Overloaded Ring Main !!

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Ohms97

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Hi to everyone on the forum. đź‘Ť

I am new to this forum and I am currently a trainee electrician. I love everything about the electrical industry and would like to start building knowledge with work colleague and forums when need to ask certain questions about jobs. 
 

So the 1st question I have is how much load can be on a ring main. Doing a simple calculation V*I I get 7680watts. But how does this work with diversity and in a kitchen ring main. My parents have had there kitchen renovated with painted doors and new work tops but have added in a larder unit which will house a combi microwave/grill. Now I am looking to plug this into the existing Kitchen ring main. The current house set up is 

Oven/cooker - 32amp MCB

1st floor sockets - 32amp MCB

2nd floor sockets - 32amp MCB

kitchen/utility sockets - 32amp MCB

1st floor lights - 6amp 

2nd floor lights - 6amp

heating - 6amp 

currently on the kitchen/utility ring is 

washing machine - 2.2kw 

dishwasher - 2.1kw 

drier - 2.2kw 

cooker hood - 80watts

utilty fan- 30watt 

kettle - 3kw 

toaster 1.5kw 

1xdouble socket 

now directly behind the larder unit is the double socket which I am looking to use for plugging in Mico/grill combi which is rated at 2.1kw. Will this be ok to do with all other appliances plugged into the same ring main. As I have added up roughly 12 kw with adding appliances above together plus the new mico/grill on this ring main but I know I was told about something that they will not be pulling full load all the time so that is why diversity comes in, so a ring main could supply a lot of appliances as they will not be pulling full load at same intervals. Reason trying to avoid pulling new cable in consumer unit is about 20metres away with concrete ceiling and new hard wood flooring. Just hoping this will be suitable and not cause issues. Hope that makes sense. Responses will be very grateful

 
You are thinking on the right lines that diversity will actually result in a far lower load than just adding up all of the connected appliances..

Even if appliances are on simultaneously, not all appliances pull their full load all of the time..

e.g. a washing machine just rotating the drum takes far less than when it is heating water for a 60degeree wash!

And kettles & toasters will only be on for a short time....

Have you got a basic clamp meter you could put around one of your meter tails..

e.g.  https://www.amazon.co.uk/Proster-Digital-Clamp-Meter-Capacitance/dp/B0821GZK9H/ref=sr_1_8?  

to see how much current is actually flowing?

The bottom line is providing the cable and protective device are correct for the circuit then worst case the MCB trips..

but reality is it will takes a fair bit more than 32A to trip the MCB..

If a short period of higher current did occur it would not be a problem... 

 
Hi SL 

thank you for the response. Yeah I think I have one somewhere that I can use👍Or can get one from local wholesalers.Will try that out. Yeah so if all appliances are on at the same time they won’t be pulling fulling load so I will be ok to plug micro/grill into existing kitchen/utility ring. The MCB is 32amp and cable 2 of 2.5mm and I am getting continuity no breaks. So if a 32amp draws current of say 36/38 amps for 15mins or so it’s not going to cause any damage. As what is deemed as a long period of overload 1 hour and above which the circuit is never going to be overloaded for that length of time ??? Is that right ??

 
Hi SL 

thank you for the response. Yeah I think I have one somewhere that I can use👍Or can get one from local wholesalers.Will try that out. Yeah so if all appliances are on at the same time they won’t be pulling fulling load so I will be ok to plug micro/grill into existing kitchen/utility ring. The MCB is 32amp and cable 2 of 2.5mm and I am getting continuity no breaks. So if a 32amp draws current of say 36/38 amps for 15mins or so it’s not going to cause any damage. As what is deemed as a long period of overload 1 hour and above which the circuit is never going to be overloaded for that length of time ??? Is that right ??


TBH you're extremely unlikely to see overloading on the ring - there are a huge number of homes in the UK with only 1 socket circuit for all of the house.

If you look at the diversity calculations in the OSG, just remember these were written a LONG TIME AGO and take no account of homes which generally have far more sockets too

 
the only thing on that list that will pull full load for any length of time is the tumble drier. My kitchen ring main turned out to be damaged when I tested it, so was put on a 20A MCB for many years until I refurbished it. I have a very similar set of appliances, and only thing I had to watch out for was switching the 3kW kettle on when the tunble drier was working along with other applainces. 

 
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