Has anyone heard of contact bounce? As contacts separate, there's resistance that creates heat. Carbon is formed due to this and is accumulated around the part. I find resistive circuits like inline duct heaters are the worst. A bouncing contact can be seen under a high speed camera. Each bounce is a separation, each separation creates heat and carbon. You may have noticed that a lot of manufacturers use a solid state relay (SSR) to pulse duct heaters now a days and the contactor remains pulled in, this helps to avoid carbon build up, wear and tear on the contactor and also tighter control. Here is a video that completely nerds out on the subject. #teachme https://youtu.be/jI-rC2FCKo4

Posted by HVAC Know It All at 2021-04-07 15:32:05 UTC