[Jim Meyer]

The benefit of having two switches is ease of programming. With them both connected to the accumulators, if you set one at 120 psi and the other at 100 psi you can program the compressor to turn on when the pressure dropps below 100 and shut off when the pressure gets to 120 psi. This way you don't have to do any "debouncing".

Last year we had problems blowing fuses on the spikes if we turned the compressor on with an accumulator pressure at 120 psi. It didn't happen very often but I believe it is good practice to not turn your compressor on unless the accumulator pressure is less than 100 psi. The easiest way to do this is with two switches. The method Joe J. mentions is also a good one but is probbably a little trickier to program. The method described by "The Lucas" allows the compressor to turn on at high pressures if you have a slow leak or a small cylinder.