Strange voltage on immersion controller

[richardspooner]

Is there an isolator switch between the boost switch and the consumer unit? Can you do a similar test there, between L&E and N&E?

Unless it is hidden under the floor boards I don't think there is one.

 

[Spark123]

I hope it isn't hidden!
Maybe worth popping the cover off the CU and seeing if the neutral for the immersion has become loose in there. Turn off all the main switches before removing the cover and be very carefull as the meter tails are still live.

 

[richardspooner]

Any idea why I am getting a near decent voltage when I test L&E or N&E?

 

[Spark123]

If the immersion had actually burnt out all together would this break the circuit? So when I am testing across L&N in this scenario would I see the voltage drop? and on either side L or N it would show the right reading?

If the immersion heater had burned out then you should still see 240v between live and neutral, and between live and earth of course.
There should be approximately zero volts between neutral and earth - the fact you have voltage there says that there is a break in the neutral upstream and you are seeing the mains voltage from the live, via the immersion element on the neutral.
If you want to check the immersion element stick your meter onto ohms and test across the element with it disconnected. You should see a fairly low resistance reading.

 

[Spark123]

I should maybe also point out that you should have a blank over that spare way in the consumer unit, also no sign of an RCD but that might be in the bottom half.

 

[richardspooner]

If the immersion heater had burned out then you should still see 240v between live and neutral, and between live and earth of course.
There should be approximately zero volts between neutral and earth - the fact you have voltage there says that there is a break in the neutral upstream and you are seeing the mains voltage from the live, via the immersion element on the neutral.
If you want to check the immersion element stick your meter onto ohms and test across the element with it disconnected. You should see a fairly low resistance reading.

This is excellent help!!

So regardless of whether the element is burned or not I should still see 240v on all the terminals up to the element?

Can you have a look at this picture and tell me where to test for resistance?

 

[richardspooner]

I should maybe also point out that you should have a blank over that spare way in the consumer unit, also no sign of an RCD but that might be in the bottom half.

RCD is in the other half and the blanking plate is on my to do list......only realised myself tonight.

Thank you for pointing it out thought

 

[Spark123]

At the switch, the two wires which go to the immersion heater - you can test for resistance there.
tbh - it doesn't sound like the immersion heater is burned out. More like a loose or broken neutral to me.
If you are not happy looking inside your CU yourself then get an electrician in tomorrow.

 

[richardspooner]

I'm happy to do it myself, just gonna wait until it's light....so if I kill the main breaker and don't touch the grid wires (tails)....I shouldn't fry?

 

[richardspooner]

Right, I tested for resistance and got a tone so that's a good thing at least,.....assume that means that the element is not burnt.

Do wires ever just work themselves loose behind a sealed CU? It just seems odd that with no moving or decorating the Neutral should just fall out somewhere......I'm not doubting you at all, it just seems strange.

 

[kkynaston]

It can still happen if the connection was not 'nipped' up tight enough, it could have very slowly become a high resistance joint, then burnt out all together

 

[RF Lighting]

Oh yes.

Far more often than you'd expect.

Infact immersions are very good at doing it, as it is a reasonably large load (within a domestic context), and will often draw full load current for several hours at a time.

 

[Spark123]

When you look inside your CU, be very careful of the larger wires which enter the main switches - these will still be live with the main switches off. Don't go poking the wires or the main switches - if you can see any metal around them areas stay well clear.

I have known wires to become loose in consumer units before yes - if they are not quite nipped up enough they can form a high resistance joint. If it is loose take it out and make sure it is nice and clean - you may even need to cut it back a bit. That is if this is your problem, there are still a few more possibilities.
The break in the neutral may be between the CU and the switch if the cable has become damaged, if there is a switch or a joint anywhere it the fault may be there. The fault may lie between the neutral rail in the CU and the main switch in the CU, the main switch itself may be faulty or there may be a break between the main switch and the mains, don't start tinkering with the main switch or the mains as I said before - these will still be live with the main switch off.

Too late

 

[radioredcat]

The meter shown earlier is an aldi one,I have one as well and they work ok for basic measurements but i will point out that all my meters give false readings when the battery is low.



andy

 

[richardspooner]

Don't worry I will be very careful when I am in the CU. Honestly, I don't need that kind of shock.

So I'll just check the neg going into the back of the fuse thingy to make sure it is nice and secure. If that is ok can I purchase a tester to check line continuity. I used one of these when I used to be a cable monkey but that was voice and data. Is there a similar device for electrics? I would rather do that than rip all my carpets up to get below the floor boards!