Question

The instructions on a low-pressure switch read "cut-out is cut-in less differential." To set the switch to cut-out at 30 psig:

A. Set the cut-in at 30 psig
B. Set the cut-in 15 psi less than the cut-out
C. Set the cut-in 30 psi less than the cut-out
D. Set the cut-in 15 psi more than the cut-out

Answer 1

To set the low-pressure switch to cut-out at 30 psig, you need to know the differential and then set the cut-in pressure higher by that differential amount. Without knowing the differential, none of the answer choices can be determined as correct.

Step-by-step explanation:

The question involves setting the appropriate values for a low-pressure switch, specifically understanding the relationship between cut-in, cut-out, and the differential. When instructions state that 'cut-out is cut-in less differential', it means that the cut-out pressure is the pressure at which the switch will turn off the system, and it is lower than the pressure at which it will turn on, which is the cut-in pressure, by the amount of the differential.

Suppose you want the switch to cut-out at 30 psig. First, you need to know the differential value, which is the difference between cut-out and cut-in pressures. Once that is known, you can set the cut-in pressure accordingly. For instance, if the differential is 15 psi and you wish to cut-out at 30 psig, you need to set the cut-in at 45 psig. That would make the cut-out, which is the cut-in minus the differential (45 psig - 15 psi), equal to 30 psig.