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.

cast_iron

robbie7730 wrote: »

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.

I tend to agree, but what else could have caused the massive heat build-up. Some sort of massive heat build up definitely occurred to melt the plastic cover, and it also travelled up the flex to indent the tank insulation.

Any chance the live and neutral cables somehow came into contact but didn't manage to trip the fuse? Is the immersion on an RCD?

Regardless of a dodgy solder joint, the source of the heat build-up needs to be ascertained. A bad connection seems like the most likely answer to this question.

Bruthal

cast_iron wrote: »

I tend to agree, but what else could have caused the massive heat build-up. Some sort of massive heat build up definitely occurred to melt the plastic cover, and it also travelled up the flex to indent the tank insulation.

Any chance the live and neutral cables somehow came into contact but didn't manage to trip the fuse? Is the immersion on an RCD?

If the 20 amp MCB failed, then either the main CU fuse would go, or the fault would blow clear. The RCD is unlikely to trip on a live - neutral contact anyway.

Them plastic covers can distort from having them covered with towels etc as the immersion head gets quite hot anyway, not saying that caused this, but just mentioning them plastic covers distort from heating easily enough.

Regardless of a dodgy solder joint, the source of the heat build-up needs to be ascertained. A bad connection seems like the most likely answer to this question.

Nothing much can be ruled out alright. A very bad solder joint maybe could be compromised by the normal heating of an immersion element. But if a properly soldered setup cant take the heat of a bad connection (which is not unheard of in immersions) which now has to conduct this heat down the element end and to a solder joint and metal base being cooled by the water, how can it take the heating from the 3kw heating element itself? Even in the cold water, you would be unable to touch them elements as they get very hot at their surface in the water. And would probably heat the metal base they are attached to more than any loose connection can.

If i just seen this without much evidence i would say the element was switched on dry. But i would say its clear thats not the case now.

I think about 750 watts (25% of rating) or so is the max heat that can be generated by a loose connection in a 13 amp (3kw) load. A fair bit of heat that can melt the cover no problem. So its conceivable this could of badly damaged the top cover and wiring of the immersion fitting alright. So maybe that did melt the solder. All i can say is how does it not happen more often so, if this element in question was soldered properly?

Maybe they should braize them if this is a possibility.

cast_iron

robbie7730 wrote: »

If the 20 amp MCB failed, then either the main CU fuse would go, or the fault would blow clear. The RCD is unlikely to trip on a live - neutral contact anyway.

I was hinting at if there was an MCB at all. It could be an old style setup, with DZ fuses. With that much heat, a live-earth fault could have occurred also and hence the lack of RCD could play an extra roll. Pure speculation, mind.

I think about 750 watts (25% of rating) or so is the max heat that can be generated by a loose connection in a 13 amp (3kw) load. A fair bit of heat that can melt the cover no problem. So its conceivable this could of badly damaged the top cover and wiring of the immersion fitting alright. So maybe that did melt the solder. All i can say is how does it not happen more often so, if this element in question was soldered properly?

That's why I'm just thinking it's maybe a bit further up the line. The OP will prob blow that theory out of the water though.

Bruthal

cast_iron wrote: »

That's why I'm just thinking it's maybe a bit further up the line. The OP will prob blow that theory out of the water though.

If it was a live neutral short, or live earth, the heat at the point of contact could be high, especially if there is a few ohms resistance there, but if there are no protective devices behind the short, the short would quickly be expected to blow itself clear.

If it was a hard low resistance/impedence direct short, then the heat dissipated would be along the entire circuit from the CU, and not concentrated in the immersion unit.

If it was indeed a bad connection in the circuit at an element end, this will be in series with the 18 ohm bath element for the worst case scenario, and so the highest heat output from a bad connection would be where the bad connection roughly equals the elements own 18 ohms, so 36 ohms total, with the element giving off 750 watts, and also the bad connection. But the bad connection would be a very concentrated 750 watts, while the element would be spread over its length, in the water. So in this scenario maybe it is remotely possible for a bad connection on the element end to cause the outcome seen by the OP.

Any lower, or higher resistance in this connection results in its 750 watts being reduced. Lower resistance and the element outputs more, higher and both the bad connection and the element output less. But even 300 or 400 watts from a very localised point maybe could do the damage described here.

The element end with the bad connection you would think would have its solder joint fail first through direct conduction if this loose connection did cause it, and then as water comes through, no more joins fail maybe.

It must be an extremely unusual one anyway. I never would of thought a loose connection could heat the immersion metal head enough to do this due to its massive heat sinking properties with water contact. But maybe it has in this case. And after calculating the roughly 750 watts in theory possible from a loose connection onto a 3 kw element, maybe it is feasable.

meercat

just to get away from an electrical fault
any chance your boiler caused this problem by building up pressure and releasing steam into cylinder causing plastic cap to melt after blowing a hole in the thermostat sheath and let water flood out?
check your expansion pipe in attic

meercat

meercat wrote: »

just to get away from an electrical fault
any chance your boiler caused this problem by building up pressure and releasing steam into cylinder causing plastic cap to melt after blowing a hole in the thermostat sheath and let water flood out?
check your expansion pipe in attic

No, the manufactures have already accepted it's a build up of heat under the head of the immersion due to a loose neutral connection, their description not mine, I just don't understand it:o also I would be an expert on heating systems although now I'm more of a expert on the correct use of a wet/dry Hoover.

Bruthal

gary71 wrote: »

No, the manufactures have already accepted it's a build up of heat under the head of the immersion due to a loose neutral connection, their description not mine, I just don't understand it:o also I would be an expert on heating systems although now I'm more of a expert on the correct use of a wet/dry Hoover.

Even though i was saying in theory a loose connection feeding a 3kw load can dissipate up to 750 watts max, it is hard to see such a connection lasting very long at anything like that wattage in such a small area such as a loose connection. The connection would likely just dissintegrate. And again, why do they insist it was on the neutral? if it was a loose connection, there is no more reason why its on a neutral than a live terminal. And why do we never see it happen on other immersions?

You should ask them this.

robbie7730

robbie7730 wrote: »

Even though i was saying in theory a loose connection feeding a 3kw load can dissipate up to 750 watts max, it is hard to see such a connection lasting very long at anything like that wattage in such a small area such as a loose connection. The connection would likely just dissintegrate. And again, why do they insist it was on the neutral? if it was a loose connection, there is no more reason why its on a neutral than a live terminal. And why do we never see it happen on other immersions?

You should ask them this.

On a new install last year a immersion was found smoking, the suppliers received a report on the installation after a investigation by the manufactures and it was found a loose neutral was at fault and they are telling me it's the same thing again, I am going to chase up the original report to explain this funky fault and I'll post it if I get it.

Bruthal

gary71 wrote: »

On a new install last year a immersion was found smoking, the suppliers received a report on the installation after a investigation by the manufactures and it was found a loose neutral was at fault and they are telling me it's the same thing again, I am going to chase up the original report to explain this funky fault and I'll post it if I get it.

Yea i wouldnt be surprised to see one smoking or melting its plastic cap etc from loose connections, i just never would of thought it could melt the solder. but just because one of their immersions failed at the neutral connection, they assume its the neutral again?

I never even noticed they were soldered at that point, although when you mentioned it earlier it did seem familiar alright having solder in that area on some of them. Its just hard to see the solder thats in contact with the water getting hot enough to melt even from a severely burning connection under the cap, unless there was a problem with the solder as well as the loose connection.

I think water has been known to seep up through the element insulating material when the outer copper jacket of the actual elemen splits in the water. It seeps up and out at the element ends under the cap. Nothing to do with this of course.

This whole thing is certainly worth keeping a good note of.

yoshytoshy

Sorry for replying late to this ,but I've seen this happen before. The water ended up coming from the soldered connection on the immersion ,because it overheated.
Someone wired the immersion wrongly and the homeowner left the immersion on while gone on holidays ,so the stat didn't kick in (don't know why the overheat didn't)

I left the old immersion with her as proof ,some builder had installed the cylinder as part of an attic conversion.

Bruthal

yoshytoshy wrote: »

Sorry for replying late to this ,but I've seen this happen before. The water ended up coming from the soldered connection on the immersion ,because it overheated.
Someone wired the immersion wrongly and the homeowner left the immersion on while gone on holidays ,so the stat didn't kick in (don't know why the overheat didn't)

I left the old immersion with her as proof ,some builder had installed the cylinder as part of an attic conversion.

Standard immersion heaters dont seem to have overheat cutouts in them.

If the bath wire is connected to bath as an example, and sink one to neutral on a single stat immersion, now the 2 elements can actually come on in series when bath is selected, at about 1.2kw output, and the stat wont switch them off. Is this similar to what mistake was made, or did you see what was done?

yoshytoshy

robbie7730 wrote: »

Standard immersion heaters dont seem to have overheat cutouts in them.

I think nearly all the pre-installed immersions have the little pop-up stat in the middle. I don't know if the one I seen was a pre-installed ,because I was so shocked at seeing the solder leaking. :eek:

Bruthal

yoshytoshy wrote: »

I think nearly all the pre-installed immersions have the little pop-up stat in the middle. I don't know if the one I seen was a pre-installed ,because I was so shocked at seeing the solder leaking. :eek:

Did you notice how it was connected, i edited the above post to show what mistake can be made, bath wire connected to bath in switch, sink to neutral(or sink wire to sink, bath to neutral), now you can have 2 elements in series with the stat not turning them off.

yoshytoshy

robbie7730 wrote: »

Did you notice how it was connected, i edited the above post to show what mistake can be made, bath wire connected to bath in switch, sink to neutral(or sink wire to sink, bath to neutral), now you can have 2 elements in series with the stat not turning them off.

I found the problem at the immersion switch ,the neutral was in the wrong spot alright. I didn't get too into it because I'm a plumber and my job was to fix the leaking immersion.
I left the old immersion there ,the girl had only got her house redecorated:(

Bruthal

So if you get the flex, and black is bath, brown is sink, and blue neutral for example....

Connect black to its correct bath terminal in switch. Connect brown to neutral of switch, and connect blue to the sink terminal in switch, both elements come on when bath is selected, and output 1.2kw, and worst of all, the stat does nothing.

When sink is selected, it works properly with stat controlling it.

The above is one possibility of incorrect wiring so the single stat immersion continously heats, and the stat has no effect when bath is selected.

Similar if sink is correctly connected to sink of switch, bath to neutral, and blue to bath terminal.

Bruthal

yoshytoshy wrote: »

I found the problem at the immersion switch ,the neutral was in the wrong spot alright. I didn't get too into it because I'm a plumber and my job was to fix the leaking immersion.
I left the old immersion there ,the girl had only got her house redecorated:(

Yea looks like that so, if the neutral of the flex is connected to one of the bath or sink switch terminals, then the stat will be out of the circuit, depending on which of the bath or sink cores is connected to the neutral, and what position the bath/sink selector is in, and the water will boil once the switch is left on.

I remember immersions years ago where the brown was actually the neutral. Im sure it was, maybe someone else will remember that?

I always double check what core is connected to what points in the immersion unit when fitting and connecting one.

yoshytoshy

robbie7730 wrote: »

So if you get the flex, and black is bath, brown is sink, and blue neutral for example....

Connect black to its correct bath terminal in switch. Connect brown to neutral of switch, and connect blue to the sink terminal in switch, both elements come on when bath is selected, and output 1.2kw, and worst of all, the stat does nothing.

When sink is selected, it works properly with stat controlling it.

The above is one possibility of incorrect wiring so the single stat immersion continously heats, and the stat has no effect when bath is selected.

Similar if sink is correctly connected to sink of switch, bath to neutral, and blue to bath terminal.

I've seen immersions wired wrongly before a few times ,they bubble like mad and steam is in the attic when left on. But I've never seen solder melting before ,maybe they don't make the immersions like they use to:(

People don't know their immersion is wired wrongly ,unless they forget to turn off the immersion

EDIT: I've also seen Gary's problem on shower switches ,switches melted because of a bad connection.

yoshytoshy

robbie7730 wrote: »

I remember immersions years ago where the brown was actually the neutral. Im sure it was, maybe someone else will remember that?
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Theres still loads of old immersions with the old braithed cable Three browns and an earth.