Hot water cylinder stat and "slack" between cut-in & cut-out.
 

Do thermostats attached to the outside of a hot water cylinder come
in different specifications?

If I set my hot water cylinder stat to a certain temperature then the
actual temp the stat cuts off at (when the temperature is rising) is
something like 10 degrees celsius DIFFERENT to the actual temp it
cuts in at (when the water in the cylinder is losing heat).

Are some stats sold with a smaller range (or "slack") between cut-in
and cut-out?

Alex Coleman wrote:
Do thermostats attached to the outside of a hot water cylinder come
in different specifications?

If I set my hot water cylinder stat to a certain temperature then the
actual temp the stat cuts off at (when the temperature is rising) is
something like 10 degrees celsius DIFFERENT to the actual temp it
cuts in at (when the water in the cylinder is losing heat).

Are some stats sold with a smaller range (or "slack") between cut-in
and cut-out?



This slack is called hysteresis, and yes, you can get thermostats with
different amounts of hysteresis - in fact, you can get ones where it's
adjustable (we have one).


--
Grunff

In an earlier contribution to this discussion,
Grunff wrote:

Alex Coleman wrote:
Do thermostats attached to the outside of a hot water cylinder come
in different specifications?

If I set my hot water cylinder stat to a certain temperature then the
actual temp the stat cuts off at (when the temperature is rising) is
something like 10 degrees celsius DIFFERENT to the actual temp it
cuts in at (when the water in the cylinder is losing heat).

Are some stats sold with a smaller range (or "slack") between cut-in
and cut-out?



This slack is called hysteresis, and yes, you can get thermostats with
different amounts of hysteresis - in fact, you can get ones where it's
adjustable (we have one).

*Some* hysteresis is a good thing - provided it's not excessive. Without
any, the boiler and pump would be for ever turning on and off for short
periods when the water temperature was near the set point.
--
Cheers,
Set Square
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