Nichrome Wire Calculator

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Procedure

  • Select convenient length
  • Select max temp - such as 550C = 1000F
  • Match gauge to proper voltage drop of 120V - ie, observe parameters that produce 120V drop - those will be the working parameters since 120V is fixed.
  • Find out max gauge that is within current limits (15A) and has correct voltage
  • Limit for 15A outlet is 1800W

Sample:

Samplenichrome.png

  • Remains within 15 amps
  • Shows correct voltage
  • Max temp - select it to match voltage - you determine max possible temp and judge whether it will burn out your system if you have temperature sensitive components
  • Note that Gauge 17 is the max fatness that stays within 1800W
  • Note: 22' of 18 ga gets us right at 120V, and 1560W. Good. But temperature of 1260F is a little high.

Nichrome2.png

Examples

8" bed

  • 12' of 26 ga draws 450 Watts.
  • This was acceptable, but burns out thermistors if placed directly on heater.
  • Point: the shorter the nichrome, the hotter it will get while remaining at the correct voltage
  • Keep conservative on the bed power,then.
  • For same power density on large bed (7W/sq in), would need 4000W of heat. Can't do that. Limit is 1800W. the question is how best to achieve it - what length of nichrome is required for a workable length, while keeping temperature lower rather than higher.

2x2 foot bed

  • 1800W limit
  • To cover bed - try 6 lines separated by 4" of space. This means 12' + 2 feet return or 14' of sleeve
  • Gauge 17, 28' long, gets max 1090 and 1570 watts
  • sleeve it in 14' of sleeve. Quite doable. needs total of 28 feet of sleeve.
  • Selection:

Finalselection.png

Shorten it by 2-4 feet to get max power and temperature.

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