SELV and PELV what is it? ? Learn the difference between the two types of transformer.
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- Опубліковано 4 жов 2024
- In this video we will answer the questions - what is a SELV circuit, what is a PELV circuit and what is the difference and if there is a difference then why does it matter?
Where do we use SELV circuits? What do the initials SELV and PELV mean? Lots of questions arise from these types of circuits, so why use one in certain installations but not use the other.
What are the implications for safety in the circuit and what should I be aware of?
There are lots of factors to take into consideration.
You may also want to view our video Extra Low Voltage and Low Voltage by clicking this link… • EXTRA LOW VOLTAGE AND ...
To view all our videos, click on the following link
/ @learnelectrics4402
SEE ALL - To view a list of all our LearnElectrics videos, click on the link below.
There are many videos on many electrical topics including Installation, Part P, 18th Edition, Testing, Certification, Lighting, Sockets, Ring Circuits and much more.
ua-cam.com/channels/YaJQnpO4XAp0yCgqzMkmfA.html
Hi David, aboslute legend for producting another fantastic video! Are you able to explain how we get the "safe to let go" voltages through bonding please? No one seems to discuss or mention this...
Where have you been!! With quality videos like this (and the rest of your playlist) you won't be long getting many thousands of subscribers.
Well, what a fantastic comment, thank you very much. Blame Covid, with my teaching work floored I needed something to do, so hence the videos. Glad you like them, there are lots to come. Yes, I need thousands of subscribers, tell your mates to tell their mates.
Thanks again. Dave
As it is said: one picture is worth of thousand words. Thank you very much! Finally I clearly revealed the mystery of uncertainty of SELV and PELV!
Thank you Victors and glad that it helped. Thank you for watching. Dave.
Can’t thank you enough for all the time and video that you doing Dave!Im constantly getting more and more knowledge from all of yours videos!
Excellent, keep going, there is always something to learn, me too.
This is such a good channel. I learn so much from your videos. Thanks.
Pleased to hear that and thanks for the support. Dave.
Thank you
Our teacher Dean Kirby has introduced this channel to the students, He is full of knowledge and experience who knows the best.
Your channel is one of the best, very easy to understand as it explains very simple and right to the point.
With using all the sources and the regulations if we need to refer to.
Many thanks guys and all the best
Amir, you are very welcome to share this channel with whoever needs to learn. The more you share it the better for everyone. And Dean Kirby too, share with everyone, our pleasure.
Thank you. Dave.
Best on the internet. I learn something from every video.
Glad to hear it and thank you for watching. Dave.
Best explanation ever!
Glad you think so, thank you.
Excellent video. Great work.
Thank you very much, appreciated.
Thank you once again Dave
You're very welcome. Thanks for watching.
Am learning alot from this channel.
I really need channel for my career.
That's good feedback, thanks Jeroboam. Lots more to come, keep learning. Dave.
I was searching for this method of explanation. Learning made a lot easier especially for those who want to go through them again later in life after learning once in college.
Equally beneficial for new learners.
Thanks 🙏
Thanks Asad. Yes, many viewers are learning a second time around. Everybody is welcome. keep watching, keep learning, its a great trade. Dave.
Asad, have at look at our video SELV AND PELV on this link.
ua-cam.com/video/2_0fZpcDYGw/v-deo.html
Are you sure about the connection between N and CPC on the primary of the SELV transformer- that would cause an RCD supplying to unit to trip. It’s our understanding that metal core / and or a barrier within the transformer is connected to earth.
Yes that's correct, the earth and neutral are divided at the service head.
The video is wrong. Never ever connect the mains Neutral and CPC wires.
Connecting one of the OUTPUTS of the PELV transformer to CPC is allowed, because that doesn't involve the mains Neutral wire. But never connect neutral and Earth on the input of a SELV or PELV transformer. As you correctly point out, that would trip the RCD.
Many thanks, this has been great help with my studies.
Brilliant Jonathan. remember there are over a hundred videos on the LearnElectrics channel and well over a hundred videos posts and articles on the website.
LearnElectrics the same as the YT channel, with dot com at the end.
Good luck with your studies, its a great trade to be in, its taken me around the world a few times. Dave.
Great video. New subscriber.
So, why would one use a PELV instead of a SELV, or vice versa? I think explaining this and giving real world examples would have been a great way to wrap up the video.
Cost, PELV is cheaper to make. If you are making thousands of something that only need a pelv transformer then those few pence difference add up over a year of manufacturing. Its always the power of numbers in factories. Thanks for watching, appreciated.
@@learnelectrics4402 How can PELV be cheaper when it requires an earthing wire? surely it's more expensive.
Great video. Well explained, thank you. I have been asked to install a light in a cupboard under the stairs in a two storey private detached house. The stairs are in two sections with a small landing between the sections. The best place to install the light is under the landing. This is the ceiling of the cupboard and is made of mdf. I am slightly concerned about fire regulations. I welcome your thoughts, please.
Thanks Mark, yes a valid point and it does matter. The best people to ask are your local wholesaler, they will have a range of high lumen lamps and fittings that have a very low wattage per lumen so they will not get as hot as an incandescent light. This can be a better option than putting some insulating material between the lamp and stairs, or do both.
@@learnelectrics4402 Thanks very much for your answer. I like the belt and braces approach.
Too right Mark. At least you can sleep at night knowing you have done all you can.
Keep safe, stay lucky. Dave
Fantastic video thank you.
Thank you Sean, glad you liked it. Dave
Thanks dave. Your time and your effort
Thank you Abdirizak, great comments. Dave.
Great educational video as usual. Your narration is so clear and diagrams very simple. I do enjoy learning like this. Thank you!
You are very welcome and your comments are appreciated. Lots more to come, Dave.
ive paid 4000 for an electricians course and these videos shit all over the course. so well explained and easy to understand. thank you
Sorry about the 4k but thanks for your comments about the channel. Keep watching, lots more to come. Dave.
This helped me out so much. Thank you!
Glad it helped Matthew. Dave.
Great video mate👍🏻
Thanks for the positive comments, they make the hard work worthwhile.
Lots more to come. Dave.
Reference the link between E and the neutral, the comment by eFIX (6MO) IS absolutely correct, the RCD supplying that circuit would trip immediately it was connected. There may be some misunderstanding as to why that is so, there will be a small voltage between N and E, this comes as a result of voltage drop along the N lead caused by any load back to the transformer, this may only be a few volts but sufficient current may flow to trip the RCD.
I should add that I cut my apprenticeship teeth on the 11th edition!! of the regs this volume was almost small enough to fit into a jacket pocket. I don't envy the electrician of today burrowing through the monster volumes or the 18th.
Great information John. I think I was taught on the fourteenth edition. A very thin book if I remember, compared to todays heavyweights. And of course, amendment 2 is due out in March.
Excellent video again. Thank you
Thank you so much. Thanks for watching.
5 star rating for you Sir
That's great, appreciated. Dave.
Brilliant stuff again, please make a video about explaining contactors! thanks
Thanks for the great comments. Lots more videos to come. We have added your request to the list. Dave.
a
Another great video ,most helpful.
Thank you Trevor, appreciated, and thanks for watching. Dave.
Another awesome video, keep up the great work.👍
Thank you Lee, glad you liked it, it makes all the hard work worth it.
Lots more videos to come, spread the word. Thanks again.
Dave
@@learnelectrics4402 Love all your videos keep them coming👍
Brilliant video. Many thanks.
Thanks for the positive comment. Many more videos on the way. Dave.
So I am trying to learn this stuff for an exam up coming. Q1/ PELV Why and WHERE would a designed PELV bit of equipment (audio/video IT) be Protected if its already ELV???? Q2/ How does it relay to the Energy Source 1, ES2 class or ES3 classes. Thanks mate
PELV is protected. It means that any problems on the primary side cannot get to the secondary side. All done by the way the Tx is manufactured. Plastic around the metal core, physical separation of primary and secondary etc.
Thanks a lot
Most welcome and thank you for watching.
Thanks, why secondary side of PELV need to be earthed? any examples about the applications using PELV instead of SELV
Can we just use SELV?
Type of construction, PELV is generally cheaper than SELV. Dave.
Good explanation. It should be mentioned though, that with the vast majority of SELVs I've checked, the interference cap between primary and secondary circuits is just a high voltage cap and not the required Y1 rated safety cap.
Thanks for watching.
Thanks alot ❤❤❤
You're welcome, thanks.
Thanks alot
Happy to help, thanks for watching. Dave.
Brilliant channel, thanks 👍🏻
Thank you Robert, great comment. lots more videos on the way. Dave.
Many thanks for your effort
You are very welcome Martin. 50 videos and counting, lots more to come.
nice video, thanks learned guy
Thank you. Appreciate your comments. Dave.
Great Video, thank you.
Thanks for your support Sam. Appreciated. Dave.
Thank you, this was very helpful.
Thank you Rhys, glad we could help. lots more videos to come. Dave.
Brilliant channel very informative keep up the good work. Would appreciate some insight & knowledge into photovoltaic systems if possible as wish to train in future to expand my skills. Thank you stay safe
Thanks for the great comments. Lots more videos to come. Dave.
Thank you so much for these brilliant and very well put videos. Could you possibly put something on regarding the difference between trailing edge and leading edge LED dimmer and lighting. Thanks
Thanks for the great comments. We've added your request to the list for future videos. Dave.
Great video thanks
Thanks Paul. Lots more to come.
I didn’t realise the primary side on the selv transformer could be referenced to earth.
In theory if you applied 12 v to the secondary side(from an external source), could you ever get 230v out the other side 🤔
Thanks for sharing, great video👍👍
That's how STEP-UP transformers work, 230 volts in and 500 volts out, or Safety Isolating Transformers 230V in and 230V out but the secondary is isolated from earth as in your typical electric shaver socket in the bathroom. Good question and thanks for the good feedback too. Dave.
Thanks again for another great video! Can you please make one video for emergency lighting and fire alarm system? Thanks again
Thanks for the great comments, appreciated. Lots more to come. Dave
@@learnelectrics4402 you are star! Also please share you social media info so we can follow you there as well!
Alireza, thanks for the feedback, most useful. Yes, Facebook will be getting some attention soon when we hope to start putting little updates on it 2 or 3 times a week. Thanks for reminding us, it is on our list. Dave.
Thank you.. 👍
Brilliant feedback. Thank you.
very good
Thanks Gary, thank you for watching. Dave.
Hey Dave, I wanted to ask, because there is no earth on the secondary side and you have a single fault on the 12v side for example why would you not get an electric shock if there is no earth return path
We have a saying, if there is no OHM for the current to go to, then the current won't leave home in the first place.
there is no electrical continuity to earth on the secondary side.
Thank you ❤️
You are very welcome Shaun, glad you find them useful.
Bux
thanks for this video =)
Thank you, appreciated. Dave.
Great vid. Have you got a video explaining star and delta at all? I have looked but cannot see it.
Not yet but what a great idea for a video. I'll get onto it, its now on my list.
Thanks for watching. Dave.
Brilliant
Thank you, your great comment is really appreciated.
Lots more videos to come.
Bux
SLEV is it safer then PLEV? if this the case why connect the earth to the secondary winding? and where can be used (PELV)
SELV and PELV transformers have slightly different construction and materials.
There are some examples of use in the video.
Hope this helps
If you not done it yet can you do one on FELV please. My exam is in November please hurry. I am doing research and reading but getting overly confused and mixing things up.
Its on the list (now). I'll see what I can do Sean.
Hey Dave, I wanted to ask because the earth is seperate in a SELV transformer why wouldn’t I get an electric shock even if there is no earth return path because you still got live and neutral which are live conductors but only at 12v but why does the return path not being there reduces the risk of an electric shock?
Have another look at the video. If you grab hold of the secondary side, there is no earth continuity from your feet back to the the secondary side, there is just no earth path. the current wants to get back to where it started from and it can't. the primary side has nothing electrical to do with the secondary side.
@@learnelectrics4402 so what you’re saying is that because the circuit is not completed the current has no where to go because what I didn’t understand was even though you touch live and neutral I thought that would just give you a little shock
@@learnelectrics4402 thanks mate so what you’re saying is primary side has L N and E but the secondary side doesn’t so in order to receive an electric shock the circuit needs to be completed with an earth being there? But because there’s no earth the current hasn’t got anywhere to go to so it disperses?
Are you sure this is correct? Earthing the neutral conductor at the primary side?
Neutral and earth are the same point electrically back at the incoming point of entry. Thanks for watching. Dave.
Thanks for answering. Then you are introducing multiple connections between the neutral conductor and earth. Right? I believe the general rule is that neutral to earth connection should only be made in one location only. Normally close to the secondary side of the supply transformer. The connection being the so called system reference conductor. I would have expected that your PELV drawing showed that neutral to earth connection was made at the secondary side of the transformer only. Why do you have it additionally on the primary side? Does it do anything there, other than creating circulating currents in the earth paths? @@learnelectrics4402
Safety Extra Low Voltage - NOT Separated !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
No, no, no.
Have a look at page 43 of the Wiring Regulations. Separated Extra Low Voltage. And also look at page 36 of the Regs book. Thanks for watching. Dave.
So Does selv act like a isolation transformer
Yes, that's it. It isolates the primary from the secondary. Thanks for watching. Dave.
@@learnelectrics4402 thanks Dave great uploads.
There an LED Driver output more then 120vDC and they write on it SELV, INVENTRONICS Driver, this name of the manufacture
If its measured open load, it may be slightly above 120v, what is it on-load, as it may drop. Check it on and off load before you make any decisions about it.
Is fire alarm system a SELV or PELV I have seen on blogger cut out the earthing wire in the circuit he did
All fire alarm systems are different Dennis. Some are using 12 volts, some are using 230V. They can be double insulated in which case they don't need the earth, some systems use the earth. Hope this helps.
@@learnelectrics4402 thanks
Hello, thank you for your nice videos. Could you suggest me some tutorial books about these topics, like selv, tnc-s systems, diversity and etc. BS 7671 talks about all of them but it is good as a source to refer but not good for education.
There are no books about the specific topics you mention, just part of other books and then only half a page which is why I have made these videos to help you.
Have a look at this video, DIVERSITY and MAXIMUM DEMAND, click on the link below
ua-cam.com/video/TV2IZtmydm4/v-deo.html
Have you been to our LearnElectrics website? Same name as the channel, just add dot com to it. You can enter a search word and all the relevant videos will come up. There are well over 100 videos and articles to help you.
Thanks for watching. Dave.
But why we even use pelv then? Why not only selv or it because of cost only?
Its just the way the industry developed, better things come along but the other methods are still used in places.
please be aware if viewing this in Australia/New Zealand, SELV is SAFE extra low voltage, ie: pure 12v or less in and out
Thanks for the input, appreciated. I've noted that. Dave.
Must the selv device comply with EN 61558-2-6?
If you want to comply with the Building Regulations then yes. If you use a different shaver socket then you are responsible for ensuring it at least meets if not exceeds BSEN61558-2-6. Hope this helps. Dave.
@@learnelectrics4402 Dave,thank you for answering.I am not a native speaker,could you please clarify the meaning of "shaver"?
Thank you.
Electric razor. A two pin connector and isolating transformer for an electric razor for trimming a man's beard.
Ok,now,i got It. The load haven't been connected to earth leads.
🤔 are SELV circuits better than PELV circuits because earth is connected to both primary and secondary on a PELV circuit? 🤷♂️
SELV circuits offer more safety than PELV. Check out the video again Lester. Because there is no earth path back to the primary side, fault current should not travel through the body to earth in a single fault condition on the secondary side. Hope this helps.
@@learnelectrics4402 thank you 🙏🏽
You a very welcome. Dave.
You didn’t give example of pelv
have another look at the video Nisar. SELV is no earth contact between sides, PELV, there is.
Why would I want anyone want to use a PELV system if SELV seems like the safest option?
Good question Patrick. PELV transformers are very slightly cheaper. In mass production, if you are making 100 million "thingys" that don't need SELV, then you can potentially save thousands of pounds. Thanks for asking. Dave.
Hanks
Glad you liked it.
Why would you want to use PELV when the SELV is the safest???
In a mass production scenario, cost. PELV is cheaper to make. Dave.
Perfect timing to find your video eh? 😂 thanks
Glad we worked the timing for you. Happy to help.