Immersion heaters 3 blown in two days!

[newcastle phill]

Im saying id meg the element before fitting.
Whose on about shower or boiler circuits

 

[stani]

Sorry, didn't read like that thought you were saying you would test the whole lot. I agree testing the jacket to element will show up if there is a fault.

 

[magicno1]

Hi

regards secondary circ then yes we do have it. In fact most of the copper pipe leaks have been on the secondary loop!!!!
although the tank in question is 2 months old there is a small amount of scale build up in the bottom of the tank but not huge amounts.
2 new elements arrived today and were fitted by me earlier. The sparks have just text to say they have just wired them in but they are not convinced they are both working!!!!!..... Strange coz they are brand new!!
anyway he's taking a look tomorrow and will let me know ASAP.

also the elements are made by heatrod.

 

[magicno1]

My two bobs worth, in my experience the main cause of immersions blowing is localised overheating. In hard water areas this is normally due to the build-up of scale, not directly on the elements themselves, although this can happen, it tends to break off the surface and falls to builds up in piles under the elements obstructing the conversion currents which carry away the heat & stop it from overheating.

I use to see these pyramids of scale left in tack by the last engineer as I replaced the element shortly after the new one had been replaced. Use a scrapper to move it way or clear it out before installing new ones.

I though it was a good candidate for the cause of failure in this case until you said that the "top one" had gone as well, if the unit has a higher level "boost" immersion & this has failed as well then that blows my theory out of the water, excuses the pun!

Does the system have a secondary return installed with the mixed system pipework ??

Seems unlikely to be over voltage, when you think you test them at 500+, now measuring the resistance of the new ones may provide useful information.

Thanks mate

both elements were on 24/7. I understand the scale theory but still the higher one blew!

 

[Ermintrude]

Top one is doing more work if. 2nd circ

 

[Bronze_tap]

Well done for putting the voltage logger!Also you can connect two elements in series, than you would have ~1/4 power, but double the voltage tolerance.Or go for larger element, and connect it through the silicon diode (would halve it's power).Or find twice as powerful 415V version of it, that would fit in the hole. Should just give the right power at 250V.Anyway, you need something with a lot of thermal headroom... (or good overvoltage protector).Obviously fixing the fault is the best, but if the neighbors are arc welding with 500A+ on the other phase of the 75 KW substation transformer it may not quite help...

 

[oz-plumber]

Is there any chance that the cylinder is being drained, or partially drained.

If the top element has blown, it may be worth checking if the water supply is adequate to keep the tanks filled during peak water usage periods.

The elements don't have to be dry for very long to cook themselves.

 

[magicno1]

Update!!!!!

fitted 2 new heaters a week ago on timers and turned off 2nd circ. all ok at the moment touch wood!!!!
RM have the blown elements so we'll see what they say after the break!

 

[Chalked]

I beg they never switch off on secondary !

 

[chris watkins]

I beg they never switch off on secondary !

Try that one again in the morning Chalked.!!

 

[Matt06]

Why Did someone not suggest a gas water heater rather than stored (electric aswell) Electric costs loads and secondary circ elements will burn out pretty often (as they are on constant) i had it last year using element as back up with sec circ burnt out in a week
That was an RM cylinder too, Remember ringing RM and they said a load of crap apparently in the instructions it says somewhere Bypass water softeners for the first 6weeks or 6 months cant remember which (I could nt find it i looked several times after the phone call)