Why do railroads use timber ties on bridges and concrete ones on the ground?

To Ground, or not to Ground?

• have a new job at a company that installs POS systems(all windows based PC, really there is a sever and several nodes, just a network) in restaurants. Restaurants need to run cheaply to be profitable. The owners often cut corners. The manufacturer suggests (STRONGLY) that everything be plugged into isolated ground outlets (the orange ones). If those are not available (which they hardly ever are) we are to use a power conditioners with ground conditioning built in. This essentially gives us an orange outlet. The cabling for these customers is seldom don by professionals. Many times the restaurant owner pulls it himself on the weekend. We do the terminations. No one here has any expertise in cabling. They are in the practice of also grounding the patch panel that all the nodes in the POS network terminate to. My thought is that this will undo all of the work that the Ground conditioning orange outlets have done by possible having a difference in ground potential or ground loop created by this panel ground. Am I crazy, or is this a risk? When I said that the cabling was seldom done by professionals, I was refering to the network cabling, not the electrical cabling. The restuarants are unlikely to get isolated outlets installed. The brand of the power conditioning is Powervar Ground Guard. I personally believe that a UPS is the best solution, but I need good evidence to convince the management at my company. We have been in business for 60 years (not new to this) the manufacturer for the POS equipment (Mircos, the best in the market) suggests the we use isolated grounds, or ground conditioning. I have not heard from them if a UPS is an accepable alternative.

• Answer:

  I don't see how you need isolated lines. I've some experience in grounds for large instrumentation systems, far larger than this one, and I never considered use of an isolated outlet. The power supplies all have isolation, and that is all you should need. My suspicion is that you have either: a) someone in your design group read somewhere that isolated lines are good, and specified them for no real reason. b) the isolated lines are to cover up a design problem such as a poor ground arrangement. As to your last bit, if it works, then it's fine. .