Measuring wattage of a heating element

[lari]

hi all, was wondering if someone could help me out with some electrical knowledge.
bought a new heating element, 240v 2500w it said on the package.(i live in the uk where mains is 230v). installed it to my 50ltr boiler and yep it took extremely long time to bring water to mash temp - almost 2.30 hours. according to some online calculator to achieve a 70c temp rise in 50 ltr of water with a 2500w element should take about 100 minutes and not 140 minutes it took me. so i grabbed my multimeter and measured the resistance of the heating element which was 30 ohms. according to this calculation R = (V x V) / P (V is the voltage P is watts) resistance should have been around 23ohms. which tells me that the heating element is around 1900w and not 2500w. am i right to assume that? wanna make sure I’m correct before i contact the seller.
cheers

 

[MindenMan]

I agree your initial resistance should be 23 ohms, but since it is 30 ohms and 230v:
(230x230)= 52900/30 ohms I get 1763 watts

 

[kwadric]

Did you measure the resistance across your wired plug or across the lugs on the element? If you measured across your plug, check across the lugs on the element. It could be that a you have a bad connection in your plug.

 

[lari]

spot on kwadric, checked the resistance directly at the lugs of the element and it was as expected - 23.8 ohms. noticed cable connectors were a bit rusty so reckon thats why i got a bad reading earlier. all clean now. problem solved. thanks everybody!

 

[IslandLizard]

You're right, that element is not what it promises to be.

For an 11 (UK) gallon / 50 liter wort boil you'd need at least 4500W, preferably 5500W. The element should be Ultra Low Watt Density (ULWD) and is typically long, folded over and wavy. The larger element surface helps to prevent scorching. Plenty of threads on that topic here.

Now if you're just heating (strike/sparge) water, any watt density element will work, but as you said it needs to be of reasonable power.

 

[lari]

its all good IslandLizard, got it sorted. dodgy connection on my end, not the heating elements fault.
as measured I’m now running my boiler with roughly 2.2kw. just finished a 40ltr batch, 48ltr boil volume. admittedly it took awhile to get going but achieved a rolling boil no probs. thats SS keg no insulation ambient temp 5c. you americans are obsessed with power not efficiency. i was amazed how well it worked. 2.2kw boiling nearly 50ltr of wort.
cheers

 

[IslandLizard]

Well that's good news then!
I just saw your post that squeezed in before mine.

It is actually more efficient to heat faster. Time x heat loss...

I'd put some insulation around that kettle. That will help a lot.