Immersion heating issue

[xtremem23]

Guys,

Anyone give me a little bit of advice before i call in the professionals.

Background:
Oil fired central heating
3 zones, upstairs, downstairs and water.
Hotwater tank, x1 top down immersion heater.

Oil fired heating and water works 100%
Immersion heater doesnt ?

What was happening:
Immersion heater was tripping the switch in the fuse box thats called "immersion heating fused spur" so i swapped out the whole unit as when this happened once before and the element was shot,so saying it was the same i drained a bit of water out and swapped it out with a new one.

What is happening now:
Immersion heater on for 20-30 mins, then bang switch is tripped in fuse box again ????

19.5ohms across element so im guessing it's good.

Anyone any ideas, is it my luck that i have a faulty unit that once heats heats up a crack appears and shorts out the element or is there anything else i can look at before pulling it out again, which i really dont wannt do.
All connections have be checked and rechecked

Cheers

 

[JohnD]

please photograph the thing that is tripping.

if that's not possible, please tell us the words, letters and numbers printed on it. All of them.

 

[xtremem23]

Its the one that says "immersion heater"

 

[JohnD]

you have cunningly provided a photo that makes it impossible to see the words, letters and numbers printed on the breaker.

Let's try one as a starter.

Does it say "B16?"

 

[xtremem23]

I have cunningly supplied a photo thats makes it impossible to see the words.

Clearly states "IMM HEATER"

There is no numbers just states "IMM HEATER" exactly like ive taken a photo of.

 

[JohnD]

OK.

that's a label stuck on the casing.

The actual thing that trips is a breaker. It will look something like this. The front part projects through the front of the enclosure so you can read the printed identifying marks.

See what I mean?

 

[xtremem23]

Took the cover off, second one in from the right.

B16 like you said

 

[terryplumb]

Have you checked carefully all the switches / timers/cable connections on the immersion circuit . If the MCB trips it's either faulty or there is a short circuit or excessive current.

 

[xtremem23]

There's no timers, just an on n off switch in the kitchen another one that always on in the airing cupboard that has the flex to the immersion heater.

I'll pull off the face plate on the wall switches to check though,maybe a bad connection in there thats causing excessive current to be drawn

 

[CBW]

Have you checked for correct voltages anywhere, eg immersion heater, spur?

 

[xtremem23]

All switches look fresh, no charring of any sorts.

Voltages when turned on:
Immersion heat stat - live side to element side 240v.
turn temperture arrow on stat to i hear a click and voltage to zero across the same.

Voltage when off at wall:
Zero

 

[terryplumb]

How many conductors are connected to the MCB for the immersion circuit. I can't see clearly on your pic .

 

[xtremem23]

Lol, terryplumb id love to be able to tell you that but what do you mean "conductors" ?

What are you thinking ?

I have noticed that it take very little to flip this breaker manually when compared to the cooker one beside it.

Clutching here at the minute

 

[terryplumb]

Conductor is the copper wire with brown pvc insulation connected to the top of the MCB for immersion circuit ,is there more than one ?

 

[JohnW2]

Lol, terryplumb id love to be able to tell you that but what do you mean "conductors" ?

"wires".

I have noticed that it take very little to flip this breaker manually when compared to the cooker one beside it.

It's not impossible that the breaker has become faulty, and far too trigger-happy (i.e. tripping when it shouldn't).

Kind Regards, John