Schneider Square D 9036/9037/9038 Electromechanical Liquid Level Controller

Tapped at top - the connecting rod is directly screwed into the top of the floating ball. The maximum recommended connecting rod length is 12.5 feet. Suitable for scenarios with small changes in liquid level. Comes with 2 stop rings (one on top and one on the bottom).

Center hole floating ball - The connecting rod passes through the center of the floating ball and can slide on the connecting rod. The maximum connecting rod length can reach 30 feet. Comes with 4 stop rings to provide a wider range of liquid level adjustment.

2.1 Buoyancy data and medium specific gravity correction

All buoyancy data is based on fresh water (with a specific gravity of 1.0) and the float is submerged at 80% (with a 20% safety margin reserved). The net buoyancy of a typical 7-inch 304 stainless steel float is as follows:

Float type net buoyancy (ounces)

Top Attack Style (304SS) 60

Central hole type (304SS) 70

Important: If the specific gravity of the medium is ≠ 1.0, buoyancy must be corrected. For example, if the specific gravity of diesel is about 0.85, the buoyancy is about 85% of that of freshwater. For corrosive liquids or oils, the original manufacturer should be consulted or 316 stainless steel float ball (model suffix S) should be selected.

2.2 Weight Calculation of Connecting Rod and Stop Ring

Each float kit includes a standard 5-foot long connecting rod (material options include brass, aluminum, 304SS). When extending the connecting rod additionally, the total weight needs to be calculated. The following are the unit weights of each material:

Material 5-foot connecting rod weight (ounces) for every additional 1-foot weight (ounces)

Brass 18.5 3.7

Aluminum 6.0 1.2

304 stainless steel 16.9 3.4

Each stop ring weighs approximately 1.5 ounces (2 top attack kits and 4 center hole kits).

Example of buoyancy verification (extracted from original factory data):

The tank is 15 feet deep and uses a center hole float ball, brass connecting rod, and 4 stop rings.

The kit includes a 5-foot connecting rod (weighing 18.5 ounces)+an additional 10 feet (3.7 x 10=37 ounces)+a stop ring 4 x 1.5=6 ounces.

The total downward weight is 18.5+37+6=61.5 ounces.

The net buoyancy of the float is 70 ounces.

Net upward force=70-61.5=8.5 ounces → positive buoyancy, no need for compensating springs.

What if the net buoyancy is negative?

At this point, it is necessary to install a compensating spring (Form C). The compensating spring is installed on the switch lever to provide additional upward lifting force. For example, the 9036 heavy-duty (Type G) factory standard already comes with compensating springs; Other models can be ordered with kits such as 9049A13 (GG), 9049A19 (DG), 9049A20 (DR/DW), etc.

2.3 Maximum Link Length Limit

Exceeding the recommended maximum length may cause the float to fail to reset or the switch to not return. The manufacturer provides the maximum length of compensating springs for different materials:

Material without compensating spring (feet) with compensating spring (feet)

Brass 10 16

Aluminum 25 41

Stainless steel 12 20

Note: The above data applies to the 9038AG1 type alternator. There are slight differences among different switches, please refer to the corresponding table.

Practical steps for installation and debugging

3.1 Installation of 9036 Open Can

Installation position: Ensure that there are no obstacles in the floating ball movement area and that the floating ball does not touch the bottom or side walls of the tank within the range of liquid level changes.

Wiring: Open the switch housing and wire according to the terminal identification (for NEMA 7/9 explosion-proof type, a sealed joint must be used and the housing must be grounded).

Adjust the liquid level action point: Release the stops on the connecting rod, place the float at the desired starting liquid level height, and then lock the stops. For top attack floating balls, the distance between the upper and lower stop rings is the liquid level difference (differential). For the center hole type, the four stop rings can be set with multiple action points such as "pump start", "pump stop", "high position alarm", etc.

Verification action: Manually raise/lower the float, listen for a crisp "click" sound from the switch, and use a multimeter to confirm the continuity of the contacts.

Special note: The connecting rod of the 9036FG30 column switch has a fixed length of 33.75 inches and cannot be extended. The action point is achieved by adjusting the position of the floating ball on the connecting rod. This switch can be converted to reverse action (contact state reversal) on site.

3.2 Installation of 9037 Closed Tank (Type E Flange/Type H Thread)

Sealing inspection: 9037E uses Quad ring sealing, apply a small amount of grease on the sealing ring before installation. The nitrile rubber sealing ring of Type H may harden under long-term high temperature, and it is recommended to replace it every 2 years (spare part 9049Z20 Viton kit can withstand higher temperatures).

Float direction: Refer to the tank drawing to determine the correct orientation of the float. The float position of Type E is divided into three types: 1, 2, and 3, corresponding to the contact action mode (Position 1- liquid lift contact closed; Position 2- liquid lift contact open; Position 3- can be selected by rotating the switch 180 °).