Maximum Demand and Diversity - A SparkyNinja Webinar

This is a recording of a webinar given on 1st April 2020.
The assessment of maximum demand and diversity has often been misunderstood or just ignored altogether on many training courses and in many publications.
In this webinar, Phil Watts from Ascot College goes through maximum demand and diversity looking at the references and resources available with some examples.
It would be good to have access to the OSG (old copies are fine) for this, but it is not essential.
You may also notice that I now have a 'JOIN' button on youtube, I have activated this as I would like to spend more time on KZbin creating content and carrying out live streams in the future and this is a great alternative way to support the SparkyNinja project, you will get access to exclusive emotes for chat and access to member only content in the future.
Stay safe, stay healthy and keep an eye out for more webinars and content.. 👍
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[@PJB71]

One of the best training videos I’ve seen. A few comments, with regards to removing the suppliers cut-out fuse. I completely understand why the DNO say we shouldn’t remove the fuse, but everyone does it. I think there should be a training course available to sparks directly from the DNO. This will eliminate some dangerous practices & put an end to that nonsense. I also think the majority of sparks completing domestic EICR, don’t take into account the max demand of an installation unless it heavily loaded.

[@jamesmcintyre5583]

Excellent video - informative and interesting. Really helped to demystify maximum demand. Many thanks. 👍

[@testingtechnicians6751]

Very good topic and materials, thanks for clearing all my doubts in this section

[@wgascoigne6538]

Really enjoy the webinars, keep up the good work guys, thank you..

[@peterwalker4029]

Been waiting for this bad boy! Cheers guys, legends

[@natarmstrong8931]

Excellent and very detailed discussion. Please may I ask about the 'design guide' that Phil was talking about. Is it the 'Iet electrical installation design guide'. I am going to buy it if it is. Thanks

[@SparkyNinja]

Yes it is

[@garylatto4191]

Another interesting one thank you guys for your time and effort 👍. did I see ud done one about testing rfc and dealing with results etc ? Thanks gary

[@krazylad84]

Thanks for the video... As this looks more realistic but what I dont understand is OSG has suggested that for dwelling lighting do 66% of the total current demand but you have just kept largest circuit on the side which was cooker and rest of all the circuits you did 40% diversity... Would that be allowed in the exam environment?

[@cobydavies5304]

This was class thank you both

[@mielerodriguez5678]

Years ago there were many domestic fires caused by the chip pan will the EV be the cause of a new spate of fires?

[@thomasbyles3075]

Quick question: what do you do about a shower circuits? 9kw = 40A. Do I use 100% of this or do I add it to the other circuits and x0.4 (40%) ?

[@krishath7085]

Great webinar, Thank you very much.

[@no_short_circuit]

Thanks for the video. As an adult learner I get the cooker circuit (40A) to be 19A (not 25A using IET Method - 31:00 minutes in)) after diversity. First 10A plus 30% of remainder (30A) = 9A. Am I doing something wrong?

[@stevethomas5849]

Food for thought.

[@EricTheHiking]

Thank you for your effort. What about distribution boards is there specific guidance or just the same principle?

[@leogrande9977]

I know this was 3 years ago however, just a few queries... For socket circuits, why does the design guide consider the MCB rating in calculating the max. demand? 40% of 32A (12.8A) seems excessive for a domestic ring circuit. Another thing, that 40% factor used as diversity factor appears to be taken at the same time of the day for all the circuits. Has the time of utilisation been considered on that 40% figure? And this load assessment is just for a single dwelling unit. What about for a multiple dwelling unit? Can you please do another webinar video for that? Thanks.

[@thomasbyles3075]

Really helpful, thank you

[@christopherrooney9564]

If i am unsure what the total load is being used when install new equipment. I fit a SPD Pro power and energy analyser. To confirm loading over a week.

[@ashmanelectricalservices4318]

That's all very well on live installation but what do you when you are the designer of an installation or need to make additions to the installation?

[@Iyengaryogawithshaun]

Thank you

[@busman2000]

Has anyone come up with a calculation app for doing that..?

[@timfanning5309]

I also made the cooker demand with diversity to be 19A even with a socket outlet it would be 24A . Where's the 25A coming from ???

[@thesocialhandgrenade8474]

26.45

[@angelofranklin1]

Personally, I believe the onsite guide and regulations are correct, You should consider 100-watt lamps regardless of LED, somebody else could move in and decided to use tungsten lamps then what? I'm not saying take the worst-case scenario but you should consider this carefully and not scrimp and save. Also some spare would be good, you just don't know the future.

[@Weaselspleen75]

Could you get an idea of maximum demand from a smart meter if installed? do they log usage over a period of time? that would be very handy.

[@alexturnbull1828]

Nice video, do you have a calculation for adding sub mains?

[@johnhoward2104]

It could be that some of your calculations for MD are wrong. Table 3.1 of the EIDG is for final cct current demand, whereas table 3.2 is for distr ccts - assessing the demand of a number of final ccts. Your calculations to determine MD were based on table 3.2, using row 9 (for domestics - 100% of the highest and 40% of the remainder). As such, these percentages were applied to the current demand of each final cct, as per the design guide. However, it would appear that the design guide does not follow its own statements. In section 3.4.1, row 9 is applied to the current demands of various ccts, which is what your calculations were based on. However the start of section 3.4.1 in the design guide says that rows 1-5 are applied to items of equipment supplied by the distr cct, whereas row 9 has the diversity factors applied to the current rating of the OCPD (In). Therefore, re your lighting ccts, for example, the 40% should be applied to the 6A In value (assuming a 6A CB), not the 4A load value, etc, etc. In short, the guide hasn't followed it's own requirements. However, worked example 4.4 in the Napit On-site Solutions book, applies it correctly. The end of the 4th paragraph of Apdx A of the OSG (2018), states 'the current demand of for any final cct which is a std final cct arrangement complying with apdx H is the rated current of the OCPD of that cct' - which suggests this relates to row 9 i.e. apply factors to In. Note 2 to table A2 in the OSG is also of great importance, stating that it is important to ensure that DBs/CUs are of sufficient rating to take the total load connected to them without the application of any diversity. So this will apply to ratings of main switches and RCCBs.

[@ashmanelectricalservices4318]

Just ordered my copy of IET Electrical Installation Design Guide... Are there any books you'd recommend for earthing and bonding preferably something with worked examples.

[@PJB71]

Guidance note 8

[@SpiritSwarm]

Okay a few things have confused me here do you apply diversity twice for exemple Lights 66% if fl Ring 100% of fl Ring 50% of fl Shower 100% of fl Cooker 10 +30% of the fl bla bla bla Then after you do that you then do 100% of the highest. Circuit ie the Cooker and 40% of the remainder so aren't you doing diversity twice and how can you take 40% of the remainder when you can't have diversity on a shower the osg says no diversity allowed someone please help me understand this go easy on me I'm still on my level 2

[@SparkyNinja]

The first is considered diversity on the circuit itself.. so a cooker wouldn't be considered to be under full potential load in a domestic setting, and a light circuit wouldn't be considered to have all of the lights in every room switched on at once. Things like instantaneous water heater would pull full demand so no initial diversity applied. The second time is to consider the utilisation of the system itself and how all the individual circuit demands reflect on the size of the distribution cable required. Would the oven be on when the shower is on etc.

[@SpiritSwarm]

Oh okay I understand now I was just little confused because the osg says no diversity allowed but you have made it clear thank you very much your videos are excellent keep up the good work