halogen heater query

Agreed - be careful with these heaters - I just threw 2 out yesterday because the internal wiring had physically burned out.

I do use them but the cheap ones are a bit of a fire hazard imo.

Cheers

Cardew wrote: »

With any type of electrical heater you get exactly the same amount of heat for the same running cost.

Actually, this is a good approximation, but it is not strictly accurate.

This statement would only be true if all electrical heaters were 100% efficient i.e. all the input electricity was directly converted into heat. Unfortunately, that is not the case.

For example, if an electric heater produces light, it uses some of the electrical input as energy to produce the light, this is an "overhead" that makes it less than 100% efficient.

Different methods of producing heat have different "overheads" and all electric heaters have their own particular "overhead" dependent upon their means and design.

If you still can't follow this, just think about lighting a room. Using the same argument, it should not matter what method you use to light the room - if you use the same amount of electrical input, you will get the same amount of illumination. This is just not correct. In the case of lighting, the difference between using different methods was so great that legislation has been passed to prohibit certain inefficient light bulbs in an effort aimed at reducing the UK's carbon footprint.

RobbieJ wrote: »

Actually, this is a good approximation, but it is not strictly accurate.

This statement would only be true if all electrical heaters were 100% efficient i.e. all the input electricity was directly converted into heat. Unfortunately, that is not the case.

For example, if an electric heater produces light, it uses some of the electrical input as energy to produce the light, this is an "overhead" that makes it less than 100% efficient.

Different methods of producing heat have different "overheads" and all electric heaters have their own particular "overhead" dependent upon their means and design.

If you still can't follow this, just think about lighting a room. Using the same argument, it should not matter what method you use to light the room - if you use the same amount of electrical input, you will get the same amount of illumination. This is just not correct. In the case of lighting, the difference between using different methods was so great that legislation has been passed to prohibit certain inefficient light bulbs in an effort aimed at reducing the UK's carbon footprint.

All lamps produce heat and light. However, the light you see hits a surface and then the light energy converts into heat so they are 100% efficient at creating heat. They are inefficient in summer as heat is not wanted. In winter we need to use the central heating more to replace the lost heat so the savings you see on your electric bill aren't exactly the savings you get as more gas is used.

Cardew wrote: »

... Or at least a guy called Albert Einstein thought that it was the case.

The clue is that "Energy cannot be created or destroyed"!...

Correct, but there is a whole electromagnetic spectrum of energy.

ilikecookies wrote: »

Interesting point.

I've wondered how design factors into the equation too. I accept that in theory a 2kw oil-convection heater will cost the same to run as a 2kw halogen heater. However there are differences. For example I have two 2kw oil-convection heaters. They are different brands and different designs. I'm sure that one heats the room quicker than the other.

I assume design does have an impact on their efficiency. For example, a newer style single radiator with fins throws out more heat than a old-style single radiator which doesn't have fins.

You mustn't confuse efficiency with effectiveness.

Both of your 2kW heaters will produce exactly the same amount of heat from the electrical energy they consume; so are both 100% efficient.

However it is perfectly possible that one heater(with the fins) dissipates heat better than the other and thus is more effective at producing heat initially.

However assuming that they have both consumed, say, 1kWh, then after power is switched off, the heater without fins will remain warmer, and thus still dissipating heat after the other heater is cold.

The point being that they both will have produced the same amount of heat for the 1kWh consumed.

A more graphic comparison would be a fan convector heater which produces almost instant heat, but no residual heat; and compare this with a oil filled radiator that is slower to produce heat(as the oil is being warmed) but has residual heat.

Again for 1kWh consumed both produce exactly the same amount of heat.