A recent addition to the Major Electronix online store are the PTC heaters from Seifert. This selection of KH 501 series heaters takes care of the same potential issues as the KH-801 series fan heaters. The difference lies in how the KH 501 heaters operate. Control cabinet heaters are typically used in situations in which humidity or condensation can collect inside the enclosure, such as in outdoor applications. Too much moisture build-up inside can cause equipment to corrode, or lead to performance failure. Using a heater such as those from the Seifert KH-501 series can alleviate that problem.

The basic features of Seifert's PTC heaters include their space saving design, broad voltage range, and greater efficiency. The space saving housing ensures that the heater won't take up too much space in the enclosure. There are five different models, ranging from 25W to 150W, with all of them operating between 110-240V. It promotes better efficiency over other types of heaters due to the self-regulating PTC resistor, which varies the heat based on the surrounding temperature. This differs from the KH 801 series fan heaters, which use a thermostat and control settings to regulate the temperature.

The term PTC stands for Positive Temperature Coefficient. This indicates that electrical resistance actually becomes greater as the temperatures rises. In other words, there will be less current flowing as the surrounding temperature increases, and more current flowing if it goes down. This is why Seifert's PTC heaters have such a large voltage range. These types of heaters make use of materials that have this positive temperature coefficient property, as opposed to the wire coils found in more conventional heaters.

All of the Seifert control cabinet PTC heaters use convective heat, indicating the way the heat is transferred through the air. The warmer air rises through the enclosure, while the cooler air sinks. For easy installation, the KH 501 series heaters all include a DIN-Rail mounting clip as well as a 2 screw terminal block.