24
5.9
Low-Water Probe for Dry-Run Protection
WARNING
Running com-
pletely dry will
damage the
pump and void
the warranty.
The purpose of
the probe system
is to sense the
loss of water and
turn the pump off
before it can run
dry.
Installation
The probe is packed with two
stainless steel hose clamps. For a pump that
is to be installed in a vertical position, clamp it
to the pipe just above the pump outlet, as
shown in the photo. Splice the two probe
wires using the splice kit components that are
packed with the probe. The assembly proce-
dure is the same as the main pump splice.
If you are NOT using the well probe, it must
be bypassed.
Connect a short wire between
the probe terminals in the junction box
(terminals 1 and 2). Do this only if you feel
certain about the reliability of the water
source. Wire size: #18 AWG ( 1mm²) or
larger.
Principle of operation
The probe contains a
mechanical float with a magnet inside. When
the probe is submerged, the float rises, and
the magnet actuates a switch. The switch
closes (makes contact) to indicate the pres-
ence of water. The switch is sealed, so the
contacts never touch the water.
If the water level drops below the probe, the
float drops, and the switch opens (breaks
contact). The controller will stop the pump and
the “Low-Water OFF” light will indicate. When
the water level recovers and switch closes
again, the controller will delay the restart for
20 minutes. This gives time for the water level
to recover. To force a quick restart, turn the
controller off, then on again.
NOTE Pumps made before October 2003
may have a different type of probe, with
wet electrodes. Either type can be used
with the PS-XXX series controllers.
The Low Water-OFF light flashes slowly for
the remainder of the day,
even if the water
recovers and the pump restarts automati-
cally. This tells you that the water source ran
low at least once since the power was
disrupted (or sun went down). To turn the
light off, reset the controller by turning it
off/
on
.
CAUTION The
low-water probe
must be posi-
tioned vertically,
within 10°. If the
pump is NOT to
be installed
vertically, find an
alternative way to
mount or suspend
the probe, so that
it is higher than
the pump, and in
a vertical position.
CAUTION Do not use a
pressure switch with a “low
water cutout” or “loss of
prime” feature as a method of
dry-run protection. A helical
rotor
pump
will maintain
pressure as it runs dry, so this
method will not work reliably.
For pressure switch information,
see Section 5.12, Pressurizing
Systems.
Potential problems with the low-water
probe in surface water
The probe has a
moving float. It is highly resistant to deposits
and debris. However, it may stick under some
extreme conditions, especially from algae or
water creatures (snails, etc.) that may be
present in surface water. Possible solutions
are:
1. Hang the probe independently of the pump
and pipe (clamped to a weight, but not to the
drop pipe). This way, it can be pulled up for
inspection or cleaning without the need to pull
the pump. (This may not be feasible if the well
casing is smaller than 6".)
2. Pull the probe out periodically (with the
pump if necessary) for testing and inspection.
The pump should stop at the moment the
probe leaves the water.
3. Wrap the probe in a protective screen
(fiberglass window screen, for example).
Substitute a different type of float switch. You
can use any switch that makes contact on rise
(normally open).
Low-water probe
installed in the
standard position,
for a pump that is
positioned vertically
