It helps knowing your background, as I can try and draw comparisons to something you find intuitive.
A fairly good analogy of electricity is water flowing through pipes. The water is the electricity, and the pipes (and valves etc) are the wires and components in the circuit. The analogy degrades fairly quickly, but works very well for basic stuff. I suggest you try and draw up a circuit diagram and post up. Don't even worry about active vs neutral, just do a single line diagram.
Voltage is then analogous to water pressure; current to flow rate. A switch is analogous to a valve.
If you have a valve (switch) that's not rated to the water (electrical) pressure (voltage), it'll burst spectacularly (arc, catch fire and burn your house down). If you have a valve that's not big enough for the flow rate, when it closes it'll hammer like crazy and physically damage itself. Switches that attempt to close an excessive current can arc and burn out, or even weld the contacts together.
Similarly, if you have lots of sprinklers branching off a main, then the main needs to be sized to the worst-case but still possible scenario. The largest load that's possible to occur, and it depends on how you operate the system:
- All sprinklers on at once - add all the loads together (big main pipeline; max running load = connected load)
- Only one sprinkler at once - the largest single sprinkler (littler main pipeline; max running load << connected load)
Electrically, the proportion of the "connected load" compared to the actual load is known as the "diversity factor". If we all designed every electrical switchboard to be rated to the connected load, we'd have no money and no copper left on earth. We design to the worst-case that's actually possible.
I can't speak for the electric brewery, but it's possible that they have determined that only a proportion of their connected load is on at any one time, and thus at any one time they cannot draw more than 10A.
If, however, they are using 10A switches with a 30A load then that's bad bad bad.
I think you've got the idea of the relays - the relay does the heavy switching, and the switch turns on the relay with a little control voltage.
Edited by klangers, 24 May 2017 - 03:05 PM.