Electrical Wiring For The Compressor - QED AutoPump AP-2 Operation Manual

AP-2 Manual
Note:
The information on compressors is for reciprocating piston compressors. A
centrifugal compressor produces about twice the air of a piston compressor
for the same horsepower.
• As a general rule, a piston-type compressor should not start more than six times per hour.
Also, a piston compressor should not operate more than 50% of the time.
• At a minimum, the air compressor should be in the 1 to 1-1/2 HP range with a 20 gallon
holding tank.
• At sea level a 1 HP air compressor provides approximately 3.5 cubic feet per minute
(SCFM) of free air.
• For compressor sizing, all down well and surface hosing and other resistance must be
known.
• The 2 and 3 HP compressors should have 60 to 80 gallon tanks.
• A 5 HP compressor should have at least an 80 gallon tank, and the 7-1/2 HP and 10 HP
compressors should have at least a 120 gallon tank.
• Storage tanks and automatic pressure shut-off switches provide a buffer so the compressor
motor can cool between each time the tank is pressurized.
• Compressors are generally equipped with a pressure activated start/stop switch. This
switch senses the pressure of the air in the holding tank (reservoir) of the compressor. The
pressure difference between when the compressor starts and when it stops may need to
be adjusted to maintain compressor starts to six times per hour. Refer to the compressor
manufacturer for guidance.

Electrical Wiring for the Compressor

• All electrical connections should be made by a licensed electrician and in accordance
with the electrical code for particular areas. The wiring should provide full motor
nameplate voltage and current at the motor terminals during start-up.
• Wiring hookup must be made so that the compressor flywheel turns in the proper
direction. There is usually an arrow on the flywheel to indicate the proper rotation
direction.
Revision 7 - August, 2007
Appendix E: Air Compressor
Page 81