Portable heaters & thermostats

macman

andyrpsmith wrote: »

Not sure why you are telling me this, the point of my post is to determine how your heater behaves when you change the thermostat setting and how it may affect the cost. Pretty obvious that running 2KW will cost twice as much as 1 KW.

And the point of my post is to tell you that it doesn't affect the overall cost. if the 'stat is set to the same temp, it will cost the same to heat it to that temp whether you use 1kW, 2kW or 10kW input. Heating it faster or slower make no difference to the overall cost.
Yes, your monitor will show twice the cost per hour, but that is simply a snapshot of the power being drawn at any one time. At twice the input, it'll heat up twice as fast, so cost exactly the same overall.
If you raise the 'stat itself to a higher setting, then yes, obviously the overall cost will then increase. That's a different scenario.

chemicalfan

Thanks for all your posts, just confirmed the logic I was applying. At the moment, I've settled for the 800W setting, based on the logic that the relay will cycle less, and as it's a cheap oil filled rad, is more likely to fail!

Let me change the scenario slightly - how about adding a second heater to the same room? So, assume 2 x 2kW convector heaters, both set to 1kW, both set on their stat to the same (middle setting). In my head, it's the same power usage as 1 heater on 2kW, but as they have different stats (one in each unit), would it be true that they'd use the same power? Or would it be different, as locally it could be warmer/cooler than the room in general? Assume that they aren't on the same wall (either opposite, or on adjacent walls)

macman

It doesn't matter if you use one heater or twenty, the energy input required to rise the temp by x degrees remains the same.
And if it was cheaper to use multiple sources (which it isn't), would not the extra capital cost of the extra heater wipe out your theoretical savings anyway?

chemicalfan

It would in theory, although there always seem to be deals that change the ball game a bit.

I guess my question was a bit guarded there - really, I was asking about how "accurate" the thermostats are on these devices. I mean, they're not room stats, they measure the temperature in the device (or very locally at best). Multiple locations of multiple heaters within a room introduce a few other variables - e.g. effect on convection currents in a room, presence of draughts in room which could be covered by a heater, etc. I get the normal physics, but as some said, no room is ideal, and therefore won't perfectly conform to the physics.

An example of why this is relevant - the heater currently in the room, heats one side of the room better than the other. The closer to the oil filled rad, the warmer it is (it's subtle, but detectable). I believe this is because the main draught comes from the other side of the room. I was thinking about putting a convector/oil filled rad over there, and keeping both turned down lower to compensate for having 2 heaters in one room. By keeping electricity consumption constant (by balancing the 2 thermostats), would the room feel warmer, or at least a more consistant temperature? I think a fan heater would do away with the issue as it'll force a "convection current", but they are a bit noisy for a bedroom.

HappyMJ

The thermostats are rubbish. You'll get used to them and change them up or down to make yourself feel comfortable.

A fan heater for a bedroom is ideal. You really only want a burst of heat as you are getting into bed then turn the heater off overnight. Using an electric blanket will keep you warm overnight at very little cost...then in the morning turn the fan heater on and get out of bed standing in front of the warm airflow. Then turning it off as you leave. The running costs are very low for that time period.

chemicalfan

Ah, but that exposes another issue - condensation. Running the heating like that is a great way to get condenation & mould growing on the walls during the winter (summer is not as bad, as you can have the windows open), thanks to the crap insulation in this rented property. I'm looking at keeping a background heat in the room, a few hundred watts running 24 hours. This is until I can find a cheap/2nd hand de-humidifier anyway.

Sadly, it's not just about money, it's about health too. Trying to keep the mould at bay whilst keeping the bills down. A tough balance.