So as I have mentioned here before I have been attempting to gain a better understanding of PLC's and automation and control systems. As part of this I have spent the last couple weeks digging in to surge protection for electronic equipment. As part of this I started looking at some of our equipment at work. One system caught my eye for apparent lack of any type of surge protection. There is an AB MicroLogix 1200 (1762-L40BWAR)whose 24 VAC relay outputs are tied to a bunch of intervening relays (IDEC RU4S-A24) that in turn switch various loads. From what I can see there is zero TVS across any of these 24 VAC relays. This piece of equipment has been running 24/7 for about 3 years now, and we have never had a problem. IDEC does offer relays with built in suppressors, but this particular model doesn't have them. This control panel and everything in it was part of a pre-built package system, that came this way from a company that builds these things all the time, so I assume that I am failing to understand something here. What am I missing?