i am busy upgrading my PV system (from 4.4kWp to 15.6kWp, now with export permission). Because of ill health i was forced to give the install to an installer (he is a registered electrician and will issue the COC). In the old install i followed @JacoDeJongh advice to use 16mm2 cables. The installer has now replaced my 16mm2 with 10mm2 cables. Is this now ok? I have 2 concerns:
If the house burns down (not caused by the electrical system) can the insurance company refuse to pay if they find out that 10mm2 cables were used instead of 16mm2? I have heard, that if you have a COC from a registered electrician the insurance company has to pay.
If it is now ok to use 10mm2 cables in a 60A DB Board, do all electricians accept this? Or could an other electrician force me to rewire the DB Board to issue the COC when i one day want to sell my house
These ratings are for 30 degrees ambient and 70 degree conductor temperature. If ambient may exceed 30 degrees you have to derate the current carrying capacity.
I have seen 10mm2 conductors on a 60A breaker inside the DB (not outside). I would personally not do it.
Moment one guy wants to reduce wiring, after the 1st oke explained why like i.e. Jaco de Jongh as an example, and I Googled/asked to confirm at the time, I don’t continue with said sparkie.
50a breaker for for my 5kva, 10mm2 wire, no-one touches it ever to reduce it.
It was paid for, it’s been working for years, don’t touch!
Same applies. If I had 16mm2 installed, and it is removed to get 10mm2, sparkie can go somewhere else.
Me, never REDUCE wiring already installed, paid for, that has the correct breaker.
My 2 cents.
Ps. If the sparkie has given the CoC, correctly (small T&C’s in that document) and their is drama, insurer will pay and sort it with out the sparkie direct. If they are sill around.
Case sample:
Paid engineer 11 years ago for a slab.
Father passed.
Son also passed.
Business closed.
CoC in hand, I have some serous questions so what now?
Bottom line I’m stuck.
Need new engineers.
I see it more and more lately that guys are pushing the limits on cables. I am still from the old school many many years ago and tend to stick to what I was taught back in the days.
1mm = 10A
1.5mm = 15A but I tend to protect it with a 10A breaker
2.5mm = 25A but I protect it with a 20A breaker
4mm = 32A
6mm = 40A
10mm = 50A
16mm = 60A
25mm = 80A
As long as the protection breaker is correctly sized it does not matter if its a 10 or 16mm cable. He could have even used 6mm if the breaker is adequately specked.
I personally would stick to my 16mm on a 60A db, but that is my personal preference.
Being part of a distribution company last year that imports cable opened my eyes to the dishonesty in cable manufacturing. The chinese for example do not stick to cable diameter as we know it, they will rate a cable based on the resistance per meter. We have imported cables rated as a 16mm that we could fit a 10mm lug on, or 35mm cables that we could fit a 25mm lug on. I queried it and was told that the cable can handle the current of a 16mm based on its internal resistance and therefore can be sold as a 16mm . I did not agree and bought my cables from local suppliers. The company mentioned above still imports cables from china, I just dont buy it.
the whole issue started when the Sparkie/Installer did not like 2 16mm2 in one termination point (in my case the RCD’s and the Change Over Switch). We agreed to add bus bars to the DB to eliminate this problem. When i came home he has removed my 16mm2 cables rewired the DB Board with the agreed to bus bars and with 10mm2 cables (we have never agreed to). I told him in no uncertain terms, that i do not appreciate this at all. On top of it he kept all the copper without even mentioned it. The problem is now, that it seems to be legal (see my reply to @JacoDeJongh). So what do i do now?
Question, is this an AC distribution board, or a DC board? Can you can show a picture?
16mm^2 is rather hard to work with, so in a way I understand why someone might drop to an acceptable lower size. Also makes it easier to make the board neat.
For DC boards I would not like it if it just barely passes. DC runs full current for hours at a time. Even if 70°C is allowed at ambient 30°C, that’s too hot. It will heat soak everything. Alright in an AC board where 60A is the peak, and most of the time you are below 80% (otherwise breakers trip… they get heat soaked). Not alright in a DC board.
I fully agree with you. Why take a chance. The problem is, that SANS 1507 does not have an installation method referring to DB’s (enclosed spaces). So which installation method do you use? If you use in conduits it would clearly be unacceptable. If you use free air all is ok. The good news is, that if we leave it on 10mm2 the insurance company lawyers do not have a leg to stand on in court to use the 10mm2 as a reason not to pay out if the house burns down. The same goes for the Sparky who has to issue a new COC if i one day i want to sell the house. He can not force me to accept to go to 16mm2 because SANS 1507 does not call for it in the DB board.
What would you do? Force the Installer/Sparkie to rewire to 16mm2 (probably at my expense) or leave it at 10mm2.
Was it his personal preference or was it not practical/possible to have 2 16mm2 conductors in one MCB terminal? Are there any restrictions as to the amount/size of conductors in one terminal or “if it fits, it is OK”?
OK, with the proviso that I am not a sparky, in that case I would not be too concerned with the 10mm cabling.
I assume the main feed into the main breaker is still 16mm^2, as well as from there to the RCD. Then I would want a 16mm^2 black cable from the RCD to the neutral bar, and a busbar linking the various breakers on the live side. And from that point on, everything else can be thinner. It will be much easier to make future modifications as well.
This is also relatively easy to ask the sparky to change (if not done already). Tell him you want at least from the main breaker, and the RCD to the busbars (neutral and live) to be 16mm^2. That’s only a little bit of wiring.
Many RCDs and MCBs rated for 60A or less only support up to a single 16mm² connection. It’s usually indicated in the datasheet and sometimes stamped onto the casing.
No. All RCD’s (I have 3) are only on 10mm2 neutrals. In fact (all neutrals) after the 60A main switch are only on 10mm2. As you can see, the red live cables are still on 16mm2. The Sparky did not mess with those.
If that is the case, i also have to change all the red supply cables after the main switch from 16mm2 to 10mm2 or use Bus Bars on the live side as well (does that even exist?)
