Problems with Immersion Tank

jasonb

Hi all...

Firstly, let me say that I know very little about all this, so apologies in advance.

We have Gas central heating (which doesn’t heat the water) and an Electric Shower, so we use the Immersion for heating enough water for washing the dishes etc. For years we had it set to come on Sink for a couple of hours in the early morning, and that was enough to get us through the day.

A while ago we had no hot water, and the Immersion Tank was cold. My Father in law, a retired electrician, had a look at it and said a new Immersion was needed. He replaced it, and it was working again.

However, we soon noticed that 2 hours on Sink in the morning wasn’t working for us anymore. The water was only warm, and it ran out quickly.

I’ve done some little tests and here’s what I’ve found out:

- The timer etc. is working fine, and the Immersion turns on and off as it should.
- If I turn on the Immersion to Sink, and check the Electricty meter, it spins a little faster than when it’s off.
- If I turn on the Immersion to Bath, and check the Electricty meter, it spins a lot faster than when it’s on Sink.
- After two hours of being on Sink, the Tank is only warm to touch, and it’s warm from the top down to maybe half way or a third from the bottom. In other words, about a half to two thirds of the tank feels warm, and the bottom is cold
- After two hours of being on Bath, the Tank is quite hot to touch, but only the top quarter or third of the tank, the rest of the Tank is cold.

So, basically, it seems to me that Sink heats more water, but at a low temp, and Bath heats less water, but at a hotter temp.

Now, I think there might be two elements in the Tank (though I haven’t looked inside it) so I’m wondering if it’s possible that the wiring has been done wrong. Shouldn’t Bath heat up more water, and Sink heat up less? Has the wiring to the Elements been switched? Or can I change the Temp settings so that Sink is a lot hotter and Bath is a little cooler, and then just remember that the switch on the wall is effectively backwards?

Any advice much appreciated, thanks!

Pete67

It sounds like wiring to the sink and bath elements are reversed. So when the switch is set to sink it's the bath element that is energised. But you should investigate why the gas heating does not heat the water. It might be just a closed valve. Everything else being equal, it would be cheaper to heat water using gas.

jasonb

Thanks Pete. So I am right in saying that the Bath element should be the longer one, and the Sink element the shorter one?

As for the Gas, it's always been like that. I've had it checked and the Gas isn't even connected to the water at all. It was put in before I owned the house, and is a bit of a mess. Sure, when I moved in, they had Gas Central heating, and a Gas Cooker connected to a Gas Cylinder out the back garden through a hole in the wall.

How easy would it be to swap the wiring on the elements? I'm no expert, I can change a plug or do a bit of wiring for an alarm or light fitting, but that's about it.

Pete67

It's straightforward enough, assuming you have a dual element and not two separate elements. Switch off the immersion at the fuse board, and remove the round metal or plastic cover on top of the immersion element and swap over the black and brown wires. The blue wire should go to the thermostat, leave it alone.
These connections carry a fair current so must be made correctly or they can overheat and cause a fire risk. No frayed wires sticking out, all strands of the conductor clamped tightly etc etc. If in any doubt get a sparks in to do it.

Sleeper12

Pete67 wrote:

It's straightforward enough, assuming you have a dual element and not two separate elements. Switch off the immersion at the fuse board, and remove the round metal or plastic cover on top of the immersion element and swap over the black and brown wires. The blue wire should go to the thermostat, leave it alone. These connections carry a fair current so must be made correctly or they can overheat and cause a fire risk. No frayed wires sticking out, all strands of the conductor clamped tightly etc etc. If in any doubt get a sparks in to do it.

Wouldn't it be be best practice to change the wireless in any switch rather than the element itself?

cruizer101

The only thing that doesn't make sense is the electricity usage. I would have thought the bath element (so presumably when sent sink on yours) would use more electricity but you seemed to say it was opposite.

jasonb

Thanks for your responses...

I was wondering about the electricity usage myself, but while I assume the bigger element would use more power, the smaller element is also a lot hotter, so I reckoned the higher temperature on the smaller element means more power being used, compared to the low temperature on the larger element. Can the temperatures of the two elements be adjusted? If so, could I just lower down the temp for the Bath switch (which seems to be the smaller element) and higher up the temp for the Sink switch (which seems to be the bigger element) and then just re-label the switch on the wall and avoid any re-wiring?

I think the next step is having a proper look at it, switching off the power and looking under the black cover to see what's going on. At the moment I have no idea if it's two elements or a dual element (or even what the different really is between those two options!). All I know is what I'm deducing (perhaps incorrectly) from the results of my tests...

jasonb

So I had a look under the cover at the wiring, and I've attached what I found.

From what I can see, and from what people have told me here, it does look like a dual element. And there's only one Temp control, which looks like it's set fairly high.

So, what I don't understand is this, why does the tank get much hotter with Bath, and only warm with Sink, if there's only one Temp control? Is it because Bath is heating only 1/4 of the tank, so it has time to get hotter, but Sink is trying to heat 1/2-2/3 of the tank, so it doesn't get as hot? In other words, if I left it on Sink for hours and hours, would the tank eventually also get hot to the touch?

And another thing I don't understand is if Bath is heating the small element and Sink the large element, and the Temp setting is the same for both, why is much more power being used when I have it set to Bath? Does choosing Bath on a normally functioning Immersion only heat more water (as it's a larger element) or does it also tell it to use more power as well? If this is the case, it could explain why choosing Bath is using more power, but it's wired to the wrong element, so not heating more water.

Anyhow, I suppose I wonder what do I do next? Do I swap the Black and Brown wires, thereby attaching Bath to the larger element and Sink to the smaller one? Will that just 'fix' everything?

Thanks...

Wearb

Is there a wiring diagram inside the immersion heater cover? I am suspicious of the wiring, but not certain without being there to have a better look.

jasonb

Nope, no wiring diagram, sorry!

Pete67

Hard to be sure without putting a meter on the terminals but that wiring looks wrong to me. The thermostat appears to be only switching one element, the one connected to the brown wire. Which means the other one could end up boiling the cylinder if left on long enough. The stat should be in the neutral so that it switches both elements, but is switching only one of the two live supplies. You need to get an electrician to check that out pronto.

Wearb

I agree with Pete. Get it looked at.

Don't know if you know that a few years ago there was a scalding death from an uncontrolled immersion heater. It boiled the water into the plastic attic tank which then gave way and scalding water came down through the ceiling.
I am not saying this just for your sake but for anyone else that might read this thread.

Good practice would be to have a cylinder stat, backed up by a correctly wired immersion.

Pete67

Looking at it again, and assuming the black wire is live when the switch is set to 'bath' I believe the two elements are connected in series with no thermostat in circuit when the switch is on 'bath'. This would explain the lower current draw in this case. It's wired completely wrong.

perry stanley

For a new immersion that looks 'old'. The new one ( most) have a reset button. The stat looks new and the wiring is suspect ie not as mentioned already. What make of immersion is it? Even cap looks aged?

jasonb

Thanks for your replies. I've turned off the immersion at the fuse box and will get an Electrician asap.

I see what you mean about the difference between the black and brown wires, the brown wire goes to the Thermostat and the black goes direct to what I'm guessing is an element.

I also see what you mean about the age, if I had to guess (and I have to, as I don't know exactly what work my Father in law did) I'd say he replaced the Thermostat and some wiring (which all look new) but not the Immersion itself.

Anyhow, I'll definitely get someone else in to fix it, and won't use the Immersion until it's done...

Thanks everyone.

Pete67

Ask the electrician to check the wiring at the switch as well - who knows what way that is, there is no guarantee it's correct either.

jasonb

Hi all...

Just thought I'd give a quick update on this.

An electrician came out, and actually confirmed that the wiring is correct. Well, it's backwards (Sink/Bath) but other than that it's fine.

However, he says the immersion element needs to be replaced, one seems to be working (the shorter sink one) but the other one isn't.

He did open an valve which means our Gas Central Heating now heats the water in the Immerison Tank, but only when the Radiators are on as well, the two systems aren't separate.

So basically we just need to get a new element and it should be ok. It's an old tank, so he thinks there could be a 36" element inside it, rather than a 24" one, but we might just get a 24" once anyhow, as we never use the 'Bath' setting (we have an electric shower and no bath) and all we want is hot water for the dishes etc.

Thanks for all your help...

perry stanley

Nice ending ...and it didnt cost the earth. Stay safe.;)

Wearb

jasonb wrote: »

Hi all...

Just thought I'd give a quick update on this.

An electrician came out, and actually confirmed that the wiring is correct. Well, it's backwards (Sink/Bath) but other than that it's fine.

However, he says the immersion element needs to be replaced, one seems to be working (the shorter sink one) but the other one isn't.

He did open an valve which means our Gas Central Heating now heats the water in the Immerison Tank, but only when the Radiators are on as well, the two systems aren't separate.

So basically we just need to get a new element and it should be ok. It's an old tank, so he thinks there could be a 36" element inside it, rather than a 24" one, but we might just get a 24" once anyhow, as we never use the 'Bath' setting (we have an electric shower and no bath) and all we want is hot water for the dishes etc.

Thanks for all your help...

Well I am still worried about that reply. When the electrician confirmed that the wiring is correct, what reason did he give for the problems you are having?

Pete67

I'm sorry, but that wiring is definitely not correct. I don't say this lightly, but you really need to get a second opinion.

jasonb

The electrician said that it wasn’t working due to the Immersion element being broken. He used a multi-meter with what I can only call a ‘claw’ on it that measured what was going through the wires, and one of them was really low when it shouldn’t be. He had another element with him to compare the wiring, he did say it was different to the newer elements (it’s the original element, so could be 30 years old).

I’m really not sure what to do now, everyone here seems to think the wiring is definitely wrong, but the two electrcians who have seen it (my Father in law and the guy I called in) both say the wiring is fine. Is anyone here based near Naas and happy to come look at it, for a 3rd opinion?

Wearb

jasonb wrote: »

The electrician said that it wasn’t working due to the Immersion element being broken. He used a multi-meter with what I can only call a ‘claw’ on it that measured what was going through the wires, and one of them was really low when it shouldn’t be. He had another element with him to compare the wiring, he did say it was different to the newer elements (it’s the original element, so could be 30 years old).

I’m really not sure what to do now, everyone here seems to think the wiring is definitely wrong, but the two electrcians who have seen it (my Father in law and the guy I called in) both say the wiring is fine. Is anyone here based near Naas and happy to come look at it, for a 3rd opinion?

Good for you for still considering that it might be wrong, because it is. I don't know why an electrician would need another element for comparison. You have been really unfortunate with you electricians, unless there is something going on with the wiring that we don't see. Even then, I have run a few scenarios through my head and I cannot come up with a way that yours could be correct.
I am assuming that that brown wire is going to the thermostat and that its positioning in the picture isn't some sort of illusion caused by a camera angle?

Stick with getting another opinion. It would only take a few minutes to see what's wrong.

Pete67

It sounds like he used a clamp meter to measure the current in both black and brown wires. As currently wired, the current will be low when the black wire is energised, as both elements are operating in series. This is not correct. In addition, although the current will be low, the water is still being heated slowly without a thermostat in circuit to limit the water temperature, and will eventually boil the cylinder if left energised for a sufficient period of time. This is an inherently dangerous situation and needs to be rectified.

When the brown wire is energised, one element will operate normally and the thermostat will limit the water temperature as it should.

A competent electrician will test the existing immersion elements for correct operation, insulation strength and current draw, and based on the test results, will advise if replacement is required. It is only a 5 minute job to rewire it correctly which may well fix all issues.

You might also ask the mods to move this thread to the electrical forum where you will hopefully get further good advice. Good luck.

Wearb

Pete67 wrote: »

It sounds like he used a clamp meter to measure the current in both black and brown wires. As currently wired, the current will be low when the black wire is energised, as both elements are operating in series. This is not correct. In addition, although the current will be low, the water is still being heated slowly without a thermostat in circuit to limit the water temperature, and will eventually boil the cylinder if left energised for a sufficient period of time. This is an inherently dangerous situation and needs to be rectified.

When the brown wire is energised, one element will operate normally and the thermostat will limit the water temperature as it should.

A competent electrician will test the existing immersion elements for correct operation, insulation strength and current draw, and based on the test results, will advise if replacement is required. It is only a 5 minute job to rewire it correctly which may well fix all issues.

You might also ask the mods to move this thread to the electrical forum where you will hopefully get further good advice. Good luck.

I did consider moving it, but I think that he has been left in no doubt about the problem at this stage and it is a sort of issue shared between the two trades. In fact you have explained it very well for him Pete, and also for future readers of this thread.

jasonb

Thanks for your replies.

Just to clarify (as much as I can) the wiring is as follows:

Wires coming from the white cable:

Brown Wire: Going to the Termostat
Black Wire: Going to a metal pin, I presume this is part of one of the elements?
Blue Wire: Going to another metal pin, I presume this is part of one of the elements?
Earth Wire: Going to a metal screw, which I think connects the whole Immersion section to the tank, and therefore Earths it.

Other wire:

Blue Wire: Going from the Thermostat to a metal pin (part of one of the elements?) which is connected by a metal bar to another metal pin.

That’s it, I hope that explains the picture better?

So, I don’t know what to do, other than continue to not use the Immersion. Could someone clearly explain to me what the wiring should be, as if it’s clearly wrong it should be easy to fix, right?

I’m concerned that if I get another Electrician, they’ll either say the wiring is fine, or decide something else is wrong etc. If I get someone else, and tell them ‘People online think the wiring is wrong’ they’ll probably just dismiss that out of hand! Once again, is anyone here, who says the wiring is wrong, based near Naas, and could they come look at it? If no-one here can come, should I be looking for a Plumber or an Electrician?

Thanks...

Wearb

jasonb wrote: »

Thanks for your replies.

Just to clarify (as much as I can) the wiring is as follows:

Wires coming from the white cable:

Brown Wire: Going to the Termostat
Black Wire: Going to a metal pin, I presume this is part of one of the elements?
Blue Wire: Going to another metal pin, I presume this is part of one of the elements?
Earth Wire: Going to a metal screw, which I think connects the whole Immersion section to the tank, and therefore Earths it.

Other wire:

Blue Wire: Going from the Thermostat to a metal pin (part of one of the elements?) which is connected by a metal bar to another metal pin.

That’s it, I hope that explains the picture better?

So, I don’t know what to do, other than continue to not use the Immersion. Could someone clearly explain to me what the wiring should be, as if it’s clearly wrong it should be easy to fix, right?

I’m concerned that if I get another Electrician, they’ll either say the wiring is fine, or decide something else is wrong etc. If I get someone else, and tell them ‘People online think the wiring is wrong’ they’ll probably just dismiss that out of hand! Once again, is anyone here, who says the wiring is wrong, based near Naas, and could they come look at it? If no-one here can come, should I be looking for a Plumber or an Electrician?

Thanks...

I can see what's wrong, but after two electricians looking at it, I am wary of advising you . Without being on the ground, there might be something else going on that I am unaware of.
Maybe ask a few of your neighbours for recommendations for an electrician.
Most experienced plumbers would know what's wrong also.

Pete67

Here is what needs to be done.

1) Test the immersion (both elements) for continuity. Record the resistance of each element separately.

2) Test the immersion (both elements) for insulation strength. Use a megger to determine resistance to earth. Replace immersion heater if required.

3) Check switch wiring - visual inspection and verify blue wire is neutral, black/brown are sink/bath respectively. Verify earth bonding is correct by measuring the L-E fault impedance.

4) If all OK, connect immersion as follows - blue wire to thermostat. Other side of thermostat to one end of each heating element - there is usually a metal bar pre-installed to join one end of each element together. Connect the brown wire to the other end of the bath element - this will be the element with the lower resistance, and finally connect the black wire to the other end of the sink element.

5) Set thermostat to 60deg C approx and test for correct operation. Replace cover on the immersion element and ensure that the wall switch is securely mounted.

This should be child's play for any electrician, so like Wearb, I am concerned that there is something else very unusual about your particular installation so I will stop short of advising you to proceed as above without all the checks being made first. Find a competent electrician and this will be sorted out once and for all.

jasonb

Sorry for the delay, I've been up to my eyes. Thanks to both of you for your replies.

What you've explained Pete makes a lot of sense. I've attached the same pic, but with the four element 'points' labelled. From what you've said about a metal bar being installed to link the two elements together, am I right in thinking that points 1 and 2 are one element (though I don't now yet if it's the Sink or Bath) and points 3 and 4 are the other one, with the metal bar going between points 2 and 4?

If the resistance of each element has to be measured separately (to identify which is Sink and which is Bath), does that mean the metal bar between the two elements will have to be disconnected, as that bar makes it impossible to measure one element without also including the other?

Also, going from your description Pete, it looks like it's clear where the wiring is wrong, with the Blue (assuming it's the neutral) going to an element, not to the Thermostat, and the Brown going to the Thermostat, not to the Bath element. Now that I understand what it should be, I agree with you, I fail to see why two electricians think the wiring is fine. Unless, of course, it's been wired in such a way that the Blue isn't the neutral, and the Brown is, but you'd think that would be dangerous for no other reason than it goes against standard convention!

Thanks...

Pete67

Ok, yes it appears that the blue and brown wires were mixed up previously. However the installation should be tested for electrical safety before simply swapping them over.

There is no need to disconnect the link between the two elements to measure their individual resistances, as they are only connected together at one end.

jasonb

Thanks Pete... My next step is to confirm which element is which (by measuring the resistance as you say), and I'm also going to look inside the immersion switch to see how that's wired. That will give me a full picture of what's what, which I can then bring to an electrician.

Thanks...

Sleeper12

I'm still scratching my head trying to figure out why someone would wire into the element itself instead of using the cable already attached to the new element & wire it to the switch?

I don't think I've ever seen it before.

Pete67

Sleeper12 wrote:

I'm still scratching my head trying to figure out why someone would wire into the element itself instead of using the cable already attached to the new element & wire it to the switch?

Looking at the picture, I don't think the element was replaced, it looks fairly elderly. The cable looks new however so my guess is that the cable from the switch was replaced, and possibly the switch as well, and given the way it was done, I would be concerned that the switch may not be wired correctly either. Hard to believe that two different 'electricians' found nothing wrong with it.

jasonb

Yep, I'm pretty certain that the elements are the originals. The Thermostat was replaced, and the wiring too I think, I don't know if the switch was. I hope to look inside the switch tonight/tomorrow and see what the wiring is like there!

jasonb

So here's an update.

Firstly, the inside of the switch. I've attached a picture, but basically inside the switch the Brown is Neutral and the Blue is Bath (with the Black being Sink). Which means (I think!) that the wiring is actually ok, as both the Immersion and the Switch have the Blue and Brown swapped over. Both Earths (from the Supply and from the Immersion) are in the same Earth hole, instead of one in each side, but I don't think that's an issue at all.

Next, the Immersion elements. I did my best to do this correctly, so let me know if I made a mess of it. First, continuity:

Looking at the Immersion 2.jpg pic (which I've attached again), I couldn't get any continuity at all between Pin 1 and any other Pin. I got continuity between Pins 2 and 3, between Pins 2 and 4 and between Pins 3 and 4.

Next, resistance. Here's what I got:

Pins 1 & 2: 6 MOhms and constantly rising
Pins 1 & 3: 1 KOhm and constantly rising
Pins 1 & 4: 1 KOhm and constantly rising
Pins 2 & 3: 2 Ohms
Pins 2 & 4: 23 Ohms
Pins 3 & 4: 23 Ohms

Resistance to Earth:

Pin 1 & Earth: 1 KOhm and constantly rising
Pin 2 & Earth: 0 Ohms
Pin 3 & Earth: 0 Ohms
Pin 4 & Earth: 0 Ohms

So, anyone want to interpret that? My completely uneducated guess is that the wiring is fine (if a little backwards), and whatever is wrong, it involves whichever element Pin 1 is attached to. I still don't know which Pins make up the two elements.

Hope all that makes sense?

gctest50

Get a plumber out to install zone valves so you can heat water independent of radiators

jasonb wrote: »

....

He did open an valve which means our Gas Central Heating now heats the water in the Immerison Tank, but only when the Radiators are on as well, the two systems aren't separate.

.,...

While the plumber is there get them to have a look at the immersion

Pete67

You can't reliably measure insulation strength with a multimeter - you need a megger which tests at 500 or 1000V. Saying that from the readings you have posted, it does look like at least one element has failed, and in addition the wiring is incorrect at both the switch and the element.

You may have this already sorted, but if not I'd suggest getting the element replaced. The new ones come pre-wired. Just make sure that the new one is the correct length or it will not be able to heat the cylinder all the way to the bottom.

One final word of warning - the old element may be very hard to remove, and if you apply too much torque to it you can tear the top of the cylinder - it is only thin copper sheet. So be very careful, ideally get a plumber or sparks who do this all the time as they will know the tricks to avoid damaging the cylinder.

jasonb

Hi Pete...

Thanks a lot, yep the next plan is get someone to come out and replace the Immersion and wire it properly while they’re here. It’s a large tank, so maybe need a 3ft immersion, but we might jut go with a 2ft one just to make it easier to put in, as we never use th Bath option anyhow, so don’t need to full tank heated.

Thanks...