Multiquip ST2037, ST2038P, ST204B, ST2047 manual Float Switch Theory, How It Works, Design Features

ST2037, 47, 47B, 38P, 40T SUB. PUMP — FLOAT SWITCHES

Float Switch Theory

Mercury monitoring is a mercury-switch actuated, liquid level control that has proven to be more economical and longer lasting than other types of liquid-level control systems, easily replacing and improving upon diaphragm switches, air bubble systems and electromechanical switches most often relied upon in the past.

How It Works

There is a tilt-sensitive mercury switch hermetically sealed within each float. As the liquid level (water) rises or falls, the float changes its angle until the mercury switch makes (close, Figure 4) or breaks (open Figure 5) the circuit. Maximum pumping range is 120 degrees. See Figure 3 below.

Figure 3. Pumping Range (Float Switch)

Pumping Range

The pumping range of the pump is determined by the float switch tether cord. Use Table 3 as guide line to determine your required pumping range. Pumping ranges are based on non-turbulentconditions. Range may vary due to water temperature and cord shape. Please note as the tether length increases, so does the variance of the pumping range.

Design Features

Constructed of rigid, durable ABS polymer ultrasonically welded. The all-steel mercury switch is held by positioning pins. Interior is filled with cell foam.

■Suitable for most liquid environments.

■Hermetically sealed.

■Thick-walled non-corrosive PVC plastic enclosure.

■Pressure tested to 60 ft. (18.2 meters).

■Mercury switch reliability, proven to 500,000 cycles.

■Standard SJO, 16-gauge, 2 conductor cord (20 ft./6.09 m).

Figure 4. Float Switch (Closed)

Figure 5. Float Switch (Open)

Table 3. Pumping Range

Tether Length	2	in.	4 in.	6 in.	8 in.	10 in.	12 in.	14 in.	16 in.
	5.08 cm.		10.16 cm.	15.24 cm.	20.32 cm.	25.4 cm.	30.48 cm.	35.56 cm.	40.64 cm.
Pumping Range	6	in.	10 in.	14 in.	18 in.	22 in.	27 in.	31 in.	35 in.
	15.24 cm.		25.4 cm.	35.56 cm.	45.72 cm.	55.88 cm.	68.58 cm.	78.74 cm.	88.9 cm.

PAGE 12 — ST2037,47, 47B, 38P, 40T SUB. PUMPS — OPERATION AND PARTS MANUAL — REV. #3 (06/15/10)