Rule 37A Super Switch Bilge Pump Float Switch

The Rule 37A is a mercury-free bilge-pump float switch for automatic pump control on 12V, 24V and 32V DC systems, with a maximum switching capacity of 20A at 12V; 10A at 24V; 6.5A at 32V.

The Rule 37A controls a non-automatic bilge pump by closing the electrical circuit as water raises the float and opening the circuit after the water level falls. It uses marine-grade blocked wire and a mercury-free snap-switch design for marine bilge installations.

Product Identification

• Brand: Rule
• Product name: Rule 37A Super Switch Bilge Pump Float Switch
• Model / part number: 37A
• Marine Scene SKU: CW-37A
• Product category: Automatic bilge-pump float switch
• Compatible system voltage: 12V, 24V and 32V DC
• Maximum switched current: 20A at 12V; 10A at 24V; 6.5A at 32V
• Pump ON level: Approx. 51 mm (2 in)
• Pump OFF level: Approx. 19 mm (3/4 in)
• Switch mechanism: Mercury-free snap switch
• Ignition protection: Yes
• Quantity supplied: One float switch

What Is the Rule 37A Float Switch Used For?

This switch is used to convert a compatible standard bilge pump into an automatically controlled system. It may also be used as the sensing switch in a compatible high-water alarm circuit where the electrical ratings and installation instructions are observed.

What Is Included?

• One Rule 37A float switch
• Factory-fitted marine-grade blocked wire

What Is Not Included?

• Bilge pump
• Panel switch
• Cable extensions and waterproof connectors
• In-line fuse holder and correctly rated fuse

Which Bilge Pumps and Electrical Systems Are Compatible?

• Compatible with 12V, 24V and 32V DC systems within the stated current limits.
• Use with a non-automatic bilge pump whose running and starting current do not exceed the switch rating.
• Can be combined with a compatible Rule three-way panel switch for automatic/off/manual control.
• Not a voltage converter; the pump, switch and panel must all suit the vessel electrical system.

How Do I Check the Electrical Rating?

The pump operating and starting current must remain within the published switch rating: 20A at 12V; 10A at 24V; 6.5A at 32V. Match the switch, pump and any panel to the same system voltage: 12V, 24V and 32V DC.

At What Water Level Does the Switch Operate?

The published switching levels are ON at Approx. 51 mm (2 in) and OFF at Approx. 19 mm (3/4 in). Installation angle, mounting position and unrestricted float movement must be maintained.

Construction and Design

• Switch mechanism: Mercury-free snap switch
• Protective cover: No external impact cover
• Built-in test feature: No
• In-line fuse holder: Not included
• Mounting base: Removable, interchangeable mounting base
• Wire size and length: 14 AWG marine-grade blocked wire; approx. 712 mm
• Ignition protection: Yes

Installation and Safety

Mount the switch on a level surface beside the pump, with unrestricted float movement and without contact from hoses, wiring or debris. Position wiring connections above the maximum bilge-water level, fit the pump manufacturer’s specified fuse, and test the switch by lifting the float before leaving the vessel unattended. The fuse protects the circuit and must be selected for the pump; it is not set by the switch maximum-current rating.

Maintenance

Test the switch through its full movement at regular intervals and keep the bilge area around it clear.

• Remove oil, dirt and debris that could restrict the float.
• Inspect the hinge, protective cover, wiring and terminals.
• Confirm that the pump starts and stops at the expected water levels.
• Investigate repeated fuse failure or intermittent operation before relying on the automatic system.

Key Features

• Automatic on/off control for compatible bilge pumps
• Mercury-free snap-switch mechanism
• Marine-grade blocked wiring
• Maximum switching capacity: 20A at 12V; 10A at 24V; 6.5A at 32V
• Ignition protected for marine use
• Larger float for increased buoyancy
• Removable base for cleaning and servicing

Frequently Asked Questions

Will this switch work with any bilge pump?
Only when the pump voltage and current are within the Rule 37A ratings. Check both running current and the manufacturer installation requirements.

At what water level does the switch operate?
The float switches on at approximately 51 mm (2 in) and switches off at approximately 19 mm (3/4 in). Installation angle and bilge movement can affect actual operation.

Does the maximum amp rating determine the fuse size?
No. Fit the fuse specified for the bilge pump and cable circuit. The switch rating is the maximum current the switch can control.

Does this product include a bilge pump?
No. This listing is for the float switch only.

Specifications