Another immersion question

Hi I fitted/wired a new pre wired immersion which after 2 days it cooked and flooded the house, the reason I have been given is due to a loose neutral there was a massive heat build up under the head of the immersion and melted the immersion solder allowing the water to flow.

Could a sparks explain to me the principle of heat build up due to a loose neutral, please and thanks, Gary.

Bruthal

gary71 wrote: »

Hi I fitted/wired a new pre wired immersion which after 2 days it cooked and flooded the house, the reason I have been given is due to a loose neutral there was a massive heat build up under the head of the immersion and melted the immersion solder allowing the water to flow.

Could a sparks explain to me the principle of heat build up due to a loose neutral, please and thanks, Gary.

Loose neutral, loose live, it would be all the same, but i cant see any scenario where a loose connection will cause the water to flood out. Never heard of it happening, and have seen a few badly burnt immersion element connections. A cylinder of water is like a massive heat sink, and a badly burning terminal would just burn until the connection fails. Never heard of immersions with solder in them either. Sounds like someones science fiction explanation maybe.

Could the cylinder of had no water in it when the immersion was first turned on? Then filled?

No the cylinder was full, the elements didn't generate the heat as the overheat stat would of kicked in, if you look at the underside of a immersion you will see solder sealing where the element probes enter the bottom of the immersion head, this solder melts at 270c ish also the plastic cover liquified, the heat was generated under the head of the immersion due to a loose neutral according to the manufactures:D

M cebee

Havent heard of this but i always remove cover and tighten connections

Bruthal

gary71 wrote: »

No the cylinder was full, the elements didn't generate the heat as the overheat stat would of kicked in, if you look at the underside of a immersion you will see solder sealing where the element probes enter the bottom of the immersion head, this solder melts at 270c ish also the plastic cover liquified, the heat was generated under the head of the immersion due to a loose neutral according to the manufactures:D

Yea but how would the bottom of the metal plate thats in contact with water heat to 270c? I cant see that happening with a loose connection ever. If the heat of the 3kw element itself never makes the top of the immersion hot enough to melt the solder, it seems practically impossible for a loose connection to manage it.

M cebee

M cebee wrote: »

Havent heard of this but i always remove cover and tighten connections

I never used a pre-wired before, I just used my meter to check things, but guess what I'll be checking next time.

slavetothegrind

i would be fairly sure the stat failed closed, thus overheating the elements, this often results in them bursting and electrically failing but in your case the solder melted first.
i have seen this first hand in electric steam generators.
i would argue the point tbh as their reasoning is flawed.

robbie7730

robbie7730 wrote: »

Yea but how would the bottom of the metal plate thats in contact with water heat to 270c? I cant see that happening with a loose connection ever. If the heat of the 3kw element itself never makes the top of the immersion hot enough to melt the solder, it seems practically impossible for a loose connection to manage it.

I don't understand what they are telling me and I would like to get my head around it, the juice this immersion pulled was immense judging buy the melted plastic left behind, to make things worse it was my mothers house I flooded:eek:

Bruthal

slavetothegrind wrote: »

i would be fairly sure the stat failed closed, thus overheating the elements, this often results in them bursting and electrically failing but in your case the solder melted first.
i have seen this first hand in electric steam generators.
i would argue the point tbh as their reasoning is flawed.

This is more likely than the manufacturers explanation, but once the cylinder is full of water, the water still can not go above 100c, so the elements will not go very much hotter than they would by heating the water to 70c.

Steam generators on the other hand have steam under high pressure, which can go far above 100c.

slavetothegrind

slavetothegrind wrote: »

i would be fairly sure the stat failed closed, thus overheating the elements, this often results in them bursting and electrically failing but in your case the solder melted first.
i have seen this first hand in electric steam generators.
i would argue the point tbh as their reasoning is flawed.

This happened once before according to the manufactures when a new install was found cooking and the investigation put it down to a loose neutral, they also tried to explain it as a heating system under piped and the pump has to be bigger to push the water round, the element is the pump and the loose wire is the small pipework and the heat generated is from the extra effort to heat the element

This immersion is from a large DIY store that's easy to get hold of.

slavetothegrind

it's not beyond the bounds of possibility that the origional solder joint was flawed and thus the early failure, any chance of a picture?

Bruthal

gary71 wrote: »

I don't understand what they are telling me and I would like to get my head around it, the juice this immersion pulled was immense judging buy the melted plastic left behind, to make things worse it was my mothers house I flooded:eek:

gary71 wrote: »

I never used a pre-wired before, I just used my meter to check things, but guess what I'll be checking next time.

They are telling you the neutral connection was loose and melted the solder. Hard to see that on immersion metal parts in contact with water.

Bruthal

slavetothegrind wrote: »

it's not beyond the bounds of possibility that the origional solder joint was flawed and thus the early failure, any chance of a picture?

This is what i would think as well, manufacturers flaws most likely.

slavetothegrind

slavetothegrind wrote: »

any chance of a picture?

bearing in mind I investigate defective installations for a living, guess what I forgot to do before I went back to the supplier with the immersion

slavetothegrind

gary71 wrote: »

bearing in mind I investigate defective installations for a living, guess what I forgot to do before I went back to the supplier with the immersion

:pac::pac::pac:

at least your mother has unshakeable love and forgiveness for you unlike any client you may have had!:p

I have fitted thousands of immersions and have seen the after effects of blown elements, I have never seen this before the cover had liquified, the wires to the elements had melted, the cable where it touched the cylinder had heat indentations on it, I tested the overheat stat with a kettle of hot water and it was fine, i get a bit nervous when things happen I don't understand, I have asked for a copy of the original report that proves their explanation, I'll stick it on here if i get it.

Bruthal

gary71 wrote: »

bearing in mind I investigate defective installations for a living, guess what I forgot to do before I went back to the supplier with the immersion

Well i can say this, take the top off any immersion, remove the stat and wiring etc, get a welding torch, and aim it at the neutral end of the element, and melt it just where the connection would be. And no doubt about it, the terminal will melt, but the meltal part of the immersion in contact with the water still will not get anywhere near hot enough to melt the solder. The simple fact is, the element stem wont transfer enough heat down its length to get the metal base to any significant temperature. It, in contact with the water is like a massive heat sink.

A loose live connection is just as likely to burn as a loose neutral one also. So why do they say the neutral?

they also tried to explain it as a heating system under piped and the pump has to be bigger to push the water round, the element is the pump and the loose wire is the small pipework and the heat generated is from the extra effort to heat the element

An explanation for sesame street.


Are the connections directly onto element ends not welded on by the manufacturers? So any that are screw terminals dont have any thermal route to the immersion metal frame anyway?

slavetothegrind

slavetothegrind wrote: »

:pac::pac::pac:

at least your mother has unshakeable love and forgiveness for you unlike any client you may have had!:p

You'd thing, the words used were "heating engineer me arse":eek:

Bruthal

gary71 wrote: »

I have fitted thousands of immersions and have seen the after effects of blown elements, I have never seen this before the cover had liquified, the wires to the elements had melted, the cable where it touched the cylinder had heat indentations on it, I tested the overheat stat with a kettle of hot water and it was fine, i get a bit nervous when things happen I don't understand, I have asked for a copy of the original report that proves their explanation, I'll stick it on here if i get it.

I seen badly melted covers alright, which is a reason i often say immersion covers should be mandatory metal.

It looks more and more like an immersion run with a cylinder not full to the top.

Bruthal

gary71 wrote: »

I tested the overheat stat with a kettle of hot water and it was fine

Thats interesting, i would not of thought any overheat stat would operate in a kettle of water, overheat stats normally operate above boiling point. Was it not just the water temp stat you tested? The water temp stat has a probe into the water, so if the immersion was run with cylinder not completely full, the water temp stat would not cut out.

robbie7730

robbie7730 wrote: »

. Are the connections directly onto element ends not welded on by the manufacturers? So any that are screw terminals dont have any thermal route to the immersion metal frame anyway?

The wires are screwed on.

I would be happy to think this is a freak incident, but I don't like being told there is a perfectly good reason and I am at fault for not understanding the basic characteristics of a wired electrical immersion:D

robbie7730

robbie7730 wrote: »

Thats interesting, i would not of thought any overheat stat would operate in a kettle of water, overheat stats normally operate above boiling point. Was it not just the water temp stat you tested? The water temp stat has a probe into the water, so if the immersion was run with cylinder not completely full, the water temp stat would not cut out.

The suppler asked for that test to be done, I put the stat which I pulled out of the immersion into boiling water and the over heat activated, the cylinder was full.
the manufactures except that this fault will happen with there immersion under curtain conditions, what I will have to do is get that information so I can put more meat on the bones of this.

Bruthal

gary71 wrote: »

The wires are screwed on.

I would be happy to think this is a freak incident, but I don't like being told there is a perfectly good reason and I am at fault for not understanding the basic characteristics of a wired electrical immersion:D

Well look at it another way, shower pull chords often badly burn from bad connections, often destroying the pull chord isolator. And there is no water to heat sink them. And the insulation melts off the first couple of inches of the cable. But it goes no further, simply because the heat dissipates as it moves further from the bad connection. And showers take up to 3 times what an immersion does, yet they never burn very far from the terminals.

Here you have an immersion, with an enormous heat sink(metal to water) at its metal base where the elements are fixed to. And a smaller CSA for this heat to conduct from that bad connection to the metal base. And they expect you to believe enough heat will transfer to this metal base, heat it to 300c, while its fully in contact with water, and melt the solder? Complete rubbish is what id say.

It really does sound more like the element on with the cylinder not full to the top. How did the element look? If cylnder was full, element should still have looked new.

The element was perfect other than the movement from the where the solder was gone.

Bruthal

gary71 wrote: »

The suppler asked for that test to be done, I put the stat which I pulled out of the immersion into boiling water and the over heat activated, the cylinder was full.
the manufactures except that this fault will happen with there immersion under curtain conditions, what I will have to do is get that information so I can put more meat on the bones of this.

The water temp stat will not turn off the immersion when the cylinder is not full of water, even if the elements are glowing red in an air filled tank.

And if the stat was stuck on, and the cylinder is full, the water will just boil in the cylinder, which will be extremely obvious to anyone in the house with the loud rumbling that would be very noticeable.

So confirming the water set point stat was working does not tell an awful lot.

Im not sure immersions have an overheat safety stat like kettles have, i dont think they have.

How did you confirm it was full? Running a hot tap will confirm it is, as no water can come out of a non full cylinder because the out flow is from that pipe right at the top of the cylinder. But tapping the cylinder is not a great way to show its completely full.

Also, definitely some immersions i fitted had the actual 4 element ends welded to wire ends, and in fact, i thought they have the neutral ends connected with a bar welded onto the ends. maybe the memory is gone again.

Bruthal

gary71 wrote: »

The element was perfect other than the movement from the where the solder was gone.

I would say the cylinder was full so, i was not trying to suggest it wasnt of course:D. Just mentioning possibilities. Although the elements can take glowing red for a fair while, i seen it before. Overall, it would melt the solder, and would melt the plastic cover, if the cylinder was not full up to the top of the element at least.

But no way i can see anything you did to do with connections caused that. Id be agreeing with slavetothegrind. It sounds like a bit of a manufacturers flaw there if the cylinder was indeed full. As Mc cebee said, i always check the connections under the cover when fitting them. But can see no way for loose connection to cause the solder melting.

This was a cylinder with the element already in it?

Bruthal

Overall anyway, with top cover melted badly, wires all burnt, solder melted, all indicate the element was on while dry, at least for part of its lenght, and the element will glow red hot like this. Another sign is i think you said the flex had heat indentations where it touched the cylinder, and the cylinder cant of got any hotter than the water inside it, unless there was no water inside it at the point the flex was touching it.

After flooding my mam's house I'm not in a great position to say how good my work is, your right to question my skill set:D

The cylinder is a high end copper cylinder, only the best for my mam( and I got it cheap) the immersion is supplied with the cylinder separate but pre-wired, it's a easy to find make and most DIYers would have access to them.

I wire a lot of immersions none of them pre-wired, I am hoping they are talking bow locks and your explanation Robbie sounds better than the pump and pipework theory, I'll do my homework and get a answer from them.

robbie7730

robbie7730 wrote: »

Overall anyway, with top cover melted badly, wires all burnt, solder melted, all indicate the element was on while dry, at least for part of its lenght, and the element will glow red hot like this. Another sign is i think you said the flex had heat indentations where it touched the cylinder, and the cylinder cant of got any hotter than the water inside it, unless there was no water inside it at the point the flex was touching it.

The water at the hot tap was a constant, the cylinder is heavily insulated so the indentations came from the heat of the cable, I'm with you on everything except a dry cylinder, the overheat stat did seem to work ok, what I will do is try the kettle test again to prove it would have kicked in if the cylinder cooked(if it had water in it of course:D)

Bruthal

gary71 wrote: »

After flooding my mam's house I'm not in a great position to say how good my work is, your right to question my skill set:D

Them sort of things can happen any of us though. So i definitely am not questioning your skills. We know the solder melted. So the Immersion metal base got to 250 to 300c probably.

So the possibilities again.....

Loose connection on neutral i cant see causing that, and absolutely not with cylinder full of water. Why only on the neutral the manufacturers mention? As the live element ends also have connections, and there would be no real difference i can think of.

Maybe flaw in solder joint from manufacturer. But if this just caused the flooding, what caused the cover to melt? And external flex to show signs of being melted?

Element on with cylinder not full of water would likely cause solder to melt, and wiring and plastic cover to melt, and the external flex to show the signs of the heat indentations from contact with cylinder. Was it heat resistant flex?

So then cylinder fills and flows out the now melted solder joint. The elements would last quite a while when on dry, but the copper would possibly look a little dis-coluored.

Bruthal

gary71 wrote: »

The water at the hot tap was a constant, the cylinder is heavily insulated so the indentations came from the heat of the cable, I'm with you on everything except a dry cylinder, the overheat stat did seem to work ok, what I will do is try the kettle test again to prove it would have kicked in if the cylinder cooked(if it had water in it of course:D)

Yea once the flow from the hot tap was constant before the immersion was used, then the cylindew was full. Even if you then turned off the water valve to the cylinder, the level cannot drop below the very top of the cylinder by running the hot taps anywhere, the taps will stop as soon as the water drops to the level of the very top of cylinder. .


The "overheat stat" i assume you mean the one that has the long probe that goes into the tube that extends into the water is not an overheat stat. It is simply the stat you set the water temp with. An overheat stat is designed to cut out electric water elements in the event they are switched on while dry. Even if that water temp stat was stuck on as i said earlier, the water would just boil in the cylinder, and that would be like a mini earthquake in the house, noise wise anyway.

So if immersion was run with no water in the cylinder, that stat you are testing will not cut the immersion out, unless the air temp in the cylinder gets to 70c, or whatever the stat is set at. The solder would long be melted by this point because the element would be red hot with not water around it.

But it seems certain the cylinder was full from what your saying. You didnt somehow get a 110v element on holidays somewhere?:D

Anyway, id never buy their loose neutral connection as an explanation. The amount of heat required would be massive to be conducted down the very low element CSA to the immersion base which is in very good contact with the water. And we would see a lot more flooded houses, as burnt connections are not unheard of in immersion elements.

Another possibility, different solders melt at different points, so maybe this had a problem. But the immersion still had an overheating problem of some sort as well. It all seems to indicate a manufacturing problem of some sort anyway.