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5.10 Automatic Control For Full-Tank Shutoff
We recommend the use of a float switch or
other means to prevent overflow of your tank.
This will stop the pump when the tank is full,
then reset when the level drops. This con-
serves ground water, prevents overflow, and
eliminates unnecessary pump wear.
PS-XXX
controllers allow the use of small signal
cable to a remote float switch, even if the tank
is a long distance away.
Float switch requirements
1. A switch must be used, not wet electrodes.
2. The preferred system requires a float
switch to MAKE contact on rise to turn the
pump OFF. This is called “normally open”
(N.O.). It may be commercially labeled as a
“pump down” switch, but here it works in
reverse, to allow pumping up.
sealed
cable clamp
cable
weight
pump off
pump on
pumping
range
QUESTION Why do we use a
reverse-action (N.O.) float
switch? (a pump-down switch
for a pump-up application)
ANSWER If the cable con-
nection is broken, the pump
will continue to operate. The
water supply will not be
disrupted (but of course, the
tank will overflow). This is the
general preference in the
industry. If you prefer the
pump to stop if the connection
is broken, use a normally
closed (N.C.) float switch
instead.
Wiring to the controller
(junction box)
The
controller (and junction
box) offers two options for
connection of a remote
switch. These allow the
use of either a “
normally
open
” (N.O.) or a “
nor-
mally closed
” (N.C.)
switch. “Normal” refers to
the status of the contacts
when the switch is DOWN
and calling for water.
Float switch cable require-
ments
1. Two wires are needed.
2. Minimum wire size #18
AWG ( 1mm²). This is good
for a distance as far as 2000
feet (600 m).
3. The cable must be suitable
for its environment.
4. If it must run a long
distance, use twisted-pair
shielded cable to reduce the
chance of damage from lightning-induced
surge. (See Section 5.2 Grounding and
Lightning Protection).
Grounding shielded float switch cable
If
you use shielded cable, connect the shield to
ground AT THE CONTROLLER ONLY. DO
NOT ground the shield at the float switch. This
will reduce surges induced by nearby light-
ning.
Wiring a “normally open switch”
Connect the switch to terminals 3 and 4 (NO and
common) and connect terminals 4 and 5 together, as illustrated.
Closing (connecting) the switch circuit turns the pump OFF
Wiring a “normally closed/reverse action switch”
Connect the switch to termins 4
and 5. Closing (connecting) the switch turns the pump ON