Overloading circuits

leicesterfan · Nov 14, 2022

Hello.

I'm in the UK, and have some questions/concerns about my kitchen set up. So the fuse box has 4 breakers/circuits for the kitchen (the lighting is on a different circuit).

One circuit covers the electric oven, gas hob ignition and a plinth heater.

I then have a single 20A rated circuit, and two 16A rated circuits feeding various sockets above the worktops. I've worked out which circuits are linked to which plug sockets by flicking off the breakers in turn.

On the 20A circuit I have the fridge freezer, washing machine and toaster
On the 16A circuit I have the dishwasher and microwave
On the other 16A circuit I have the kettle and coffee machine (my wife has just bought an air fryer too, and the best place would be next to the double socket where the kettle/coffee machine live).

Now of course not all of these are running at the same time, but I'm getting paranoid that if I've got the dishwasher going, I can't use the microwave and vice-versa. If I've got the washing machine going, I can't use the toaster and vice-versa, and if I've got the kettle going, I can't use the coffee machine and vice versa. If I then put the air fryer on and needed the kettle, I'd have to unplug it and use a socket on another circuit (where nothing else is running!?)

Am I being overly cautious and thinking about things too much? Surely unless you're in a new build, you're not going to have umpteen dedicated circuits for the various appliances. Surely lots of people have a kettle and toaster on the same double socket and have both on at the same time?

Thanks

MJPD29 · Nov 14, 2022

I think your being over cautious. I've been in offices where an entire kitchen is covered by one 16a or 20a mcb. You shouldn't have any issues.

James · Nov 14, 2022

generally speaking, you are over thinking it.

the thing to worry about is devices that draw a large current continuously.

a kettle and toaster combination, although it may be over the 16A, is not going to cause any issue as the overload is for a short period of time.
i.e. a circuit designed to handle 16A will not suffer any damage if run at 30A for a couple of minutes.

Avo Mk8 · Nov 14, 2022

leicesterfan said:
Am I being overly cautious and thinking about things too much?

I would suggest you are!
I think you'll find that the combination of appliances you mention will not trip your MCB's, because the appliances combined current does not amount to a sustained overload, and the electrical sensitivity of the MCB is less than you might think.
If your interested in the technicals, see below for the multiple(s) of current drawn vs the time taken to trip.
A big overload from a fault condition obviously cuts off the power quickly, but an extra few amps will not, and this is (well, should be) taken into consideration in the design of the wiring in your house.

[ElectriciansForums.net] Overloading circuits

pc1966 · Nov 14, 2022

As above, a modest overload for a short time is not a problem.

The thermal curve of the MCB is designed to mirror the damage profile of typical cables, i.e. if the MCB's stated rating is correctly selected for the cable's continuous capacity then it will protect the cable for all of the combinations of overload.

leicesterfan · Nov 14, 2022

Thanks everyone. Put my mind at rest a bit!

So a kettle running at 13 amps and coffee machine at 5 amps, on a 16 amp circuit is likely to be okay even though it exceeds the stated load, given we're talking a minute or two?

Whereas cooking with a 13 amp air fryer for half an hour whilst running the 5 amp microwave is a bad idea given this would be a sustained use, even though the draw is the same?

James · Nov 14, 2022

its not as simple as that, an air fryer will not use 13A for any length of time.
it has a thermostat and will turn on and off constantly whilst cooking. if i had to take an educated guess, i would say 3 to 5 amps on average over a period of time once it has got up to temperature.