Hi .This video shows how to calculate cable and circuit breaker (fuse)for the design current. Bigger size cable is always better but cost much more. Hope it will help in your DIY projects. Thank You for watching Please Subscribe
Thanks for a clearly explained video. Just a point to remember when referring to a six millimetre cable it refers to the cross sectional area of the copper and not the diameter of the copper wire. Back when I started in home renovation, I would measure the copper wire with a vernier and then wonder why 6 mm was not the diameter ? Of course not - 6 mm refers to the area - it should be written 6 mm2.
Interesting. I hadn't realised just how much running cables through insulated walls makes to the amperage rating of the cable. It's definitely, something to keep in mind when adding insulation to existing walls, ceilings etc.
I am an electrician ,and on cookers you should allow for diversity , this is an allowance in the electrical ie regs, that means you would never have the cooker on full load ,talking the full 10kw while cooking ,( every oven and ring on full power) this means a 32A CB would be OK with 4mm cable for a short run and 6mm for a long run of cable.
Thank you very much for your clear instruction and for following the regulations guidelines. I hope you can do much more youtubes about this subject. I have learnt lots from this.
I like this simple approach to calculating the design. I can't see a problem with using cable that's over-rated at is has less resistance and can cope with future changes to circuit usage. Diversity is an optional consideration if you don't want to spend too much on cabling etc. but it takes no account of future usage, so having larger cables is fine if you want to pay for it.
What do you mean take the "diversity" into account? Is that the tollerance of the cable? O you mean 1 usage of voltage between L1 and L2 ? He choose 230 Volt and that is between L1 and Neutral, so there is no square 3
Howdy. Nice presentation of rating the thermal overload case. There is, however, another equally important aspect. The short cicuit case. There must be enough "short force" feeding the breaker to enable fast breaking (=magnetic triggering) of the breaker. In my location the power companies will provide information of how much short current is available at the service cable junction. From this point forwards one must calculate the short current at the most distant appliance or socket and choose a breaker that will fast trigger. If the short current is too low to deliver fast triggering the short current will flow until the thermal breaking happens. The socket wiring will run way too hot and there is a real fire hazard present. Regards.
at 1:15 talk about cable size 6mm, 2.5mm and 1.5mm. Iit should be read as 6mm square, 2.5mm square and 1.5mm square instead. Many thanks for this video!
Hiya. I'm enjoying your videos Buddy. Just thought I'd mention it, as you did choose to use a cooker as your example. Don't forget to apply diversity as it is highly unlikely to ever reach its maximum demand due to the thermostats in the cooker rings. In your example (44 A) it would be the first ten amps (10 A) then 30% of the remaining amps (approx. 11 A) PLUS 5 A if there's a socket outlet on the cooker isolator. So, your 44 A has gone down to 26 A. The next MCB up from that is a 32 A. I'd still use 6mm cable though.
Kevin McNicholas I've always been told to use 10mm by my boss..I suppose this would save money if working for yourself.. I've recently sat the 2391-52 exam,no one could give me a exact way too work out maximum demand/ diversity nt even in bs7671 book
cater4anytink Yeah, I know what you mean. I suppose it would be useful to if the oven was ever upgraded again. It's a trade off though, isn't it? If customer wants to pay for cable that is far and away able to deal with the demand, fair enough. Thing is though, why don't we do rings in 4mm instead of 2.5mm? Because of cost, that's why. And if your wiring a lot of houses that's going to be a lot of wasted money. If customer is willing to pay the extra i.e. maybe £45, let's say, instead of £30 then yes, do it in 10mm. Diversity is covered in the On-site guide.
cater4anytink checkout the best sparky in the U.K. he knows the regs in his head, can tell you the reg and the page its on, his name is john Collins, his training place is in dudley West Midlands, he is a great trainer, he used to teach at sbc college, he teaches in small groups, like two! On different meters, as everyone has different meters, etc, everyone knows him, especially the regs guys, ex military,
smartchip John Collins? Ha, ha... you mean 'Johnnie Ace'!! Oh, he's great. I love watching his vids. Very knowledgeable and puts things over in a way anyone can understand. Johnnie Ace, (tsk,tsk), is on the case. That's a great catchphrase. 👍🏼
This is quite a broad topic. You managed to explain the most important parts, excluding the formulae. For heavier loads we (central Europe) usually use 3 phase circuits.
Most of the domestic-houses here DO use 3 phases + neutral. AC Voltage LN 230V, LL 400V, main fuses are 3 x 25A or 3 x 20A and current limiters inbuilt in the electrical power meter. Electric stove usually uses 3 phase, so does the heat pump, and other various bigger loads.
A very simplistic look at the cooker circuit, you need to take diversity into account as the load is thermostatically controlled and therefore wouldnt pull the full load all the time.
Thank you for yoir explanation, I only have one note: When you get the current you divided power over voltage without the power factor.. it should be P/(V*pf) so the current will be 48 A , then you should select a cable size according to that.
i now 1mm cu wire can hold max 8 amp without voltage drop 0.05% in lenth 100 meter and don't get hot so (1mm 8amp) , (1.5mm 12amp) , ( 2.5mm 20amp) , (4mm 32amp) , (6mm 48amp) , (10mm 80amp) , (16mm 128amp) and thanks for your great video.
hold on , you should also take in to account the method of installation , the various conditions it will pass through (example , you may go through insulation and then into free air which operate at different temperatures
One thing to remember regarding cookers... If it is a three phase connection than that 44 is divided by 3, which means you can connect each of the phases separately and the cable size does not have to be bigger than 2.5mm and size of three breakers collectively has to be 20 Amps each (44x1.25=55÷3=18.33)
After waiting two weeks for a new cooker from a place that has the same name as a god, I paid for it to be put in. A bit more than £100. They said they could not do it. That I can only have a cooker thats 20 amp. I did not watch them try. My lights went off and on many times. So I went to see what the hell was going on. My fuse box says 32A . I have to wait 30 days to get my money back.
You have explain the calculation to obtain circuit breaker amp size and from there, select the cable size based on the table. But, I am curious about the calculation to obtain wire size. Why using 1.5 cable for ac for for example can cause it overheat. What is the maximum by calculation for current to pass through wire certain size.
