220v. 230v, 240v, 250v?

[John-SJW]

I saw an oven that was rated at 3,100 watts. Now most would say that cannot be fitted on final ring circuit as rule of thumb. But:
3,100 watts draws amps of:
14.09 amps @ 220v
13.47 amps @ 230v
12.91 amps @ 240v
12.4 amps @ 250v

If the installation is 240v or 250v then it safely inside the 13 amp of a final ring circuit.

The question is, and the regs aficionados can help here, what is the voltage that should be used to assess, as maybe the voltage will vary in an installation over the years.

 

[telectrix]

Look at at a plug. It always says 13A, 250V. That is 3.2 kW.

250V is the voltage rating of the plug assembly. nothing to do with calculating the wattage. the current rating is 13A, whether the voltage is 250V , 230V, or even 110V.

 

[LastManOnline]

14.09 amps @ 220v
13.47 amps @ 230v
12.91 amps @ 240v
12.4 amps @ 250v

John was correct with his calculations (in connection with the Bosch hob) though more by accident than design. It's down to the fact the hob (a, resistive load) has a power limiter built in to it, causing the hob in effect to behave like an inductive load. So a reduced voltage in this(very unusual case) would in fact lead to the current rising until the power limiter kicks in.

This latest contribution from me has the potential to be included in the..... "that's another 60 seconds of my life I will never....." but I thought I, d share it anyway.

 

[Lucien Nunes]

But an induction hob is not a resistive load, it's a CW radio transmitter inside a feedback loop. Even without the limiting function its behaviour is arbitrary and whatever the makers want it to be. I don't know whether the default behaviour of domestic induction hobs approximates to constant power.

And surely the limiting function sets the maximum current, not power? Granted, as far as the user experience is concerned the power is being limited, but it makes no sense to throttle the current below the circuit rating when the voltage is high.

 

[LastManOnline]

But an induction hob is not a resistive load, it's a CW radio transmitter inside a feedback loop. Even without the limiting function its behaviour is arbitrary and whatever the makers want it to be. I don't know whether the default behaviour of domestic induction..........

Well, at least I got the bit about...... "That's another 60 seconds of my life......." correct?

 

[static zap]

Once you add intelligence to an appliance , you really need to know you
way around the software ,and overload protection circuits.
( and HOPE it remembers its configuration/settings faultlessly )
.. I think you can have things , Too conductive for this technology ..

 

[John-SJW]

John was correct with his calculations (in connection with the Bosch hob) though more by accident than design.

I got them right. As I just pressed the right buttons.

 

[John-SJW]

The characteristic curve isn't quite right or the markings are wrong, the characteristic must become asymptotic at a value no greater than 19.5A for a 13A fuse, or it wouldn't comply with the 1.5 rule going back to the 14th for close protection, and they are the same fuses now.

It could take up to 4 hours to operate of course.

Thanks.

Now going back to the 3.7kW Bosch hob on a 13A plug. At 220v to 250v it will draw below the 19.5A (1.5) limit of the 13A fuse. They must have taken diversity into account, as would a hob be on full belt for 2 hours? How often would the hob run over 13A even with a big Christmas dinner? If it was running over a 13A current draw, for how long on average?

So the makers have deemed that a 13A fuse can cope with a 3.7kW hob. As it is not a portable appliance I would question if it should even be on a plug - but that is another point.

 

[static zap]

a 13A fuse can cope with a 3.7kW hob.

There is a big gap between COPE , and good design !.
( Wait n see how many RCF are damaged charging cars as well in winter )
... All weak points will be discovered ... without Arc thingies !

 

[John-SJW]

There is a big gap between COPE , and good design !.
( Wait n see how many RCF are damaged charging cars as well in winter )
... All weak points will be discovered ... without Arc thingies !

Well they will have to install a proper EV charger with a dedicated 6mm cable.

13A sockets are for portable appliances which do not draw a sustained high current. To fully charge an EV with a 13A socket will Take a few days - not what the socket and plug were designed for.