"R D S" wrote in message
...
On 04/05/2021 22:13, Tim+ wrote:


Today however, it was getting uncomfortably warm in our hall.

I should add to my prior post, everyone I live/work with* has no respect
for a thermostat and will ramp them up to max in the bizarre hope that
they will heat an area up more quickly.

Anyone who has had a gas oven will be familiar with the concept of a high
gas mark (temperature) giving a higher power (gas flow) than a low one. In
other words, from cold, gas mark 9 followed by gas mark 4 when it's up to
temp will result in the oven getting up to the final temperature of gas mark
4 quicker than gas mark 4 from the start: a gas "regulo" controls both power
and on/off cycling temperature. I presume once the oven is at temp, it
alternates between virtually off (just enough to keep the burner alight) and
full, in a similar way to an electric oven, but when it's heating up from
cold, the rate of heating is controlled by the gas mark setting. I presume
that's still the case; we've always had an electric oven, but my parents
have gas and I'm basing my comments on how their oven behaved.


When we changed our previous house and our present house from (in each case)
a conventional thermostat to Hive, we noticed that the temperatures remained
a lot more constant. I think originally the temperature stayed within about
+/- 3 degC of the required value, whereas it's now within about +/- 0.5 degC
(*). That's ignoring any additional temperature rise due to the sun (the
room where the thermostat lives is south-facing) which sometimes causes a
temperature rise that outweighs the fact that the central heating then
doesn't come on as much.

I imagine that solid-state temperature sensors have no hysteresis at all,
and the control circuit has to have a defined amount of hysteresis built in
to avoid the boiler turning on/off too frequently.


(*) Looking at today's figures, the temperature on the Hive is set to change
from 17 (overnight) to 21.5 (from 0800). The actual temperature overnight
dropped gradually to a low of 18.5 at 0630, then rose to reach a steady
state of around 21 by 1000, and from then until now it's varied from 21.1 to
21.9. With Hive, you don't have the boiler timed to go off overnight, you
simply set a lower desired temperature overnight which means it usually
never comes on (because actual desired) but occasionally comes on if it's
a cold night and the actual drops below the desired.