17
4.11 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 conserves ground water, prevents overflow, and
eliminates unnecessary pump wear. PS 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 com-
mercially labeled as a “pump down” switch, but
here it works in reverse, to allow pumping up.
Float switch cable requirements
1. Two wires are needed.
2. Minimum wire size #18 AWG (1 mm
2
). This is good
for a distance as far as 2,000 ft (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 4.2,
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
lightning.
Wiring to the controller (junction box) The control-
ler (and junction box) offers two options for connection
of a remote switch. These allow the use of either a “nor-
mally open” (N.O.) or a “normally closed” (N.C.) switch.
“Normal” refers to the status of the contacts when the
switch is DOWN and calling for water.
QUESTION Why do we use
a reverse-action (N.O.) oat
switch? (a pump-down
switch for a pump-up application) — AN-
SWER If the cable connection is broken,
the pump will continue to operate. The
water supply will not be disrupted (but of
course, the tank will overow). 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.) oat
switch instead.
Figure 14: Float switch scheme
Figure 16: Wiring a “normally closed/reverse action float switch”
Connect the switch to termins 4 and 5. Closing (connecting) the switch turns the pump ON
Figure 15: Wiring a “normally open float 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
sealed
cable clamp
position pump off
pumping range
float switch
UP: closed
DOWN: open
normal: open
UP: open
DOWN: closed
normal: closed
if cable is shielded,
ground this end only
if cable is shielded,
ground this end only
position pump on
cable weight
float switch
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