Murphy Switch

[Orn Jonsson]

Murphy.......

The one I have seen was a "MERCURY" Contactor type switch used in a heating application. Apparently the vacuum sealed chamber with liquid mercury provided a lot longer life in a high AMP switching than your typical contactor would have......


O Jonsson

 

[catserveng]

The term "Murphy Switch" comes from the oil patch, and specifically refers to the line of mechanical gauges with switch contacts that were used for protection circuits for engines, compresors, generators, etc. The button on the front of the gauge was to over-ride the contact during startup, usually a low lube oil pressure shutoff or warning device. The primary manufacturer of these switch gauges is the Frank W Murphy company, but there are other manufacturers as well. In later systems there was a latching relay added, that also got called the Murphy switch, to indicate if a fault had occured, and to reset it, the button onthe front had to be pushed in.

Hope this helps. The switch gauges and relays aren't as popular as they once were, especially with small electronic controls being cheaper and actually more reliable (at least to some people).