Bilge Pumps, Part II
Bilge pump electrical components—float switches, manual
switches, wiring, and so forth—must be capable of handling
the loads imparted on them by the bilge pump under all
operating conditions. This float switch was not defective; it
was simply underrated for the pump’s ampere draw.
independent of both the vessel’s house battery switch
and the distribution panel’s main circuit breaker. Wired
in this manner, the boat can be left with the pumps
operational but nearly all DC circuits de-energized,
which is the safest approach for fire prevention. This is
often accomplished either by supplying the bilge pump
fuses or circuit breakers with a dedicated power supply
from the house battery bank (sometimes in the form of a
subpanel) or by establishing a separate, always-energized
bus at the distribution panel from which bilge pumps
are powered. Either way, all relevant ABYC guidelines
regarding over-current protection must be followed; i.e.,
every conductor must be protected by an appropriately
sized fuse or circuit breaker.
Where over-current protection is concerned, some
prefer fuses, rather than circuit breakers, for bilge pump
protection, believing that a breaker is too easy to
inadvertently turn off. Because of their ease of use and
“resetability,” I still prefer breakers, provided they are
equipped with locks. (Purpose-made locks are available
from most marine electrical panel manufacturers and
circuit breaker suppliers.) The fuse or circuit breaker
should be sized in accordance with the pump
manufacturer’s guidelines. Of course, it also must
protect the wire being used to supply the pump, but if
the wire is rated for no more than a 10 percent voltage
drop and the pump manufacturer’s specified fuse/breaker
is used, then this will almost certainly be the case.
SWITCHES
Even the most powerful bilge pump will be of
little use if it can’t be reliably turned on and off, both
automatically and manually. Manual switches should
be conveniently located at the helm or electrical panel.
They must be of the highest quality and also should be
rugged and reliable. Avoid spring-loaded momentary
“on” switches for manual pump activation. If your
automatic float switch fails while your boat is flooding,
the last thing you want is for you or a crew member
to be stuck holding this switch in the “on” position.
Instead, go with a positive on-off switch, and wire
the automatic portion of the pump circuit so that it
is always energized via the pump’s fuse or (
lock-equipped) circuit breaker. This makes it unlikely that
you’ll forget to leave the pump in automatic mode.
Perhaps the most critical aspect of a switch is its
ampacity. A bilge pump switch must be capable of
contending with the pump’s steady-state ampere draw,
as well as its locked-rotor ampere draw. Under no
circumstances should the switch’s ampacity be less
than the over-current protection serving the circuit.
Automatic switches, which live in the bilge attached
to or next to the pump, clearly play a critical role in
the reliable operation of your bilge pump system. If
you visit your local chandlery or page through a parts
catalog, you will encounter a wide variety of automatic
bilge pump switches, and it seems that new models
are introduced each year. Attempting to cover in this
article even a portion of those that are available would
be difficult, indeed. I will, however, share with you
some wisdom about float switches that I’ve garnered
from 20 years of working in the marine industry.
When looking at automatic switches, begin by
checking out the warranty. Two years is a minimum;
five is my preference. While every switch was “new”
or “just introduced” at some point in its life, when it
comes to this critical component, I’d much rather go
with “tried and true” or “proven.” Visit PMM’s chat
rooms and other cruiser forums to find out what other
boaters have to say about the model of switch you are
considering. While these reviews and comments must
often be taken with a grain of salt, a preponderance of
approving or disapproving votes can be telling.
My preference in automatic float switches is for the
