4.4kW on a plug?

[ban-all-sheds]

IF all 4.4kW were on or off together and only switching on and off with the thermostat I would not be so comfortable with it being on a plug.

If it were a 9660W item, would you be comfortable with it on a 20A circuit with a 20A switch and (let's assume they exist) a 20A outlet plate?

 

[EFLImpudence]

For a usual cooking appliance, I would.
By usual, I mean several smallish elements - not two 4830W ones only on/of together.

It's just that 18A through a plug doesn't seem like good idea.

 

[ban-all-sheds]

For a usual cooking appliance, I would.
By usual, I mean several smallish elements - not two 4830W ones only on/of together.

But someone could turn all of the elements on together.

It's just that 18A through a plug doesn't seem like good idea.

But 40A through a 20A switch is OK?

 

[EFLImpudence]

But someone could turn all of the elements on together.

They could, but, however likely, as you know, the diversity formula seems to work.

But 40A through a 20A switch is OK?

Just as OK as through a 20A MCB or outlet plate (let's assume they exist).

 

[ban-all-sheds]

So does diversity work for a 4400W cooking appliance?

And if 40A is OK through 20A accessories, why isn't 19A OK through 13A ones?

 

[EFLImpudence]

So does diversity work for a 4400W cooking appliance?

I would say not if the full load is the only option.
If that is, indeed, the case in this thread then apparently I am wrong.

And if 40A is OK through 20A accessories, why isn't 19A OK through 13A ones?

Perhaps it is or should be (I am only querying plugs) but some plugs don't like a 13A constant - some do, though, so may be due to construction.


On the subject of switches, no matter what the rating, they all seem to have contacts that are just two hemispherical points (pimples?) with very small contact areas which carry and make and break the full load.

 

[flameport]

And if 40A is OK through 20A accessories, why isn't 19A OK through 13A ones?

13A contains a fuse, which by design will get excessively hot at currents above 13A and cause damage to the fuseholder contacts.

 

[ban-all-sheds]

What about 40A through a 20A fuse? Or whatever - the actual values don't really matter, the fact is that there is a space in the diversity calculation for an OPD to be overloaded to a point below which it will operate within the duration of the overload from a cooker, but way above its In.

Don't get me wrong - I wouldn't put a 4.4kW cooking appliance on a plug either, but I think it is useful to challenge the groupthink (or group unthink) and to pursue the question of why we happily accept Ib ≤ In ≤ Iz when Ib = (Imax -10) x 0.3 + 10 except when In=13.