connecting Nichrome wire

[gauravkothari23]

hi all.
I want to make a small 220v heater. so i brought some Nichrome wire guage 30(0.3mm).
i just want to ask if i can connect my Nichrome wire directly to 220v plug... or do i need to add any circuit between.

 

[d123]

If the wire heats up enough to serve as a heating element, wouldn't that be bad for the plug?

 

[KlausST]

Hi,

current depends on resistance. Resistance depends on length of your wire.

--> if the wire is too short: the wire will burn or blow the fuse.

Klaus

 

[BradtheRad]

To see a safe 220V heating element, look in your toaster. Its element glows red. It is several hundred watts. Picture how you would change it, to make the heater you want.

Length can be doubled to draw 1/2 the Amperes, 1/4 the W.

Length can be shortened to draw more A. There is a point where it would be so short it will burn up.

Diameter can be reduced, and it would glow hotter with less A, and probably burn up.

Diameter can be increased, and it would draw more A.

This is not much of a solution.

A light bulb is often used as a small heating element.

 

[andre_luis]

just want to ask if i can connect my Nichrome wire directly to 220v plug... or do i need to add any circuit between.

If you are referring to the repacement component used in hot taps or electric shower, keep in mind that they are sized such that the electric power is mechanically actuated when a kind of diaphragm feels a minimum pressure inside, and closes the electric contact. This ensures that the resistance will not burn due to overheating, it will be guaranteed a minimum flow of water for heat dissipation.

 

[FlapJack]

gauravkothari23, You can not solder nichrome wire because the solder does not stick and it would probably melt anyway, so you must make a mechanical connection with a rivet or using a nut and bolt.

The high temperature of the nichrome wire must be kept in a safe enclosure rated for high temperatures to prevent fire. And the connections from the nichrome wire to the power cord must be in this enclosure for safety.

There are two ways to actually do this. 1st way, just one rivet or bolt connects the nichrome wire and the "appliance cord" wire to a heat resistant insulator. The appliance cord will have a copper eyelet crimped on the end with no plastic feral. Appliance cords are rated for high temperature for these applications. In the USA we can go to the hardware store and easily buy this high temperature appliance cord.

If the nichrome is very hot with a lot of thermal mass than an extended connection would be made. two rivets or two bolts separated with a thin strip of copper between them to dissipate the heat. Connections would be nichrome wire on one side and the appliance cord on the other. The length of the copper strip would be chosen so the temperature limits of the appliance cord are not exceeded.

 

[andre_luis]

gauravkothari23, You can not solder nichrome wire because the solder does not stick and it would probably melt anyway

In fact, but usually these heating elements are sold with terminals that allow fastening by screws. Not necessary to say that fixation needs to be very tight, particularly with high currernts in order to avoid sparks and further oxidation.

 

[FvM]

Every body is assuming high temperatures involved with the heating application. But the OP told effectively nothing about the application. An electric blanket uses nichrome wires too, but they are not particularly hot.

 

[gauravkothari23]

yes.... i have connected 1.6mm diameter 2 meter Nichrome wire directly to 220v A.C. current....
As soon as i connected the wire and plug it to A.C. socket the fuse of my place got blown up, without heating the wire.
Basically This thing happen when short circuit takes place....
why did this happen....
do i need to coil this wire....??

 

[d123]

Is your plug fused? If not you should put a fuse betwen the wire and the plug to stop the mains switch(es) from tripping while you're experimenting. Can you calculate/Have you calculated the current (or maybe heat in this case) that should flow through the wire/heating element so as to choose an appropriate fuse or similar safety device?

Not sure about this, heaters and nichrome wire are not things I understand, but if you're not joking, wouldn't making it into a coil be like making an inductor and make matters worse?

Search online for heater schematics to get some idea of how they are put together.

- - - Updated - - -

Find an online AC current calculator, that should explain why that happened, I looked but it's taking a long time to find a quick-fix calculator, and you know your multiple parameters better (...don't you?).

This link calculates resistivity for nichrome.

I don't know if AC is like DC for calculating, but 1.6mm^2 * 2m = 12.5 ohms (I think)
~220VAC/12.5 = 17.6A (presumably enough to trip a circuit breaker as houses are only 16A, I think...)
that would be a lot of current, possibly bad maths, but it makes you think and be a bit cautious about plugging unknown things in to see what happens

http://www.endmemo.com/physics/resistance.php

 

[FvM]

According to ohms law: I = V/R

1.6 mm², 2 m gives 1.4 ohm rather than 12.5 ohms for Nichrome with 1.1e-6 ohm*m resistivity, so obviously the fuse will blow.

 

[BradtheRad]

Once I dismantled a broken electric blanket. For no reason I have kept the 25 feet of vinyl covered nichrome element I got out of it.

The current-carrying wire is about 34 gauge. It is fragile. It is reinforced with a wrapping of fiber and wire.

2 ohms per inch. This adds up to 600 ohms.
So, in the USA it draws 0.2 A at 120VAC.
24W.

 

[D.A.(Tony)Stewart]

Supplier specs vary in the range of 15 Ohms/meter for Nichrome depending on metal content ratios.

Power and temperature rise depends on length and density of wire ( coiled or linear)
Normally short lengths are used for hot wire cutting of plastic film or foam.

How small in watts is your heater? For fragility reasons, you may need to immerse in oil or ceramic or have some mechanical support structure such as mica. between wire mesh.

 

[gauravkothari23]

U mean.... more the length of wire, more the current drawn....
I want nearly 120 to 140 ℃ temperature. using a 1.6mm diameter wire..
What should be the length of it....

 

[KlausST]

Hi,

U mean.... more the length of wire, more the current drawn....

No, it's the other way round: the more the length, the more the resistance, the less current.

In the first post you talked about 0.3 mm now you talk about 1.6mm. Do you have two different wires?

If so, then use the thinner one.

***
You can calculate the resistance on your own. You need to know the specific resistance of nichrome.
Multiply this value with the length and divide it by the cross sectional area of the wire.
You will find all informations at wikipedia, and a lot of other sources in the internet.

Klaus

 

[FvM]

I want nearly 120 to 140 ℃ temperature. using a 1.6mm diameter wire..
What should be the length of it....

The question doesn't make much sense. The temperature depends strongly on the available heat dissipation, e.g. wire free in air or in contact to other material, thermal conductivity of the support, air velocity...

You'll find some empirical formulas in engineering text books, but it's probably simpler to determine the required heater current in a test.

1,6 mm diameter (= 2 mm², I assumed 1.6 mm²) has even lower resistance about 0.55 ohm/m. I presume you have chosen the wire gauge for a reason. You won't achieve reasonable wire length with 220 V supply, instead a low voltage transformer should be used.

 

[gauravkothari23]

The question doesn't make much sense. The temperature depends strongly on the available heat dissipation, e.g. wire free in air or in contact to other material, thermal conductivity of the support, air velocity...

You'll find some empirical formulas in engineering text books, but it's probably simpler to determine the required heater current in a test.

1,6 mm diameter (= 2 mm², I assumed 1.6 mm²) has even lower resistance about 0.55 ohm/m. I presume you have chosen the wire gauge for a reason. You won't achieve reasonable wire length with 220 V supply, instead a low voltage transformer should be used.

i have chosen the wire guage for non reason.
any wire guage will work. but i want the output of nearly 120-140℃..
my cabinet or available space to install the wire is nealy 12inch × 8inch × 2inch(LxBxH).
voltage is not the matter.. can also use it with 12v... if it meets my requirements....

- - - Updated - - -

i have tried with 0.1mm wire...... length=1 meter... voltage 220v AC... but the wire blown up is just a micro seconds... so now i tried with 1.6mm wire.... but it shorted and the plug got tripped

 

[KlausST]

Hi,

i have tried with 0.1mm wire...... length=1 meter... voltage 220v AC... but the wire blown up is just a micro seconds... so now i tried with 1.6mm wire.... but it shorted and the plug got tripped

If you did your calculations you found out that thicker wire makes things worse.

Klaus

 

[gauravkothari23]

Hi,



If you did your calculations you found out that thicker wire makes things worse.

Klaus

Yes.. as per the results i got in both the cases... the thicker wire is worse....
but when i connect my 0.1 wire to 220v.... it blowned up.... so now i have to increase the lenght of it.... which is not possible because of limites space in my cabinet...
can i connect the same thinner wire to 12v dc... what is the calculation needed to be done

 

[FvM]

i have tried with 0.1mm wire...... length=1 meter... voltage 220v AC... but the wire blown up is just a micro seconds... so now i tried with 1.6mm wire.... but it shorted and the plug got tripped

Surely not micro seconds. But it's too much power (about 350 W) for this tiny piece of wire though.

People might be able to help you specifically if you tell what you want to achieve.