Chpater 5.2.2.2 - Common Voltages

Electric radiant heat encompasses a broad range of products, each of which utilizes
the range of voltages appropriate to the product category. As a result, electric radiant
heaters may be found for each of the common voltages. Residential and light
commercial products are normally available in both 120- and 240-V models. In some
cases dual-voltage models are available. Commercial usage often requires 208- or
277-V models, whereas industrial applications sometimes require 480 V. Voltage is
often country-specific. For example, most of Western Europe is 220 V, Japan is 100 or
200 V, and China is 220 V.

Voltage drops due to line resistance is the reduction in voltage that can occur between
the power source and the load. For most applications, this is not a factor, but
where long feeds are required, the drop must be calculated to determine the impact
on the rated output of the equipment shown.The wire material, diameter, and length
determine resistance. The product of the resistance and the current is the voltage
drop. For electric heat, if the drop is more than 1 percent, the equipment sizing should
be carefully reviewed because, as we will see, the wattage output drop is much larger.

Voltage drop due to inability of the energy source to provide power at the normal
levels results in a much larger corresponding drop in resistance heat output.This will
become very apparent as we discuss power, the rate of moving or changing energy.
We measure electric power in watts (W).

The following chart provides the unit of measure and abbreviations used for the
common descriptors used in discussing basic electrical principles: