Electric Heating Co., Inc

Resistance to Change

Each gage of resistance wire has a fixed measure of resistance (ohms) per unit of length. When we receive a specification for watts and volts for a heater, the required resistance is calculated and a coil of appropriate length is designed by computer. When voltage is applied to that resistance coil, the specified level of wattage, and corresponding heat, is produced.

The initial tolerance for the resistance specification is +5%/-10% which will supply -5%/+10% against the wattage specification ... better to be on the strong side when it comes to wattage.

Last week we discussed how the chromium content of the NiCr wire is depleted during the life of the heater. This process can be measured by monitoring the decreasing room temperature resistance of the wire. however, due to an increased temperature coefficient of resistance, the resistance of the wire at operating temperature will be nearly equal to that of the heating element when it was new.

Check out our postcard in Machine Design !!!

http://ndx.nextdecks.com/designdeck/august_07/

Dalton Electric Heating Co., Inc (978)356-9844
28 Hayward Street Ipswich, MA 01938 USA

(C) Copyright 2006 - 2007. Dalton Electric Heating Co, Inc. All Rights Reserved.