Immersion Heater Failure - Twice

[WindyWard]

After the immersion heater failed, I tested that a current could pass through the elements with the heater in situ, and it could not. I isolated the water flow, drain from the bottom of the hot water cylinder and extracted the element. It was visibly split. I have replaced the element with thermostat and it worked wonderfully for 5 days. The second one now fails to heat the water.

Before I embark on the same process, is there any lessons I could learn from i.e. the second one failing must be statistically unlikely?

 

[seco services]

check the stat don't just need resetting

 

[powell30]

Statistically...yes. Take it out and return it as faulty.....as long as your sure external factors are not to blame.....ie faulty electrics etc. If your in a hard water area make sure you get one made for the job (there is a difference and will save you replacing again in 12-18 months

 

[keithc135]

New immersion heater thermostats differ from old ones in that they have a non resetting trip which is designed to pop if the element gets too hot. They are supposed to prevent continual overheating and eventual failure by forcing the user to investigate why the water is cold but in reality they are ridiculously sensitive and will trip out if you accidentally insulate the electical cover plate with a pair of socks etc on top of it!! You can manually reset it by removing the cover plate and pressing the plastic pin back in. Worth taking a look before you go through the pain of removing the element again.

 

[Softus]

The second one now fails to heat the water.

Before I embark on the same process, is there any lessons I could learn from i.e. the second one failing must be statistically unlikely?

Probability has nothing to do with it - you still need to diagnose the fault. You already know how to do that, so I don't understand why you haven't done it yet.

What temperature limit is the new rod thermostat set at?

 

[WindyWard]

Thank you all.

Temperature was set to 60, and the top of the heater has not been covered. The element was bought to cope with Hard water as this matches my understanding of the area.

Didn't think to reset the stat, I'll try that this evening.

cheers

 

[powell30]

As softus has pointed out tho, pressing the reset may get you up and running again but if you don't sort the reason why it tripped you will just be back to square one.

Have you had any outages in the last few days? Blown any bulbs or fuses? all these things can trip the reset button on some circuits. If not you may be lucky and it's a one off.....if not.....

 

[WindyWard]

powell30, that's an interesting question, on the same day that the first immersion heater failed the house alarm tripped. I found no reason for the alarm going and concluded that it was a power drop even though no circuit breakers had tripped. I didn't call out the alarm people to investigate to save the 100GBP. That said there was no activity to note when the second one failed, but I guess a closer inspection of the electrics is warranted.

thanks again.

 

[simond]

The reset will not be tripped by external means, it is a simple thermal switch.

Your immersion heater stat may be faulty, or you may be taking the water too hot eg: from an alternative heat source.

Or it might not be the stat at all and the second element could have failed.

You really need to do some simple testing with a multimeter to move forward. I'm going to sound like Agile now, but surprisingly few plumbers understand electrics.

If the element has failed you should investigate whether there are accumulated limescale deposits in the water cylinder touching the element. If this is the case you'll be changing elements till the cows come home.

 

[WindyWard]

Stat needed to be reset, after doing this and dropping the temperature to 50 it worked fine last night and this morning. It still makes me question why the stat tripped. This may just be because the new element is that much more efficient to the old one that failed, the water temp does feel hotter now. I will now check the rest of the system. Anyway, hopefully this is the end, but if not your accumulated advice will be followed - especially re the electrics and the interesting note on limescale.
thank you

 

[Softus]

Stat needed to be reset, after doing this and dropping the temperature to 50 it worked fine last night and this morning.

You have set the temperature too low.

It still makes me question why the stat tripped.

If you want help in finding the answer then you need to post full details of the rest of the heating system that's attached to you cylinder. These full details might simply be a statement that your cylinder is a direct one, but we still need to know whether single or dual, whether top or side mounted, and size of cylinder.

This may just be because the new element is that much more efficient to the old one that failed

No - that's a nonsense theory.

the water temp does feel hotter now.

In that case the old thermostat was calibrated differently to the new one.

I will now check the rest of the system.

Anyway, hopefully this is the end...

It isn't though, because you've fixed a symptom and not the problem.