Couple of weeks ago I got a phone call from our tenant who mentioned that
there was no hot water - the flat has electric only, and all hot water
provided by an immersion heater in a direct tank.

They'd managed to leave the immersion switched on for about a day, and it
had not only heated the 120l tank, but the large cold storage tank above it
(I estimate it must be 250 or 300l at least) to a rather scary temperature.
After that, they said it didn't do any better than lukewarm, and then packed
up altogether.

Well, after spending couple of weeks phoning him to get access to the flat
(suspect he'd been avoiding my calls, he owed us rent....) and sorted the
problem out.

I'd been idly speculating upon what the problem might have been whilst
waiting to do the job, perhaps the thermostat had packed up, etc etc.
Heater was open circuit when tested, so drained the tank down and whacked in
a replacement, no problems.

But, can anyone spot what could have been the problem with the heater....

http://www.olifant.co.uk/Olifant/Pub...ks/RSAN-62XF2E


The immersion heater is now connected via a timer...!!!



--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

In an earlier contribution to this discussion,
RichardS noaccess@invalid wrote:

Couple of weeks ago I got a phone call from our tenant who mentioned
that there was no hot water - the flat has electric only, and all hot
water provided by an immersion heater in a direct tank.

They'd managed to leave the immersion switched on for about a day,
and it had not only heated the 120l tank, but the large cold storage
tank above it (I estimate it must be 250 or 300l at least) to a
rather scary temperature. After that, they said it didn't do any
better than lukewarm, and then packed up altogether.

Well, after spending couple of weeks phoning him to get access to the
flat (suspect he'd been avoiding my calls, he owed us rent....) and
sorted the problem out.

I'd been idly speculating upon what the problem might have been whilst
waiting to do the job, perhaps the thermostat had packed up, etc etc.
Heater was open circuit when tested, so drained the tank down and
whacked in a replacement, no problems.

But, can anyone spot what could have been the problem with the
heater....

http://www.olifant.co.uk/Olifant/Pub...ks/RSAN-62XF2E


The immersion heater is now connected via a timer...!!!


Look like several problems to me.

1. Vent pipe dipping into water in header - thus setting up a thermo-syphon
system which heated up the header tank
2. Immersion element over-heated and bent until it touched the thermostat.
The stat was then driven by the element rather than the water temperature,
and cut out prematurely - providing only tepid water
3. Element finally failed altogether

If I'm right about (1), you'll need to fix this, or the problem will recur.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

1. Vent pipe dipping into water in header - thus setting up a
thermo-syphon
system which heated up the header tank

I concur. Normal heating expansion shouldn't heat the cold cistern. This
needs to be fixed urgently, as (a) it isn't safe and (b) it must be costing
a fortune keeping the barely insulated cold cistern at 60C using
electricity.

Christian.

P.S. I would always fit a dual thermostat immersion with a manual reset trip
set 10C above the main operating thermostat. These are required for unvented
cylinders, but heartily recommended for other types of cylinder too.

"Set Square" wrote in message
...
In an earlier contribution to this discussion,
RichardS noaccess@invalid wrote:

Couple of weeks ago I got a phone call from our tenant who mentioned
that there was no hot water - the flat has electric only, and all hot
water provided by an immersion heater in a direct tank.

They'd managed to leave the immersion switched on for about a day,
and it had not only heated the 120l tank, but the large cold storage
tank above it (I estimate it must be 250 or 300l at least) to a
rather scary temperature. After that, they said it didn't do any
better than lukewarm, and then packed up altogether.

Well, after spending couple of weeks phoning him to get access to the
flat (suspect he'd been avoiding my calls, he owed us rent....) and
sorted the problem out.

I'd been idly speculating upon what the problem might have been whilst
waiting to do the job, perhaps the thermostat had packed up, etc etc.
Heater was open circuit when tested, so drained the tank down and
whacked in a replacement, no problems.

But, can anyone spot what could have been the problem with the
heater....

http://www.olifant.co.uk/Olifant/Pub...ks/RSAN-62XF2E


The immersion heater is now connected via a timer...!!!


Look like several problems to me.

1. Vent pipe dipping into water in header - thus setting up a
thermo-syphon
system which heated up the header tank
2. Immersion element over-heated and bent until it touched the thermostat.
The stat was then driven by the element rather than the water temperature,
and cut out prematurely - providing only tepid water
3. Element finally failed altogether

If I'm right about (1), you'll need to fix this, or the problem will
recur.


Hmm, thanks, I hadn't considered this. I'll check it when I'm back there
next week (there's nothing like a simple job for throwing up all sorts of
nasties that need to be put right, is there!).

I'm not entirely sure that the vent pipe is dipping into the header though
because when I drained the tank this would have surely either 1) siphoned
water out of the header, or 2) drained the header to the depth of the vent
pipe, and I didn't hear the header valve opening to replenish the level. I
had thought that in this case the header heated up simply through conduction
and convenctive currents set up within the feeder pipe to the HW tank.

Still, the timer will go a long way to preventing future occurrence, because
it's set to heat the tank in the morning, and they are unlikely to get
through an entire tank in the day (electric shower used far more than the
bath).

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

"Christian McArdle" wrote in message
et...
1. Vent pipe dipping into water in header - thus setting up a
thermo-syphon
system which heated up the header tank

I concur. Normal heating expansion shouldn't heat the cold cistern. This
needs to be fixed urgently, as (a) it isn't safe and (b) it must be
costing
a fortune keeping the barely insulated cold cistern at 60C using
electricity.

Christian.

P.S. I would always fit a dual thermostat immersion with a manual reset
trip
set 10C above the main operating thermostat. These are required for
unvented
cylinders, but heartily recommended for other types of cylinder too.



this is the first time it has been known to happen, though (heating the
storage tank). They say that the immersion was left switched on for a day,
I have suspicions that it was far, far longer than that, though...

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

In article , RichardS
noaccess@invalid.? writes
Couple of weeks ago I got a phone call from our tenant who mentioned that
there was no hot water - the flat has electric only, and all hot water
provided by an immersion heater in a direct tank.

They'd managed to leave the immersion switched on for about a day, and it
had not only heated the 120l tank, but the large cold storage tank above it
(I estimate it must be 250 or 300l at least) to a rather scary temperature.
After that, they said it didn't do any better than lukewarm, and then packed
up altogether.

Well, after spending couple of weeks phoning him to get access to the flat
(suspect he'd been avoiding my calls, he owed us rent....) and sorted the
problem out.

I'd been idly speculating upon what the problem might have been whilst
waiting to do the job, perhaps the thermostat had packed up, etc etc.
Heater was open circuit when tested, so drained the tank down and whacked in
a replacement, no problems.

But, can anyone spot what could have been the problem with the heater....

http://www.olifant.co.uk/Olifant/Pub...ks/RSAN-62XF2E


The immersion heater is now connected via a timer...!!!

Sticky stat?, see below, ouch . . . .
http://www.cibse.org/index.cfm?actio...92&TopSecID=16
--
fred

In article ,
RichardS noaccess@invalid wrote:
this is the first time it has been known to happen, though (heating the
storage tank). They say that the immersion was left switched on for a
day, I have suspicions that it was far, far longer than that, though...

If the stat had stuck on, and it was left on without being used, the steam
from the boiling water will heat the header tank over time.

--
*One nice thing about egotists: they don't talk about other people.

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

In an earlier contribution to this discussion,
Dave Plowman (News) wrote:

In article ,
RichardS noaccess@invalid wrote:
this is the first time it has been known to happen, though (heating
the storage tank). They say that the immersion was left switched on
for a day, I have suspicions that it was far, far longer than that,
though...

If the stat had stuck on, and it was left on without being used, the
steam from the boiling water will heat the header tank over time.

I guess this must be the case - since it has apparently prompted a change in
the regs - but I don't quite understand it.

I would expect the steam to come out through the vent pipe and to fill the
attic with steam rather than heating the header tank (unless the vent pipe
dips into the water). Surely, to heat the water in the header, the steam
would have to come up the cold fill pipe from the bottom of the cylinder -
which seems unlikely. Am I overlooking something?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On Fri, 16 Jul 2004 20:57:38 +0100, Set Square wrote:

I would expect the steam to come out through the vent pipe and to
fill the attic with steam rather than heating the header tank
snip
Am I overlooking something?

When a cylinder boils the expanding steam in the cylinder forces hot
water out of the vent pipe and thus into the header tank. Normally
making loudish thumps and bangs as it does it.

--
Cheers
Dave. pam is missing e-mail

"RichardS" noaccess@invalid wrote in message ...
Couple of weeks ago I got a phone call from our tenant who mentioned that
there was no hot water - the flat has electric only, and all hot water
provided by an immersion heater in a direct tank.

They'd managed to leave the immersion switched on for about a day, and it
had not only heated the 120l tank, but the large cold storage tank above it
(I estimate it must be 250 or 300l at least) to a rather scary temperature.
After that, they said it didn't do any better than lukewarm, and then packed
up altogether.

Well, after spending couple of weeks phoning him to get access to the flat
(suspect he'd been avoiding my calls, he owed us rent....) and sorted the
problem out.

I'd been idly speculating upon what the problem might have been whilst
waiting to do the job, perhaps the thermostat had packed up, etc etc.
Heater was open circuit when tested, so drained the tank down and whacked in
a replacement, no problems.

But, can anyone spot what could have been the problem with the heater....

http://www.olifant.co.uk/Olifant/Pub...ks/RSAN-62XF2E


The immersion heater is now connected via a timer...!!!


so the thermostat was shorted?

Regards, NT

In article ,
Set Square wrote:
I would expect the steam to come out through the vent pipe and to fill
the attic with steam rather than heating the header tank (unless the
vent pipe dips into the water). Surely, to heat the water in the header,
the steam would have to come up the cold fill pipe from the bottom of
the cylinder - which seems unlikely. Am I overlooking something?

The vent pipe outlet could be pretty close to the top of the water, and
blasting steam at that will heat it up. As the water in the cylinder
boils, it will draw water in from the header tank - so it will, to a
certain degree, recirculate. I've certainly seen this with a central
heating system pumping over.

--
*A backward poet writes inverse.*

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

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

On Fri, 16 Jul 2004 20:57:38 +0100, Set Square wrote:

I would expect the steam to come out through the vent pipe and to
fill the attic with steam rather than heating the header tank snip
Am I overlooking something?

When a cylinder boils the expanding steam in the cylinder forces hot
water out of the vent pipe and thus into the header tank. Normally
making loudish thumps and bangs as it does it.


Yes, but that doesn't really explain how the whole header gets heated up to
a very high temperature.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

"N. Thornton" wrote in message
m...
"RichardS" noaccess@invalid wrote in message
...
Couple of weeks ago I got a phone call from our tenant who mentioned
that
there was no hot water - the flat has electric only, and all hot water
provided by an immersion heater in a direct tank.

They'd managed to leave the immersion switched on for about a day, and
it
had not only heated the 120l tank, but the large cold storage tank above
it
(I estimate it must be 250 or 300l at least) to a rather scary
temperature.
After that, they said it didn't do any better than lukewarm, and then
packed
up altogether.

Well, after spending couple of weeks phoning him to get access to the
flat
(suspect he'd been avoiding my calls, he owed us rent....) and sorted
the
problem out.

I'd been idly speculating upon what the problem might have been whilst
waiting to do the job, perhaps the thermostat had packed up, etc etc.
Heater was open circuit when tested, so drained the tank down and
whacked in
a replacement, no problems.

But, can anyone spot what could have been the problem with the
heater....

http://www.olifant.co.uk/Olifant/Pub...ks/RSAN-62XF2E


The immersion heater is now connected via a timer...!!!


so the thermostat was shorted?

Regards, NT


I dunno, but I've got it here still. If I get a spare moment, I'l stick it
in a pan of water, bring to the boil, and watch how it's resistance
characteristic changes.

I was just impressed by how catastrophically the whole thing had failed.


--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

In message , RichardS
writes


I dunno, but I've got it here still. If I get a spare moment, I'l stick it
in a pan of water, bring to the boil, and watch how it's resistance
characteristic changes.

I was just impressed by how catastrophically the whole thing had failed.


I came to this thread a bit late

Richard, if you really have problems, ring me on 01923 229224

--
geoff

"RichardS" noaccess@invalid wrote in message ...
"N. Thornton" wrote in message
m...

so the thermostat was shorted?

Regards, NT


I dunno, but I've got it here still. If I get a spare moment, I'l stick it
in a pan of water, bring to the boil, and watch how it's resistance
characteristic changes.

I was just impressed by how catastrophically the whole thing had failed.

The thermostat switches power to the heater off when teh water reaches
the desired temp. If the whole thing cooked itself to death then
almost certainly it was thermostat failure that caused it. If thats
whats happening, the solution is to replace the thermostat on the
tank.

The stat may come as part of the new element assembly, depending on
the design. If the element assembly has a temperature dial on it, and
you didnt remove that bit, it will now have a new thermostat already.


Regards, NT

Still, the timer will go a long way to preventing future occurrence,
because
it's set to heat the tank in the morning,

The timer is a red herring. When I use my immersion, I leave it on 24 hours
a day. Better to fit a immersion with 2 thermostats. One being a manual
reset overheat type.

Christian.

"RichardS" noaccess@invalid wrote in message
. ..
Couple of weeks ago I got a phone call from our tenant who mentioned that
there was no hot water - the flat has electric only, and all hot water
provided by an immersion heater in a direct tank.

They'd managed to leave the immersion switched on for about a day, and it
had not only heated the 120l tank, but the large cold storage tank above
it
(I estimate it must be 250 or 300l at least) to a rather scary
temperature.
After that, they said it didn't do any better than lukewarm, and then
packed
up altogether.

Well, after spending couple of weeks phoning him to get access to the flat
(suspect he'd been avoiding my calls, he owed us rent....) and sorted the
problem out.

I'd been idly speculating upon what the problem might have been whilst
waiting to do the job, perhaps the thermostat had packed up, etc etc.
Heater was open circuit when tested, so drained the tank down and whacked
in
a replacement, no problems.

But, can anyone spot what could have been the problem with the heater....

http://www.olifant.co.uk/Olifant/Pub...ks/RSAN-62XF2E


The immersion heater is now connected via a timer...!!!



--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk


This looks like a good idea for the NG. If people come up with an
interesting problem
that they have solved, why not post it and see if others can do it. This
sort of thing is
used on training programs where faults are set- in cars for example. I'd
certainly like
the challenge.


Peter Scott

On Sun, 18 Jul 2004 10:34:24 +0100, "Peter Scott"
strung together this:

This looks like a good idea for the NG. If people come up with an
interesting problem
that they have solved, why not post it and see if others can do it.

Aren't there already enough unsolved problems on here already?!
--

SJW
A.C.S. Ltd

"Peter Scott" wrote in message ...

This looks like a good idea for the NG. If people come up with an
interesting problem
that they have solved, why not post it and see if others can do it. This
sort of thing is
used on training programs where faults are set- in cars for example. I'd
certainly like
the challenge.


You did ask for it.......

a hoover was being used to draw water up a pipe - yes, stupid - but it
sucked rather better than expected. It sucked the water right the way
up and shot it out the back. The chap who did it was unharmed, and no
trip/fuse/RCD tripped. Explain.


Regards, NT

PS dont try this at home, or anywhere else, it really is dangerous

It sucked the water right the way up and shot it out the back.
The chap who did it was unharmed, and no trip/fuse/RCD tripped.
Explain.

Water isn't very conductive. Most of it would have gone through the
impellor, rather than the motor.

Christian.

(N. Thornton) wrote in message om...
"Peter Scott" wrote in message ...

This looks like a good idea for the NG. If people come up with an
interesting problem
that they have solved, why not post it and see if others can do it. This
sort of thing is
used on training programs where faults are set- in cars for example. I'd
certainly like
the challenge.


You did ask for it.......

a hoover was being used to draw water up a pipe - yes, stupid - but it
sucked rather better than expected. It sucked the water right the way
up and shot it out the back. The chap who did it was unharmed, and no
trip/fuse/RCD tripped. Explain.


Regards, NT

PS dont try this at home, or anywhere else, it really is dangerous

Just because it is powered by electricity doesn't mean that water
can't pass through it without hitting a live part. In fact there are
quite a number of vacuum cleaners specifically designed to suck up
liquids (though they are also designed not to throw them out the
back!).

One possible way to design a "standard" vacuum cleaner is to use the
"exhaust" air to cool the motor - this could well lead to fireworks
when used to suck up water. However, there are at least two reasons
to not design it in this way:

1) Just because you don't market it as a "wet and dry" machine doesn't
mean that users won't try to clean up liquids or mixed wet/dry stuff -
if you can find a cost efficient way to not electricute your dumber
customers you should probably do it.

2) Even though the air is filtered before being expelled it will still
be relatively dusty - if this passes through the motor it is likely to
seriously reduce its lifespan.

In article ,
Lurch wrote:
This looks like a good idea for the NG. If people come up with an
interesting problem
that they have solved, why not post it and see if others can do it.

Aren't there already enough unsolved problems on here already?!

Leave IMM out of this.

--
*Dance like nobody's watching.

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

"Christian McArdle" wrote in message . net...
It sucked the water right the way up and shot it out the back.
The chap who did it was unharmed, and no trip/fuse/RCD tripped.
Explain.

Water isn't very conductive. Most of it would have gone through the
impellor, rather than the motor.

Christian.


its a cylinder hoover where all flow goes through the inside of the
motor. 2 core lead, no RCD anywhere, and just not enough current to
pop the fuse. Remarkably it emptied the whole damn tank - and it was
no small tank.


Regards, NT

(Matt Beard) wrote in message . com...
(N. Thornton) wrote in message om...


You did ask for it.......

a hoover was being used to draw water up a pipe - yes, stupid - but it
sucked rather better than expected. It sucked the water right the way
up and shot it out the back. The chap who did it was unharmed, and no
trip/fuse/RCD tripped. Explain.


Just because it is powered by electricity doesn't mean that water
can't pass through it without hitting a live part. In fact there are
quite a number of vacuum cleaners specifically designed to suck up
liquids (though they are also designed not to throw them out the
back!).

One possible way to design a "standard" vacuum cleaner is to use the
"exhaust" air to cool the motor - this could well lead to fireworks
when used to suck up water. However, there are at least two reasons
to not design it in this way:

1) Just because you don't market it as a "wet and dry" machine doesn't
mean that users won't try to clean up liquids or mixed wet/dry stuff -
if you can find a cost efficient way to not electricute your dumber
customers you should probably do it.

2) Even though the air is filtered before being expelled it will still
be relatively dusty - if this passes through the motor it is likely to
seriously reduce its lifespan.


Actually hoovers are usually designed so the full airflow goes through
the middle of the motor. Max airflow minimises size weight and cost of
the motor, and cost is all in todays marketplace. Sure, there are
downsides as well as upsides.

The hoover in question was such a beast. The water went through the
motor, all over all the rotor stator and commutator connections.


Regards, NT

N. Thornton wrote:
(Matt Beard) wrote in message . com...
(N. Thornton) wrote in message om...


You did ask for it.......

a hoover was being used to draw water up a pipe - yes, stupid - but it
sucked rather better than expected. It sucked the water right the way
up and shot it out the back. The chap who did it was unharmed, and no
trip/fuse/RCD tripped. Explain.
snip
Actually hoovers are usually designed so the full airflow goes through
the middle of the motor. Max airflow minimises size weight and cost of
the motor, and cost is all in todays marketplace. Sure, there are
downsides as well as upsides.

The hoover in question was such a beast. The water went through the
motor, all over all the rotor stator and commutator connections.

When I do this, i typically (after removing hose from water) turn the
electricity off at the plug, then empty hoover, and leave to run for a
couple of minutes to get it nice and dry before turning off.
Less chance of various stuff rust/corroding.

its a cylinder hoover where all flow goes through the inside of the
motor. 2 core lead, no RCD anywhere, and just not enough current to
pop the fuse.

Ah. With a 2 core lead, no earth and plastic/rubber wheels, you're never
going to get enough earth leakage to blow the RCD even if it existed.

Clean water is surprisingly non-conductive. I'm not surprised it didn't blow
the MCB or fuse.

Christian.

Ian Stirling wrote in message ...
N. Thornton wrote:

You did ask for it.......

a hoover was being used to draw water up a pipe - yes, stupid - but it
sucked rather better than expected. It sucked the water right the way
up and shot it out the back. The chap who did it was unharmed, and no
trip/fuse/RCD tripped. Explain.

When I do this, i typically (after removing hose from water) turn the
electricity off at the plug, then empty hoover, and leave to run for a
couple of minutes to get it nice and dry before turning off.
Less chance of various stuff rust/corroding.

You do this regularly?? You seem like a good reliable chap, but why do
I doubt you for once It does mean the water intake and output are
connected straight to the mains.

Regards, NT