I've been doing some CH mods so have it drained down. And decided to use
the backup immersion for the first time in years. It's in a header tank
fed open vented storage system. Switched it on about an hour before I
wanted my shower which was fine and at normal sort of temperature - but
it's a temperature controlled one anyway. Then sort of forgot and left it
on. A couple of hours later there was a strange noise - soon realised the
storage cylinder was boiling. And pumping water and steam into the header
tank. Switched off the immersion. Carefully ran off some boiling water,
Should have made tea, I suppose. ;-) About an hour later went to do the
washing up. Only tepid water. Where had the tank of near boiling water
gone?

--
*I'm already visualizing the duct tape over your mouth

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

On 2008-06-02 00:13:11 +0100, "Dave Plowman (News)"
said:

I've been doing some CH mods so have it drained down. And decided to use
the backup immersion for the first time in years. It's in a header tank
fed open vented storage system. Switched it on about an hour before I
wanted my shower which was fine and at normal sort of temperature - but
it's a temperature controlled one anyway. Then sort of forgot and left it
on. A couple of hours later there was a strange noise - soon realised the
storage cylinder was boiling. And pumping water and steam into the header
tank. Switched off the immersion. Carefully ran off some boiling water,
Should have made tea, I suppose. ;-) About an hour later went to do the
washing up. Only tepid water. Where had the tank of near boiling water
gone?

Is the heater at the top or bottom of the cylinder?

In article 48439006@qaanaaq,
Andy Hall wrote:
I've been doing some CH mods so have it drained down. And decided to
use the backup immersion for the first time in years. It's in a header
tank fed open vented storage system. Switched it on about an hour
before I wanted my shower which was fine and at normal sort of
temperature - but it's a temperature controlled one anyway. Then sort
of forgot and left it on. A couple of hours later there was a strange
noise - soon realised the storage cylinder was boiling. And pumping
water and steam into the header tank. Switched off the immersion.
Carefully ran off some boiling water, Should have made tea, I suppose.
;-) About an hour later went to do the washing up. Only tepid water.
Where had the tank of near boiling water gone?

Is the heater at the top or bottom of the cylinder?

It's a conventional top entry one which goes most of the way down the
cylinder. The only slightly unusual thing is the cylinder is tall and slim
to fit the available space - although still a stock size.

My only guess is that once the boiling occurred, *all* the water in the
cylinder gets forced into the header tank. But it can't have happened that
quickly as it didn't overflow.

I see TLC sell thermostats with an extra cutout which are the norm these
days - can they be retro-fitted to an older immersion?

--
*I'm not being rude. You're just insignificant

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

On 2008-06-02 07:32:41 +0100, "Dave Plowman (News)"
said:

In article 48439006@qaanaaq,
Andy Hall wrote:
I've been doing some CH mods so have it drained down. And decided to
use the backup immersion for the first time in years. It's in a header
tank fed open vented storage system. Switched it on about an hour
before I wanted my shower which was fine and at normal sort of
temperature - but it's a temperature controlled one anyway. Then sort
of forgot and left it on. A couple of hours later there was a strange
noise - soon realised the storage cylinder was boiling. And pumping
water and steam into the header tank. Switched off the immersion.
Carefully ran off some boiling water, Should have made tea, I suppose.
;-) About an hour later went to do the washing up. Only tepid water.
Where had the tank of near boiling water gone?

Is the heater at the top or bottom of the cylinder?

It's a conventional top entry one which goes most of the way down the
cylinder. The only slightly unusual thing is the cylinder is tall and slim
to fit the available space - although still a stock size.

My only guess is that once the boiling occurred, *all* the water in the
cylinder gets forced into the header tank. But it can't have happened that
quickly as it didn't overflow.

I suppose that could be possible. 3kW wouldn't reheat the cylinder
*that* quickly.


I see TLC sell thermostats with an extra cutout which are the norm these
days - can they be retro-fitted to an older immersion?

Not sure on that one. Would be convenient if it does :-)

On Mon, 02 Jun 2008 07:32:41 +0100, Dave Plowman (News) wrote:

My only guess is that once the boiling occurred, *all* the water in the
cylinder gets forced into the header tank. But it can't have happened
that quickly as it didn't overflow.

Once the vent is spurting water it circulates between the header tank and
cyclinder. I wouldn't expect an overflow at all, unless the the thermal
expansion of the entire volume of water is enough to cause it.

As to only tepid water an hour later, are you sure that immersion extends
way down the tank? A tall thin tank and the immersion on the dome at about
45 degress angle would perclude having a really (30 or 36") long one...

Either that or there was still some circulation after you switched of the
immersion and you noticed the boiling fairly quickly, so the header tank
was still full of cold water. Check that there is a decent gap between the
end of expansion pipe and the water in the tank to prevent gravity
circulation.

--
Cheers
Dave.

Dave Plowman (News) wrote:

I see TLC sell thermostats with an extra cutout which are the norm these
days - can they be retro-fitted to an older immersion?

AFAIK, yes :-)

--
Andy

"Dave Plowman (News)" wrote in message
...
In article 48439006@qaanaaq,
Andy Hall wrote:
I've been doing some CH mods so have it drained down. And decided to
use the backup immersion for the first time in years. It's in a header
tank fed open vented storage system. Switched it on about an hour
before I wanted my shower which was fine and at normal sort of
temperature - but it's a temperature controlled one anyway. Then sort
of forgot and left it on. A couple of hours later there was a strange
noise - soon realised the storage cylinder was boiling. And pumping
water and steam into the header tank. Switched off the immersion.
Carefully ran off some boiling water, Should have made tea, I suppose.
;-) About an hour later went to do the washing up. Only tepid water.
Where had the tank of near boiling water gone?

Is the heater at the top or bottom of the cylinder?

It's a conventional top entry one which goes most of the way down the
cylinder. The only slightly unusual thing is the cylinder is tall and slim
to fit the available space - although still a stock size.

My only guess is that once the boiling occurred, *all* the water in the
cylinder gets forced into the header tank. But it can't have happened that
quickly as it didn't overflow.

I see TLC sell thermostats with an extra cutout which are the norm these
days - can they be retro-fitted to an older immersion?

The one I fitted "fitted":-) If you get my drift.

Have you tried this again under control to see if you did have a full
cylinder of boiling water?

Adam

In article ,
ARWadworth wrote:
Have you tried this again under control to see if you did have a full
cylinder of boiling water?

As I said earlier I had a decent shower out of it - then left it on, which
is when it boiled. So it is heating a decent amount of water.

--
*Never slap a man who's chewing tobacco *

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