Couldn't thank you more for putting up this video. Large details of cable sizing are summed up beautifully in 15 minutes video. There could be many more topics to cover but for beginners like this much more than I could expect for. Thank you
Thanks for the video......I studied this years ago and didnt understand it at all...........God knows how I passed my exams but going over it again here was very useful and made me realise I learned most things on the job :-)
Cogibear after studying how did you get into paid employment?, I’m currently studying level 2 electrical installation (C & G), I’m worried about how I’ll find a job?
I think Ib should be used instead of In when dealing with the Ca rating (i.e. It=Ib/Ca) to determine the appropriate cable size due to elevated ambient temp.
Dear Sir, I would be very grateful if you could tell me which type of MCB is suitable for each of the following home appliances: - Split air conditioner. - Fridge. Electric stove. - the oven. - microwave. - dish washer. - Washing machine. Clothes dryer. Thank you very much sincerely Khalid
Hello This video helped me a lot to prepare for my exam. I got just one question for Cg factor (grouping factor ) for example when I got my circuit and I run it along with two other circuits the factor should be for 2 circuits or for 3 circuits ? I'm confused on that :/ I want to thank you for spending time to explain this sort of things to people. Really useful keep up good work.
The end of the video misses the 80% rule and the 0.95% of cmin to be applied to the Tabulated Zs value in 7671 to allow for voltage fluctuations and a 50c rise in cable temp from the 7671 Tabulated Zs values when testing without load at about 20c in the field. The true max Zs permissable is actually only 1.10ohm.
Hi thanks for your great video! Just a quick question is the design current the rating of an appliance or is it the load after diversity. So a Hob for example if it is a 7kw rated Hob would the design current be the amount of amps after diveristy ie: first 10amps then 30% of the remainder? Many thanks.
Lol 12:13- "we don't really need to remember all that....." We just need to remember hundreds of 'tables' to make it easier.... Useful vid though. Now in 2023 (18th) 32A BS60898 is tabulated at 1.37 and corrected in OSG for 80% as 1.1 ohms
Hi chris, thanks for the video, I am new and learning. Can you recommend which books I can buy just specific to Cable Size Calculations and the relevant BS Standards to purchase, as lectured in your video
Chris, Thanks very much for this video is was very helpful. i have a couple of points/questions. 1. i thought when you have applied the rating factors to your cable this value is then called Iz? You seem to call this It? 2. At 8:55 i think your formula for Zs should have the R1+R2 in brackets, so Zs=Ze+(R1+R2) 3. When calculating the Zs you adjusted the figure for operating temperature of the conductor. if i was going to use the max Zs value in the on site guide i presume i do not need to do this adjustment? Thanks again for posting such good videos
+mikebizzleuk Hi Mike, When you divide In by rating factors the result is It, It is the minimum current rating of a cable which is needed to carry the required current under the conditions indicated by the rating factors. Iz is the current which a cable could carry under the conditions indicated. If you select a cable and than multiply it by the rating factors it will show you the current which the cable could carry under the given conditions, this is known as Iz. points 2 and 3, you are correct. hope this helps, Kindest regards Chris
+mikebizzleuk Hi Mike, It shown in a calculation is the minimum current carrying capacity of a cable which would be suitable for the circuit being calculated. Iz however is the current which a particular cable could carry when multiplied by the rating factors affecting it. As an example a 2.5mm which is has an It of 27A with a rating factor for Ca of 0.94 and Cg of 0.85 would have a current rating of 27 x 0.94 x 0.85 = 21.53A under those conditions. It is the current rating given to the cable in the tables in appendix 4. The rest of your assumptions are correct.
Yes, good point re, R1+R2. 'Big' r1+'big' r2 are never separated. They become one in the calculation for Zs so yes it should read '(R1+R2)' to confirm line and cpc resistance as one figure. 'little r1' etc is separate from 'little r2' as in, continuity...
I checked table 41.3 in BS 7671 for 32 A and type B circuit breaker , I found the value of ZS = 1.15 not 1.44 as mentioned in the video (1.44 is for type 1 circuit breaker not for type B)
Why in most houses as new build are all circuits in 2.5 twe. Even in loft. Surely some would have higher temperatures than others. But I have always seen 2.5 for sockets 1.5 for lighting 6mm for cookers and 8 for electric showers. Thanks for any help
Good explanation sir. Here I have a small doubt, please. As per standards, Up to 4kw have to take single phase i.e 230V, but here it is 7kw here we have to consider 3phase.( Is this correct or wrong, can u please explain)
Couldn't thank you more for putting up this video. Large details of cable sizing are summed up beautifully in 15 minutes video. There could be many more topics to cover but for beginners like this much more than I could expect for.
Thank you
Chris videos are great! Even if you are fully qualified its always good to refresh the brain. keep up the good work 👍
Bcos of this great guy i managed to finish my college assignment thank you sir...
Very nicely explained. Just need to rewatch a few times for it to go in!
If you had the kind of brain that takes in and retains stuff like that, there's no way you would be working on a site with tools in hand!
This video is excellent, wished there was more people that could teach this way - Thank you
Glad it was helpful!
im learning more from your videos then my course thanks man
Thanks for the video......I studied this years ago and didnt understand it at all...........God knows how I passed my exams but going over it again here was very useful and made me realise I learned most things on the job :-)
Cogibear after studying how did you get into paid employment?, I’m currently studying level 2 electrical installation (C & G), I’m worried about how I’ll find a job?
Thank you for posting this video. A well explained calculation procedure! Very useful.
I used the Ci rating factor from the OSG accidentally. Easily done. It's not surrounded by insulation, just laying on top
Hi, I would suggest table 7.1 of the on site guide may be of help to you. I have a video on you tube which guides you through the use of this table.
I think Ib should be used instead of In when dealing with the Ca rating (i.e. It=Ib/Ca) to determine the appropriate cable size due to elevated ambient temp.
great video i wish some would make a video on how you do a cable call for the AS/NZS3000 - AS/NZS3008 Australia standards
Dear Sir,
I would be very grateful if you could tell me which type of MCB is suitable for each of the following home appliances:
- Split air conditioner.
- Fridge.
Electric stove.
- the oven.
- microwave.
- dish washer.
- Washing machine.
Clothes dryer.
Thank you very much
sincerely
Khalid
Type B for everything other than air conditioning type C for that would be best
@@chriskitcher - or, do some basic electrical science study if you haven't already..
Hello This video helped me a lot to prepare for my exam. I got just one question for Cg factor (grouping factor ) for example when I got my circuit and I run it along with two other circuits the factor should be for 2 circuits or for 3 circuits ? I'm confused on that :/
I want to thank you for spending time to explain this sort of things to people. Really useful keep up good work.
Great explanation. We use this to show our apprentice, although we are on 18th edition now the principles the same
The end of the video misses the 80% rule and the 0.95% of cmin to be applied to the Tabulated Zs value in 7671 to allow for voltage fluctuations and a 50c rise in cable temp from the 7671 Tabulated Zs values when testing without load at about 20c in the field. The true max Zs permissable is actually only 1.10ohm.
i just want to add that the circuit protective device i assume is supposed to be B type 60898 not 6098
Hi thanks for your great video! Just a quick question is the design current the rating of an appliance or is it the load after diversity. So a Hob for example if it is a 7kw rated Hob would the design current be the amount of amps after diveristy ie: first 10amps then 30% of the remainder?
Many thanks.
Great video Chris, I'm doing 2396 at the mo and I have a quality teacher but always good to go over it for the bits I couldn't wrote down in time
what the bloody hell??? I'm 40 years old and I just realised that 20% is the same as multiplying by 1.2!!!!
Lol 12:13- "we don't really need to remember all that....."
We just need to remember hundreds of 'tables' to make it easier....
Useful vid though. Now in 2023 (18th) 32A BS60898 is tabulated at 1.37 and corrected in OSG for 80% as 1.1 ohms
What if my load is not just a load, it’s 6x motors in parallel
Hi chris, thanks for the video, I am new and learning. Can you recommend which books I can buy just specific to Cable Size Calculations and the relevant BS Standards to purchase, as lectured in your video
just to make a note in a new bs7671 18th edition, the voltage drop is in the table 4D4B and isn't on 4D5
What is CPC? in impedance calculations to get R1 + R2 = 6.44? Was this from a table?
Rich Gallagher circuit protective conductor. Look at page 196 on site guide for r1 + r2 values
Great video thanks
Great video. Thank you Sir
Chris, Thanks very much for this video is was very helpful. i have a couple of points/questions.
1. i thought when you have applied the rating factors to your cable this value is then called Iz? You seem to call this It?
2. At 8:55 i think your formula for Zs should have the R1+R2 in brackets, so Zs=Ze+(R1+R2)
3. When calculating the Zs you adjusted the figure for operating temperature of the conductor. if i was going to use the max Zs value in the on site guide i presume i do not need to do this adjustment?
Thanks again for posting such good videos
+mikebizzleuk
Hi Mike,
When you divide In by rating factors the result is It, It is the minimum current rating of a cable which is needed to carry the required current under the conditions indicated by the rating factors.
Iz is the current which a cable could carry under the conditions indicated. If you select a cable and than multiply it by the rating factors it will show you the current which the cable could carry under the given conditions, this is known as Iz. points 2 and 3, you are correct. hope this helps,
Kindest regards
Chris
+mikebizzleuk
Hi Mike,
It shown in a calculation is the minimum current carrying capacity of a cable which would be suitable for the circuit being calculated. Iz however is the current which a particular cable could carry when multiplied by the rating factors affecting it. As an example a 2.5mm which is has an It of 27A with a rating factor for Ca of 0.94 and Cg of 0.85 would have a current rating of 27 x 0.94 x 0.85 = 21.53A under those conditions. It is the current rating given to the cable in the tables in appendix 4. The rest of your assumptions are correct.
Yes, good point re, R1+R2. 'Big' r1+'big' r2 are never separated. They become one in the calculation for Zs so yes it should read '(R1+R2)' to confirm line and cpc resistance as one figure. 'little r1' etc is separate from 'little r2' as in, continuity...
Exam in a few hours si I thought I would give you a like and subscribe. Thanks
i think it should be bs en 60898
Is say 100 amp from 12 volt putting as much stress on a cable as 100 amp from say 230 volt ?
I checked table 41.3 in BS 7671 for 32 A and type B circuit breaker , I found the value of ZS = 1.15 not 1.44 as mentioned in the video (1.44 is for type 1 circuit breaker not for type B)
Zs values have been adjusted since this video was recorded.
You need to use the green book AMD No1: 2011
now is 1.37
kalimba De luna this was prob the 17th amendment.
Why in most houses as new build are all circuits in 2.5 twe. Even in loft. Surely some would have higher temperatures than others. But I have always seen 2.5 for sockets 1.5 for lighting 6mm for cookers and 8 for electric showers. Thanks for any help
Shaun Beard diversity
Well presented Chris. Thanks
Good explanation sir.
Here I have a small doubt, please. As per standards, Up to 4kw have to take single phase i.e 230V, but here it is 7kw here we have to consider 3phase.( Is this correct or wrong, can u please explain)
3 phase i.e 415V
Its a great video
excuse my ignorance but where is table L1 in the OSG?
If your using the green book then its I1 and not L1
page 190 in yellow copy
So we must put money by paying your book in order to fully understand your explanation...
It not his book it’s city in guilds which u need anyway if you want to pass the course
good video Chris.
Very helpful in completing my design assignment for level 3 2365.
Fr bro helped me complete my design table
Magnificent
New app. for cables calculation
I designed it...
Pls.enter link doun
Regard..
How to calculate MV cable?
Is There any formula for cable size calculation for given load,without using any table reference
Dharmendra Kumar
No, u need to get cable current carrying capacity without that u can not find.
How do u work out size of CPC? @ 10:47
Twin and earth comes with CPC already calculated if you're using a 10mm2 live conductors then you'll have a 4mm2 CPC
If you wanna calculate the CPC you need to use the adiabatic equation
See Table F4(i) On Site Guide
thankyou so much you don’t understand how long i was trying to find that for
J