# 120v up to 160v or 220v down?

• posted

I have built an annealer using 6 ea. 220v 5000 watt nichrome wire elements. I have put two elements in a series, thus there are 3 sets of two elements. The temperature I need to reach is 1000°. So far in testing It reaches 820° running on 110 volt. I'd rather not run it on

220v simply because the element life will be shortened. I was thinking that perhaps just another 40 or 50 volts would be enough to reach the needed 1000°. How can I get voltage stepped down from 220 volts to around 160 volts or thereabouts? Or 120volts increased to about 160 volts. Can I put a rheostat on one leg of the 220 volt and lower it to 50 volts and leave the other at 110 volt? Since the product needed is just heat would this idea work putting in 110volts on one end and approx. 50 volts in on the other end? Am I a amateur or what? Thanks for any ideas or help. Jerry
• posted

| I have built an annealer using 6 ea. 220v 5000 watt nichrome wire | elements. I have put two elements in a series, thus there are 3 sets of | two elements. The temperature I need to reach is 1000?. So far in | testing It reaches 820? running on 110 volt. I'd rather not run it on | 220v simply because the element life will be shortened. I was thinking | that perhaps just another 40 or 50 volts would be enough to reach the | needed 1000?. How can I get voltage stepped down from 220 volts to | around 160 volts or thereabouts? Or 120volts increased to about 160 | volts. | Can I put a rheostat on one leg of the 220 volt and lower it to 50 volts | and leave the other at 110 volt? | Since the product needed is just heat would this idea work putting in | 110volts on one end and approx. 50 volts in on the other end? Am I a | amateur or what? | Thanks for any ideas or help. | Jerry

Let's see. These elements are designed for 5000 watts individually at

240 volts, and you have 2 in series and worry about the life of each?

Based on a nominal of 240/120 volts, your 5000 watt element is 11.52 ohms and would draw a current of 20.833 amps. You might want to measure the resistance and report that for more accurate calculations.

Two elements in series is 23.04 ohms. Running that at 120 volts results in a current of 5.208333 amps. Three sets in parallel (7.68 ohms) draws a total of 15.625 amps for a total of 1875 watts.

Running that same setup at 160 volts (your estimated target) would draw

20.833 amps for a total of 3333.333 watts. To get that current from 240 volts would be a resistance total of 11.52. Subtract 7.68 from that and you have 3.84 ohms. At 20.833 amps that 3.84 ohms will dissipate a total of 1666.667 watts.

Are you prepared to have 1666.667 watts of dissipation in such a resistor?

You could build such as "resistor" with 37.5 100-watt light bulbs wires in parallel. You could hit it on the mark with 50 75-watt light bulbs. Maybe you can realize the power wasted here (not the full wattage in each bulb, since they would be "seeing" only 80 volts, but a substantial amount).

A transformer would normally be a better option ... but ...

... you may have another option:

Wire 3 elements in series (with 2 series in parallel). One set of 3 in series would be 34.56 ohms, and draw 6.944 amps of current on 240 volts for a total of 13.889 amps between them. Now your annealer power is

3333.333 watts. That's the same wattage you would get with the other wiring arrangement at 160 volts.

The above assumes I understand your setup correctly (especially the part about each element being designed for 5000 watts at 240 volts individually) and did my math correctly. You can help out by actually testing the true resistance of each element, and the resistance of the current configuration (2 series, 3 parallel) in whole, to see if things are as expected. And if wiring the suggested way (3 series, 2 parallel) can be done easily, set it up and just measure its resistances to see if you get the expected 17.28 ohms.

Having 6 elements is a common way for wiring flexibility for both single and three phase power sources, so I'm assuming you have access to all 12 element leads to wire it any way.

• posted

How much are you willing spend? Using a variac you could hook it to 220 and tap off what you need. You may have to spend something in the \$200 range to get a variac in that power range. They are available on ebay.

• posted

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.