This document provides an overview of power basics for technician training, including terminology, control panels, pumps, power sources, sensors, instrumentation, and valves. It discusses typical voltage standards for North America and internationally, control panel configurations, pump power requirements, dual power source management, sensor signal types and intrinsic safety, and actuated versus solenoid valve operation.

1. Technician Training: Power Basics

2. Power Basics
o Terminology – Voltage, Power, Current, Phase & Hertz
o Control Panels – Basics, Single or Dual Power
o Pumps – Basics, Phases & Types
o Dual & Single Power Sources
o Sensors & Instrumentation – Signals & Safety
o Valves – Actuated & Solenoid

3. Terminology
o Voltage - Alternating Current
 Typically 120, 208-240, 480 VAC
o Voltage - Direct Current
 Typically 24 VDC
o Voltage AC Phase – Single or Three Phase (1 PH / 3 PH)
o Voltage AC Hertz – 60 HZ (US) and 50 HZ (INTL)
o Power – US is Horsepower (HP), INTL is Watts (W)
o Current – Amps or Milliamps (A, mA)

4. Control Power
o Control Panel Power US
 120VAC – 1Phase – 60HZ
o Control Panel Power INTL
 230VAC – 1 Phase – 50 HZ
o Transform within the Panel to 24VDC for Sensors and Control Relays
o Signal wiring between panels and devices may be 120VAC or 24VDC
 120VAC may allow for combining light and signal power within
common conduit and also minimize voltage drop
 24VDC preferred for sensors

5. Control Panel
o Single or Dual Power Drop to Skid
 Some designs require a single or dual power feed,
typically 480VAC-3Phase, to an equipment
assembly
 In this case all power management and distribution is done internally to
the control panel
 The panel will likely include additional power transformers and circuit
breakers for this purpose

6. Pump Power
o Pump Power US Standards
 < 1 HP is 120VAC/1 Phase/60Hz
 > 1 HP is 480VAC/3 Phase/60Hz
 Submersible Pumps is 208VAC/1 Phase/60Hz
 If 3 Phase is not available, 208VAC/1 Phase/60Hz
Sometimes there is an alternate 3 Phase, 208 to 230VAC/3 Phase/60Hz
o Pump Power International Standards
 < 1 HP is 230VAC/1 Phase/50Hz
 > 1 HP is 480VAC/3 Phase/50Hz

7. Dual Power Source
o Most critical fuel systems have dual power sources for redundancy
o It is important to manage these sources so that they are independent from
each other
 Monitored with control panels by auto-switching, if A fails then B
engages – typically without any effect on the controllers
o Valve & Pump Control for Dual Power Source
 Some systems are designed to allow for either of two redundant control
panels to operate a single device such as a valve or motor starter
o These are important difference from Service Station systems which often
allow for the assumption that control devices share a common power source

8. Sensors and Instrumentation
o Power is typically 24VDC
 Standard wire is often used for level sensors
 More sensitive instruments may require twisted and shielded cables for single
integrity
 Sensor and Instrumentation wiring should be in separate conduit from AC wiring
o Looped Powered Sensors
 Some sensors require a separate power source from the signal wiring
 Other devices are loop powered, where only 2 wires are needed with power and
signal conveyed along a common path
 Leak Sensors
 Flow Switches

9. Sensors – Signal Type
o ON-OFF signals are typically 24VDC with a small amperage determined by the
load
o Analog signals are either variable voltage, 0-10VDC output, or variable current
commonly 4-20 mA output (24VDC)
o Pulsed data signals are also used for certain types of transmitters, typically
with some type of proprietary characteristic

10. Sensors – Intrinsic Safety
o Sensors used in hazardous electrical areas may be either explosion-proof or
intrinsically safe
 Explosion proof – designed to contain the energy of an explosion or a
flammable liquid/vapor
 Intrinsically Safe – Limit the energy within the hazardous area to an
amount insufficient to cause a spark
 The device has low energy requirements, the source panel has an
intrinsic barrier to limit the energy conveyed to the sensor, and the
conduit/wire systems is isolated for non-intrinsic safety wiring.

11. Valves
o The most common actuated valves are electric actuated
 Pneumatic actuated valves are not practical due to the lack of a reliable
dry air source
o Solenoid Valves are commonly used for ON-OFF flow control
 Benefits: fail-safe closed & operate simply
 Downfall: require continuous energy in some applications which will
shorten their life & significant power requirements and amp draws that
may exceed the fuse limits
 Typically 120VAC, 240VAC, or 24 VDC
 De-energized/Energized coils in the solenoids can create a power surge
that can damage the PLC or other control interfaces, for this reason they
are isolated by relays

12. Valves (cont.)
o Actuated Ball Valves & Butterfly Valves
 Electric actuators used for quarter turn valves are usually 120VAC
(sometimes 24 VDC & 240 VAC)
 Valve torque specification needs to be matched with actuator torque
capacity
 Benefit of actuated valves is that there is no power required to maintain the
valve position (unlike solenoids) open or closed; valves typically have limit
switches for position feedback
 Limit switch feedback in many actuators is the line voltage
 If 24VDC feedback signals are required the actuator may need to be
ordered with auxiliary limit switches