22 Electrical & Controls Practice Questions & Answers

1. 1. A technician measures 24 volts across a station circuit and 0.4 amps flowing through it. Applying Ohm's law, what is the resistance of that circuit?

   • A.24.4 ohms
   • B.0.017 ohms
   • C.60 ohms✓ Answer
   • D.9.6 ohms

   Ohm's law states V = I × R, so R = V ÷ I. Dividing 24 volts by 0.4 amps gives 60 ohms; multiplying or adding the two supplied values produces the other choices.

   Source: Irrigation Association, Electrical Troubleshooting Student Workbook — Ohm's law (V = I × R)Report a problem with this question

2. 2. A station works intermittently and the technician suspects the field wire's insulation is nicked. With the controller off and the wire disconnected, he measures resistance from that station wire to a screwdriver driven into moist soil. Which reading indicates damaged insulation?

   • A.About 900,000 ohms, safely above the sound-insulation value
   • B.About 3,000 ohms, far below the value sound insulation gives✓ Answer
   • C.About 45 ohms, matching the coil resistance of the solenoid
   • D.An OL display, showing that no path exists between the wire and earth

   Sound insulation isolates the conductor from earth, so a wire-to-earth test should read very high — hundreds of thousands of ohms. A reading of only a few thousand ohms means current is leaking to ground through damaged insulation, which is why the station operates only some of the time.

   Source: Irrigation Association, Electrical Troubleshooting Student Workbook — insulation resistance (wire-to-earth) testingReport a problem with this question

3. 3. With the controller unplugged and the common lifted off the terminal strip, a technician reads from the station 4 terminal to the common wire and the meter displays 'OL'. What does that reading indicate?

   • A.The circuit is shorted and is drawing more current than the station allows
   • B.The circuit is normal and that valve should open whenever it is called
   • C.The circuit is fine but the meter must be switched to volts instead
   • D.The circuit is open — a broken wire, a bad splice or a failed coil✓ Answer

   'OL' means the resistance is beyond the meter's range, so no complete path exists between the station terminal and the common. That is an open circuit — a broken conductor, a failed splice or an open solenoid coil — not a short, which would instead read far below the normal band.

   Source: Irrigation Association, Electrical Troubleshooting Student Workbook — interpreting field resistance readingsReport a problem with this question

4. 4. A controller keeps reporting a fault on station 7 and shuts that station down. With the power off, the station 7 wire reads about 2 ohms to the common. What condition does that reading describe?

   • A.A short in the field wire or the coil, with excess current flowing✓ Answer
   • B.An open in the field wire, so no current can reach the solenoid at all
   • C.A high-resistance splice that lets the valve open only intermittently
   • D.A normal reading for a healthy solenoid on a long field wire run

   A complete solenoid circuit normally falls in the generally accepted 20–60 ohm band. A reading of only a couple of ohms means the station wire and common are joined by a fault path, so current rises far above what the output can supply and the controller protects itself by faulting that station.

   Source: Irrigation Association, Electrical Troubleshooting Student Workbook — short-circuit diagnosis at the terminal stripReport a problem with this question

5. 5. A controller powers up normally and steps through its program, but no zone runs. Tested at the terminal strip, every station reads open. What should the technician suspect first?

   • A.Every solenoid coil in the system burned out during the same cycle
   • B.The common wire is disconnected at the controller or broken ahead of valve 1✓ Answer
   • C.The transformer has failed and no longer feeds the station outputs
   • D.The program has no start time, so the stations are never energized

   Every station shares one common conductor as its return path. If that path is broken, no station can complete its circuit, so all of them read open and none operates even though the controller itself is healthy. A single dead zone would instead point to that station's wire or solenoid.

   Source: Irrigation Association, Electrical Troubleshooting Student Workbook — common wire faultsReport a problem with this question

6. 6. Station 1 runs normally, but stations 2 through 6 will not run and all of them read open at the terminal strip. Where is the fault most likely to be?

   • A.In the controller board, which lost the outputs for stations 2 to 6
   • B.In the transformer, which can no longer feed more than one station output
   • C.In the common wire, broken somewhere downstream of the first valve✓ Answer
   • D.In the common wire, where it lands on the controller terminal strip

   The common returns current from every valve, and the valves are tapped onto it in sequence along the run. A break past valve 1 leaves station 1 with a complete path while everything downstream of the break is open. A break at the controller would have killed station 1 as well.

   Source: Irrigation Association, Electrical Troubleshooting Student Workbook — isolating common wire breaksReport a problem with this question

7. 7. A technician is about to measure the resistance of a station circuit at the controller. Which procedure gives a valid reading?

   • A.Shut the power off but leave every field wire landed on the strip
   • B.Shut the power off and lift the common off the terminal strip before reading✓ Answer
   • C.Leave the power on and read across the station and common terminals live
   • D.Leave the power on but select ohms, so the meter corrects for the voltage

   A meter measures resistance by sending its own small current through the circuit, so any live voltage falsifies the reading and can damage the meter. Lifting the common also prevents the other stations' coils from being read in parallel with the one under test.

   Source: Irrigation Association, Electrical Troubleshooting Student Workbook — voltmeter and ohmmeter procedureReport a problem with this question

8. 8. With the controller energized and station 3 manually started, a technician reads 0 volts between the station 3 terminal and the common terminal, while the other stations each read about 24 VAC. What does this point to?

   • A.A break in the field wire running from the controller to valve 3
   • B.A failed transformer feeding the whole low-voltage side
   • C.A shorted solenoid on valve 3 pulling that terminal down
   • D.A failed output for that one station on the controller board✓ Answer

   The terminal strip is upstream of the field wiring, so what is measured there reflects only the controller's own output. If neighbouring stations produce their normal 24 VAC while this one produces none, the transformer and the common are proven good and the switching device for that station has failed.

   Source: Irrigation Association, Electrical Troubleshooting Student Workbook — station output voltage testingReport a problem with this question

9. 9. When the 24 VAC solenoid on an automatic remote-control valve is energized, what does it actually do?

   • A.It heats a bimetal strip that flexes and unseats the valve poppet
   • B.It pushes the diaphragm down against the valve seat and seals the outlet
   • C.It drives a small motor that rotates the flow-control stem fully open
   • D.It lifts a plunger that opens the exhaust port above the diaphragm✓ Answer

   A solenoid converts electrical energy into mechanical movement: the energized coil lifts a plunger off the exhaust port of the bonnet chamber. Venting that chamber is what allows inlet pressure to raise the diaphragm, so the solenoid never touches the diaphragm itself.

   Source: Irrigation Association, Landscape Irrigation System Installation & Maintenance — solenoid operationReport a problem with this question

10. 10. In a normally closed, pilot-operated diaphragm valve sitting under mainline pressure with the solenoid de-energized, what actually holds the valve shut?

    • A.Inlet water bled into the bonnet chamber pressing down on the diaphragm✓ Answer
    • B.Downstream pressure trapped in the outlet pushing the diaphragm onto the seat
    • C.The solenoid plunger clamping the diaphragm mechanically onto the seat
    • D.A heavy spring beneath the diaphragm held down by the flow-control stem

    Inlet pressure bleeds through a small port into the bonnet chamber above the diaphragm. Because the upper surface is the larger area, that pressure produces a greater downward force than the inlet pressure acting below, keeping the valve seated; opening the exhaust port relieves it and the valve opens.

    Source: Irrigation Association, Landscape Irrigation System Installation & Maintenance — remote control valve operationReport a problem with this question

11. 11. Two 24 VAC solenoids are connected to the same station wire and the same common so that both valves open together. Compared with a single solenoid, this arrangement:

    • A.Leaves resistance and current unchanged because the voltage is fixed
    • B.Doubles both the resistance and the current, since the loads simply add
    • C.Doubles the circuit resistance and therefore halves the current drawn
    • D.Halves the circuit resistance and roughly doubles the current drawn✓ Answer

    Two coils on one station are in parallel, not in series: each has the full 24 volts across it and each draws its own current, so the combined resistance is half that of one coil and the current roughly doubles. That extra draw can exceed the station output and trip the controller's protection.

    Source: Irrigation Association, Electrical Troubleshooting Student Workbook — parallel solenoid loads on one stationReport a problem with this question

12. 12. In a conventionally wired system, why can a single white common conductor serve every valve on the controller?

    • A.Because each station wire carries direct current, which needs no return
    • B.Because the common isolates each valve so no current returns to the equipment
    • C.Because each station wire forms its own circuit that returns on the common✓ Answer
    • D.Because each valve is wired in series, one loop feeds them all in turn

    Each station output and the shared common form a separate parallel circuit through one solenoid, so current leaves on the station wire and returns on the common. Because only one station is energized at a time, a single return conductor can serve them all.

    Source: Irrigation Association, Electrical Troubleshooting Student Workbook — control circuit wiringReport a problem with this question

13. 13. A valve about 1,500 feet from the controller hums but will not open, and the voltage measured at the solenoid is far below the 24 VAC leaving the controller. What is the correct correction?

    • A.Intercalate a step-up transformer in that station's wire at the controller
    • B.Run a lighter, higher-gauge wire so less current is lost along the way
    • C.Run a heavier, lower-gauge wire to that valve per the valve maker's chart✓ Answer
    • D.Run a second common wire beside the existing one to raise the voltage

    Resistance rises with length, so a long run drops voltage and can leave the coil with too little to pull the plunger in. A thicker conductor (a lower AWG number) has less resistance and restores voltage at the valve; the manufacturer's wire-sizing chart gives the gauge for the run length.

    Source: Irrigation Association, Landscape Irrigation System Installation & Maintenance — control wire sizing and voltage dropReport a problem with this question

14. 14. A specification calls for a heavier conductor than 18 AWG on a long control run. Which choice meets it, and why?

    • A.24 AWG, because a thinner jacket allows a thicker copper core inside
    • B.22 AWG, because the gauge scale is unrelated to conductor size
    • C.20 AWG, because a higher gauge number means a thicker conductor
    • D.14 AWG, because a lower gauge number means a thicker conductor✓ Answer

    The American Wire Gauge scale runs backwards: as the gauge number falls, the conductor's diameter rises. 14 AWG is therefore heavier than 18 AWG and has less resistance per 1,000 feet, which is why long runs are specified with lower numbers.

    Source: Irrigation Association, Landscape Irrigation System Installation & Maintenance — American Wire Gauge sizingReport a problem with this question

15. 15. Which combination of wire choices matches accepted practice for a 24 VAC irrigation control circuit?

    • A.Direct-burial wire no smaller than 18 AWG, with white kept as a spare station wire
    • B.Direct-burial wire no smaller than 18 AWG, with white used only as the common✓ Answer
    • C.Any insulated wire at all, provided each station colour changes at every splice
    • D.Indoor thermostat cable no smaller than 22 AWG, with red used as the common

    Control wiring must be manufactured for direct burial and is specified at 18 AWG minimum, with white reserved industry-wide for the common so any technician can identify the return conductor. Reusing white for a station or dropping below 18 AWG breaks that convention and invites voltage-drop and identification errors.

    Source: Irrigation Association, Landscape Irrigation System Installation & Maintenance — control wire selection and colour conventionReport a problem with this question

16. 16. How must a splice in a 24 VAC valve wire be made and located in the field?

    • A.With a wire nut wrapped in electrical tape, buried in the pipe trench
    • B.With a waterproof connector, buried beside the mainline and flagged
    • C.With a crimp sleeve soldered and coated, laid directly in the backfill
    • D.With a waterproof direct-burial connector, inside a valve box with slack✓ Answer

    A 24 VAC splice sits in wet soil, so it must use a connector listed for watertight direct burial; water in an unprotected splice creates a leakage path that shows up as an intermittent or shorted station. Housing the splice in a valve box with enough slack to lift it above grade lets it be tested and repaired later without excavating.

    Source: Irrigation Association, Landscape Irrigation System Installation & Maintenance — waterproof splices and valve box placementReport a problem with this question

17. 17. The grounding specifications the Irrigation Association publishes for irrigation control equipment require the grounding circuit's earth resistance to be no greater than what value?

    • A.10 ohms✓ Answer
    • B.700 ohms
    • C.50 ohms
    • D.1 ohm

    Ground electrodes only protect equipment if the path to earth is low enough in resistance to carry a surge away, and the recommended specification the association hosts sets a 10-ohm ceiling verified with a ground-resistance tester. Where a site reads higher, additional electrodes are added until the measurement falls within the limit.

    Source: ASIC Recommended Specifications for Irrigation Grounding, hosted by the Irrigation Association — 10-ohm maximumReport a problem with this question

18. 18. Lightning strikes a tree 200 feet from an irrigation system without touching any equipment, yet the controller board and several solenoids are found destroyed. What is the usual explanation?

    • A.The strike heated the copper conductors until the insulation melted
    • B.The strike drained the controller's backup battery and erased the clock
    • C.The strike reversed the polarity of the 24 VAC feeding each solenoid
    • D.The strike induced a surge onto the buried wiring, which carried it in✓ Answer

    A strike does not have to make contact: its electromagnetic field induces a high-voltage transient in nearby buried conductors, and that surge travels along the field wiring into the controller and the coils. Bonded grounding and surge arrestors are installed to divert that energy to earth before it reaches the equipment.

    Source: ASIC Recommended Specifications for Irrigation Grounding, hosted by the Irrigation Association — surge protectionReport a problem with this question

19. 19. With the power off and the common lifted, a station reads within the generally accepted 20-60 ohm band, yet the valve still does not open when the controller calls it. What has that reading ruled out?

    • A.The controller output, which must be delivering its rated voltage
    • B.The transformer, which must be supplying its full secondary output voltage
    • C.The field wiring and the solenoid coil, which form a sound circuit✓ Answer
    • D.The valve diaphragm, which must be seating correctly on the seat

    A resistance test only examines the path from the terminal strip through the station wire, the coil and the common. A reading inside the normal band proves that path is continuous and correctly loaded, so the remaining suspects are the controller's own output, the transformer, or a hydraulic problem at the valve.

    Source: Irrigation Association, Electrical Troubleshooting Student Workbook — interpreting a normal solenoid circuit readingReport a problem with this question

20. 20. A controller is completely dead. At the transformer the technician reads about 120 VAC on the input leads and about 0 VAC on the output leads. What is the conclusion?

    • A.The transformer has failed and no longer steps the voltage down✓ Answer
    • B.The station solenoids are shorted and pulling the output down
    • C.The branch circuit breaker feeding the controller has tripped open
    • D.The common wire is broken somewhere out in the valve field

    The primary side proves the branch circuit and the connection to it are live, and the secondary side shows what the transformer is producing. Normal input with no output means the windings themselves have opened, so the failed component is the transformer rather than the supply or the field wiring.

    Source: Irrigation Association, Electrical Troubleshooting Student Workbook — transformer primary and secondary testingReport a problem with this question

21. 21. The receptacle that powers a controller is dead, and the breaker serving it trips again immediately each time it is reset. What is the appropriate step for the irrigation technician?

    • A.Replace the tripping breaker in the panel and re-energize the circuit
    • B.Move the controller's plug to a different circuit inside the same panel
    • C.Refer the line-voltage branch circuit to a licensed electrician for repair✓ Answer
    • D.Bypass the breaker with a jumper until the panel can be replaced later

    A breaker that trips immediately on reset indicates a fault on the 120 VAC branch circuit, which is line-voltage work outside the irrigation technician's scope and governed by the electrical code. The technician's boundary is the low-voltage side; the branch circuit belongs to a qualified, licensed electrician.

    Source: Irrigation Association, Landscape Irrigation System Installation & Maintenance — line-voltage work and qualified personsReport a problem with this question

22. 22. A pump must start whenever an irrigation station is energized. How is that connection made correctly?

    • A.Wire the pump motor leads straight to the P/MV and common terminals
    • B.Wire the pump across the transformer's 24 VAC secondary terminals
    • C.Wire the pump through a pump start relay driven by the P/MV output✓ Answer
    • D.Wire the pump to a spare station terminal so it starts with that zone

    The P/MV terminal supplies only a small 24 VAC control current, so a motor connected to it will destroy the controller output. A pump start relay lets that small control current close a separate contactor that switches the pump's line-voltage circuit, which must be installed to the electrical code.

    Source: Irrigation Association, Landscape Irrigation System Installation & Maintenance — pump start relay wiringReport a problem with this question

Practice questions based on the Irrigation Association's published Certified Irrigation Technician content — basic irrigation principles, basic electrical principles and basic hydraulics — together with standard irrigation installation, hydraulics and backflow-prevention references. This site is not affiliated with or endorsed by the Irrigation Association. Irrigation work is governed by local plumbing and irrigation codes, water-purveyor rules and licensing that vary by jurisdiction; backflow assemblies in particular must be selected, installed and tested to the rules in force where you work. Confirm current exam requirements with the Irrigation Association before testing. About IA certification →