Figure 2-41. Differential Switch
a. Differential Switch (Figure 2-41).
l System must be operating to make adjustment.
l Contacts can be visually checked for opening and closing or checked with a
(1) Remove differential adjustment cap (6).
(2) Turn the differential screw (3) clockwise to widen the difference.
(3) Turn the differential screw (3) counterclockwise to lower the pressure difference.
(4) Table 2-3 gives the desired differential setting.
(5) Gages on top of control panel show differential pressures (between black and red arrow pointers on dial face).
(6) The sensitivity adjustment (7) governs the point at which the contacts (4) open. This should not be adjusted
unless a more sensitive differential of less than 5 psig is desired.
(a) Maximum sensitivity is the largest spread between on and off operations of the controls (± 1 psig)
(b) Minimum sensitivity is the smallest spread between on and off operations of the controls (± 1 psig).