Hot water tank not keeping heat

ForestBluebells

I only took a picture of the part that needed replacement but I can take the cover off and take a picture of the burnt cable. The electrician did say it’s odd for it to have burnt in that way

Bendy_House

Some element of mystery remains.

The most common cause of a burnt cable is a poor electrical connection at the screw terminals - that becomes high resistance, overheats, and it's this that 'burns' the cable from that point. But, if it's a screw-terminal, then in theory the immersion element itself should be fine, so no drain-down required.

If, on the other hand, it's a 'fixed' cable connection - ie part of the immersion element assembly - then that suggests an inherent fault or weakness as S62 says, and should be brought to the manufacturer's attention. And, yes, the whole caboodle will require replacing - so drain-down.

I hope this doesn't remain a mystery, FBb - or we will track you down and, well, you know...

Bendy_House

Looks like there might be 'spade' connectors going to the actual element. I wonder if this is where the issue lies?

Should be fixable, tho', I'd have thought?

If the element does need replacing, FBb, then sit down before you are given the bill... A 'titanium' element and a drain-down (requiring two trades)... :-(

Section62

ForestBluebells said:

I only took a picture of the part that needed replacement but I can take the cover off and take a picture of the burnt cable. The electrician did say it’s odd for it to have burnt in that way

Only do that if you won't be placing yourself in danger - the electricity supply to the heater should be fully isolated before doing that, not just turned off at the switch/timer.

In fact the electrician should have disconnected it completely because of the risks involved. But don't assume he's done that, you need to be sure.

The oddness of the burning is really why I think it would be useful for you to share a picture and contact Heatrae Sadia.  Sometimes cable gets brittle with age and the heat and the insulation cracks and can fall off, but you wouldn't expect that with wire used in the manufacturing of an immersion heating element.  If it was 'yellowing' rather than burning I'd be less surprised.

For the fault to have progressed to the point where the heater was only working intermittently is also strange. Burning of the cable insulation wouldn't normally stop the heater working unless it reaches a point where a live conductor is in contact with another conductive part, when (hopefully) a fuse or trip will cut the power. The heater then shouldn't start working again by itself.

ForestBluebells

Hope you can see clearly how much it’s burnt?

coffeehound

Yes you wouldn't have thought it would necessarily need the immersion replacing; those Ti elements should have a long life.  

ForestBluebells

coffeehound said:

Yes you wouldn't have thought it would necessarily need the immersion replacing; those Ti elements should have a long life.  

Should I try a different electrician?

ForestBluebells

The electrician turned the fuse off as there’s a switch in the cupboard too 

Section62

ForestBluebells said:

coffeehound said:

Yes you wouldn't have thought it would necessarily need the immersion replacing; those Ti elements should have a long life.  

Should I try a different electrician?

No, the element does need to be replaced because there is something seriously wrong with it.

The usual reason why immersion heaters fail is because the corrode and water gets into them - and that causes the electric to trip. But the symptoms you had weren't really consistent with that and the material the element is made from made that less likely to be he cause (I think that is what coffeehound means, and I certainly agree with that)

The fault you've got here is almost certainly that part of the electrical circuit is overheating for some reason.  The heat is enough to melt the plastic and there has possibly been some smouldering to get that amount of blackness.

I would definitely send that picture to Heatrae Sadia for their information, along with a clear picture of the serial number/data plate, and ask them for their thoughts.  They may request you or the plumber sends the heater to them for further examination, and if you are lucky they might even offer to cover some of your costs (if you don't ask you won't necessarily get)

ForestBluebells

Thank you I will see what they say, I’ll report back when they respond and once I managed to get it fixed