[Question] COC on old house

[JacoBru]

Good day to all

I have a situation which I would like to get some answers too:

I was asked to do an electrical inspection on a house which is quite old now I have a couple of questions if anybody can help me.

1. The breakers in the DB board has no kA rating on them. Do they need to be replaced? If I can quote SANS 10142 Edition 2

If you have a look at SANS 10142 Edition 2 under 8.5.3 Inspection it says:
• During inspection, confirm that all protective devices are capable of withstanding the prospective short-circuit current.

If there is no kA rating on the breaker, how can I be sure the breaker is going to withstand the PSCC that I have measured/calculated at the point of supply or control from the supplier.

And how can I the complete my COC at section 4 point 3 correctly which read:
• “ All protective devices are capable of withstanding the prospective fault level”


Then secondly. The house still has steel conduit throughout. On the socket outlets they still use the conduit as earth. If you open the plugs, there is no physical earth wire on the socket outlets. Do you need to pull in an earth to each socket outlet or how do one go about rectifying this problem.


Thanks beforehand for any input

[Lindley]

I think your fault level is very important and you must know what it is I will say change the circuit breakers to the standard which is right and correct towards what SANS is saying.

[ians]

In a house in KZN for example...The KA rating would generally be 2.5 ka...(which is the lowest fault level breaker) I would use common sense and allow it...Check the side of the breaker..sometimes the inform is stamped on the breaker...In a factory where the ka rating is extremely important due to the size and location of the transformer...it would have to indicated on the breaker...calculations and a test would be a smart thing to do.

Steel pipes and earthing on plugs...a very common issue...do a loop impedance test at the socket outlet...if the reading is not within spec...use a tek screw and a short piece of wire with a lug...if still not right...install an earth wire from the closest earth point (best from the DB)

[AndyD]

I'm not a fan of the earth being supplied from the closest point (a different point to the live and neutral), it means that future alterations or damage to one circuit has a knock-on effect on another. I'd always pull a CPC through from the DB which is easier said than done with old steel conduit so more often than not I'd rewire with a new cable using old wires as draw wire.

If you can't establish beyond reasonable doubt what the KA rating of the breakers is they should be replaced. I guess there might be a case for leaving the old breakers if you measure the PFC and it's way below the value of the lowest KA rating that any breakers on the market are manufactured to.

[SiyaM]

Morning JacoBru
Reg 6.12.1.3 states "A wire way shall not be used as an earth continuity conductor". That should address your concern.