CIT - Certified Irrigation Technician Controllers and Programming 2 — Questions and Answers

Question 1: A client wants to water their lawn at 6:00 AM but the system has 4 zones that cannot run simultaneously due to insufficient water supply. The controller should be programmed to:

Run all zones at 6:00 AM on the same program
Stack zones sequentially on the same program with a 6:00 AM start time (Correct answer)
Create 4 separate programs with staggered start times
Use cycle and soak on all zones simultaneously

Correct answer: Stack zones sequentially on the same program with a 6:00 AM start time

When zones cannot run simultaneously, they should be stacked sequentially on the same program with a single start time. The controller will automatically run each zone in sequence after the previous one completes, starting at the programmed time.

Zone stacking is the standard approach for residential and commercial controllers with limited water supply. When multiple zones are assigned to the same program with a single start time, the controller runs them sequentially — Zone 1 starts at 6:00 AM, Zone 2 starts when Zone 1 finishes, and so on. Creating separate programs with staggered start times is problematic because the technician must manually calculate end times, and any runtime changes require recalculating all start times.

Question 2: What is the purpose of a 'rain delay' feature on an irrigation controller?

Permanently disables the controller during rainy months
Suspends irrigation for a user-selected number of days, then automatically resumes normal scheduling (Correct answer)
Reduces run times by 50% during rain events
Activates the rain sensor override

Correct answer: Suspends irrigation for a user-selected number of days, then automatically resumes normal scheduling

The rain delay feature temporarily suspends all programmed irrigation for a specified number of days (typically 1-7 days) after a rain event. After the delay period expires, the controller automatically resumes its normal watering schedule without reprogramming.

Rain delay is a convenience feature that allows the homeowner or technician to quickly pause irrigation after significant rainfall. Unlike turning the controller off (which requires remembering to turn it back on) or using a rain sensor (which responds automatically to rainfall), rain delay is manually activated and automatically expires. Most controllers offer 1-7 day options. This feature works alongside rain sensors — even if a rain sensor has dried out and allowed watering to resume, the rain delay can keep the system off longer if the soil is still saturated.

Question 3: A controller is described as having 'non-volatile memory.' This means:

The memory can only store one program at a time
Programming is retained even if power is lost (Correct answer)
The controller uses cloud-based storage
The memory must be reset after each power outage

Correct answer: Programming is retained even if power is lost

Non-volatile memory retains all programmed schedules, station run times, and settings even during power outages. When power is restored, the controller resumes normal operation without reprogramming.

Non-volatile memory (NVRAM or EEPROM) is standard in modern irrigation controllers. Unlike older controllers that used volatile RAM with battery backup, non-volatile memory does not require a battery to maintain programming. However, most controllers still include a battery to maintain the real-time clock during power outages, so the correct date and time are preserved. Without the clock battery, the schedule would still be stored but would resume at the wrong time of day.

Question 4: A smart controller uses evapotranspiration (ET) data to adjust irrigation schedules. ET-based controllers primarily calculate water needs based on:

Soil moisture sensor readings
Historical rainfall data only
Weather parameters including temperature, humidity, wind, and solar radiation (Correct answer)
Flow sensor readings from each zone

Correct answer: Weather parameters including temperature, humidity, wind, and solar radiation

ET-based smart controllers use weather parameters — temperature, humidity, wind speed, and solar radiation — to calculate the evapotranspiration rate and adjust irrigation run times accordingly. This allows the controller to apply only the amount of water the landscape has lost.

Evapotranspiration is calculated using weather data, most commonly via the Penman-Monteith equation (used for reference ET). The four primary inputs are temperature, relative humidity, wind speed, and solar radiation. Some controllers receive this data from on-site weather stations, while others use regional ET data from weather networks. The controller then adjusts run times based on the calculated ET rate, soil type, slope, plant type, and sprinkler precipitation rate. This is fundamentally different from soil moisture-based controllers, which use direct soil measurements rather than weather calculations.

Question 5: When programming a controller for cycle and soak, what is the primary purpose of the soak time between cycles?

To allow the pump to cool down
To allow water to infiltrate into the soil and prevent runoff (Correct answer)
To reduce water pressure in the mainline
To let the controller reset between programs

Correct answer: To allow water to infiltrate into the soil and prevent runoff

Cycle and soak divides a zone's total run time into shorter cycles with soak periods between them. The soak time allows water to infiltrate into the soil, particularly on slopes or clay soils, preventing surface runoff and improving irrigation efficiency.

Cycle and soak is essential when the precipitation rate of the sprinklers exceeds the soil's intake rate (infiltration rate). For example, clay soils may have an infiltration rate of only 0.1 inches per hour, while spray heads may apply water at 1.5 inches per hour. Without cycle and soak, most of the water would run off the surface. By breaking a 12-minute run time into three 4-minute cycles with 20-minute soak periods, the water has time to percolate into the root zone. This is especially critical on slopes where gravity accelerates runoff.

Question 6: A two-wire decoder irrigation control system differs from a conventional multi-wire system in that it:

Requires a separate wire pair for each zone valve
Uses only two wires to communicate with and power all field decoders and valves (Correct answer)
Cannot accommodate more than 12 zones
Does not require a grounding connection

Correct answer: Uses only two wires to communicate with and power all field decoders and valves

A two-wire decoder system uses a single pair of wires (plus a ground) to communicate with and power all field-mounted decoders. Each decoder has a unique address and activates its associated valve when signaled by the controller, greatly reducing wiring requirements.

Two-wire decoder systems are ideal for large commercial and golf course installations where running individual wires to each valve would be impractical and expensive. A single pair of communication wires runs throughout the site, with small decoder modules installed at each valve or group of valves. The controller sends encoded signals (typically using a modulated DC signal) that each decoder recognizes by its unique address. This can reduce wire by 80% or more on large sites. Decoders can typically handle 1-6 valves each, and modern systems can manage hundreds of stations on a single two-wire path.

CIT - Certified Irrigation Technician Controllers and Programming 2

A client wants to water their lawn at 6:00 AM but the system has 4 zones that cannot run simultaneously due to insufficient water supply.
The controller should be programmed to: