Sunday, January 24, 2010

Project: Adequate Current For The Bilge Pump

Eolian has 3 bilge pumps, at various levels in the bilge.  Each is controlled from this panel, mounted just to starboard of the companionway stairs.

The primary pump is a huge 3700 gal/hr pump, which needs 14 amps at load.  The other pumps are smaller.  (Number two has a bell wired in parallel with it, so that when it runs, the bell serves as an alert.)

Eolian's showers drain into the bilge and are pumped overboard by the #1 pump.  Some have said to me that it is a shame to be running the bilge pump so often.  But I have a warm feeling when I am showering and the bilge pump kicks on.  It is a frequent check of the serviceability of this important system, which otherwise might never be tested until it was absolutely required to be running. 

But apropos to the subject of this post, the wiring to all three bilge pumps was 12 gauge.  Tho 12 gauge wire would have been adequate to serve the large pump, it was inadequate to serve all three pumps running simultaneously.  Having all three pumps running at once is not a situation I would want to see, but should it happen, I would certainly want there to be enough power supplied that all three *could* run simultaneously.  So step 1  was to pull the 12 gauge wire and replace it with 10 gauge.  The breaker in the power panel was upgraded to 30 amps too.

I had originally thought that this was the end of the job.  But later, when I was running the pump manually, trying to scavenge as much water from the bilge as possible, I noticed that the pump ran considerably faster when I held the "Off-Auto-Manual" switch in Manual.  Hmmm.  The only difference between Auto and Manual is that the current for the pump has to pass thru the float switch when Auto is used.  I checked the connections (I had made them) they were soldered and still solid.  Despite being rated for this pump, it was apparent that the bilge pump switch was limiting the performance of the pump.

So I installed a relay.  Having had less than stellar luck with conventional mechanical relays on board, I found a solid-state relay that would do the job for a pittance on eBay.  This one is rated for 40 amps, and only requires a few milliamps to trip.  That is, with the relay in place, the float switch only has to switch a few milliamps - the current to the pump goes directly thru the relay.

The difference was like night and day.  Not only did the pump run better - it ran better than when I had used the Manual position on the switch panel earlier. 

If you have a high-capacity bilge pump onboard, I strongly recommend you install a relay too, in order to get all the performance you paid for from your pump.

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