On Fri, 27 Nov 2020 19:49:06 GMT, Pamela
wrote:

On 13:55 27 Nov 2020, Caecilius said:

I've got a large house with gas central heating which I use during
the day. It gets cold overnight in the bedroom though, so I use a
2KW electric convection heater with the thermostat set to about 18
C on a timeclock which switches on between midnight and six am
(boiler comes on again at six).

This was a great improvement last winter, and it only uses one or
two KWh overnight which must be cheaper than heating the whole
house with gas.

This year I want to improve the solution to keep the temperature
more constant (there's a big hysteresis on the convection heater
thermostat) and remove the bimetallic thermostat clicking noise.

I think I want electronic switching to remove the clicking noise
and allow a lower hysteresis plus an external temperature sensor.
Maybe something that's closer to a temperature controlled dimmer
switch instead of a standard bimetallic thermostat.

My plan is to put this temperature controller between the
timeclock and the heater, and set the heater thermostat to
something like 25C as a fail-safe.

Has anyone found or built something like this? I'm sure I can't
be the only person who want a constant overnight bedroom
temperature without running the main house heating.

If you can't find anything along those lines, then a low power
oil-filled electric heater might do the job. You could leave it on
all night or, alternatively, if you use the stat it wouldn't trip as
frquently as a convection heater.

I don't know if my arithmetic is out of date but I seem to recall
electricity is about 3 times the price of gas, watt for watt.

If so then heating one room overnight with electricity might cost
the same as heating 3 with gas. Someone is bound to correct me if
I've gone wrong.

The bedroom area is only about 6.5% of the house area, so the
difference would need to be much greater than 3:1.

I've measured the overnight consumption of the electric heater, and
it's just under 1KWh at the moment which seems quite reasonable to me.