I'm new to Electrics and i must say this tutor is genuinely concerned about imparting knowledge and information about this subject. I am thankful for the opportunity to have stumbled upon this TH-cam page. A career change is in the making. Well done Guru!!!!!
I wish I had a tutor with such a brilliant approach explaining this topic with a passion more than lecturing. I am so grateful and saddened that you come 23yrs late. Your just Brilliant👏👏👏👏👍👍
Great comments, thank you. I have always tried to teach the way that I would like to have been taught. I had one very, very, good boss, Mike, who took the same approach that I now take. he was a fantastic mentor. I wish I'd stayed with him and learnt more.
Great explanation as ever Dave. @14.20 in the video you correctly explain, that with the bonding in place, during a fault all metalwork (exposed and extraneous) will rise briefly to mains potential. I completely agree, but, the customer is standing on the general mass of earth during this brief fault period, so would therefore still feel the effects of the fault current through his body!! Shock😵💫 Great videos Dave, keep them coming mate👍👍
It is generally assumed that the customer, or you, would be stood on a synthetic carpet, floor tile, wearing shoes etc. that will all limit current flow compared to a bare hand on a metal part. bathrooms are areas of concern because we may be have more exposed bare skin in a bathroom. Good question, hope this helps.
You thank us for watching and say it really is appreciated. It's the other way round, thanks for making these simple to understand videos - it REALLY is appreciated.
Great video again and thank you.Can you please make some videos about fault finding especially how to trace a circuit or a faulty RCD or how to perform a ramp test on a RCD.Thank you
Another great explanation with really easy to understand clips. Why do we never show cast iron soil pipes or copper waste pipes that go to ground, as they still exist ? keep up the good work .
Hi Dave I have a question i hope you can just give me a little clarification on . When carrying out preliminary cable design for a given circuit we use this formula = ( milliohms per metre x Length x multiplier Factor for maximum operating temperature ). Do we still need to use the the maximum operating temperature factor for the given cable type in the above formula if we use the Zs measured value (the 80% rule ) against the protective device . example A Radial circuit is wired in 2.5mm 1.5mm , the Length is 25M the Calculated value by design would be ( 19.51 x 25 x factor 1.2 ) divided by 1000 which would = ( R1+R2) as 0.58 Ohms obviously add this value to the Ze and then check against the protective device Zs measured value ( 80% rule ) to confirm is this value complies . or would we just use the formula this way ( 19.51 x 25 ) divided by 1000 = ( R1+R2 ) = 0.48 ohms added this value to the Ze then check against the Zs measured value of the protective device . I just cannot find a straight answer on this and from watching your very hugely informative videos on the subjects in the past the formulas you use do not have the temperature factor included which has made me wonder if this is because of the 80% measured rule Zs for protective devices .
The data in the Wiring Regs book is the figure WITHOUT temperature adjustment. Data in the OSG is with the 80% temperature adjustment applied. The Zs in the OSG is made up of Ze PLUS R1+R2 with the 80% applied to it. The Zs in the osg will always be smaller than that shown in the Regs book. Always apply the 80% rule before adding to the Ze. Hope this helps. Dave.
Hi Dave Just a quick question, you used a metal mirror in a bathroom as an example and to not earth it. If there was say a light up over it for some reason and one day the live wire from the light came in contact with the mirror, I take it the mirror would become live and if it was earthed it would trip the circuit. At the moment I'm working in a water tower, water pipes coming up out of the ground Extraneous parts to be earthed, but there are also metal ladders bolted to the wall all the way up the tower. I'm being told to earth them from the pipes but they cannot introduce a potential into the building so I'm thinking it might not be the best thing to do, but them again if for some reason or another a live cable came in contact with one of the metal ladders it would become live?? Where does one draw the line tho. Really enjoying your videos, learning so much from them.
I was making reference to a non-electrical stand alone shaving mirror, the sort you can buy from the chemists and place on your bathroom shelf for a shave. No electrical connections.
Thanks again for he video. I think I understand what your'e trying to explain, but can I ask (1) in a bathroom with a shower, surely it's unlikley that (under fault conditions) a person can touch the exposed conductive part of the shower and basin taps at the same time? (2) if the taps are equipotentially bonded and the person is (say) washing his hands and nowhere near the shower and a fault develops in the shower - is he not likley to get a shock as he's not touching the shower and hence at a different potential?
We are just linking all the parts together. It doesn;t matter which goes to where, this was just an example. You can link the taps to the shaver or the light, your choice. Whichever is convenient. Thanks for watching.
The cpc is only applicable to a _final_ circuit. In short, a circuit from the consumer unit. It is a parallel neutral wire. If a fault on the final circuit the return is back via the cpc with a high current flow as little resistance is in the cpc - most of the time. This high current trips the circuit's breaker.
Exactly John, there are so many little things that are just assumed when a slight change could make for better understanding. Great comment. Thanks. Dave.
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I'm new to Electrics and i must say this tutor is genuinely concerned about imparting knowledge and information about this subject. I am thankful for the opportunity to have stumbled upon this TH-cam page. A career change is in the making. Well done Guru!!!!!
What great comments. Thank you. Very much appreciated, There are over 250 videos on the channel. Dave.
I wish I had a tutor with such a brilliant approach explaining this topic with a passion more than lecturing. I am so grateful and saddened that you come 23yrs late. Your just Brilliant👏👏👏👏👍👍
Great comments, thank you. I have always tried to teach the way that I would like to have been taught. I had one very, very, good boss, Mike, who took the same approach that I now take. he was a fantastic mentor. I wish I'd stayed with him and learnt more.
Brilliant as always. Not only do I use your videos to learn but as a great refresher and clarifier. Keep up your amazing work. Thank you
Thanks for the support, appreciated.
Great explanation as ever Dave. @14.20 in the video you correctly explain, that with the bonding in place, during a fault all metalwork (exposed and extraneous) will rise briefly to mains potential.
I completely agree, but, the customer is standing on the general mass of earth during this brief fault period, so would therefore still feel the effects of the fault current through his body!! Shock😵💫
Great videos Dave, keep them coming mate👍👍
It is generally assumed that the customer, or you, would be stood on a synthetic carpet, floor tile, wearing shoes etc. that will all limit current flow compared to a bare hand on a metal part. bathrooms are areas of concern because we may be have more exposed bare skin in a bathroom. Good question, hope this helps.
You thank us for watching and say it really is appreciated. It's the other way round, thanks for making these simple to understand videos - it REALLY is appreciated.
Well, let's say that we all appreciate each other. Thanks for your support. Dave.
Your use of images and explanations are fantastic as always. Thank you so much for your content and the time you put in to get these videos out.
You're very welcome and thanks for the great comments, appreciated. Dave.
As someone that is a sparky but no longer does that job, that was a brilliant explanation and a good piece of revision.
So glad it helped, thank you.
Brilliant mate. You make it so easy to understand. I wish you worked at our college.
Thanks for the confidence, appreciated. Good luck with your courses. Dave.
Cheers.....Great info. Thank you for your time and efforts in producing these videos.
My pleasure and thanks for the comments. Dave.
Very informative video, which you have put a lot of work into --many thanks Dave
Thank you David, always appreciate your support.
As usual simply the best !
Glad you think so, appreciated.
As always Informative and helpful video for everyone.
Thank you, thanks for watching. Dave.
thank you so much you are very nice teacher and knowlegable
You are welcome, great feedback. Dave.
Thanks for the great work
My pleasure, thank you.
*Excellent.*
Thank you, appreciated.
Great video again and thank you.Can you please make some videos about fault finding especially how to trace a circuit or a faulty RCD or how to perform a ramp test on a RCD.Thank you
Good point, I will add it to the list. Thank you.
Another great explanation with really easy to understand clips. Why do we never show cast iron soil pipes or copper waste pipes that go to ground, as they still exist ? keep up the good work .
Yes they do, and I know of four houses with lead waste pipes. Good reminder.
Hi Dave
I have a question i hope you can just give me a little clarification on .
When carrying out preliminary cable design for a given circuit we use this formula = ( milliohms per metre x Length x multiplier Factor for maximum operating temperature ).
Do we still need to use the the maximum operating temperature factor for the given cable type in the above formula if we use the Zs measured value (the 80% rule ) against the protective device .
example
A Radial circuit is wired in 2.5mm 1.5mm , the Length is 25M the Calculated value by design would be ( 19.51 x 25 x factor 1.2 ) divided by 1000 which would = ( R1+R2) as 0.58 Ohms obviously add this value to the Ze and then check against the protective device Zs measured value ( 80% rule ) to confirm is this value complies .
or would we just use the formula this way ( 19.51 x 25 ) divided by 1000 = ( R1+R2 ) = 0.48 ohms added this value to the Ze then check against the Zs measured value of the protective device .
I just cannot find a straight answer on this and from watching your very hugely informative videos on the subjects in the past the formulas you use do not have the temperature factor included which has made me wonder if this is because of the 80% measured rule Zs for protective devices .
The data in the Wiring Regs book is the figure WITHOUT temperature adjustment.
Data in the OSG is with the 80% temperature adjustment applied.
The Zs in the OSG is made up of Ze PLUS R1+R2 with the 80% applied to it.
The Zs in the osg will always be smaller than that shown in the Regs book.
Always apply the 80% rule before adding to the Ze.
Hope this helps. Dave.
Hi Dave
Just a quick question, you used a metal mirror in a bathroom as an example and to not earth it. If there was say a light up over it for some reason and one day the live wire from the light came in contact with the mirror, I take it the mirror would become live and if it was earthed it would trip the circuit. At the moment I'm working in a water tower, water pipes coming up out of the ground Extraneous parts to be earthed, but there are also metal ladders bolted to the wall all the way up the tower. I'm being told to earth them from the pipes but they cannot introduce a potential into the building so I'm thinking it might not be the best thing to do, but them again if for some reason or another a live cable came in contact with one of the metal ladders it would become live?? Where does one draw the line tho.
Really enjoying your videos, learning so much from them.
I was making reference to a non-electrical stand alone shaving mirror, the sort you can buy from the chemists and place on your bathroom shelf for a shave. No electrical connections.
love you
Thanks for compliments, appreciated.
Thanks again for he video. I think I understand what your'e trying to explain, but can I ask (1) in a bathroom with a shower, surely it's unlikley that (under fault conditions) a person can touch the exposed conductive part of the shower and basin taps at the same time? (2) if the taps are equipotentially bonded and the person is (say) washing his hands and nowhere near the shower and a fault develops in the shower - is he not likley to get a shock as he's not touching the shower and hence at a different potential?
We are just linking all the parts together. It doesn;t matter which goes to where, this was just an example. You can link the taps to the shaver or the light, your choice. Whichever is convenient. Thanks for watching.
The cpc is only applicable to a _final_ circuit. In short, a circuit from the consumer unit. It is a parallel neutral wire. If a fault on the final circuit the return is back via the cpc with a high current flow as little resistance is in the cpc - most of the time. This high current trips the circuit's breaker.
Thanks for the input John. Appreciated.
I have met electricians practicing for 30 years who do not know this.
I think we both have and its so important to understand it.
If the earthing cable, bonding and cpc conductors were different colours all the confusion over this topic would dissipate.
Exactly John, there are so many little things that are just assumed when a slight change could make for better understanding. Great comment. Thanks. Dave.