Category Archives: Formulas, Conversions & Calculations

Common Resistance Wire Trade Names

Posted on February 22, 2013 by admin

Trade Name Cross Reference

MWS Wire IND. Carpenter Tech. Driver-Harris Harrison Hoskins Jelliff Kanthal
MWS-875 Alchrome 875 HAI-FeCr AI 25 Alloy 875 Kanthal A-1
MWS-800 Evanohm Karma HAI-431 Chromel R Alloy 800 Nikrothal L
MWS-675 Tophet C Nichrome HAI-NiCr 60 Chromel C Alloy C Nikrothal 6
MWS-650 Tophet A Nichrome V HAI-NiCr 80 Chromel A Alloy A Nikrothal 8
MWS-294 Cupron Advance HAI-CuNi 102 Copel Alloy 45 Cuprothal 294
MWS-180 180 Alloy Midohm HAI-180 Alloy 380 Alloy 180 Cuprothal 180
MWS-120 Balco Hytemco HAI-380 Alloy 120
MWS-90 90 Alloy #95 Alloy HAI-90 Alloy 290 Alloy 90 Cuprothal 90
MWS-60 60 Alloy Lohm HAI-60 Alloy 260 Alloy 60 Cuprothal 60
MWS-30 30 Alloy #30 Alloy HAI-30 Alloy 230 Alloy 30 Cuprothal 30

Posted in Formulas, Conversions & Calculations |

Nichrome 80 – Ohms Per Inch of Closed Helix

Posted on July 11, 2011 by admin

Ohms per inch of closed helix

AWGSize

(Thickness)

 Outside Diameter of Helix in Inches
3/4 5/8 1/2 3/8 1/4 7/32 3/16 5/32 1/6 3/32 1/16 1/32
14 .446 .365 .283 .202 .121 .101
15 .638 .523 .408 .293 .178 .148 .120
16 .895 .735 .575 .415 .255 .215 .175 .135
17 1.32 1.08 .851 .617 .383 .325 .266 .208 .150
18 1.89 1.56 1.22 .891 .559 .475 .392 .309 .226
19 2.60 2.14 1.69 1.23 .779 .665 .551 .438 .324
20 3.72 3.07 2.42 1.78 1.13 .967 .805 .644 .482
21 4.53 3.58 2.63 1.68 1.45 1.21 .971 .733 .496
22 4.98 3.67 2.36 2.03 1.70 1.37 1.05 .719
23 7.02 5.18 3.34 2.88 2.42 1.96 1.51 1.05
23 7.02 5.18 3.34 2.88 2.42 1.96 1.51 1.05
24 4.69 4.05 3.41 2.78 2.14 1.60 .865
25 6.87 5.94 5.02 4.10 3.17 2.25 1.32
Posted in Formulas, Conversions & Calculations |

Helical Coils

Posted on July 11, 2011 by admin

This data has been compiled as an aid to the manufacturers of helical coils and show the approximate current in amperes required to heat the coils in the open air to the indicated temperatures under the conditions specified.

No. B & S Diam. Inches Temp, 400° F.
Temp, 204° C.		 600
316		 800
427		 1000
538		 1200
649		 1400
760		 1600
871		 1800
982		 2000° F.
1093° C.
14 .064 5.07 7.99 11.03 14.17 17.38 21.41 25.64 30.06 34.66
15 .057 4.14 6.69 9.65 12.23 15.17 18.30 21.53 24.85 28.23
16 .051 3.34 5.29 7.33 9.45 11.62 14.62 17.83 21.25 24.86
17 .045 2.94 4.39 6.31 7.95 9.89 12.37 14.77 17.40 20.16
18 .040 2.41 3.78 5.20 6.65 8.14 10.00 11.92 13.94 16.03
19 .036 2.11 3.25 4.59 5.89 7.23 8.88 10.62 12.42 14.30
20 .032 1.56 2.53 3.56 4.64 5.77 7.15 8.60 10.13 11.71
21 .0285 1.30 2.11 2.96 3.87 4.81 6.11 7.22 8.52 9.89
22 .0253 1.12 1.74 2.39 3.03 3.69 4.74 5.89 7.13 8.46
23 .0226 .980 1.53 2.10 2.69 3.29 4.15 5.07 6.04 7.08
24 .0200 .950 1.45 1.96 2.47 3.00 3.67 4.36 5.08 5.83
25 .0179 .820 1.25 1.70 2.15 2.61 3.19 3.80 4.44 5.08
26 .0159 .660 1.04 1.44 1.86 2.28 2.76 3.26 3.77 4.29
27 .0142 .560 .862 1.17 1.48 1.80 2.19 2.60 3.02 3.46
28 .0126 .390 .663 .893 1.18 1.45 1.80 2.17 2.56 2.97
29 .0113 .310 .509 .705 .918 1.14 1.45 1.78 2.14 2.52
30 .0100 .270 .445 .623 .791 .980 1.26 1.58 1.91 2.28

.040 through .010 based on coiling on an arbor .12 diameter and stretched to twice the close wound lengths.

Posted in Formulas, Conversions & Calculations |

Current Temperature Characteristics of Nichrome (straight wire)

Posted on July 10, 2011 by admin

Showing approximate amperes necessary to produce a given temperature. Applying only to straight wires stretched horizontally in free air.

No. B & S Diam. Inches Temp, 400° F.
Temp, 204° C.		 600
316		 800
427		 1000
538		 1200
649		 1400
760		 1600
871		 1800
982		 2000° F.
1093° C.
12 .081 11.34 15.91 20.27 25.53 31.77 39.03 46.73 54.80 63.01
13 .072 9.73 13.53 17.21 21.61 26.89 33.06 39.60 46.41 53.31
14 .064 8.34 10.50 14.59 18.30 22.76 28.01 33.56 39.31 45.11
15 .057 7.15 9.78 12.38 15.50 19.26 23.73 28.44 33.30 38.17
16 .051 6.13 8.31 10.50 13.11 16.30 20.10 24.10 28.20 32.30
17 .045 5.31 7.18 9.13 11.30 13.90 16.90 20.30 23.60 27.00
18 .040 4.66 6.26 7.90 9.75 11.96 14.51 17.37 20.48 23.08
19 .036 4.09 5.46 6.84 8.41 10.30 12.45 14.87 17.78 19.73
20 .032 3.58 4.77 5.92 7.25 8.86 10.69 12.72 15.43 16.87
21 .0285 3.14 4.16 5.13 6.26 7.63 9.17 10.88 13.40 14.40
22 .0253 2.76 3.63 4.44 5.40 6.56 7.87 9.31 11.63 12.33
23 .0226 2.42 3.16 3.84 4.67 5.65 6.76 7.97 10.09 10.54
24 .020 2.12 2.76 3.32 4.01 4.86 5.80 6.82 8.76 9.01
25 .0179 1.84 2.42 2.90 3.44 4.15 4.97 5.86 6.96 7.72
26 .0159 1.58 2.09 2.52 3.00 3.61 4.31 5.06 5.97 6.63
27 .0142 1.34 1.80 2.19 2.62 3.14 3.73 4.37 5.12 5.69
28 .0126 1.18 1.55 1.90 2.28 2.73 3.23 3.77 4.39 4.88
29 .0113 1.02 1.34 1.65 1.99 2.37 2.80 3.25 3.76 4.39
30 .010 .875 1.16 1.43 1.74 2.06 2.43 2.81 3.22 3.59

.040 through .010 based on coiling on an arbor .12 diameter and stretched to twice the close wound lengths.

Posted in Formulas, Conversions & Calculations |

Size and Approximate Cold Resistances of Various Alloys for Common Wattages

Posted on July 6, 2011 by admin
Watts at
Operating Temperatures
Nichrome V
Ohms at 75° F.		 Nichrome
Ohms at 75° F.		 Recommended
B. & S. Sizes
110-120 Volts 220-240 Volts 110-120 Volts 220-240 Volts 110-120 Volts 220-240 Volts
100 123.52 494.09 118.10 472.40 Max. 26-30 Min. Max. 29-33 Min.
150 82.347 329.38 78.732 314.93 26-30 29-33
200 61.761 247.04 59.050 236.20 25-29 28-32
250 49.409 197.64 47.240 188.96 24-28 27-31
300 41.174 164.69 39.366 157.46 24-28 27-31
350 35.291 141.16 33.742 134.97 23-27 26-30
400 30.881 123.52 29.525 118.10 22-26 25-29
450 27.449 109.80 26.244 104.98 20-24 23-27
500 24.704 98.817 23.620 94.479 20-24 23-27
550 22.458 89.832 21.472 85.889 19-23 22-26
600 20.586 83.345 19.683 79.730 19-23 22-26
650 19.004 76.016 18.170 72.679 18-22 21-25
700 17.646 70.584 16.871 67.486 18-22 21-25
750 16.468 65.874 15.745 62.982 18-22 21-25
800 15.440 61.766 14.762 59.055 18-22 21-25
850 14.532 58.128 13.894 55.577 17-21 20-24
900 13.724 54.897 13.122 52.487 17-21 20-24
950 13.002 52.009 12.431 49.726 17-21 20-24
1000 12.352 49.409 11.810 47.240 16-20 19-23
1050 11.764 47.055 11.247 44.989 16-20 19-23
1100 ..229 44.918 10.737 42.946 16-20 19-23
1150 10.741 42.964 10.270 41.078 15-19 18-22
1200 10.2936 41.174 9.8418 39.367 15-19 18-22
1250 9.8817 39.527 9.4479 37.792 14-18 17-21
1300 9.5016 38.006 9.0845 36.338 14-18 17-21
1350 9.1497 37.599 8.7480 35.992 13-17 16-20
1400 8.8229 36.292 8.4356 34.743 13-17 16-20
1450 8.5188 34.075 8.1449 32.579 12-16 15-19
1500 8.2347 32.938 7.8732 31.493 12-16 15-19
2000 6.1761 24.704 5.9050 23.619 10-14 13-17
2500 4.9409 19.764 4.7240 18.896 9-13 12-16
3000 4.1174 16.469 3.9366 15.746 8-12 11-15
Posted in Formulas, Conversions & Calculations |

AWG Wire Gauge Calculator / Converter

Posted on June 21, 2011 by admin

Convert from inches or millimeters to AWG

Diameter: Standard (inches) | Metric (mm)

AWG:

AWG Number Ø [Inch] Ø
[mm]		 Ø [mm²]
6/0 = 000000 0.580 14.73 170.30
5/0 = 00000 0.517 13.12 135.10
4/0 = 0000 0.460 11.7 107
3/0 = 000 0.410 10.4 85.0
2/0 = 00 0.365 9.26 67.4
1/0 = 0 0.325 8.25 53.5
1 0.289 7.35 42.4
2 0.258 6.54 33.6
3 0.229 5.83 26.7
4 0.204 5.19 21.1
5 0.182 4.62 16.8
6 0.162 4.11 13.3
7 0.144 3.66 10.5
8 0.128 3.26 8.36
9 0.114 2.91 6.63
10 0.102 2.59 5.26
11 0.0907 2.30 4.17
12 0.0808 2.05 3.31
13 0.0720 1.83 2.62
14 0.0641 1.63 2.08
15 0.0571 1.45 1.65
16 0.0508 1.29 1.31
17 0.0453 1.15 1.04
18 0.0403 1.02 0.823
19 0.0359 0.912 0.653
20 0.0320 0.812 0.518
21 0.0285 0.723 0.410
22 0.0253 0.644 0.326
23 0.0226 0.573 0.258
24 0.0201 0.511 0.205
25 0.0179 0.455 0.162
26 0.0159 0.405 0.129
27 0.0142 0.361 0.102
28 0.0126 0.321 0.0810
29 0.0113 0.286 0.0642
30 0.0100 0.255 0.0509
31 0.00893 0.227 0.0404
32 0.00795 0.202 0.0320
33 0.00708 0.180 0.0254
34 0.00631 0.160 0.0201
35 0.00562 0.143 0.0160
36 0.00500 0.127 0.0127
37 0.00445 0.113 0.0100
38 0.00397 0.101 0.00797
39 0.00353 0.0897 0.00632
40 0.00314 0.0799 0.00501
Posted in Formulas, Conversions & Calculations |

Heating Element Calculations & Ohm’s Law

Posted on June 20, 2011 by admin

Heating Element Calculations

In order to make the basic calculations for the design of heating elements the following formulas, known as Ohm’s Law, are essential:

Volts = Amperes x Ohms Calculator
= x

Watts = Volts x Amperes Calculator
= x

Watts = (Amperes) 2 x Ohms Calculator
= x

Useful Coil Formulas

Length of one turn of wire = π (Outside coil dia. - wire dia.) Calculator
= π ( - )

Number of turns of wire per inch of coil = 1 / Wire Dia. Calculator
= 1 /

Length of wire in 1″ of closed coil = π(Outside coil dia. - Wire dia.) / Wire dia. Calculator Calculator

Resistance per inch of closed coil = π(Outside coil dia. - Wire dia.) (resistance / ft. of wire) / 12 (Wire dia.) Calculator

Length of coil = Total resistance of coil / Resistance per inch of closed coil Calculator
= /

Combining the above formulas given above we get the complete formula for coil calculations.

Length of Coil = Coil Resistance x Wire Dia. / .262 (Coil Outside Dia. - Wire Dia.) (Resistance / FT. of Wire Used) Calculator

Wire Resistance = (Ohms / Cir. Mil. Ft.) / Diameter2 (expressed in mils.) Calculator

Strip & Ribbon Resistance = (Ohms / Sq. Mil. Ft.) / Thickness (Mils.) x Width (Mils.) x Correction Factor Calculator

  • The correction factor will be .94 or .83 depending on ratio of thickness to width.
    See the pages on strip resistance for change over from 6% or 17% correction.

Wire Wt. = πr2 x Length x Lbs./Cubic Inch Calculator

Strip Wt. = Thickness x Width x Length x Lbs./Cubic Inch Calculator

Ohms/Sq. Mil. Ft. = Ohms/Cir. Mil. Ft. x .7854 Calculator
= x .7854

Posted in Formulas, Conversions & Calculations |