On Wed, 3 Dec 2008 10:07:33 -0800 (PST), wrote:

- as would possibly a gravity circulated solid fuel stove.

Which are explicitly forbidden as a means of heating unvented HWCs.

That's why you do it with a pump...

Not relevant and bad practice with or without and unvented HWC. You simply
can't turn a solid fuel stove off like you can a gas or oil boiler. A
stove with a boiler must, under all circumstances including electricity
power failure, have some means of dumping the heat. Be that into a
heatstore or once that is hot a radiator as well.

--
Cheers
Dave.

Doctor Drivel wrote:

"John Rumm" wrote in message
et...

They all have electric immersions, which fail more easily.

Even if that were true

This is true.

(which I doubt), a large proportion are unlikely to ever be heated via
the immersion, given the added cost compared to doing it with the boiler.

A boom is a boom.

And as scary as Basil Brush.

--
Cheers,

John.

/================================================== ===============\
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Doctor Drivel wrote:
"Tim Downie" wrote in message
...
Doctor Drivel wrote:
"Tim Downie" wrote in message
...
Doctor Drivel wrote:
"fred" wrote in message
...
In article , Reentrant
writes

Not really the same but this is what happened when the
Mythbusters deliberately disabled all the safety features on an
American-style water heater:

http://www.youtube.com/watch?v=ekEHfihiNz4

Oh god, tell me it's not the one where they had to weld it shut
and upgrade it to 10kW to get it to do what their agenda wanted
it to?

10kW was so they did not wait too long. It did go booooom.

Very poor science then.

I am not interested in the science, it went boom. Big boom.

I think that says it all.

It said boom.

I think someone who puts themselves forward as some sort of heating expert
but doesn't understand the importance of good science is a lot scarier.

Tim

"Tim Downie" wrote in message
...
Doctor Drivel wrote:
"Tim Downie" wrote in message
...
Doctor Drivel wrote:
"Tim Downie" wrote in message
...
Doctor Drivel wrote:
"fred" wrote in message
...
In article , Reentrant
writes

Not really the same but this is what happened when the
Mythbusters deliberately disabled all the safety features on an
American-style water heater:

http://www.youtube.com/watch?v=ekEHfihiNz4

Oh god, tell me it's not the one where they had to weld it shut
and upgrade it to 10kW to get it to do what their agenda wanted
it to?

10kW was so they did not wait too long. It did go booooom.

Very poor science then.

I am not interested in the science, it went boom. Big boom.

I think that says it all.

It said boom.

I think someone who puts themselves forward as some sort of heating expert
but doesn't understand the importance of good science is a lot scarier.

It think it amazing when someone doesn't know when something goes boom.

"Doctor Drivel" wrote in message
...

"Tim Downie" wrote in message
I think someone who puts themselves forward as some sort of heating
expert but doesn't understand the importance of good science is a lot
scarier.

It think it amazing when someone doesn't know when something goes boom.

So you still can't understand the relevance of the difference between a 3kw
input and a 10kw input then?

Tim

"Tim Downie" wrote in message
...

So you still can't understand the relevance of the difference between a
3kw input and a 10kw input then?

I can't imagine any sealed heat store losing heat faster than a 3 kW heater
can put heat in.
Therefore a 3 kW heater will cause such a system to explode if the safety
measures are disabled.
In fact I have known an /uninsulated/ vented tank boil when an immersion
heater stat went faulty.

"dennis@home" wrote in message
...


"Tim Downie" wrote in message
...

So you still can't understand the relevance of the difference between a
3kw input and a 10kw input then?

I can't imagine any sealed heat store losing heat faster than a 3 kW
heater can put heat in.

Possibly not. My point is though that it's incredibly bad "science" to mess
about with a variable and assume that it won't make any difference. You
can't assume that it will make no difference.

Therefore a 3 kW heater will cause such a system to explode if the safety
measures are disabled.
In fact I have known an /uninsulated/ vented tank boil when an immersion
heater stat went faulty.

True, but that's at atmospheric pressure. BP rises with pressure.

I'm not denying that there is a risk of explosion, but like all risks, it
needs to be put in perspective. How many deaths have there been in the UK
from exploding unvented cylinders? There was a recent death from an
unvented cylinder that I can remember.

Tim

Tim Downie wrote:
"dennis@home" wrote in message
...

"Tim Downie" wrote in message
...

So you still can't understand the relevance of the difference between a
3kw input and a 10kw input then?
I can't imagine any sealed heat store losing heat faster than a 3 kW
heater can put heat in.

Possibly not. My point is though that it's incredibly bad "science" to mess
about with a variable and assume that it won't make any difference. You
can't assume that it will make no difference.

Therefore a 3 kW heater will cause such a system to explode if the safety
measures are disabled.
In fact I have known an /uninsulated/ vented tank boil when an immersion
heater stat went faulty.

True, but that's at atmospheric pressure. BP rises with pressure.

I'm not denying that there is a risk of explosion, but like all risks, it
needs to be put in perspective. How many deaths have there been in the UK
from exploding unvented cylinders? There was a recent death from an
unvented cylinder that I can remember.

I remebber a couple of recent fatal incidents with vented cylinders...
never heard of any with unvented in this country yet.

--
Cheers,

John.

/================================================== ===============\
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Thu, 04 Dec 2008 09:55:49 +0000, John Rumm wrote:

I remebber a couple of recent fatal incidents with vented cylinders...

IIRC not caused by failure of the cylinder but by bad installations
allowing hot water to circulate via the plastic header tank leading to its
failure.

never heard of any with unvented in this country yet.

Maybe the guidelines regarding installation and/or inspection mean that
bad installations are very rare. ducks

--
Cheers
Dave.

On Wed, 03 Dec 2008 17:10:08 +0000, Doctor Drivel wrote:

Quite possible on a very old neglected system. Expect many of this
blows in 10, 20 years time as the install base rises.

Damn! I'm getting dangerously close to agreeing with this man ;-)


(The only difference is I'm thinking "a few" rather than "many".)

--
John Stumbles -- http://yaph.co.uk

Hypnotising Hypnotists Can Be Tricky

On Thu, 04 Dec 2008 09:55:49 +0000, John Rumm wrote:

I remebber a couple of recent fatal incidents with vented cylinders...
never heard of any with unvented in this country yet.

Correction: incidents with vented *systems*, not the cylinders per se. It
was the plastic cold water storage tanks in the attic that actually
collapsed: the cylinders did not./pedantic

And in those cases if the vented cylinders had had the same sorts of
thermostats on the immersion elements that are mandatory for unvented
systems the incidents almost certainly would not have happened.


--
John Stumbles -- http://yaph.co.uk

Bob the builder / it'll cost 'yer
Bob the builder / loadsa dosh

Tim Downie wrote:
I'm not denying that there is a risk of explosion, but like all
risks, it needs to be put in perspective. How many deaths have there
been in the UK from exploding unvented cylinders? There was a recent
death from an unvented cylinder that I can remember.

B*ggerit! Meant "vented" in that last sentence.

Tim

On Wed, 03 Dec 2008 17:36:58 +0000, John Rumm wrote:

Even if that were true (which I doubt), a large proportion are unlikely
to ever be heated via the immersion, given the added cost compared to
doing it with the boiler.

I come across a number of places where I find the immersion heater
switched on despite the central heating system working. To many
householders it's just a switch in the airing cupboard that does something
magical and if it happens to be switched on and everything works, they
leave it that way.

Having the main thermostat and the safety cutout both fail to danger is
extremely unlikely and I'm sure the probability of any given unvented
installation being subjected to these conditions is very, very remote.
However as the number of unvented installations - and installations that
aren't safety checked periodically - increases, so the probability of
*some* of those installations failing to danger increases. And the
*consequence* of such failure is Not Good (tm).


--
John Stumbles -- http://yaph.co.uk

Many hands make light work. Too many cooks spoil the broth.

Doctor Drivel wrote:
"fred" wrote in message ...
In article , Reentrant
writes

Not really the same but this is what happened when the Mythbusters
deliberately disabled all the safety features on an American-style
water heater:

http://www.youtube.com/watch?v=ekEHfihiNz4

Oh god, tell me it's not the one where they had to weld it shut and
upgrade it to 10kW to get it to do what their agenda wanted it to?

10kW was so they did not wait too long. It did go booooom.

I haven't seen the episode for some time but I don't remember them saying
they'd changed the heating element.
What wattage would be normal for a 52 (US) gallon tank? Isn't that somewhat
larger than a typical UK cylinder that would have a 3kW immersion heater?
Cases of real-life explosions mentioned here -
http://kwc.org/mythbusters/2007/11/e...water_hea.html

--
Reentrant

"John Rumm" wrote in message
et...

I remebber a couple of recent fatal incidents with vented cylinders...
never heard of any with unvented in this country yet.

There are millions of vented systems, not many unvented ones.

On 3 Dec, 20:06, "Dave Liquorice"
wrote:
On Wed, 3 Dec 2008 10:07:33 -0800 (PST), wrote:
- as would possibly a gravity circulated solid fuel stove.

Which are explicitly forbidden as a means of heating unvented HWCs.

That's why you do it with a pump...

Not relevant and bad practice with or without and unvented HWC. You simply
can't turn a solid fuel stove off like you can a gas or oil boiler. A
stove with a boiler must, under all circumstances including electricity
power failure, have some means of dumping the heat. Be that into a
heatstore or once that is hot a radiator as well.

--
Cheers
Dave.

That's why you have a heat leak radiator (and a thermostatically
controlled stove)

T

YAPH wrote:
On Wed, 03 Dec 2008 17:36:58 +0000, John Rumm wrote:

Even if that were true (which I doubt), a large proportion are unlikely
to ever be heated via the immersion, given the added cost compared to
doing it with the boiler.

I come across a number of places where I find the immersion heater
switched on despite the central heating system working. To many
householders it's just a switch in the airing cupboard that does something
magical and if it happens to be switched on and everything works, they
leave it that way.

Having the main thermostat and the safety cutout both fail to danger is
extremely unlikely and I'm sure the probability of any given unvented
installation being subjected to these conditions is very, very remote.
However as the number of unvented installations - and installations that
aren't safety checked periodically - increases, so the probability of
*some* of those installations failing to danger increases. And the
*consequence* of such failure is Not Good (tm).


My particular take on that, which I have mentioned before, was a
property I lived in for a short while. The immersion heater had a time
switch - the sort with segments that click in or out. The previous
occupant (and owner) had wondered why the water was always hot when she
only ran it for an hour or two a day. But the switch was wired the
wtrong way round - the 'on' poistion for a segment had the effect of
'off' (and vice versa). So inadvertently it was ON 22/24.

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

"Tim Downie" wrote in message
...

"dennis@home" wrote in message
...


"Tim Downie" wrote in message
...

So you still can't understand the relevance of the difference between a
3kw input and a 10kw input then?

I can't imagine any sealed heat store losing heat faster than a 3 kW
heater can put heat in.

Possibly not. My point is though that it's incredibly bad "science" to
mess about with a variable and assume that it won't make any difference.
You can't assume that it will make no difference.

You are a very confused man. But, probably clear in your own mind.

How many deaths have there been in the UK from exploding unvented
cylinders?

This one wants to see bodies first before the are outlawed. There is no
need for unvented cylinders when vented heat banks are around. Zero risk is
what you aim for.

"Dave Liquorice" wrote in message
ll.net...

Maybe the guidelines regarding installation and/or inspection mean that
bad installations are very rare. ducks

There are many unvented cylinders poorly installed by cowboys. 90% of these
unvented cylinder will not be tested each year as they should be. When they
get old and the valves fail, then expect booms - probably in 10, 20 years
time,a few a year.

"Reentrant" wrote in message
...
Doctor Drivel wrote:
"fred" wrote in message ...
In article , Reentrant
writes

Not really the same but this is what happened when the Mythbusters
deliberately disabled all the safety features on an American-style
water heater:

http://www.youtube.com/watch?v=ekEHfihiNz4

Oh god, tell me it's not the one where they had to weld it shut and
upgrade it to 10kW to get it to do what their agenda wanted it to?

10kW was so they did not wait too long. It did go booooom.

I haven't seen the episode for some time but I don't remember them saying
they'd changed the heating element.
What wattage would be normal for a 52 (US) gallon tank? Isn't that
somewhat larger than a typical UK cylinder that would have a 3kW immersion
heater?
Cases of real-life explosions mentioned here -
http://kwc.org/mythbusters/2007/11/e...water_hea.html

It doesn't matter what the kW was. Using 1kW can cause a boom, it takes
longer.

"YAPH" wrote in message
...
On Wed, 03 Dec 2008 17:10:08 +0000, Doctor Drivel wrote:

Quite possible on a very old neglected system.
Expect many of these blows in 10, 20 years
time as the install base rises.

Damn! I'm getting dangerously close to
agreeing with this man ;-)

This is a good sign, the therapy is working.

(The only difference is I'm thinking "a few" rather than "many".)

As few are serviced I would say many. Before the authorities tighen up and
get them all annually serviced and tested properly (which takes time to test
all failure systems), they have to see a death.

"YAPH" wrote in message
...

Having the main thermostat and the safety cutout both fail to danger is
extremely unlikely and I'm sure the probability of any given unvented
installation being subjected to these conditions is very, very remote.
However as the number of unvented installations - and installations that
aren't safety checked periodically - increases, so the probability of
*some* of those installations failing to danger increases. And the
*consequence* of such failure is Not Good (tm).

Those who vehemently defend unvented cylinders over near zero risk DHW only
vented heat banks, are plumbers who have the G3 approval ticket and make
money out of it. Their own money making overrides any safety issues in
their tiny heads.

Doctor Drivel coughed up some electrons that declared:


It doesn't matter what the kW was. Using 1kW can cause a boom, it takes
longer.

Not if the cylinder can lose 1kW by radiation/convection, in which case it
will reach stable state and stay there forever.

Doctor Drivel wrote:
"Tim Downie" wrote in message


You are a very confused man. But, probably clear in your own mind.

Confused by idiocy, yes.


How many deaths have there been in the UK from exploding unvented
cylinders?

This one wants to see bodies first before the are outlawed. There is
no need for unvented cylinders when vented heat banks are around. Zero
risk is what you aim for.

Zero risk is a goal of fools.

From the moment of conception until the day you die your life is filled with
risk. Sensible risk reduction is what you aim for.

A car has far more killing potential but it requires no mandatory testing
until it is at least 3 years old.

Tim

Tim S wrote:
Doctor Drivel coughed up some electrons that declared:


It doesn't matter what the kW was. Using 1kW can cause a boom, it
takes longer.

Not if the cylinder can lose 1kW by radiation/convection, in which
case it will reach stable state and stay there forever.

Don't bother with logic, he won't understand.

Tim

"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


It doesn't matter what the kW was. Using 1kW can cause a boom, it takes
longer.

Not if the cylinder can lose 1kW by radiation/convection,

You really don't know.

Doctor Drivel wrote:
"YAPH" wrote in message
...

Having the main thermostat and the safety cutout both fail to danger
is extremely unlikely and I'm sure the probability of any given
unvented installation being subjected to these conditions is very,
very remote. However as the number of unvented installations - and
installations that aren't safety checked periodically - increases,
so the probability of *some* of those installations failing to danger
increases. And the
*consequence* of such failure is Not Good (tm).

Those who vehemently defend unvented cylinders over near zero risk
DHW only vented heat banks,

But it's not zero is it? You can't ignore the deaths from vented cylinder
systems if you are trying to prove that one system is safer than another.

(Sorry, I'm using logic again. Unfair I know.)

Tim

That's a good point that I'd fogotten about so that risk needs to be added
to the vented tank side of the equation. After all, if you've no loft tank
then that can't happen. I wonder how how many deaths have resulted from
this? Not a lot I'll wager but then probably not too many people have been
killed in the UK by unvented cylinders either.

I seem to remember the recent infamous one (baby died on first day in
new property IIRC) didn't have the cut out switch in the immersion
so one failure and the plastic header tank gave way.

Doctor Drivel coughed up some electrons that declared:


"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


It doesn't matter what the kW was. Using 1kW can cause a boom, it takes
longer.

Not if the cylinder can lose 1kW by radiation/convection,

You really don't know.

Neither do you...

Reduction ad absurbdum - 1mW will never blow such a cylinder up, unless the
insulation was near perfect.

10kW is pretty likely to blow it up regardless of insulation, ambient
temperatures etc.

Somewhere in betwee, there will acheivable equilibrium states that do not
exceed the operational pressures of the vessel.

Is that too hard for you?

Malcolm wrote:

That's a good point that I'd fogotten about so that risk needs to be added
to the vented tank side of the equation. After all, if you've no loft tank
then that can't happen. I wonder how how many deaths have resulted from
this? Not a lot I'll wager but then probably not too many people have been
killed in the UK by unvented cylinders either.

I seem to remember the recent infamous one (baby died on first day in
new property IIRC) didn't have the cut out switch in the immersion
so one failure and the plastic header tank gave way.

My recollection was that the vent from the safety relief valve had been
lead into the plastic cold water storage tank and that when the
immersion failed on hot water was dumped into the cold tank, causing the
tank to collapse and scald the baby in the room below.

Steve Firth wrote:
Malcolm wrote:

That's a good point that I'd fogotten about so that risk needs to
be added to the vented tank side of the equation. After all, if
you've no loft tank then that can't happen. I wonder how how many
deaths have resulted from this? Not a lot I'll wager but then
probably not too many people have been killed in the UK by unvented
cylinders either.

I seem to remember the recent infamous one (baby died on first day in
new property IIRC) didn't have the cut out switch in the immersion
so one failure and the plastic header tank gave way.

My recollection was that the vent from the safety relief valve

?

IIRC it was a vented cylinder that just boiled over through the
expansion/vent pipe into the loft tank. Don't think there was any "safety
relief valve" other than the open pipe. In fact, I think any sort of valve
on an open vented system is illegal.

had
been lead into the plastic cold water storage tank and that when the
immersion failed on hot water was dumped into the cold tank, causing
the tank to collapse and scald the baby in the room below.

That bit's certainly right.

Tim

On Thu, 4 Dec 2008 15:09:31 -0000 someone who may be "Tim Downie"
wrote this:-

IIRC it was a vented cylinder that just boiled over through the
expansion/vent pipe into the loft tank. Don't think there was any "safety
relief valve" other than the open pipe. In fact, I think any sort of valve
on an open vented system is illegal.

Any sort of valve?

Can't an open vented system have a valve on the feed and expansion
pipe? Can't have valves (presumably including taps) on the domestic
hot water pipes? Can't have a pressure relief valve fitted in case
some vulnerable pipework ices up? Every open vented system I have
seen must be illegal.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

David Hansen wrote:
On Thu, 4 Dec 2008 15:09:31 -0000 someone who may be "Tim Downie"
wrote this:-

IIRC it was a vented cylinder that just boiled over through the
expansion/vent pipe into the loft tank. Don't think there was any
"safety relief valve" other than the open pipe. In fact, I think
any sort of valve on an open vented system is illegal.

Any sort of valve?

Can't an open vented system have a valve on the feed and expansion
pipe? Can't have valves (presumably including taps) on the domestic
hot water pipes? Can't have a pressure relief valve fitted in case
some vulnerable pipework ices up? Every open vented system I have
seen must be illegal.

Bl**dy pedant. You know what I meant. Valve on the expansion/overflow.

Tim

"Tim Downie" wrote in message
...
Steve Firth wrote:
Malcolm wrote:

That's a good point that I'd fogotten about so that risk needs to
be added to the vented tank side of the equation. After all, if
you've no loft tank then that can't happen. I wonder how how many
deaths have resulted from this? Not a lot I'll wager but then
probably not too many people have been killed in the UK by unvented
cylinders either.

I seem to remember the recent infamous one (baby died on first day in
new property IIRC) didn't have the cut out switch in the immersion
so one failure and the plastic header tank gave way.

My recollection was that the vent from the safety relief valve

?

IIRC it was a vented cylinder that just boiled over through the
expansion/vent pipe into the loft tank. Don't think there was any "safety
relief valve" other than the open pipe. In fact, I think any sort of
valve on an open vented system is illegal.

had
been lead into the plastic cold water storage tank and that when the
immersion failed on hot water was dumped into the cold tank, causing
the tank to collapse and scald the baby in the room below.

That bit's certainly right.


Not quite. Plastic header tanks are designed to withstand such an event
(although one would be advised to change them afterwards) for safety
reasons, as there is the possibility of boiling water entering them. They
can only do so if they are properly supported. This one wasn't, just
supported by the joists. When it was subjected to the boiling water it
*deformed* and collapsed. It wouldn't have done if evenly supported
underneath.


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

Tim Downie wrote:

Steve Firth wrote:
Malcolm wrote:

That's a good point that I'd fogotten about so that risk needs to
be added to the vented tank side of the equation. After all, if
you've no loft tank then that can't happen. I wonder how how many
deaths have resulted from this? Not a lot I'll wager but then
probably not too many people have been killed in the UK by unvented
cylinders either.

I seem to remember the recent infamous one (baby died on first day in
new property IIRC) didn't have the cut out switch in the immersion
so one failure and the plastic header tank gave way.

My recollection was that the vent from the safety relief valve

?

IIRC it was a vented cylinder

Oh, righto, I thought it was a sealed system with a substandard
installation.

Is it possible to buy non plastic header tanks?

I looked, but couldn;t find anything...

YAPH wrote:
On Thu, 04 Dec 2008 09:55:49 +0000, John Rumm wrote:

I remebber a couple of recent fatal incidents with vented cylinders...
never heard of any with unvented in this country yet.

Correction: incidents with vented *systems*, not the cylinders per se. It
was the plastic cold water storage tanks in the attic that actually
collapsed: the cylinders did not./pedantic

I was thinking of two - one where the plastic header tank got back
filled with hot and failed, and another where a cylinder ruptured and
dumped hot water on sleeping people below.


And in those cases if the vented cylinders had had the same sorts of
thermostats on the immersion elements that are mandatory for unvented
systems the incidents almost certainly would not have happened.

Indeed. Which makes dribble's claims even less convincing.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

"Steve Firth" wrote in message
.. .
Tim Downie wrote:

Steve Firth wrote:
Malcolm wrote:

That's a good point that I'd fogotten about so that risk needs to
be added to the vented tank side of the equation. After all, if
you've no loft tank then that can't happen. I wonder how how many
deaths have resulted from this? Not a lot I'll wager but then
probably not too many people have been killed in the UK by unvented
cylinders either.

I seem to remember the recent infamous one (baby died on first day in
new property IIRC) didn't have the cut out switch in the immersion
so one failure and the plastic header tank gave way.

My recollection was that the vent from the safety relief valve

?

IIRC it was a vented cylinder

Oh, righto, I thought it was a sealed system with a substandard
installation.

Wouldn't have had a header tank in that case. ;-)

Tim

On 4 Dec, 14:05, Tim S wrote:

Not if the cylinder can lose 1kW by radiation/convection,

In which case you need to insulate it! (for practical domestic values
of area, volume and max. temp)

Andy Dingley coughed up some electrons that declared:

On 4 Dec, 14:05, Tim S wrote:

Not if the cylinder can lose 1kW by radiation/convection,

In which case you need to insulate it! (for practical domestic values
of area, volume and max. temp)

Yeah I know

It was a rebuttal to Dribble's generalised statement.