how to test if immersion heater is knackered

[matt1e]

As a matter of interest I just had to buy two immersion heaters. Same make. One measured 17 Ohms, the other 22 Ohms. So I don't think that the difference between 230V or 240V is worth talking about!

might be same make but wont be same rating unless
a) one is knackered or
b) your meter is

 

[ban-all-sheds]

c) or they are the same make but different ratings.

 

[matt1e]

c) or they are the same make but different ratings.

quite! (I sort of thought I'd covered that ban but thanks anyway )

 

[Goldberg]

Never had the luxury of a proper spanner, so it is visible with an open-ended tool.

I bet you have an impressive open-ended tool. How long is it?

Where's your spirit of adventure....

I reserve it for moving/terminating live tails...

 

[BS3036]

might be same make but wont be same rating unless
a) one is knackered or
b) your meter is
c) or they are the same make but different ratings.

Well, in fact they are both the same manufacturer, and both specified as 3kW, but one is 11" and the other 27". I'm not sure you can draw too much of a conclusion without knowing what the resistance of each becomes at normal working temperature though. It is quite a difference though, isn't it.

 

[safesinbad]

If you have a clamp meter handy try puting it round the live wire of the supply load at the switch and if the element is working the meter will show the current that it is drawing.

 

[partpdoctor]

hi
the definitive method to condemn the element is to

1 check with a test lamp to the element line terminal and earth
2 isolate again
3 disconnect neutral to element
4 re-energise and check voltage at line stud of heater again to earth
5 now check neutral stud to earth. no voltage proves an open element

best wishes
alan

 

[Taylortwocities]

That's not a definitive method.
What about insulation resistance live and neutral to earth?

The element may be have continuity but have a fault between the element and earth. Your method will not show this, but the element will still be faulty.

 

[Goldberg]

hi
the definitive method to condemn the element is...

I disagree.

Your method will find an element that's open circuit, but some leak to earth without going open circuit, and often in a very subtle way.

An IR test will show this up, but I've always delivered a correct diagnosis with nothing more than an ordinary multimeter.

 

[matt1e]

hi
the definitive method to condemn the element is to

1 check with a test lamp to the element line terminal and earth
2 isolate again
3 disconnect neutral to element
4 re-energise and check voltage at line stud of heater again to earth
5 now check neutral stud to earth. no voltage proves an open element

best wishes
alan

ffs

the definitive method to condemn the element is to

1 check with a test lamp to the element line terminal and earth

never ever take earth as a first point of reference this is a classic plumbers mistake (at least most of the ones ive come across,but not all mind you)
it will save you condemning brand new boiler pcbs because its easy to clamp on to the boiler casing and prob L for 240 and declare voltage there, not working so pcb knackered! by all means use the case if its easier but probe for neutral first
in this situation i.e no fuses/mcbs etc operated power switched on then

the definitive method to condemn the element is to
1 take off element cover and check with a test lamp(if you like! I remember my old fault finding days well) or your multi meter to the element line terminal and neutral terminal (actual ends of element)
240(ish)? and no signs of heat? then element gooshed (can be checked with a continuity test)
0v (ish) then start working backwards via stat as (for now) fault lies elsewhere

 

[Jamesbelton5]

hi, going back to the original question, if there is live & neutral at the element terminals and it doesn`t get hot, its fooked (no need to test it)

Thats what I need a simple answer...getting power...not doing whats its meant to = replace (assuming Fooked is Northhamptonshire for broken )

 

[holmslaw]

..

 

[sparkyspike]

As a matter of interest I just had to buy two immersion heaters. Same make. One measured 17 Ohms, the other 22 Ohms. So I don't think that the difference between 230V or 240V is worth talking about!

Have you ever put your meter across a light bulb to measure the resistance?

 

[ricicle]

3 disconnect neutral to element
4 re-energise and check voltage at line stud of heater again to earth
5 now check neutral stud to earth. no voltage proves an open element

best wishes
alan

Not really good advice for a DIYer as they might not be expecting the 'Neutral' stud to be at 240V in a healthy element (although granted they shouldn't even be messing around in there if not sure what they are doing)

This method does not take into account the IR of the element

Most healthy elements I have ever tested are in the region of 19 - 20 ohms