The IET is carrying out some important updates between 17-30 April and all of our websites will be view only. For more information, read this Announcement

Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 36 replies
  • Subscribers 31 subscribers
  • Views 6405 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Appliance Ratings and 13A plug tops

statter
Hello

I looked last year for portable heating and not surprisingly there was little above 2.5kW rating.  All the old 3kW stuff has long gone.

I was surprised however to find a wide range of steam irons rated at 3000W and even 3100W.  (that's almost 13.5A at 230V).  I realise of course that irons are likely to be much more intermittent than heating and that 13.5A is very unlikely to blow a 13A fuse but it cant be good practice to overload plug/ socket like this.  A decent ironing session can still be hours ……   OFC at 240v its under 13A but 230v has been the standard for ages now.   In my experience many socket/ plug combinations are marginal approaching their rating so deliberate overloading will only make matters worse over time.  I would have thought that these appliances wouldn't qualify for CE marking and couldn't be sold legally?  Does anyone know if there is a BS or EN for small appliances?


Thanks


Peter
Parents
  • 0
    Maximum power expected under "operating conditions" is usually quoted in standards where necessary.


    Therefore I think it's always safe to assume the power is at the operating temperature (hence my addition of this in my previous post).

    However, being very very pedantic, the temperature coefficient of resistance for heating element wire is usually orders of magnitude lower than the temperature coefficient of resistance for copper.


    For example, constantan has a temperature coefficient of resistance at 20 ºC of -0.000074 whereas copper has a temperature coefficient of resistance of 0.004041


    Hence, there would be very little noticeable change in resistance of constantan wire in the range 20 to 120 ºC (120C is often the rating of the thermal fuse in an iron).


    I can confirm this is the case, because I have checked heating element resistances in many types of equipment at 10-20 º C when the operating temperature of the element is around 100 to 130 ºC, using a rough power calculation. You could also check this for yourself, say with a tumble dryer or simple convector heater.


    Oven elements are subject to higher temperature changes, so you will see some difference between the resistance at 250 ºC , say, than 20 ºC ... and some ovens with self-cleaning capability may perhaps get up to 400 ºC
Reply
  • 0
    Maximum power expected under "operating conditions" is usually quoted in standards where necessary.


    Therefore I think it's always safe to assume the power is at the operating temperature (hence my addition of this in my previous post).

    However, being very very pedantic, the temperature coefficient of resistance for heating element wire is usually orders of magnitude lower than the temperature coefficient of resistance for copper.


    For example, constantan has a temperature coefficient of resistance at 20 ºC of -0.000074 whereas copper has a temperature coefficient of resistance of 0.004041


    Hence, there would be very little noticeable change in resistance of constantan wire in the range 20 to 120 ºC (120C is often the rating of the thermal fuse in an iron).


    I can confirm this is the case, because I have checked heating element resistances in many types of equipment at 10-20 º C when the operating temperature of the element is around 100 to 130 ºC, using a rough power calculation. You could also check this for yourself, say with a tumble dryer or simple convector heater.


    Oven elements are subject to higher temperature changes, so you will see some difference between the resistance at 250 ºC , say, than 20 ºC ... and some ovens with self-cleaning capability may perhaps get up to 400 ºC
Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines