Relays and bilge pumps?

I understand how to wire a bilge pump and switch setup but is there any difference when you wire a diaphragm style pump that is inline, not in the bilge and not right next to the switch? It seems like a waste of wire and a very long wire run to run power from the panel to the switch in the bilge and then back to the pump in the engine room Probably 25ft of wire. Obviously the issue of voltage drop can be addressed by using very heavy wire but it would seem to make sense to use a relay? Just a thought.... Thanks, RT

Electronic Bilge Switch

A relay is just another electromechanical device in your boat to fail when you
really need it I installed an electronic Bilge Pump Switch and (3) Way Operating Switch with Breaker directly to the 12V Buss so it operates when I turn Off the 12V Main Panel when not onboard. Just wire up with #12 and be done with it :nerd:

Happy Working Bilge Pump

I think that relays in any form or fashion, such as a bilge pump circuit, battery combiner, etc...any critical application, have no place on a boat. All relays eventually fail.
Howard Keiper
Berkeley

Actually upon reading I found that those Ultimate Bilge Switches sold on www.tefgel.com appear to have a relay built in..... I understand that relays can fail but it is just as likely that the heavy gauge wire required by a large pump and long runs, the load this places on the switch, etc. will also corrode and allow enough voltage drop or just kill the switch from overload to negate the benefit of the large pump. You pick your poison. RT

In this instance however, six of one isn't the same as half dozen of the other. It is true that the runs of heavy wire could be eliminated by the judicious use of a relay, and I wouldn't hesitate to use a relay in a circuit that wasn't life or vessel critical...such as a starter solenoid or a windlass control (room for debate here, I suppose); but I think that a bilge pump failure or combiner failure when you're not likely to be aboard, can translate directly into disaster, as you won't be around to rap on the thing to make it work..the relay, that is.
howard keiper

Any electrical circuit will need to become a closed loop, you must connect all the components via wire to make the system function. whether a relay is added or not you still must run wire from the power to the switch to the pump to ground. as long as you complete the circuit from power thru the pump to ground however, where the switch is added in is of no consequence as it only serves to break the completed circuit. that may help in figuring out the most efficient wire run. adding a relay will only change the demand on wire size as the load of the pump will need heavier wire from power to ground than the switch needs to complete the circuit. A relay is basically a switch and adding it in adds a second switch to the system not replaces one. in fact it adds another complete circuit as you now must run from power to the switch to the relay (now the load) to ground, and then from power to the relay to the pump to ground. I don't know if this all sounds like a confusing mess, but it is the long way to the answer ...just run the shortest reasonable run with adequately sized wire and be done. simple is the key and fancy is complicated and doubles what can fail. Good luck, Edd

Maybe I should clarify the situation on my boat. The bilge pump wiring leaves the DC panel, the breaker is powered independent of the main switch, down to the current bilge pump/float switch combo. When the diaphragm bilge pump replaces the current centrifugal it will be mounted in the engine space. There are really no other alternatives for mounting. This means the wiring would now run from the DC panel to the float switch in the bilge and then back through the same spaces, past the DC panel, through the battery box area, and into the engine space to the diaphragm pump. The wiring run will be quite long and since it essentially doubles back to its source the situation is ideal for the possible use of a relay. Given that it takes @100ma to close a 30amp relay the bilge wiring could be quite compromised and still drive the relay without voltage loss, etc. to the pump. The pump wiring remains high and dry out of the bilge. Wiring and installing a relay in this application is very simple as it would be right behind the DC panel.

Bilge pumps produce some interesting ideas/opinions. I feel that trusting a bilge pump to keep your boat afloat when you are away is useless. If there was a catastrophic failure while the boat was on the mooring at 2am, unless the alarm was extremely loud, the batteries would be depleted and the boat would sink long before anyone noticed. I just don't believe in any battery based system lasting long enough. For routine rain water/packing drip the pump/switch combo is great. The situation is entirely different if you are on board. I'm okay with not even bothering with a float switch on a large backup "disaster" pump. If you are on board then flipping the switch is simple enough and leaves the notoriously unreliable flaot switch out of the system.

So am I sure I want to use a relay in my system? Not really. Its an idea I wanted to explore. I understand the pros and cons of complexity having fought through it with my charging system. So we will see..... Depends on how many amps the final pump choice requires and how much I want to spend on a bilge pump switch. Since I have changed Rule switches as frequently as socks the expensive switch is tempting. We'll see.

RT

Remote Bilge Pump Switch/Breaker

Wire your Bilge Pump from your Positive Buss at the Battery to a Remote (3) Way Switch/Breaker. Use the Panel Breaker for other Loads
Should shorten your wire runs :nerd:

I like this article on bilge pumps: http://www.sailnet.com/forums/gear-maintenance-articles/19937-devising-better-bilge-pump.html. The point there is, your high capacity bilge pump, with its heavy gauge wire requirement, should not be wired to an automatic switch. You could run wire from the battery, through an inline fuse and a switch, directly to the pump. Ground it to wherever your grounding point is.

Now if you want a remote switch in the cockpit, replace the on-off switch above with an on-off-on three position switch, for example: http://www.jamestowndistributors.co...&familyName=Sealed+3+Position+Toggle+Switches.

On closes the circuit, off opens the circuit, and remote routes the circuit through a relay, wired to your remote switch. All the convenience of a remote switch with the safety of a local switch!