| I do not mind installing an overload relay, as such, except that it is | a cost issue. Fuses are cheaper. (unless I can find something at that | junkyard). Realistically speaking, the idler is not going to bind. If | contacts to capacitors break, yes, I could have a stall issue, which | would be addressed by properly sized fuses. | | A relay is more exciting and possibly a little more convenient (it is | resettable, I do not need to buy new fuses when a fuse burns out), but | in reality will provide about same protection. | | Am I mistaken? |
Your 220V home circuit breaker has two poles, but each pole is connected so that if one leg has an overcurrent, it will trip, taking the other leg out with it. Otherwise, one leg will still be hot, presenting a very ugly hazard. Fuses cannot provide this protection, and as such, are a single shot deal. Overloads, on the other hand, have various trip conditions that can be selected for, and they take all three phases out at the same time, which is the safety you need.. Ask your supplier for assistance in picking them, I don't have that information at hand anymore. While motor starters have the contactor and the overload physically attached to each other, electrically they're pretty much the same so one brand ought to be usable with another even if you can bolt them together. Just for the sake of the record, a motor starter consists of a set of three large contacts, possible auxiliary contacts (usually clipped or screwed) and the overload. The overload has three fuse looking elements that are called heaters. When the heater gets to a certain point in its thermal cycle, it will bend and trip the overload, which actually just opens it's own auxiliary contact and the contactor opens up. The solenoid on the contactor is wired through this overload contact, so in order to reset it you usually have a reset button to push. To add a little more confusing information, starters are given sizes, according to NEMA, thus you have a starter for a given range of motor sizes. http://www.southlandelectric.com/Thermal%20heater%20elements.htm has a lot that info that might help you understand better. The overloads are sized to match as well.