Hi,

my daughter lives in a purpose built first floor flat (1980's)

She's been there 3 years. Recently, she has complained about
alarmingly loud "bangs" and "groans" when she runs the hot
tap to fill a bath. I've not heard the noises myself (yet).

She has a combination hot and cold water cylinder (Fortec
is the name that comes to mind?) -- the small cold tank
sits on top of the larger hot water tank - heating by immersion
heater.

She is in a very hard water area and when she moved in
I removed handfulls of limescale deposits from the cold water tank.

Mains pressure was good last time I checked (thumb over
kitchen tap test...)

The immersion heater is on a timer and she says it is most
likely switched on when the noises occur (not 100% certain
though)

So, before I go and experience the noises myself, can
anyone suggest what might be happening here and how
I can determine, and hopefully fix, the cause of the noise?

Many thanks

p.s just found this link to a similar sort of cylinder:

http://www.heatandplumb.com/acatalog...y linder.html

On Mon, 04 Aug 2008 11:03:44 +0100, Mike Smith wrote:

She's been there 3 years. Recently, she has complained about
alarmingly loud "bangs" and "groans" when she runs the hot
tap to fill a bath. I've not heard the noises myself (yet).


First off I'd check that the immersion thermostat is actually shutting off
and not letting the heater boil the water. Asking her if the water is
scalding would be a reasonable indication that that might be the problem.

If that seems OK I'd suspect air getting into the system which might be
caused by the ball-float filling valve not filling the small header
cistern properly.

--
John Stumbles

I can't stand intolerance

"John Stumbles" wrote
On Mon, 04 Aug 2008 11:03:44 +0100, Mike Smith wrote:

She's been there 3 years. Recently, she has complained about
alarmingly loud "bangs" and "groans" when she runs the hot
tap to fill a bath. I've not heard the noises myself (yet).


First off I'd check that the immersion thermostat is actually shutting off
and not letting the heater boil the water. Asking her if the water is
scalding would be a reasonable indication that that might be the problem.

If that seems OK I'd suspect air getting into the system which might be
caused by the ball-float filling valve not filling the small header
cistern properly.


John,

thanks for the reply. |t looks as if you have pretty much hit the nail
on the head. When I got there I found the water in the cold tank
was warm to the touch and I could hear the immersion heater
was active.

The element thermostat was set to 70 -- it was probably set that high
to help in getting a full bath out of a small hot tank.

But my guess is the water was actually much hotter than 70, it
certainly was scalding. So, I removed the thermostat and tested
it in a jug of water from the kettle. An ohm-meter showed it was
switching when placed in/taken out of the water from the kettle.

So, perhaps the thermostat is tempermental and "sticky"?

I've now switched it down to 55 degrees, and heard it switch off
after a bit. I've left daughter with insturctions to keep a log
of bangs and whistles to verify they only occur when the heating
is on. (She also has instructions to switch the thing of at the isolator
switch if it becomes too alarming).

Is this failure mode typical of immersion thermostats, or could the
problem be that the immersion element is all scaled up, and
"insulating" the thermostat from the real water temperature?

If the water continues to come out scalding, I guess the next logical
steps are a new thermostat and, if that doesn't work, a new
immersion element? (I hope not, as I have a pretty poor record
of removing the damn things from corroded tanks...)

Thanks again

--Mike

If the water continues to come out scalding, I guess the next logical
steps are a new thermostat and, if that doesn't work, a new
immersion element? (I hope not, as I have a pretty poor record
of removing the damn things from corroded tanks...)

Thanks again

--Mike




Wouldn't it be great if we used CopperSlip on the threads of immersion
heaters. After all, the thread is not the seal - the flange does the
sealing. The trouble is that when they are fitted it is usually assumed they
will be a permanent fit.