Good points. This isn't the system I would put in starting with a
blank slate but it's a good solution for this particular boat.
I might have gone with the big pump, little pump setup if I'd thought
of it sooner. I'd already increased the second bilge discharge size
and put in the second line before I realized the backflow problem. My
sump will handle one line but not two.
I also committed to the two pumps when I was thinking in terms of
solid state switches that would never wear out. Basic pumps are a lot
cheaper than the ones with integral switches and I figured the pumps
would go first. Now I'll probably be replacing float switches as the
wires fatigue and break. I hope to find a way to work insolid state
switches down the road.
I plan to keep it pretty well dried out with the hand pump so it won't
run much anyway.
I'll be adding the dedicated starting battery to this boat before
setting off on long trips but, for now, I'm comfortable with this set
up.
--
Roger Long
"Jeff" wrote in message
...
Please note - my comments are not intended as criticism, only points
for others to consider while evaluating their own system.
Roger Long wrote:
...
The best place for an over ride switch is in the bilge where you
can see what's going on. The best switch for that environment is a
second float switch in series as back up before water reaches the
stuff you really don't want to get wet. Just pick up the switch.
good point - I may add that to my setup.
Did you see my obsessive pump threads? If not, check this out:
I've been following this set of threads and while I admire your
persistence and ingenuity, I can't help but think that this solution
is just a bit too complicated and expensive for the ordinary person.
http://home.maine.rr.com/rlma/Bilge.htm
This system is designed around some peculiarities of the boat we
just bought but does have some advantages:
* High capacity
Quite true, but this is just a matter of picking larger pumps. Many
small boat owners think they only need a small pump, but in fact
they are at greater risk because they have less reserve flotation.
A small leak on a small boat could quickly bring the boat down to
where a faulty cockpit drain (or a transom door) permits faster
flooding.
* Complete dual redundancy
Quite true, but any two pump system will do this. The alternate
2-pump approach would be a small pump that handles the frequent rain
leaks and stuffing box drips (and perhaps get replaced every year or
two), and a large pump (or even two) that only gets used for larger
volumes. Of course, a lot depends on the shape of the bilge.
* Equal battery drain
I have no idea why this is important. Unless you have serious
problem, the pumps shouldn't run more than an hour or so a week, for
a total of maybe 10 Amp-hours. There is no way you'll be able to
balance usage better than this.
This really goes back to our discussion of a dedicated starting
battery. I may have told this story before, but the one real, on
the water, rescue of a sinking boat that I've done was a case of a
boat that grounded, opening a leak at the shaft. The crew had
decided to sleep until the tide came back up, and when they floated
free in the morning they discovered that the bilge pump had drained
the battery so they were unable to start the engine or use the
radio.
There are some advantages to draining each battery equally, but the
huge disadvantage is that when you run down one, you'll also have
run down the other.
* Protection against slosh "chirping" without having to put
cofferdams with small drains that might clog around the switches .
A simple baffle should prevent sloshing without clogging, but this
is very installation dependent.
* Large activation range so long, large diameter hoses won't cause
an endless backflow cycle.
Ten feet of 1 1/8 hose is less than 100 cubic inches, or well under
half a gallon. Its hard to tell from the pictures what the full
surface area of your bilge is, but a 10 foot long bilge by 8 inches
would only have an eighth of an inch worth of back flow.
On the other hand, if there is a small sump, say 10"x10", the back
flow would be about an inch. In this case a small pump, with a
small hose could be used nicely to handle the minor leaks. 3/4 inch
hose has about half the cross section of 1 1/8 inch hose.
Actually, in your case, a small pump with a small hose, mounted low,
would completely eliminate the need for the low switches and the
relays. It would cost less, be more reliable, have more capacity,
and mean that the large pumps only run if the small pump is
overwhelmed. A Rule-Mate 500 or 750 has a built in switch with a
range close to 2 inches and costs $48 to $68.
BTW, a hidden cost of your setup is that it will not turn on unless
you have 4 inches of water. On the hypothetical 10' by 8" bilge
that is about 15 gallons or 120 pounds of water. On average, this
is twice the weight of the small pump setup.
...