Recommendations for diode circuit protection

I have a boat with a 24V electrical system. The bilge pumps are controlled by two different circuits: (1) a 20A 24V Bocatech switch connected at the breaker panel and (2) a float switch connected directly to the battery. The pump is rated at 4 Amps 24V with a recommended fuse of 7.5A. The pump has only one 24V+ wiring connection and a ground. Both switches are wired to the 24V+ pump wire. I have two concerns: 1) The Bocatech switch is damaged by backflowing current which occurs if the float switch activates the pump; 2) Would the pump be receiving 48V if both the float switch AND the Bocatech switch were activated at the same time? I have been told that I need a 20 Amp diode between the Bocatech switch and where its wire joins the float switch wire to the pump. I have three switches in a helm area so it would be nice to have a clean and durable wiring setup for the three switches. Also, is there a concern related to the both switches being activated at the same time and damaging the pump? If so, is there a recommended solution? Wiring Schematic is attached
Bilge Pump & Bocatech Switch Wiring.pdf (57.2 KB)


In response to your questions:

  1. This is not a problem. Assuming that you connected the indicator ground lead (shown unconnected in the drawing) the indicator would illuminate when either switch is closed, which presumably would be a useful function.

2)No. The missing indicator ground aside, the drawing looks fine as is.

As an aside, pushbutton switches of that basic style are often described as “anti vandal” switches. A selection of such can be found listed here, should you care to browse.

Thank you for such a quick response. Can you recommend the diode to use and possible an efficient method of making the connections of three of the Bocatech switches which are are adjacent to each other? I would simply cut the existing brown outgoing wire and extend it to a connection block or something similar where I could connect the diodes and 6 wires. In regards to question #2, it seems odd that two different circuits connected essentially in series wouldn’t present 48 volts to the bilge pump if they were both switched on.

Sorry, I understand now. The two circuits are essentially parallel circuits, correct?


It’s an unnecessary complication that I’d suggest skipping entirely. As mentioned, the indicator would then reflect status of the powered circuit, regardless of which switch is active.

We’ve got hundreds of wire splice connectors to choose from; use whatever suits your situation. Qualtek’s Q5-4X adhesive-lined heat shrink tube is also a product I like to keep around for that sort of occasion.

Beyond that, the specifics of how you go about the task are really up to you, and not something for which we can offer step-by-step guidance.