Corrosion issue in immersion heater

[Barbs706]

Hi, Im having a bit of an issue with my immersion heater. In the last 4 months, I have gone through 3 immersion heaters (all titanium ones). The sleeve where the thermostat sits in is literally rotting away with a month or so resulting in hot water rising out of the sleeve, into where all the wires are and spilling over the sides. I have added some photos in my album for you all to view, so you can see how bad it is. There is pitting and gauges all along the copper sleeve. Does anyone have any idear what could be causing this?
Thanks

Untitled

• Barbs706
• 22 May 2012
• 1

Untitled

• Barbs706
• 22 May 2012
• 1

 

[dcawkwell]

I would say there is an electrical fault causing electrolysis and eating away
at the copper.

The copper tank has has a small current running through it.

 

[Barbs706]

Could that be down to a faulty earth connection? I forgot to mention, in the pictures I uploaded I had cleaned the copper sleeve. It was covered in a bluey-greeny crumbly residue when I pulled it from the tank.
Thanks

 

[Burnerman]

Is your immersion heater earthed?
John

 

[Barbs706]

There is an earth cable, and it was correctly wired up before I unwired it. Now, if it actually works thats another question! How can I test the earth? Is that a job for an electrician?

 

[Burnerman]

The earth cable actually keeps you safe - you won't get a dangerous shock if its connected.
Check the polarity of the immersion heater wiring.....black or blue is negative or neutral (-) and red or brown is positive or live (+).
The earth will have its own connection (green / yellow) often to a threaded post terminal.
The other end of the immersion cable will go back to the fused spur on the wall, where the earth will continue to the consumer unit.
John

 

[Barbs706]

I should of checked the polarity before I unwired it, I forgot to look. But, the 3 times I have had it changed, I have had 3 diffrent plummers fit it for me. So I would of thought they would have wired it correctly. Is there any way I can check the earth connection to the consumer unit?
Thanks

 

[Burnerman]

The immersion heater live cable will go to a thermostat first, and then continue directly to the element.
The neutral cable will go directly to the other element connection.
These connections will be clearly marked.
So long as the earth connection is there (at the immersion end) its sure to be connected at the double pole wall switch - unless someone's been in there
You'd need a multimeter to check continuity to the consumer unit, ideally.
John

 

[ChrisR]

Never seen a stat sheath corrode like that.
Do you have very soft water?

 

[Burnerman]

Crazy, huh Chris....I think Mr. Cawkwell has his finger on the issue.
I've never seen one like this.
John

 

[Barbs706]

I have just found a picture I took earlier off the heater with all the wires still connected and it looks as it is wired correctly (brown directly into thermostat etc). Because my immersion is far away from my consumer unit, how do I use a multimeter? My multimeter leads are quite short. There is a nearby socket that I could reach. Could I test the immersion earth to the nearby socket earth?

 

[Barbs706]

Never seen a stat sheath corrode like that.
Do you have very soft water?

I live in an extremly hard water area actually!

 

[Dan Robinson]

I have seen this on poor quality sensor pockets. We put it down to chlorine being used to clean the cold water tanks feeding the building.

 

[dreadnoughtheating]

Two words.Sacrifical anode.

Needs a new one.

DH

 

[picasso]

Is your cylinder heated by a boiler with the immersion as back up or is the immersion the only means of heating the cylinder ?