In article , says...
In message , Will burbled:

The older type thermostats used to control upto about 85=B0C, so
the chances are that yours was set higher than recommended. The lower
temperature that you are reading at the tap is likely to be partly due
to heat losses in the delivery pipework.

The thermostat should not switch in its mid-point at room
temperature, perhaps it had not fully cooled from its time in the
tank? The fact that you have two stats that operate very closely to
each other indicates that they are unlikely to be faulty as such,
unless they both came from a faulty batch...
=20
The thermostat that was switching at room temperature was the new one fro=
m=20
the box (which is now also giving 56=B0C water), so hadn't been near the =
tank=20
yet. That 56=B0C is measured at a tap close to the tank having run the t=
ap=20
for a few minutes (to let the pipes heat up and everything).
=20
I just think something's funny when I can't even get to the "factory pres=
et"=20
temperature of 60=B0C when I have the thermostat up full.
=20
is there a chance I might need an 11" thermostat? I don't know how big t=
he=20
heater is, but I read somewhere that using the wrong thermostat can affec=
t=20
its operation...?
=20
=20

=09You won't get an 11" stat into an 11" immersion heater, as the=20
pocket isn't long enough.

=09The problems occur when a 7" stat is put into an immersion heater=20
fitted vertically (or nearly vertically), as it switches the heater off=20
prematurely when the top "layer" of water reaches its set temperature.

=09Since your heater in use is the bottom one (or should be!) then a =20
7" stat is correct for the application...

--=20
Regards,

Will.