Immersion heater not working

[Dane2594]

Hi,
I've bought a house and been here a year now but the immersion heater is not working now. It randomly stopped one day so I bought a new element/stat and swapped them over. It's a basic cylinder with a single element entry at the top. I've replaced it of a similar element of the same size (27") and still no joy. I took it back and swapped it out under warranty and again still no joy.

I wired it up the same as the old one, and the new one came with a diagram which confirms it is correct.

I can replace things around the house I've replaced all plug fronts and light switches as well as adding some new lights throughout the house but my electrics especially terminology is basic.

I grabbed a multimeter and thought I'd give it a go myself as I've had not one but two plumbers round and both say 'it should be working but I don't know why' and pretty much ran out the door, I'm assuming fault finding isn't worth their time and came just to do an easy swap.

Live to earth is 240v
Neutral to earth is 240v
Live to neutral is 0
Resistance is 20 ohms.

there is power both sides of the Thermostat (in and out) and when turning it down to 0 it shuts power off to one side (cable running to element). The overheat reset is pushed in.

I'm stuck with this and I can't get a sparky round to look at it until next week, it's been 10 days without hot water and it's not good!

Any help would be much appreciated and remember to dumb it down for me

 

[stem]

They are right! it should be working, and I think you have come to that conclusion yourself, hence your post here.

Whilst the voltage is present, is there something restricting the current flowing? A 3kW immersion will require about 13A. So, for example, there may be a poor connection at the consumer unit or switch. Or, the switch contacts maybe pitted or burned, which would allow you to see a voltage, but not let sufficient current flow.

If you could by-pass the wiring at the switch, (or timer) purely as a test, and see if it works then, that would allow them to be eliminated from your enquiries.

You could always wire a fly lead to the immersion and plug it in just as a test, that would confirm that the element and overheat trip are OK or not. If it does work, don't be tempted to leave it like that though.

 

[JohnD]

looks like a high resistance fault in the supply. Perhaps the wall switch is burned out or someone put a nail through the cable.

It could also be a wiring error, but you say it used to work.

 

[Dane2594]

I don't think it's a wiring error as it was working for 6 months up until the day it died and I haven't touched it at all since being in the house.
The cables look new from the switch to the element but the wall switch itself looks a bit older so I'll give that a swap and see where that gets me.
Nothing should have pierced any cables either as nothing has been done around the house for the likes of a nail or screw to be piercing anything.

Thanks for your help

 

[Dane2594]

They are right! it should be working, and I think you have come to that conclusion yourself, hence your post here.

Whilst the voltage is present, is there something restricting the current flowing? A 3kW immersion will require about 13A. So, for example, there may be a poor connection at the consumer unit or switch. Or, the switch contacts maybe pitted or burned, which would allow you to see a voltage, but not let sufficient current flow.

If you could by-pass the wiring at the switch, (or timer) purely as a test, and see if it works then, that would allow them to be eliminated from your enquiries.

You could always wire a fly lead to the immersion and plug it in just as a test, that would confirm that the element and overheat trip are OK or not. If it does work, don't be tempted to leave it like that though.

That a very helpful post thank you. I did think about bypassing the switch to see if that was the problem as you have said, but wasn't sure about the safety of it being mains. I won't leave it like this as it will be without the fuse.

I did take the switch apart yesterday there was no evidence of pitting, but the negative terminal was about one turn loose and by what's been said could possibly be it, with a bit of luck it's burnt out!

I'll get home this afternoon to see what amps is being drawn and hopefully that gives me a clue if the switch is no good. I'm at work at the moment but as far as I remember the element had a stamp of 15a and the fuse in the wall is at 30a. I know that won't make a difference in the running of it and the problem I've got, but is this OK or should I also scale it down to a 15a if there ever was a problem in the future?

For some reason your post only showed up for me an hour ago which is strange as the newer reply was the only one showing, but it's been a great help so thank you.

 

[Madrab]

If you have Neutral (N) to Earth (E) at 240v and 0V from Live (L) to Neutral then you have a fault. I'd be back looking at a possible issue with the wiring, specifically the Neutral if it's showing 240v to/from Earth. Check your supply voltage to the fused spur and check you have -

L > N = 240v
L > E = 240v
N > E= 0v

If you do then check the wiring to the element for continuity. If you have the same results as you found, 240v from N > E then I'd be checking for continuity back to the consumer unit.

 

[Agile]

I really don't see what the problem testing it is!

It just needs to have 240v across the live and neutral at the inlet connections to the heater.

Then 240v across the element itself.

If so then it must work! If the parts are OK !

I don't see why any plumbers were unable to identify the problem. Unless of course they thought that you did not intend to pay them for the diagnosis.

My experience is that people who have started to change parts themselves seem to think that a professional should come and give a free diagnosis. One of their "tricks" is to ask for a free estimate to do the repair !

I always would charge for any visit !

 

[stem]

Methinks Dane2594 has inadvertently transposed his results.

Neutral to earth is 240v
Live to neutral is 0

Hopefully he will be along soon to clarify.

 

[Agile]

Based on what he quoted there is no neutral connection.

But he might well have realized that himself and certainly at least one of the TWO plumbers who visited would have done!

But only if they expected to get paid!!!

If on arrival they realized he was touting for a free diagnosis it is not surprising they would have been in a hurry to leave and not to waste any more time. But people who say they give "free estimates" lay themselves open to that as you cannot give an estimate until you have diagnosed the problem!

 

[DP]

Dane, I can see what the problem is from what you posted at the start of the thread

By the way, the plumbers that came to see you, were you reluctant to pay them as agile suggests?
Were you looking for a freebie fix?

 

[Dane2594]

I was/am more than happy to pay anyone to fix and I have been happy to since day one, not having hot water is horrible. I did not give off any impression of that sort to either of them.
One plumber came in with a torch and neon screwdriver to hand only, tapped the connections and said 'there's power here I have no idea why it's not heating it' and that was the end of his visit.
The second one measured the values and seems to think they are right so he does not see why it's not heating. He thinks that the values mentioned in my first post are all correct and there shouldn't be a voltage across L-N which conflicts with what's being said here.

If it was working before what would cause the values to change since it died for no reason and was not touched before hand.

Methinks Dane2594 has inadvertently transposed his results.


Hopefully he will be along soon to clarify.

Yes sorry I have conflicted what was said.
The values are at the element/stat -
L-E 240
N-E 240
L-N 0.

At the wall switch
input -
L-N 240
N-E 0
L-E 240

The wall switch output (to the heater element)
L-N 0
N-E 240
L-E 240

Going by this the wall switch needs replacing as the input/outputs are different. This has not been touched at all until today and it used to work up until the hot water stopped so the wires haven't been touched in there just to clarify in case someone thinks it's been wired wrong.

Again thanks for the many replies and help offered.

 

[Agile]

Seems the neutral pole in the switch is not making contact.

A bodge repair would be to link the N in to the N out to test!

But that should not be done as a permanent repair as the element should be powered from a two pole switch!

Tony

 

[Agile]

For anyone to attend to do a repair on an immersion with only a neon screwdriver beggars belief.

Even so I would have been able to identify that fault with just a neon.

They are not inherently safe and so I would not use one seriously as I always have a meter with me. Even had a meter when on holiday in Mahe!

 

[Dane2594]

Seems the neutral pole in the switch is not making contact.

A bodge repair would be to link the N in to the N out to test!

But that should not be done as a permanent repair as the element should be powered from a two pole switch!

Tony

I was thinking about joining the two neutral wires together to see if it would then work.

I've checked the wires and they are all tight with plenty ofcontainer
so I'm assuming if I join the two neutral wires together and it works I'll need a new switch? If so I'll pop down somewhere like screwfix today and get one. Would a 13a fused spur be sufficient? There isn't anything on this one to compare it to. Apart from having a 30a fuse.
Something like this? http://www.screwfix.com/p/british-g...odEXAK7Q#product_additional_details_container
If I'm not allowed to put links for any reason I'll remove it.

Thanks

 

[ianmcd]

Your Immersion uses a double pole switch for a reason, when it is switched off it cuts the Live and the neutral supplies, do no mess around with it get someone that knows what they are doing