Immersion heaters 3 blown in two days!

[magicno1]

Hard water??????

 

[zzzjim]

Have you had street lights in area re-furbed recently ?
( 3 phase is funny stuff when it gets out of balance )

Parents had an electric kiln , is getting it on a different supply an option ?

 

[efficiencyman]

250v should be fine for an immersion heater and within its designed limits.

I agree with that upto a sceptical ( should ) I have had to change hundreds some years have I been supplied with a bad batch ? I have asked that a few times.
Regards Hard Water No not in 24 hours

 

[magicno1]

Not sure re the lights but will ask.
regards faulty batch possible but in my opinion pretty unlikely
will pose the question re three phase!
thanks

 

[magicno1]

Gotta pop out on a call so I'll pick it up later so keep your thoughts coming please!

 

[dancinplumba]

Simple answer NO to both !
As your sparks would have tested for N - E faults The only case I have had like this in 50+ years was on a 3 phase site where 415 volts was found due to a bad install !
It happened at time of colour harmonisation, Blue instead of black when the blue was a phase colour.

How do you know ? Are you on the job ?

 

[efficiencyman]

Let us know mode of failure, usually gives good clues as to why they have failed in such a short time. Titanium, incaloy or cheapo rubbish, ???? signs of element burn out ?
That 3 phase case I had was a 415 volt wiring mistake ( not mine ) but found it wired like that by original installers.
Ask your sparks to check for any doggy connections or possibility of 415 volts

 

[efficiencyman]

How do you know ? Are you on the job ?

Nah Mate, retired now but loved my job.
Experience counts for a lot, learn something everyday can`t get out of the habit even now, just have a bit more time.

 

[magicno1]

Let us know mode of failure, usually gives good clues as to why they have failed in such a short time. Titanium, incaloy or cheapo rubbish, ???? signs of element burn out ?
That 3 phase case I had was a 415 volt wiring mistake ( not mine ) but found it wired like that by original installers.
Ask your sparks to check for any doggy connections or possibility of 415 volts

Fitted two two new titanium yesterday. Both set at 50 degrees at 3pm.
both blown today at 11am. Bottom one blew the rcd and the stat but not the overheat. Element was split and burst nearly all the way around.
top one split stat gone but didn't take the rcd or overheat!
previous original heaters two months old incalloy both set roughly the same both shot to pieces again although the bottom one took the rcd and stat but the top one didn't take the rcd just the stat but both never went out on overheat!

previous to fitting this tank they had a megaflo and we were forever changing the elements!
also a lot of the plumbing is plastic barrier pipe connected to copper and I have lost count of the leaks I've fixed there. The copper seems to be corroding in the speedfit joints almost crumbling away.
Do you think this could be related?????
i didn't do the original plumbing it was done about 6 years ago

 

[Ch4 plumbing]

I've no experience of water softeners, have they got one and could that be affecting things?

 

[magicno1]

No softener

 

[zzzjim]

Do electrics look any good ( earth bonding of at least some ? )

 

[Chalked]

Interesting one this!
please keep us informed how you get on.

out of interest, has the property got a wire type damp proof course? Came across one years ago that was touching the oil line behind an aga. It was shorting down the oil line and where a price of plastic coating on the 10mm copper line was damaged the copper turned to dust.

 

[efficiencyman]

The short life failures seems like an over voltage intermittent fault or a faulty batch.
Regards the previous problems you describe Galvanic action over a period could be a possibility but not the recent blow outs.
Yes, I think the crumbling copper is related to this, I would cross bond all pipe work to cylinder before fitting new elements, to rule out galvanic action.
Interesting one this, I will follow thread !
please keep us informed how you get on.

 

[magicno1]

The short life failures seems like an over voltage intermittent fault or a faulty batch.
Regards the previous problems you describe Galvanic action over a period could be a possibility but not the recent blow outs.
Yes, I think the crumbling copper is related to this, I would cross bond all pipe work to cylinder before fitting new elements, to rule out galvanic action.
Interesting one this, I will follow thread !
please keep us informed how you get on.

Thanks for all your help and ideas. Back to it today to try to get to the bottom of it!

 

[magicno1]

Ok

talked to RM and Rodstat who make the heaters today.
still really none the wiser but they are sending out two replacement elements and want the damaged ones back. They think it could be a faulty batch but unlikely!
we are going to run both elements together and wire them through a timer to limit their usage through the night.
This I know doesn't address the electrical issue but we have to start somewhere. The sparks are putting in a monitor of some description to see what happens over 25 hr period.

if they both blow again within say 2- 3 days back to the drawing board!!!!

 

[turnpin]

Do love an update...will no doubt help someone down the line when you finally resolve this....regards Turnpinunk:

 

[magicno1]

Do love an update...will no doubt help someone down the line when you finally resolve this....regards Turnpinunk:

Pleasure

 

[stani]

If your getting 251volts at peak period for demand I.e. 5 o,clock I would be looking to a serious over voltage during the over night off peak period, if the monitoring cannot show up. The voltage overnight I would be looking at bringing your energy suppliers in to investigate.

 

[chris watkins]

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.

 

[stani]

Chris, do you mean test at 500 as in insulation resistance, these are not made to work at that voltage, only that the insulation is still intact, and you wouldn't really test the equipment at 500v

 

[chris watkins]

Chris, do you mean test at 500 as in insulation resistance, these are not made to work at that voltage, only that the insulation is still intact, and you wouldn't really test the equipment at 500v

Yes, realised what I put. DOL. but what I think I was getting at is the break down of the insulating powder failure.

 

[stani]

Yes, see what you mean, it will be good to get a definitive answer on this one, especially if they are going through so many.

 

[newcastle phill]

Well an insulation tester does indeed test at 500v.
Mine tests at 500 and 1000v - and those are industry standard tests.
You need the potential across to discover faults in the insulation between the earthed case and current carrying element. These faults may not show at 220v and do manifest at higher.
There are only micro amps during these tests and they are perfectly acceptable on class 1 equipment and indeed obligatory.
You only test at 250v on items with surge protected devices

 

[stani]

Phil, are you saying you would test for insulation resistance with equipment fitted I.e. A shower or you would test a boiler circuit with the boiler connected.