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How does electricity in your home get there in the first place?

Updated: Jun 12

The image shows how power flows from the electricity grid and into your home. It flows through the Cut Outs Main Fuse and then into the meter, and from here the Isolator Switch (if one is fitted) and then into your Consumer Unit or Fusebox!
The flow of electricity from the National Grid into your Consumer Unit (Fuse Box)

In the image above you can see how the electricity flows from outside your home, into the Cut Out where it's split to provide the earthing and neutral and live conductors, from here it flows around and into the Consumer Unit where all the electricity is divided up into the circuits that power your home!


All of this might not be something you’ve ever noticed, or you may have but just take it all for granted… but perhaps you have or would like to know more then read on or you can watch the video!



As part of your home electrical installation you’ll have a Main Fuse… commonly sat next to your electricity meter. This is the main bit of protection before your Consumer Unit, and it is owned by the DNO (District Network Operator - National Grid) and just like a fuse in your plug… it is designed to blow under fault conditions and cut the power to your home, and I have been to properties where, thankfully, this has been the sole protector of human life!! Check out the saucepan below…


The image shows how powerful and dangerous electricity can be when it is unchecked... this cooker fault blew a hole in this saucepan!! The cooker was old but because there was no RCD protection the fault wasn't detected - the Consumer Unit was upgrade and the customers home is now far safer!
The power of electricity!!

The cooker became faulty and as the homeowner didn’t have an RCD (Residual Current Device) the fault wasn’t detected until it completely failed and blew a hole through her saucepan! The current generated was so great (100A+) that the Main Fuse was blown and so thankfully, the power was cut.


The image shows the main cut out, the fuse housing, the earthing and the electricity meter. An isolation switch was also fitted so that I can cut the power legally.
The different parts of a typical electrical installation in a home

The “Cut Out” is the bit of plastic that surrounds the fuse… it houses the fuse. In a smaller home you can expect to find a 63A fuse, with a medium sized home up to 80A, and then more commonly now, 100A. This means that the “Maximum Demand”, or electricity that your home can produce shouldn’t exceed the size of the fuse within the Cut Out! In large properties and commercial settings we get to the topic of 3-Phase supplies… where there are 3x100A fuses to cope with the extra demand, and now we have solar and EV becoming more common new houses are now being supplied with a 3-Phase power supply, however most houses are currently only Single Phase (i.e. 1 x 100A Fuse).


So, for example, let’s say that you live in a smaller property with a garage and from time-to-time you use power tools in the garage while in the house you have Sunday Roast in the oven, at this time quite a lot of energy might be getting consumed but it still won’t be over that 63A (this is a lot!)... 


Electricians use Amps to tally up the supply… so, let's say you have a smaller property and have an older 63A Main Fuse… BUT, you’re looking to make a few upgrades, a new Electric Shower and you want a new EV! To work out how many extra amps a new shower and EV will consume we use the “Power Triangle”... Power divided by Volts = Amps! 


EV Point 


7200w230v  = 31.30A 


Electric Shower


10500w230v = 45.64A 


All of a sudden… we have a possible 76.94 of extra Amps (although Maximum Demand states that not all of your household items will be on full power all of the time!)… BUT, if you’re in the garage doing a little DIY and your other half is cooking the Sunday Roast, while charging the car and the teenager is having a shower… the 63A fuse could be close to breaking point! Now, this isn’t a problem as if it did we would just call the DNO (National Grid) and they would be out that same afternoon (in most cases) to put a new fuse in, but they might opt for an 80A or 100A fuse instead now! 


That’s it really, that is what the Main Fuse is there to do, and it’s what the Cut Out is, it’s just a “house” for your Main Fuse! Simple! In some cases, when I am looking over your intake equipment, I may suggest to the DNO that the Cut Out is old and could do with upgrading, and this can include a provision for a new earth supplied by the DNO and at the same time the fuse could be changed to match the supply demands within your home. 


If you need any information, or electrical work completed, please contact your Local Electrician on 01761 325 007! You can also read some of my reviews from previous customer here: https://www.spellerssparks.co.uk/spellers-sparks-electrical-services-gallery

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