Immersion Thermostat and element - Burnt Out after 4 months!

[bmouthboyo]

Hi Guys,

I replaced my immersion element as it was very old with a Tesla Titanium Immersion Heater Element 27" from screwfix in February.

It is connected to a timer whereby we tend to just use 1hr or 2hr boost when needed, no other time.

Today the water wasn't heating so I had a look at the timer and it kept instantly breaking the output LED and found this:

Timer fuse was OK and breaker had not flipped. Any idea why this would have happened? It did have the cover on, although insulation tight up against the side but not covering it.

It looks almost corroded under the cap in only 4 months. Is this something that merits a replacement by screwfix? I can't see what I could have done to cause this. Could there be a slight leak when hot and under pressure causing the rust? Thermostat was set to 60c.

Any help much appreciated.

 

[Newboy]

Assuming that the immersion was being used regularly, it looks like a poor (high resistance) electrical connection has caused the conductor to overheat.

 

[muggles]

Agree it looks like a bad connection.

 

[bmouthboyo]

Assuming that the immersion was being used regularly, it looks like a poor (high resistance) electrical connection has caused the conductor to overheat.

Agree it looks like a bad connection.

Really? What would explain the rust coving so much inside the cap?

This is how I had it installed 4 months ago:

Not sure what I could have done differently?

I am surprised the timer fuse or breaker didn’t trip!

I tried replacing the live from the star but the timer output goes off instantly. Is there a way to test my element or is it most likely goosed?

 

[endecotp]

Where did you get the bit of brown wire that burnt from? It’s possible that it was too thin - though I’d say a poor connection is more likely.

The rusting / discolouration is a result of the slow fire.

The neutral and earth wires look to be wrapped around the screws, i.e. I can see the end of the wire coming out the other side; the live seems to be under one side only.

The element may be fine; check the continuity.

Where is the bit of wire in your second photo from? Is that the same as in the first photo?

 

[bmouthboyo]

Where did you get the bit of brown wire that burnt from? It’s possible that it was too thin - though I’d say a poor connection is more likely.

The rusting / discolouration is a result of the slow fire.

The neutral and earth wires look to be wrapped around the screws, i.e. I can see the end of the wire coming out the other side; the live seems to be under one side only.

The element may be fine; check the continuity.

Where is the bit of wire in your second photo from? Is that the same as in the first photo?

Hi endecotp,

The second photo with wire in is the remains of the brown live wire from the thermostat to heating element in the first picture, it was what came supplied with the thermostat from what I remember. I assumed the stripped end was adequate as the manufacturer supplied it that way. Bit annoyed really.

live and neutral would have been me striping it back and wrapping around the screws. Still not sure why the fuse / breaker didn't trip, worrying!

 

[Newboy]

Still not sure why the fuse / breaker didn't trip, worrying

The fuse/breaker only trips when there is too much current flowing through the circuit. In your case there was nothing that would cause the circuit to overload.

 

[bmouthboyo]

The fuse/breaker only trips when there is too much current flowing through the circuit. In your case there was nothing that would cause the circuit to overload.

I see.

So is it worth taking this back to screwfix if no longer works as I am not entirely sure what I could have done differently.

On a side note to test the element and thermostat do i just:

Element: Use Ohm test with mulitmeter. If so what resistance should I see?
Thermostat: Check continuity?

Thanks

 

[Gasguru]

16 to 20 ohms is typical and thermostat should be less than an ohm (subtract lead resistance of course).
I'd have "wrapped" the live wire around the screw.

 

[endecotp]

So is it worth taking this back to screwfix if no longer works as I am not entirely sure what I could have done differently.

No, you shouldn’t take it back.

You should have fixed the wire to the terminal more securely. If you really can’t work out how to do that, get a professional to do it next time. There is a substantial fire risk from this sort of mistake.

 

[bmouthboyo]

No, you shouldn’t take it back.

You should have fixed the wire to the terminal more securely. If you really can’t work out how to do that, get a professional to do it next time. There is a substantial fire risk from this sort of mistake.

Went to Screwfix today to buy a new immersion and whilst there thought I would check how it is wired and if me being such an 'amateur' should have left it to a professional. Turns out the wire that burnt out for me was pre-installed after all:

They agreed to give a refund when I remove the old one.

So now it begs the question what the hell went wrong with the first one to burn out like that? Is there anything else that could have caused this?

 

[just pumps]

Looking closely at the 2 photo`s there are difference`s with the cable, the cable clamp (bridge), the screws and the route of the cables.

 

[endecotp]

what the hell went wrong with the first one to burn out like that?

We’ve already told you; the connection at the screw terminal was poor. Or - less likely - that wire was much too thin.

If that’s because it was supplied in poor condition, then that’s a problem that should be reported; it sounds like you have done so and I hope they investigate properly.

 

[bmouthboyo]

We’ve already told you; the connection at the screw terminal was poor. Or - less likely - that wire was much too thin.

If that’s because it was supplied in poor condition, then that’s a problem that should be reported; it sounds like you have done so and I hope they investigate properly.

Hi endecotp,

I wasn't being arsey I am just genuinely concerned if this might happen again and trying to trace my steps to be sure I didn't do anything wrong. I am a fairly experienced DIY mechanic enthusiast but just moved into my first home so new to electrics etc. Safety is paramount but I always like to learn new things and give it a try, but never want to cut corners.

I just wondered if anyone had any other explanations as to what I could have done differently.

Should I remove the wiring of this one and redo it with thicker gauge wire and wrapped around the terminal?

 

[bmouthboyo]

Looking closely at the 2 photo`s there are difference`s with the cable, the cable clamp (bridge), the screws and the route of the cables.

Hey, sorry what do you mean in difference? Between the Brown wire in my original installation and the new one with white wire? They both cam installed when I purchased them. On the immersion description it says "Pre-Wired Safety Thermostat" https://www.screwfix.com/p/tesla-titanium-immersion-heater-element-27/75262.

I took that to mean leave that connection alone and screw in the thermostat and the incoming wiring.

Is there anything I could have done differently?

Thanks