Maximum current for a unit supplied from a 13A socket, taking supply voltages into account.

There are really two parts to this question,


1. It is not unusual to see units quoted as 230V, 13A 3kW, based on this I can only assume that these are mutually exclusive as the tolerance on the voltage will take this condition beyond 13A and 3kW, therefore to maintain 13A at 230V + 10% the power at 230V 3kW must be lower! Is this the case, or should products be designed around 253V, 13A, 3kW?


2. In this case the condition to exceed 13A is an absolute worst case, supply voltage at 253V (230V+10%) and all components at the top of their tolerance (the heating elements we use are +/-5% on power, which makes up more than 90% of the power usage).


Given the unit only operates at full power during its warm up phase (approx 40min) and then runs at around 2kW, and the (un)likelyhood of the voltage and element tolerences all being at the top end, I am being advised that it is acceptable to design the unit around this basis 


Max current

13.8A  (253V, Elements +5%),

13.14A (253V, Elements Nominal)

12.5A (240V, Elements Nominal).


However, I as a typically cautious engineer, would see 13A as an absolute maximum and should be based on the worst case conditions.


What would your thoughts be on the above?

There are really two parts to this question,


1. It is not unusual to see units quoted as 230V, 13A 3kW, based on this I can only assume that these are mutually exclusive as the tolerance on the voltage will take this condition beyond 13A and 3kW, therefore to maintain 13A at 230V + 10% the power at 230V 3kW must be lower! Is this the case, or should products be designed around 253V, 13A, 3kW?


2. In this case the condition to exceed 13A is an absolute worst case, supply voltage at 253V (230V+10%) and all components at the top of their tolerance (the heating elements we use are +/-5% on power, which makes up more than 90% of the power usage).


Given the unit only operates at full power during its warm up phase (approx 40min) and then runs at around 2kW, and the (un)likelyhood of the voltage and element tolerences all being at the top end, I am being advised that it is acceptable to design the unit around this basis 


Max current

13.8A  (253V, Elements +5%),

13.14A (253V, Elements Nominal)

12.5A (240V, Elements Nominal).


However, I as a typically cautious engineer, would see 13A as an absolute maximum and should be based on the worst case conditions.


What would your thoughts be on the above?