Electrical Schematic

PAGE 10
LANCASTER HYDRO-FORCE™
3-Wire Control Boxes
Single-phase three-wire submersible motors require the use of control boxes. Control boxes through
1 hp offer:
•Capacitor-start induction run (CSIR) design - contain a starting capacitor and a starting relay.
•Quick-disconnect design - disconnects the control box starting capacitor and starting relay from
the electrical system when the lid is removed.
•Cable terminals accepting up to #8 AWG copper wire.
•Painted steel enclosure with multiple knockouts - rated NEMA 3R for indoor or outdoor
installation:
ᵒ DO NOT locate in direct sunlight.
ᵒ In order to maintain NEMA 3R, plug all unused openings.
CAUTION: The control box is an above ground component of the submersible motor providing easy
access to the starting system so you can perform maintenance without pulling the motor from the
well. Be certain that the control box and motor hp and voltage match.
The Start Relay
Thepotential(voltagesensing)relayhasnormallyclosedcontacts.Whenpowerisrstapplied,both
motor windings (main and start) are energized. The relay’s normally closed contacts place the start
capacitor in the circuit (in series) with the start winding, providing extra torque to bring the motor up to
speed. The relay does this by sensing the voltage across the start winding. At the initial moment when
powerisrstapplied,thevoltageacrossthestartwindingisnothighenoughtoopenthecontacts
of the relay. The relay is designed to pick up, open its contacts, and disconnect the start capacitor
fromthestartwindingwhensufcientvoltageisgenerated.Sincethevoltagegeneratedbythestart
winding is proportional to motor speed, the relay will open only when the motor has started and is
approaching normal running speed. When the windings approach full speed, they magnetize the
relay’s coil and physically break the connection (opens the relay contacts) to the start winding. This
takes both the start winding and start capacitor out of the circuit, leaving the motor to run only on the
main winding.
The Start Capacitor
The start capacitor provides more starting torque to bring the motor up to full speed. Start capacitors
are designed for intermittent service only and have a high microfarad (MFD) rating. When used with
a potential relay, a start capacitor requires a bleed resistor soldered across its terminals. The bleed
resistor will lengthen the relay and capacitor life when the motor cycles (run time) are short due to, for
example,anundersizedpressuretankprovidinginsufcientdrawdowngallons.Wheneveramotor
cycles on, start capacitors are left with a high voltage DC charge during the run time. If the motor runs
several minutes, most of this charge is lost within the capacitor itself and an added bleed resistor
would not be needed. However, following a very short run time the start capacitor could discharge
through the relay contacts as they close during coast-down, causing arcing and overheating of the
relay contacts. The added resistor bleeds off the charge within seconds, preventing sticking relay
contacts and/or erratic relay operation especially where short cycling is likely to occur.
For specic ratings of individual components, refer to the CONTROL BOXES chart on the
OPERATING DATA PAGE.