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Hi

Ive just brought a oil filled radiator not massove but 1.5 kw with 3 settings how many amps would this use?  I was thinking about 7 top heat!!  Would only use prob 2nd heat setting

thanks

 See here...

http://www.ukcampsite.co.uk/chatter/display_topic_threads.asp?ForumID=6&TopicID=253438&SearchPagePosition=1&search=electric+hook+up&searchMode=phrase&searchIn=Topic&forum=0&searchSort=dateDESC&ReturnPage=Search

If you scroll down there is a conversion chart on there

Quote: Originally posted by Bob61 on 14/3/2012

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6.521739130434783 amps to be precise

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For the same heater you will get less amps at 220 volts than 240 volts,

240 volts 1500W, 6.25A, same heater at 220 volts 5.729166666

Saxo1

If you pass a given voltage through a given resistance you will get a given amps i.e.

1 volt through 1ohm = 1 amp

10 volts through 1 ohm =10 amps

The resistance of the heater is constant,a 1500 watt 230v rated heater has a resistance of 35.266666666 ohms, using the formula:

 I=V/R  230volts divided by 35.266666666 = 6.5217392 amps

I=V/R  240 volts  divided by 35.266666666= 6.8052931 amps

I=V/R  220 volts  divided by 35.266666666 =6.2381852 amps

Using P=VI at 230 v the power is 1500watts ,at 240v the power is 1565 watts ,at 220v the power is 1434 watts.

That is why the spec plate sometimes gives a voltage range of 220v to 240v /1850 to 2200 watts.

Not that this is of any relevance to the OP

Saxo1

The heater load won't be purely resistive - most likely inductive as well as capacitive, so it's not correct to calculate resistance to 9 decimal places.

I don't think we can know what is the input power of the heater at different voltages as it depends on the characteristics of the heater internal power supply (is it constant current or constant voltage being delivered to the heater element), or neither perhaps as it's probably simple AC?

For the benefit of the OP and to keep things simple, I would calculate at nominal voltage 230V with the nominal power stated on the spec plate (1500W?) and add 10% for safety margin.

So it's 7.2A

Quote: Originally posted by Kelper on 15/3/2012

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Quote: Originally posted by Bob61 on 14/3/2012

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6.521739130434783 amps to be precise

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Not sure what system you're using ... but my maths tell me that 1500/240 = 6.25 ... precisely

However ... as voltage is seldom delivered at exactly 240 ... hence the oft quoted 220-240 range ... you'd get 6.8181818181 etc at 220.

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 Now look what you've started!!

The oft quoted range for the UK is, as you say, 220-240v. Being an average sort of Joe Soap I, like lots of other average Joe Soaps, take that as a 230v average.

1500 watts divided by 230 volts = 6.521739130434783 amps (according to my highly accurate computer calculator provided by Microsoft.

Quote: Originally posted by Vin Blanc on 15/3/2012

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Ohms law states that for a given wattage, the current (amps) will rise as the voltage drops.

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Quote: Originally posted by Lisamitt on 14/3/2012...a oil filled radiator not massive but 1.5 kw with 3 settings how many amps would this use?

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Quote: Originally posted by sanhozay on 16/3/2012

Quote: Originally posted by Vin Blanc on 15/3/2012Ohms law states that for a given wattage, the current (amps) will rise as the voltage drops.

This is not Ohm's law. Ohm's law equates current, resistance and voltage: V = IR.

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The equation you are referring to is P = VI. Current would have to decrease when voltage increased in order to produce the same power. But then I think you are interpreting the power rating of an appliance as meaning it has a constant power output, which is not the case.

The power rating is for a quoted voltage, usually 230V. If the voltage was higher, the current would be higher and the power consumption higher. It's the resistance that's the constant, not power.