern about the secondary cable protection to his outbuilding. First of all just to clarify: There is 2 types of RCD's (EL) 1. RCD with oveload protection and 2. RCD without overload protection. The secondary cable from the main house db is wired from a isolator not a curcuit breaker so no protection for the cable. Need to install a single pole or double pole curcuit breaker to protect the cable. If the sub db board is fitted with RCD's with overload protection it can be used as a main switch and marked as such. If Rcd does not include overload a 2 pole curcuit breaker must be added before the RCD. @frivan if it is marked or used as MAIN SWITCH it needs to interrupt the L & N should it be Main db or sub db.

So if I understand correctly, I can just put in a 60A circuit breaker (based on thickness and lenght of the wire) after the isolator and that is sufficient cable protection? What if the cable runs underground? Say plumbers or whoever hit that cable to the outbuilding, the supply would then only then be cut off at 60A? It's an armoured cable so unlikely, unless they use heavy earth moving equipment

[TaliaB]

15 minutes ago, rinners said:

So if I understand correctly, I can just put in a 60A circuit breaker (based on thickness and lenght of the wire) after the isolator and that is sufficient cable protection? What if the cable runs underground? Say plumbers or whoever hit that cable to the outbuilding, the supply would then only then be cut off at 60A? It's an armoured cable so unlikely, unless they use heavy earth moving equipment

That is correct the cable in the ground is a SWA ( armoured cable) a double pole 60 amp curcuit breaker will be adequate if the cable size is 16mm² to protect it or disconnect during short curcuit.Your main cable entering your house from council side is protected by a 60 amp breaker. What is the cable size in mm² running to your outbuldings? You need to pair cable size to breaker rating very important.

[rinners]

3 hours ago, TaliaB said:

That is correct the cable in the ground is a SWA ( armoured cable) a double pole 60 amp curcuit breaker will be adequate if the cable size is 16mm² to protect it or disconnect during short curcuit.Your main cable entering your house from council side is protected by a 60 amp breaker. What is the cable size in mm² running to your outbuldings? You need to pair cable size to breaker rating very important.

I think it's a 10mm² cable, 25-30m long

The other is a 4mm², maybe 10-15m long

Edited May 11, 2023 by rinners

[TaliaB]

6 hours ago, rinners said:

think it's a 10mm² cable, 25-30m long

60 amp curcuit breaker

 

6 hours ago, rinners said:

The other is a 4mm², maybe 10-15m long

30amp curcuit breaker

[RikusW]

@Thunderdolt
https://www.theforumsa.co.za/documents/SANS10142-1_ED3TC067_SC06_DSS.pdf

You need a double pole circuit breaker on the input and output of the inverter

https://resource.capetown.gov.za/documentcentre/Documents/Procedures, guidelines and regulations/Embedded_generation_schematic_drawings.pdf

7.12.5.1.1 Overcurrent protection and isolation shall be located as near as
possible to the output terminals of each alternative supply unit, except where
the cable connecting the unit to the distribution board is mechanically
protected and is regarded to be within the fault-free zone of the distribution
board where protection is installed. The circuit-breaker magnetic
characteristic shall have a low threshold value in view of the high impedance
in the case of a generator or of the current-limiting characteristics in the case
of a static inverter UPS. Downstream coordination shall take this into
account. To be consistent with the rest of this part of SANS 10142,
overcurrent protection is required for the protection of the conductors, but
might also provide protection to the alternative supply unit.