Water heater element resistance test

[mcummins7]

Can anyone give me the usual reading for a 9 inch element? I presume it's the easiest way to test if it's good or not.

 

[telectrix]

a standard element is around 20ohms , L/N. so somewhere in that region. that will only tell you if it's continuous or open circuit though. do an IR test at 500v, L/E and N/E. both should read in excess of 2Mohms.

 

[One_of_them]

do you know the rating of the element?

usually, i think.....eg 6kW

230x230=52900
52900/6000 = roughly 8ohms good element

 

[mcummins7]

so far then, I've got anywhere between 8 and 20 ohms. Could you put some identity's Sparky_FM to your figures please..........(ie., what does the two 230 values stand for........I've got the 6Kw one------------------ and what is the original equation?

 

[MarkieSparkie]

mcummins7, ignore spark_FM you will be extremely unlikely to have a an element greater than 3kW in a domestic situation, in which case approximately 20ohms would be correct for a 3kW element. spark_FM calculation was ohms law, Voltage squared/Power=Resistance, however domestic elements are usually rated at 240V and that should therefore be used in any calculation.

 

[telectrix]

a 3kw heater is 13A, so R=V/I, R=230/13=17.69ohms. a 6kw will be 1/2 that. bear in mind that the cold resistance will be a bit lower.

 

[mcummins7]

Cheers folks - understood loud and clear

 

[One_of_them]

as i explained with the "...eg" my reply was only an example and I understand usually domestic only have 3kW but the same principle applies

Might be rated at 240V but I always base my calculations on 230V....dont know about anybody else these days?

cheers

 

[pushrod]

R = v²/p is the formula you need

but tbh a few ohms either way and it is working