We use the immersion heater on the hot water cylinder sometimes. The
other day the 18" thermostat broke and I replaced it this morning. What
interested me was the old one failed to `on', so the heater heated lots
until it was making such a noise that we noticed. I'm surprised the
failure state isn't off. What would happen if I didn't turn it off?
Also, on removing the old one, the plastic casing around the terminal
for one of the wires is distorted as if it had melted slightly. Perhaps
that occurred at the same time as the stat. failed.
Both new and old are 16A on a 3kW heater.
Failure modes of thermostats allow failure to occur to the on or off
When installing an immersion, it is a good idea to select one with two
thermostats. One will be a normal one set to the required temperature. The
other should be a manual reset one set 10 degrees higher. This way, the
consequences of thermostat failure are reduced. Unvented cylinders are
required to have such immersions, but they are a good idea for any cylinder.
On Wed, 10 Dec 2003 16:18:01 +0000, Sam Norris wrote:
The water would boil, the space where the cold tank would fill with much
steam/condensation/humidity the cold tank would heat up.
Eventually if the cold tank was inadequately suppported and/or missing its
lid it might collapse and drop scalding water below. This is the way
someone was killed recently.
However the noise is enough to make any resonable curious person switch
off the heater.
Ed Sirett - Property maintainer and registered gas fitter.
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