On Sat, 25 Sep 2004 15:04:06 +0100, Pete C
wrote:

On Fri, 24 Sep 2004 19:03:07 +0100, Peter Hawkins
wrote:

The immersion heater in my house is of a type I haven't seen anywhere
else. There are no elements in the main tank. Instead the element is
mounted inside a small vertical cylinder plumbed into the side if the
tank but seperate from the main tank. Its mounted vertically with the
element upside down and fitted from the bottom (which makes it hard to
see the stat setting without a mirror). The secondary cylinder is 3
inches diameter and about 15 inches long.

A while back I noticed that running the immersion even for a short
time produced dangerously hot water. Ther was also a bubbling noise
from the cylinder when the immersion was on.

So I replaced the stat (7") set it for 60 and thought that would be
that. Same problem.

Hi,

If the thermostat is set to 60°C, the reading might not be that
accurate. 60°C is 'hand hot', you should be able put your hand in for
short while with only temporary discomfort! It's still way above
shower temperatures, if you're concerned about kids/elderly in your
house it might be worth fitting a TMV blending valve to reduce the
temperature of the hot water from the cylinder.

Also is the secondary cylinder connected to the main cylinder top and
bottom? If the thermostat is reading the temperature of the water from
the bottom of the cylinder you might be better off connecting it via a
pipe stat on the top pipe returning to the main cylinder. Also check
the second cylinder is not scaled up.

cheers,
Pete.


The secondary cylinder has its bottom attachement pint about 6 incles
from the main cylinder bottom. The top disappears via pipe into the
wall.

I drained the tank and removed the secondary cylinder today. It was
full of gunk. Flushed it out with high hopes that it might be the
problem that Owain mentioned about. Howver the problem is still there.
I notice that when the immersion runs the top 1/3 of the 2nd cylinder
is extremley hot while the bottom 2/3 is cold. So the t'stat isn't
seeing the really hot stuff. Next thing to try is a new element. Jim
mentioned above that only the top may be heating, thats what it feels
like.

Mind you getting the element out will be a *******. The little
secondary gives no purchase for the element spanner, and the fixing
looks seized up. I imagine if I apply too much wellie the cylinder
will distort !

If anyone is interested see this link for a picture

http://www.fortbaxter.demon.co.uk/hot_tank.jpg

Peter