Blowing fuses in the bilge system

[hellosailor]

Taking everything at face value, if the float switch is installed in series with the HOT LEAD to the pump, a short from any exposed metal on the switch into the bilge could blow the fuse. (Assuming a good ground exists into the bilge and the water is very conductive.) If the float switch was installed in the GROUND SIDE of the pump, that could not happen, a short would only turn on the pump.

But I've got to agree with Boracay, especially if a three-way (on/off/auto) bilge switch is used, the wiring can be deceptively simple yet confusing. AFAIK you cannot wire a float switch up IN SERIES and still have it function on a standard 3-way switch, so the question is...what is the whole setup, really?

Two minutes with a multimeter will answer the question of whether the float switch is creating a ground short. If it isn't--the problem is somewhere else in the wiring.

[Alan Wheeler]

I hate to be so pedantic, but we'll just have to disagree. I think that an excited electron placed into the saltwater in the bilge of a steel boat will have a pretty easy time finding its way back to the negative post of a battery.

Yes it may. But not in a current enough to blow the fuse. How do I know" because it has happened to me twice now with a flooded bilge to the level of my wiring. Open up the floor and I was greeted by a fizzing green broth and the wires were all terminated in strip connectors, so only mm's apart. I now have all my connections inside IP rated plastic boxes to protect the terminations. But the salt water did not produce a path strong enough to take out the fuse. Maybe it is because the pumps are of reasonable size and all are 10 or 15A fused. Maybe a small pump that has a 5 would blow the fuse, but ??

[ribbony]

Hi All

I have not been back out to the boat to answer some of the earlier questions, however a few more points for the other questions raised:

10A fuse installed for the Rule 1500 pump that requires a 7amp fues in the instructions.

No 3 way switch as yet (cause the shop only had 10A switches and I like 15 amp for durability) just a simple on/off type.

Thanks everyone !

[Zach]

Does the pump run prior to the fuse popping?

I just swapped out a Rule that had a plastic wire tie wedged into the impeller, locking up the motor, which killed it. Dead short once locked up...

Also, did you wire the float switch directly off the battery? I've seen that done before. Possible that wires are spliced in to the pump opposite polarity? That would be a dead short to the battery, with an open circuit with the panel switch off. Does the pump ground out to the panel, or does it use a common ground somewhere else? A chafed through positive wire on a common ground would do it if the water level is above a bonded component like a through hull.

Do you have a pump that only has 6 inches of wire coming off of it? Shrinking butt connectors and shrink tubing on top are about the only way to go... If a regular nylon butt connector is underwater somewhere that will do it too.

Good luck with it! I always have the best success with this stuff by disassembling the system and testing everything individually. Start with the biggest problem you can think of and work backward to more complex things.

[ribbony]

We went out to the boat today and sorted out the float switch issue. We ran a complete new wire to and from the switch with a 10amp crt breaker, it worked fine after that. So, I can not explain what the cause was of the initial problems, something I did or faulty wires in the first install. The new circuit has no indicator light and no switches, just the breaker and a direct connection to the battery (for the off season when nothing else is on).

Thanks for all the help.