Next message: Stan Gardner: "Re: lv-ab: Red over green lights for sailboat"
Thanks for the answer. I use a switch I got from West, advertised as their
best (can't remember the brand). It's a plastic tube, about 3" dia X 6"
long, mounts vertically. The make two versions, one with a high water
alarm built in. I have the cheaper model which has worked flawlessly for
me for 5 years with no maintenance, and reasonable hysteresis.
BTW, I just bought a high water alarm built primarily for detecting water
in your basement, but it runs on a 9V battery, has low battery warning, and
hopefully is loud enough to hear at the helm. Cost, under $10. I'll let
you know how it works.
Stan,
S/V Seabird V
At 07:30 AM 9/8/2003 -0700, Hugh Barrass wrote:
>Stan,
>
>I think the issue is hysteresis.
>
>For those who don't understand the term, the idea is that most people
>would like their bilge pump to run for a reasonable length of time & then
>stay idle for a long time before running again. If you imagine a perfectly
>precise world, then the level of water in your bilge will rise to the
>level of the trip switch, the pump will come on for an infinitesimally
>short time, drop the water level below the trip switch & shut off. Within
>a very short time later the water level will have risen to the level of
>the switch again & the cycle repeats.
>
>Using the delay, you could mount the trip switch a little higher. The pump
>will switch on when the water level reaches the trip switch; the pump will
>lower the water level by some amount below the trip switch (60 seconds of
>pumping) and buy some extra time before it comes on again.
>
>Most trip switches have hysteresis built in but this is rarely enough to
>compensate for boat rocking etc. therefore many automatic bilge pump
>systems turn on and off at annoyingly frequent intervals - causing people
>to switch them off at night :-(
>
>Hugh.
>
>Stan Gardner wrote:
>
>>I know this was discussed before, but I can't remember the issue. It
>>seems to me that if the float switch is properly placed there is no need
>>to continue to run after it trips. My bilge has about 2" of water in it
>>when the pump shuts off. Much of this is water that leaks back down from
>>the pump. If the pump were to run another 60 seconds it would be running
>>dry. What am I missing?
Stan Gardner ~~~_/) ~~~ NPTest, Inc.
Senior Mechanical Engineer 150 Baytech Drive
Tel - 408 586 6532 San Jose, CA
95134-2302
FAX - 408-586 4662 Email -
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