Went to run a bath this morning and found only cold water coming out of the
hot tap. A quick look at the circuit breaker box, the immersion has its own
terminal, showed that switch still in the on position so it hadn't tripped
overnight.

Took the plastic cover off the immersion element and one of the wires has
just melted, more like exploded actually, away from its terminal. The wiring
inside it is the positive mains wire goes to the thermostat, a black wire
comes out of the other side of that to one immersion terminal and the
neutral mains wire goes to the other immersion terminal.

It's the black wire out of the stat that has melted from the immersion
terminal. On the wire is a little sticker saying only replace with a similar
link wire or summat and do not remove this sticker. The immersion is only 18
months old so is it just a crap make or should I be looking for something
else that could have blown the wire apart but not tripped the circuit
breaker? The wiring from the wall socket to the immersion is pretty old now
(25 years maybe) but it's the pukka heavy duty stuff and anyway it's not
that that has failed. The broken link wire is part of the immersion kit.

It would be a soldering job to replace this bit of wire anyway which I guess
I could do rather than drain the whole thing down and fit a new immersion
but I'd rather not bother if the failure is indicative of a bigger problem
that's only going to recur anyway.
--
Dave Baker

In an earlier contribution to this discussion,
Dave Baker wrote:

Went to run a bath this morning and found only cold water coming out
of the hot tap. A quick look at the circuit breaker box, the
immersion has its own terminal, showed that switch still in the on
position so it hadn't tripped overnight.

Took the plastic cover off the immersion element and one of the wires
has just melted, more like exploded actually, away from its terminal.
The wiring inside it is the positive mains wire goes to the
thermostat, a black wire comes out of the other side of that to one
immersion terminal and the neutral mains wire goes to the other
immersion terminal.
It's the black wire out of the stat that has melted from the immersion
terminal. On the wire is a little sticker saying only replace with a
similar link wire or summat and do not remove this sticker. The
immersion is only 18 months old so is it just a crap make or should I
be looking for something else that could have blown the wire apart
but not tripped the circuit breaker? The wiring from the wall socket
to the immersion is pretty old now (25 years maybe) but it's the
pukka heavy duty stuff and anyway it's not that that has failed. The
broken link wire is part of the immersion kit.
It would be a soldering job to replace this bit of wire anyway which
I guess I could do rather than drain the whole thing down and fit a
new immersion but I'd rather not bother if the failure is indicative
of a bigger problem that's only going to recur anyway.

If the link wire is like the one on an immersion heater I bought recently,
it will have been spot welded onto the heater terminal. If that joint got
hot and burnt through, it must have been a duff weld. You may be able to get
a good joint using some sort of clamp-on connection. Failing that, you'll
have to replace the immersion heater.

You should complain to the supplier of the immersion heater. I would be
inclined to ask them to supply *and* fit a replacement - but I'm not sure
how far you would get.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In article ,
Dave Baker wrote:
Went to run a bath this morning and found only cold water coming out of
the hot tap. A quick look at the circuit breaker box, the immersion has
its own terminal, showed that switch still in the on position so it
hadn't tripped overnight.

Took the plastic cover off the immersion element and one of the wires
has just melted, more like exploded actually, away from its terminal.
The wiring inside it is the positive mains wire goes to the thermostat,
a black wire comes out of the other side of that to one immersion
terminal and the neutral mains wire goes to the other immersion
terminal.

It's the black wire out of the stat that has melted from the immersion
terminal. On the wire is a little sticker saying only replace with a
similar link wire or summat and do not remove this sticker. The
immersion is only 18 months old so is it just a crap make or should I
be looking for something else that could have blown the wire apart but
not tripped the circuit breaker? The wiring from the wall socket to the
immersion is pretty old now (25 years maybe) but it's the pukka heavy
duty stuff and anyway it's not that that has failed. The broken link
wire is part of the immersion kit.

It would be a soldering job to replace this bit of wire anyway which I
guess I could do rather than drain the whole thing down and fit a new
immersion but I'd rather not bother if the failure is indicative of a
bigger problem that's only going to recur anyway.

Sounds like that link wire had a poor (high resistance) connection causing
it to run hot and melt - you also see this in sockets where the screws
haven't been tightened properly.

I'm not quite sure what you mean about it being a solder job to fix -
surely the link wire is removable to allow the fitting of the immersion
and or thermostat? If things are so melted that the terminals no longer
exist then replacement is the only real option - they're not that
expensive. The thermostat can be replaced easily - it should just pull out
after disconnecting, the immersion requires draining down.

I'd normally say contact the makers about a free replacement when
something fails this early - but this has all the signs of faulty
installation. Even if the link wire came attached to one or the other that
terminal should still have been checked for tightness on installation.

--
*Marriage changes passion - suddenly you're in bed with a relative*

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Baker wrote:

It's the black wire out of the stat that has melted from the immersion
terminal.

How was said wire originally connected to the element, or is that
unclear because of the damage? I think this connection is usually a
0.25 in. push-on blade type, so the wire end would have had an
uninsulated crimp receptacle. If this was loose or the crimped
connection wasn't properly made it could easily lead to the symptoms
described.

On the wire is a little sticker saying only replace with a similar
link wire or summat and do not remove this sticker.

The wire's insulation will have a high temperature rating - 105 or 180
deg., probably.

The immersion is only 18 months old so is it just a crap make or

Who installed it? Was the tightness of _all_ connections checked at the
time?

should I be looking for something else

Check the resistance of the element (should be around 18-20 ohms for a 3
kW heater) also check the insulation resistance to earth at 500 V DC
(several megohms at least). After repair (if repaired) check with a
clip-on ammeter that the current drawn is around the 12-13 A mark.

It would be a soldering job to replace this bit of wire anyway

I wouldn't recommend soft soldering because of the high temperature
these leadouts reach. I suppose you could try silver soldering a bare
wire and applying heatshrink insulation after, but then you risk
cracking the ceramic bushing. Also the other end of the wire, if it
goes into a screw terminal on the 'stat will probably need a crimped
bootlace ferrule.

I suspect you will end up replacing the heater. At least if it's only
been in for 18 months it shouldn't be too difficult to get out...

--
Andy

In article ,
Dave Baker wrote:
Took the plastic cover off the immersion element and one of the wires
has just melted, more like exploded actually, away from its terminal.
The wiring inside it is the positive mains wire goes to the thermostat,
a black wire comes out of the other side of that to one immersion
terminal and the neutral mains wire goes to the other immersion
terminal.

Just thinking on, are these spade terminals? Rather like Lucar ones? If so
Huge is having the same problem.

--
*The problem with the world is that everyone is a few drinks behind *

Dave Plowman London SW
To e-mail, change noise into sound.

"Andy Wade" wrote in message
...
Dave Baker wrote:

It's the black wire out of the stat that has melted from the immersion
terminal.

How was said wire originally connected to the element, or is that unclear
because of the damage? I think this connection is usually a 0.25 in.
push-on blade type, so the wire end would have had an uninsulated crimp
receptacle. If this was loose or the crimped connection wasn't properly
made it could easily lead to the symptoms described.

The element terminal has a crimp connector, basically an open ended box made
of about 0.75mm thick metal welded or soldered onto the end of it and the 2
inch bit of wire was crimped into this at the factory. Whether there was
also solder on the joint there is no longer clear. Nothing is replaceable or
pull-offable. The other end of the wire goes to the stat with a screw
connection tightened by yours truly when I fitted it all 18 months ago and
still completely tight and unmelted.

Maybe I can lever open the box with a small screwdriver to get another bit
of wire into it but it'll be tricky in situ.

Check the resistance of the element (should be around 18-20 ohms for a 3
kW heater) also check the insulation resistance to earth at 500 V DC
(several megohms at least). After repair (if repaired) check with a
clip-on ammeter that the current drawn is around the 12-13 A mark.

Resistance of the element is 14 ohms. That's about as much as I can check
easily.
--
Dave Baker

"Dave Plowman (News)" wrote in message
...

Sounds like that link wire had a poor (high resistance) connection causing
it to run hot and melt - you also see this in sockets where the screws
haven't been tightened properly.

I'm not quite sure what you mean about it being a solder job to fix -
surely the link wire is removable to allow the fitting of the immersion
and or thermostat?

The link wire doesn't need to be removeable to fit it to the stat. It just
needs the stat to be in place so the link wire doesn't have to be 2 feet
long. The element terminal end was crimped up and non moveable from the
factory and that's the end that's blown. Maybe a bad crimp connection.

I'd normally say contact the makers about a free replacement when
something fails this early - but this has all the signs of faulty
installation.

Cheeky scrote.

Anyway I doubt I kept a receipt for something costing 20 quid so I'll
probably just have to drain the bugger down yet again and fit another one.
--
Dave Baker

In article ,
Dave Baker wrote:
I'm not quite sure what you mean about it being a solder job to fix -
surely the link wire is removable to allow the fitting of the immersion
and or thermostat?

The link wire doesn't need to be removeable to fit it to the stat. It
just needs the stat to be in place so the link wire doesn't have to be
2 feet long.

But at least one end has to be removable - or is the immersion and
thermostat one unit now?

The element terminal end was crimped up and non moveable
from the factory and that's the end that's blown. Maybe a bad crimp
connection.

Sounds like it. I've not come across this type.

I'd normally say contact the makers about a free replacement when
something fails this early - but this has all the signs of faulty
installation.

Cheeky scrote.

Wasn't implying you fitted it. ;-)

Anyway I doubt I kept a receipt for something costing 20 quid so I'll
probably just have to drain the bugger down yet again and fit another
one.

Even without a receipt a crimped connection shouldn't fail, so might be
worth having a go if you remember where it came from. They're *meant* to
be more reliable than a screw terminal.

--
*Why is the third hand on the watch called a second hand?

Dave Plowman London SW
To e-mail, change noise into sound.

On Sun, 27 Jul 2008 15:10:24 +0100, Dave Baker wrote:

Anyway I doubt I kept a receipt for something costing 20 quid so I'll
probably just have to drain the bugger down yet again and fit another one.

Drain down? Drain a little bit off more likely (unless the immersion's at
the bottom of the cylinder).

If you drain it all down the cylinder tends to move around when you're
unscrewing the immersion, rather than the weight of water holding it in
place.

You *did* make sure the gate valve feeding the cylinder was OK/replace it
with a lever valve, last time, didn't you? Or I bet you wish you had done. ;-)


--
John Stumbles

Teenagers: tired of being harassed by your stupid parents?
Act now! Move out, get a job and pay your own bills, while
you still know everything!

In article ,
Roger Mills wrote:

If the link wire is like the one on an immersion heater I bought
recently, it will have been spot welded onto the heater terminal. If
that joint got hot and burnt through, it must have been a duff weld.

Ah - that might explain it.

--
*When the going gets tough, use duct tape

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Baker wrote:

Resistance of the element is 14 ohms. That's about as much as I can check
easily.

Unless it's a 4 kW heater (v. unusual) that's suspiciously low and
suggests that the element might be en-route to self-destruction...

--
Andy

On 28 Jul, 10:12, Andy Wade wrote:
Dave Baker wrote:
Resistance of the element is 14 ohms. That's about as much as I can check
easily.

Unless it's a 4 kW heater (v. unusual) that's suspiciously low and
suggests that the element might be en-route to self-destruction...

--
Andy

Or the meter was one of those £5 from the market stall onesg

In an earlier contribution to this discussion,
Andy Wade wrote:

Dave Baker wrote:

Resistance of the element is 14 ohms. That's about as much as I can
check easily.

Unless it's a 4 kW heater (v. unusual) that's suspiciously low and
suggests that the element might be en-route to self-destruction...

Are you sure? According to my calculations, it needs to have a resistance of
about 19 ohms when *hot*. But presumably the resistance when cold will be
less than this - but I don't know by how much.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Roger Mills wrote:

Are you sure?

Fairly, unless his meter is telling fibs.

According to my calculations, it needs to have a resistance of about
19 ohms when *hot*. But presumably the resistance when cold will be
less than this - but I don't know by how much.

Nichrome has quite a low temperature coefficient of resistivity[*]. The
increase in resistance when hot will be around 3% which is about an
order of magnitude less than the discrepancy in Dave's measured figure.
Try measuring the resistance of a kettle element (a) cold and (b)
immediately after boiling.

[*] Some data he
http://www.resistancewires.co.uk/pro...chrome_80.html

--
Andy

In an earlier contribution to this discussion,
Andy Wade wrote:

Roger Mills wrote:

Are you sure?

Fairly, unless his meter is telling fibs.

According to my calculations, it needs to have a resistance of about
19 ohms when *hot*. But presumably the resistance when cold will be
less than this - but I don't know by how much.

Nichrome has quite a low temperature coefficient of resistivity[*]. The
increase in resistance when hot will be around 3% which is about
an order of magnitude less than the discrepancy in Dave's measured
figure. Try measuring the resistance of a kettle element (a) cold
and (b) immediately after boiling.


[*] Some data he
http://www.resistancewires.co.uk/pro...chrome_80.html

Sounds fair enough - assuming that that's what the resistive element is made
of, and that it runs at about 300 degC, which seems reasonable.

In that case, yes, the resistance of the OP's element is a bit low!

[I was probably thinking of things like light bulbs - which run *much*
hotter, and where there *is* a significant increase in resistance when
they're hot.]
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!