taken2often wrote:DSPP makes a statement about thermostats, that I do not agree with. A 3kw Fan heater sitting in the middle of the room, will raise the comfort level very fast and then switch off. A wall mounted radiator of any type takes time to heat up, that heat is being absorb by the fabric off the building so it can take some time to bring the room up to comfort level.
This brings me to your point Scott. With a time clock, obviously depending on insulation and drafts the temperature could be well below the recovery time to bring the room up. My flat never goes below 16 degrees, even then it can take some time to come up to 21. Ok I have high ceilings and tall and wide windows, but I now find my running cost spot on.
It is considered one of the best systems under good insulation condition the Air Sourced or ground sourced heat pump, combined with a good concrete based underfloor system that takes very little power to maintain the mass heat once established at the beginning of the season. This is run as a constant at the preset temp
The idea that switched off saves money switched on costs money is held by many
This is a matter of science & engineering, so we can determine a correct answer if we examine things carefully.
Let's say the room starts at 15C. The thermostat is set to 20C. The fan heater is switched on, and runs for (say) 15-mins and raises the local air temperature to the 20C, and the fan heater switches off.
Now the local air temperature is 20C, but the plaster & bricks & woodwork & general building fabric are only just a smidge over 15C. So what happens is that heat starts quite rapidly leaking into the building fabric. Typically the thermostat will have a hysterisis of about 1C, so when the local air temperature falls to 19C the fan will come back on. Basically for the first few hours the fan will be operating pretty constantly bringing the adjacent parts of the building fabric up to 20C.
You can now see that see far as the thermostat is concerned it does not matter what the heat source is. Whether it is a gas-fed wet loop radiator or a electric fan heater, or a pair of exercising sweaty teenagers, it is all the same to the thermostat.
As an extension of this you will now be able to explain to your friends & family why it is better - if possible - to install insulation on the outside of a building's fabric, rather than the inside. As a thought experiment consider what the local air temperature curve will look like in a small room as the sun crosses the window .....
regards,
dspp