Iron v Copper for heating

[elfcurry]

I want to make a low temperature (<30C), low wattage (<30W) heater for keeping wine warm enough during fermentation in a cool room.

I thought about using common green plastic covered garden wire. Since it's the current through a resistance which generates the heat, would there be any disadvantage to using iron instead of copper? It would be temperature controlled and I can't see any problems but maybe you can.

 

[Speakerguy]

You are looking for something called "a 30W light bulb".

 

[elfcurry]

Thanks. It could work but it's not ideal, being fragile and a fixed shape.
I think wire is convenient because I can make it flat.

 

[crutschow]

Iron wire would be better than copper since it has a higher resistance. But you may still need a fairly long length to achieve a high enough total resistance to get only 30W from the mains voltage. 30W at 220V requires a resistance of 1600Ω.

 

[Mosaic]

Peltier junctions are flat and very efficient heaters as they heat from 2 sources, the wattage u put in and the heat pump action. You will need a finned heatsink & a fan to spread the heat around though.
You need a 12-16VDC supply to do it.

If u want to run off mains....use a series of higher wattage ceramic block resistors or wire wound resistors. For a 120V supply, which gives an rms of 120V * .7071 = 84.85 V. Power = VI.
I=P/V =30/84.85 = .354 A
V=IR, so, R= V/I, = 340 Ohms of resistance required.

For best radiant action get a number of 5W resistors....perhaps 11 , 30 - 33 Ohm units, string 'em in series, paint 'em black. Array them in a grid to radiate the heat from the bottom of the space. Job done.

 

[crutschow]

If u want to run off mains....use a series of higher wattage ceramic block resistors or wire wound resistors. For a 120V supply, which gives an rms of 120V * .7071 = 84.85 V. Power = VI.
I=P/V =30/84.85 = .354 A
V=IR, so, R= V/I, = 340 Ohms of resistance required.

Mains voltage is given in RMS volts not peak, thus you do not need the .7071 conversion. For 30W the desired resistance is V²/30 = 480Ω.

 

[Mosaic]

Corrected....

 

[4pyros]

Get a reptile warmer from your pet store. Flat heat in many low wattages. Andy

 

[elfcurry]

Thanks all.
I wrote a better response but it was removed by the software.

[edit]
So it does let me post now but it lost my careful reply.

My mains here is 240V so V squared/R
gives R around 2 k Ohms.

I won't risk losing another a long answer.

 

[KeepItSimpleStupid]

Take a look here: Flexible Heaters flexible heaters. Remember, you can operate them with a Variac.

 

[elfcurry]

Thanks, but I'm not looking for purchasing recommendations on ready-made items, I was asking for advice about whether iron was inherently unsuitable for a heating element and no-one has brought up a problem, which is good. Analogy: going to a cookery class and instead of getting help about how to cook a meal, being advised to order a pizza.

I'll go ahead and experiment with the iron wire and use a microcontroller, temperature sensor, LCD display and solid state relay as I did before with a seed heater.

Thanks all.