Maximum Demand & Diversity for Electrical Installations
2015 ж. 22 Мау.
152 150 Рет қаралды
Methods of determining the maximum demand for an electrical installation.
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This man can take complete bollocks and make it understandable, many thanks John !
marky marks haha class and very true 🤣
The world doesnt deserve this man. What an absolute top bloke
Good Sir, countless students lives you have saved!
Wonderful! In four years as a trainee and improver electrician, I have never found anything that explains D & D so clearly.
removed all of my worries in 20 minutes. A very clear example of how a teacher who truly understands a subject can explain the subject matter in a very simple and understandable way.
Thanks for a very good talk. Back in the 1980s I ran a small NICEIC firm, and on an inspection day, the subject of diversity came up. I said that the diversity recommendations in the regs. (15th edition back than - unchanged today) resulted in exaggerated maximum demand figures. The inspector agreed. He said that the electricity suppliers had vast experience, and that, for domestic installations without storage heaters, they allowed six watts per square foot - and that was when, for domestics, the only forms of lighting were tungsten filament lamps, or fluorescent tubes. You calculate loads on 230 volts: this is the official pressure, but the suppliers are crafty, and in most parts of the UK, the supply is 240 volts, and quite often near 250. Taking a very untypical case of a property of 2,500 square foot, using 6w/sqare ft., without storage heating, gives a maximum demand of just 65A! An aside: one lighting circuit in any domestic is very bad practice, as, in the event of a fuse blowing or a breaker tripping, the whole place would be cast into darkness after dark. This could cause great danger on staircases, especially for elderly, unwell, or frail folk.
I've just spent 3 hours going through a range of your videos and just had to leave a comment to say thanks. What a superb learning exercise that was. Thanks so much.
Thank you so much for taking the time to post this video. Superb, crystal clear, explanations of everything. Totally invaluable. Bless you
Thanks so much for the help! This video has shed some much needed clarity on a particularly cloudy part of BS7671 :)
Nice one John - another top quality video telling the very important stuff in such an easy to follow and understand way
I was scratching my head, looking at the tables. . . thank you so much for the explanation. . . make sense now.
As Usual John...all good stuff. I was recently in a property with two consumer units 100Amp main switch...one running the home...the other running the storage heaters...which did make me wonder about the incommers from the DNO.....holding up under the load of the whole housing estate drawing maximum load overnight.....I suppose there would be no ice on the footpaths outside, as an added bonus of the possible overheating.....In your example you cannot have any storage heaters at all...although this home had them, albeit, on a separate consumer unit....and it had been like this from day one...working fine...Addaed to the were four 32 amp fuses on the main board Kitchen sockets, upstairs sockets, downstairs sockets, cooker point. plus a 45amp shower fuse....crazy stuff according to the regs.... One board 1x 45 amp...4 x 32 amp....1 x 16 Amp and 3 x 6 amp...and then the storage heater board... full of 16 Amp fuses x 5.......
Your sense of humour is hilarious!!! 👍🏻 great great videos !
Brilliant mate struggled massively with this concept in college your way of explaining it was simple yet greatly effective thanks john✌️
Thankyou John!Very consise and informative as always. Another excellent tutorial.
Thank you so much! This is exactly what I needed to know and you explained it so clearly and simply. You are a born teacher xox
John you are my “ go to “ Electrician when I need a course refresh. Brilliant presentation as always
Great video John , working my way through your videos, really helpful 👍
JW you are legend, thank you for making things easy to understand 👌🙌
Thankyou for your excellent explanation of electrical wiring, you explain it so simply and is very helpfull. Thanks
Thanks you just helped with my design project for college! You made this easy to understand. Thank you so much!
Thanks john for putting the video up much appreciated :D
Hi Thank you for extremely good explanations. Your teaching methods are excellent. Best regards Jo
A very good presentation. By a true professional
So I just had my exam today on the electrical installation theory and technology unit of my course and this video helped me a lot with understanding demand and diversity so thank you very much for the video. ☺️☺️
Love the video. I understood the whole thing first time. Nice one👍
David Elgood. JIB Approved since 1973 still working. Its a pity that the IET does not consult some one like you before they print the IET Regulations. I am amazed that the new regulations about fuse boards are now being changed to metal to "contain a fire". We are told that most fires are caused by a loose neutral connection. I wrote to Wylex MD and pointed out that the old wooden fuse board had two retaining screws for the mains cables, and a deeper depth for the cables. These were when it was 16mm tails. We now have 25mm tails and a smaller depth for these cables but ONLY ONE SCREW FIXING. I copied this to the IET and received a reply, that we should ensure that we tighten the fixing screws correctly. I thought prevention of a fire is better than containing a fire! The meter has two fixings for cables but the part where the fire starts has only one.
If multi stranded tails were used this would resolve the problem of meter tails being loosened merely by moving them, it would help save electricians finger joints as well
why is it that the main incomers are not in clamps like you see for the meter connections, the other thing that is dim to me is that they suggest on a TT supply you should have an type s 100ma which makes sense to protect single insulated cables as you might not have enough current line to earth to blow the main fuse, but to me the danger is the tails that you can't clamp as tight as you should be able too first knock of the tail and they are loose in the connection. not so bad now with the stuffing glands. but still it's silly
Brilliant video, really appreciate it, thank you John.
Many thanks Mr. John.
Thanks John! Another really helpful video
Your a legend. Great videos and great explanations. Thank you for all your good work
JW, Thanks for making this. I have liked it and sorry I hadn't done that before as I have watched it a few times!!
Thank you so much John
Thanks very much John, I'm preparing for my NVQ and I must say watching your videos helps me a lot in my studies. Thanks again and keep on doing the videos. Cheers Richard
He does explain everything very well and makes it understandable. When are we going to see him tickle the ivorys however.
Excellent presentation thank you Sir
Really clearly explained so many things I could ask you. I would love you to explain selection and erection of equipment in part 5 of the BS7671 19th edition esp cross- sectional areas of conductors
Thank you very get much This is exactly what I needed
Great video John
This is so much more sensible than what we do in America. A 50 amp stove/oven requires cabling that can take 50 amps continuously. It's such a waste of materials.
Thanks JW
what A legend this man is!
The trouble with the MD calc on ring mains is if you have 3 rings its 57 amps. thats ony 3 mcb's. by the time you stick a hob a oven, immersion you soon nudge up to 100 amps & often exceed it. I find working out maximum demand a waste of time as its just not accurate enough, its always way, way over the actulal load. There should be a new method entirley utisling a clamp meter & introducing certain loads for existing propertys
Hi Thank you for a very well presented video. Ring main diversity/demand: can the circuit be limited to 20A with a 20A MCB. This is in order to only use 20A in the calculation instead of 32A. Best regards Jo
Thank you very much.
Very informative, thank you
Incredible video thanks a lot
Thanks John for clearly explaining diversity. Now I am know what's going on Please more films like this.
All 300+ other videos arranged by category here: kzhead.infoplaylists
Beautiful logic - the woe's of bs7671!
great videos john very informative and educational having this insite from your vids is great knowlege for me thinking of becoming a sparks in the furture you would be very respected also in the college classroom keep up the good work many years in the trade gas safe plumber wayne
Thank you 🙏
John hi. Excellent video and thank you for sharing your knowledge with us. What about a high rise buildings? Lets say 50 floors skyscraper with 50% of the building offices and the remaining 50% residential luxury flats. How can we apply maximum demand and diversity?
thank you
It's really helpful.🤗🤗
I can see why you might apply the diversity calculation to a circuit breaker for a given arrangement of appliances but I don't think the diversity calculation should compromise the wiring, which should be chosen for the maximum possible amperage to avoid future rewiring of the house. It also has a lower wiring resistance, which might offer more options for the choice of circuit breakers.
Thanks for sharing 👍
I just love your dulcet tones Jhon; woof woof howl !!, !!
Fantastic very clear and easy to understand, just one question John, what with the use of LED lights theses days and the current they draw is so small why do we still need to use a 6AMP breaker ? Surly a 2 amp or a 3 amp would be suitable? I know no one makes circuit breakers which current ratings less than 6AMP so maybe it’s time they did ? Fantastic video John as always 👍👍👍❤️⚡️
I’ll show this to my wife. She seems to manage to get all the lights at once 😂
You have the same issue too?
Brilliant
Thanks for the reply to my previous post John. I've got something that you may find interesting to cover or maybe not! I've added a few usb charging sockets in our house, I installed a metal clad version in my workshop, whilst using it to charge my phone, I took a call with it plugged in, I quickly noticed a buzzing in my ear and what felt like electrical shock. I tested between the iPhone's metal case and the earth and had 96v AC. Again tested it to the gnd connection on the USB socket to earth and again, unsurprisingly same voltage. To cut a long story short I tested the units in the house which are better quality MK units and to my surprise I had the same reading. I'm assuming it's to do with emc components? Would love to hear your views on this!
It's the EMC parts as you rightly said, these can be a big and destructive nuisance. An example is computer peripherals, generally a desktop PC is earthed, not all peripherals ie printers are earthed. If all of the peripherals are plugged in before the mains supplies are connected things are generally OK. However if the "data cable" between a printer and PC are connected after the devices are plugged into the supply the "floating" chassis of the printer (usually sitting at roughly half supply voltage) finds it's ground via the PC. Many years ago in the days of parallel printer ports I encountered MANY motherboards that worked fine EXCEPT for the parallel port as a result of destroyed semiconductors. I have seen similar happen with external USB hard drives where they use external power, frequently the USB interface in the drive caddy fails as a result of being connected to the PC after being connected to their supply. The "tingle" you got from your phone should be at a safe level of current...
thanks a lot
This video was exactly what I needed to confirm the selection of the protective device for a new cooker circuit. Customer has a new double oven with induction hob which I had to phone the brand manufacturer for the maximum demand which tops out at 13.9KW ! ! ! The appliance manual specified 6mm cable but did not state the maximum demand. So 60.4 Amps. 10A + 30% of 50.4A (16A rounded up) with no additional socket is 26A (rounded up). To me this seems mighty low when you consider the appliance's rated maximum demand. I'd be much more inclined to install a 40A breaker rather than a 32A as the cable is good up to 47A (clipped direct)? Any thoughts?
As JW explained the diversity calculation chart in the OSG is a guide. As an electrical engineer you will have a wealth of experience and can use your own diversity calculations. You will probably find that the calculations in the OSG are on the conservative side and so in practice they will be less. Be aware that if you are designing circuits you should have Professional Indemnity insurance because if you under estimate the loading of the circuit which results in the circuit breaker overloading (or worse) then your client will have leave to start legal action. Also you appear to be using the nominal voltage of 230V to calculate the connected load, you should be using the actual voltage which is usually nearer to 240v (when the nominal voltage in the UK was changed from 240v to 230v this was done so that appliances where manufactured to the same nominal voltage across the EC the electrical supply companies did not change the winding settings on all their transformers in the UK so the actual voltage in the UK is still 415/240 volts).
Superb
I'm sure lighting circuits draw more that 1380W, because my Dad used to walk around the house, turning lights off saying 'It's like Blackpool Illuminations in here!' and I'm sure they use more than 1380w.
I changed my dad's house to literally all led and he still goes around turning everything off. FML.
@@barrybritcher That's because old people who lived through the depression know what it's like to not take anything for granted and conserve everything you can. Which is the right way to live, anything beyond that is wasteful.
John a brilliant tutorial excellently executed. Its been over 20yrs of not understanding diversity thank you again for sharing your priceless knowledge..
Im doing 2 electrical installs of houses that need expected loads for each property for DNO to supply. how would you calculate amps for each property
Hi John,,,, So what happens if you have the circuits you have suggested along with the storage heaters? Is it a no go?
Have an 9Kw electric shower, Electric oven, 3 ring mains, 2 16Amp spurs (attic and conservatory) 2 lighting and 40 Amps out to the workshop/office and Eon just changed my incomer fuse from 100Amp to 60Amp........
Fantastic video as always John. Do you think there will ever or in the near future plans to down rate fuses/mcb's or even conductor size. I'm not an electrician and there is possibility a clear reason why not! Looking at your calculations and your explanations no (certainly modern) house would get near to a 6A load on a lighting circuit for example. I understand the protective device is there to protect the wiring?
Mk18T Yes, the MCB or whatever else is there to prevent the wiring being damaged, and even the smallest 1mm cable has a rating far above 6A. However using a smaller rated protective device will reduce the amount of energy if a fault occurs, so there is some sense in using smaller devices. 3A MCBs are available and could be used for lighting circuits.
The protective device i.e the earth cable or now called CPC is to protect your life by having a path to earth hence to the centre taping of the transformer and back to your fuse/ mcb and cutting of the power to what ever caused the problem .
cheers J...informative as always is one phase limited to 100 amps ? and to have 2 shower and 1 cooker circuit would always require having additional phases ?
damon btc Usually yes - above 100A you would normally get 3 phase, 100A for each phase. It's possible to have a single phase supply above 100A, such as a 200A supply, but generally not supplied like that as it's better to load the three phases equally, and it's usually easier to fit a 3x100A supply.
For ring mains it says 100% of the point of highest utilisation, not whole ring main aggregated, I.e. a “point of utilisation” is one socket ore more particularly whatever is likely to be plugged into it. ?
Surely if you put the hob and oven you mention with a combined loading of 50A it will trip the 32A circuit breaker when it's all switched on from cold? Or am I not understanding something here?
Having watched your videos with aspects of the clarity that you explain, I find myself in a situation that seems perplexing to the internet in terms of regs vs manufactures, I have had an oven and Hob in my Flat, new about a year ago and have purchased two new products of oven and Hob as relocating the initial appliances in the flat above mine as the oven and Hob have failed in this property, I own both and so decided to upgrade my own and put the fairly new ones in the flat above to replace failed ones, the oven and Hob both state that they require a fused spur connection and I wanted to know if this could be done from the 45 amp cooker box that is supplied with 6mm cable and protected by 32amp at the consumer board. The Hob has a moulded plug on Zanussi and was plugged into cooker box the oven has a flex that was connected to the 45amp cooker box hard wired,, I have had no issues but feel that the oven is not protected other than by the 32amp fuse in consumer unit. Is it better to take two fused switched double pole units or a double gang switched socket. And what cable to take from cooker unit to said spur. I would appreciate your input on this as the community seem divided. In advance this is in the UK and the consumer units are both protected modern ones. Yours respectfully David
A 32A circuit can have various things on the end - a connection plate, a double socket, single socket, FCU with 13A fuse, or various combinations of both. There are advantages and disadvantages for all of those. However generally go with whatever the appliance is supplied with - so if it has a plug, fit a socket, if the instructions state a 13A CFU then fit one of those. 32A for a single oven is fine - the only protection is for a short circuit, and the 32A MCB will do that. There is no need for overload protection, a single appliance can't overload anything as it's power rating is fixed. Cable needs to be suitable for the load - for a single oven, 1.5mm² flex is common, although nothing wrong with using larger sizes provided they will fit into the terminals on the oven.
I thank you very much fore taking the time to put my mind at rest, I have investigated a little further and decided on a 45amp dual appliance outlet plate with one going to a single socket and the other to a 13amp DP S/W fused connection with 6mm cable supplying both matching the 45 amp cooker unit with the load going from each appliance one by plug and the other into fused connection. And a similar approach for the other two but the Hob is an AEG and recommends hard wiring. Again thank you.
Hi John.... Using your example of 97Amps total....great with a 100 Amp main switch in a Consumer Unit..but, what is the suppliers main fuse is only 60 Amps?
If only 60A fuse, then you can't have an installation which requires more than that. The supplier may be able to fit a larger fuse in some circumstances, or the supply can usually be upgraded if you pay for it.. Otherwise you are limited to the 60A, so no electric showers or other high loads.
Had a new meter fitted 2 weeks ago and they changed our fuse down to 60A and put a big sticker on it without asking if it was OK!
Diversity was discussed on a respected training course I attended recently and appears to have been calculated very differently for an entire installation. You calculated diversity on each circuit & added them up (which appears straightforward), whereas they appear to have applied the 100% + 40% of Item 9 in Appendix A of the OSG to the entire installation. The wording for item 9 is a little unclear - "Standard arrangement of final circuits" and you seem to suggest this is used for sockets only. So I'm confused as to which approach is right or whether both are? This is the example they gave us for a consumer unit with 4x32A circuits (cooker + kitchen + downstairs + upstairs rings), 1x40A (shower), 2x6A (lighting) Total =180 Amps Diversity for entire installation: 40Ax 100% + 140A x 40%(.4) = 40A + 56A which totals 96 Amps They also mentioned allowing 20% for redundancy.
Either way is ok, and there are probably other methods that could be used. The point is to get to some reasonable assessment of what the likely maximum load will be, it's the end result which matters, not how you get there.
very lovely english man! nice watching
What about the maximum demand & diversity for the following consumer units, how should I do the calculation for these? Should they be calculated using the "sockets" formula: dishwasher machine, washing machine, tumble dryer, fridge, cooker hood, coffee maker, food processor?
Come teach us please, we need somebody like you
Such a brilliant set of resources! By watching a combo of your vids we've managed to safely wire up our greenhouse heating benches! An (admittedly token gesture) tenner has been put your way - worth every penny
As ever, I understood every word . Many thanks!!!
Thanks John, It's a pleasure to listen to someone that lives in the real world of electrical education. I often wonder how many regulation editions are to be printed in the future? Electricity hasn't changed at all, so why many regulation editions? i know It's a learning curve but one that should be learnt a long time ago. It's not a Harry Potter novel! I will vote for you to be the last author of 'Electrical Regulations The Final Chapter'!!!
Hi can you please give some advice on calculating the maximum load and supply need for a office conversion. It is being converted to 14 small 1bed room flats with individually kitchen bathrooms each flat having it's on 6 way consumer unit and the communal area having a similar 6 way board all lighting is led. Thanks
I love your videos as they explain concepts to a keen DIYer like me. I understand all you say here but I'm confused about the Max Demand overnight if you included storage heaters. The DNO fuse in my property is 100A (I have storage heaters). At 28.15 in your example you say the total demand would be 97A. If you then add 44A (in your example at 25.05) the total demand would be 141A. Would this not blow the DNO fuse or is the assumption that the other overnight power consumption is very low?
It's assumed that other consumption at night will be minimal, so you can use a large proportion of the available capacity for the heaters. The idea behind electricity being cheaper at night was from a time where there was very little usage overnight as most businesses were closed, and it was beneficial to encourage people to use more then, as shutting down power stations was not practical or desirable. This concept is now incorrect as many businesses use electricity 24/7 and as electric car charging becomes more popular, overnight loads will be significant even without electric heating.
Thank you very much for your prompt reply
I think the key point is not to assume that everything will be at full tilt all of the time and pulling the max In rating of each breaker. This would mean a '150A' dno fuse would be needed just in case..
Another great explanation, thanks John
Great video again John - you should put your electrical videos on DVD Well worth £20 of anybodys money. Thanks again
That means the all the 'Morons' could not watch the videos ??
Energy can not be created or destroyed.Let it flow...
Many thanks for yet another informative video. This place, a 3-bed link-detached house on a large development built in '82, has a looped supply as do most of the neighbouring houses. No idea why - the builders didn't save any cable hooking them up like this, only thing they saved on was a connection to the supply for each pair. Each house should have a 60A fuse with this arrangement but many, including mine, appear to have a 100A fuse, and of course if a property is the second one on the looped supply there's no way of telling it is. I wonder how many have a 40A power shower and a calculated demand of >90A.
from current maximum demand can we find the TCL?
Thanks John! It's interesting to see how the UK standards differ from ours in Canada.
A very informative video, thank you.
that was incredibly interesting and helpful do you do courses or can you recommend any? I'm a service engineer for commercial catering and it's not possible to become a commercial electrician now sadly. atleast not without quitting my job and that's just not an option ☹ i was thinking of doing the 17th edition course pat testing and eic electrical competency what do you think? should I be doing something else as well? 😊 appreciate any advice you could give
I've been doing a lot of the same work as you, Looked at getting qualified as an electrician so I could install single and three phase outlets for equipment like extractors, gas isolation, ovens and pot washers etc. Was told the only way to do it realistically was to qualify as an inspector and do the work then act as an inspector to check my own work! (this was from someone who trains apprentices who are on day release)
BRILLIANT CHEERS
Do you have a dvd out of all the information. If possible can you make a simple dvd of common faults found in a house hold £20-£30 is worth the knowledge you giving out
lucky lee just subscribe to his channel for free.
Hi John hope your well I have a numpty builder who has convinced a customer she wants 15kw of electric underfloor heating which is 65 amps on the ground floor of her house which includes multiple room.I haven’t been to the job yet to look at the mains but assuming they have a 100amp bs88 on 25mm tails could this be installed I’ve been told they have a gas hob and no electric showers but I’m still thinking this is not a good idea but the builder is insisting this is what she wants
Theoretically it could be done, but suggest contacting the DNO to confirm if the supply is actually capable of such a massive extra load. Almost certainly would have to be notified to them anyway, that's the equivalent of 2x electric vehicle chargers. It will cost a fortune to run in any case, and is just about the worst possible choice for heating. Take what the customer pays for gas now, and multiply it by 5.
Thanks John your a legend.
Hi John. I want to install 2 electric showers (10.5 & 8.5 kW). Can i run both of the 40a mcb dedicated shower circuit if i take a feed from the 1st shower and put a 30a fused spur feeding the 2nd electric shower?
No. A 10.5kW shower is more than 40 amps on it's own, 8.5kW is 35+ amps and both together is 80+ amps which is 2x a 40A device and is more than plenty of buildings have for everything. If you must have 2 electric showers a device will be required to ensure they can't be used at the same time, such as www.garo.co.uk/categories/priority-non-priority-cons-uni The real solution is to install a stored hot water system rather than attempting to heat water on demand.
@@jwflame thanks John
Sometimes the OSG figures don't add up and the clamp on ammeter has to come out to verify your common sense real world reckoning. No matter how many socket outlets you have, the same number of appliances will get plugged in. Only the number of extension leads and adapters will differ. Do you really have to rate a 3kW motion-activated hand wash in a home workshop as a continuous load? My static caravan has a high electrical load due to electric panel heating, washing machine, tumble dryer and a couple of years ago the pathetic LPG cooker was changed to a LPG hob with electric oven. To prevent overloading of the pitch supply, I installed a neat arrangement with a current sensor (AcuAMP ACS150-AE-F) and Normally Closed contactor, which is set up to disconnect the panel heater circuit when the cooker circuit draws more than 2A. This works really well in practice due to thermal inertia of the panel heaters.
hi john. Can you put a 32Amp breaker for a circuit that has on it 2.5 mm cable and 10Amp power points. If so, why not have all power circuits this way instead of the standard 20-25Amp breaker?
No, 2.5mm² cable is rated about 26A maximum, it's only permitted on a 32A if installed in a ring arrangement which effectively has 2 conductors to each point. Otherwise the maximum is 25A, or less depending on how it is installed.
@John Ward -I discovered my Split system air con is on a dedicated circuit, has a 32A RCBO and all with 2.5mm² cable. the aircon runs normally 2500W capacity 8100W. I have recently run off it just 1 power point for a small toaster. everything seems fine at the moment. if there's something wrong...well... maybe the installer put in the wrong cable? What would be the easy fix? I replace it with 4mm² or 6mm² cable? if so; would the powerpoint and toaster be fine? then again the aircon must of been like this for years, a toaster now shouldn't make much of a difference... I got a feeling I got nothing to worry about....what do you think?
It's the wrong cable, 2.5mm² on a 32A device is not protected against overload. 4mm² will probably comply, assuming the circuit isn't particularly long.
thanks john... I will replace the cable... I just need to know..... I want to leave the 2.5mm cable that I got coming off the cable to the air-con. I don't think it will never have 32 Amps going through it, is this ok?
You sound like a robot, I like it!
12:52 For sockets
Hi jw....I'm moving to the Philippines the power over there 230v 60hz....UK power tools are 240v 50hz.... How can I get from 60 Hz to 50hz. So that I don't brun out my .uk tools in the Philippines...What can I buy that will drip 60hz to 50hz ?????
You would need a frequency converter, which will most likely cost more than the tools did. If the tools have 240V motors they will most likely run 20% faster. if they are battery items, and the 240V is for the charger, it's very likely that the charger will work fine on 60Hz. Anything that has an electronic power supply may also work on 60Hz, many such things are designed to work on a range of voltages and frequency.
@@jwflame thank you verry much
this might sound stupid, but the mains switch will that trip????
+Allen Goldsmith No, the main switch is just that - a switch only, it has no overload or other protection at all.