A very convenient feature, “seasonal adjust,” or “water budgeting,” can cause program overlap or delay program operation if not used carefully. This feature allows the operator to decrease or increase (at one time and in set percentage increments) the controller’s programs without the need to shorten or lengthen each station’s run time.

What do great backyard barbecues, a comfortable retirement and programming a 24-station controller all have in common? Planning.

As controllers are specified with the greater station counts required for larger or more diverse landscapes, programming requires even more careful consideration. The challenge in effectively using controllers with 24 or more stations is how to properly tailor the programs to meet the needs of the plant material. There are usually more programming options available in bigger clocks, as well as a greater number of features to help control larger landscapes. And while programming options and features add flexibility, they also tend to increase the complexity of the programming task. Following are a few things to consider when programming large controllers.

Usually there are three, four or even more programs available to "break out" system controls for various irrigation requirements. For example, in hot weather, lawn areas may need water every day, while shrubs, trees or plant material under drip irrigation require differing schedules.

But with multiple program capability, it’s possible to group "like" plant material into separate programs, allowing each plant type to have its own watering schedule. The trick is meeting all of the site’s requirements in the time available for irrigation. There are a number of features that make this possible.

The more flexible controllers have calendars that offer days-of-the-week watering, day-interval watering and odd/even date watering. This flexibility allows the programmer not only to adapt the day cycle to plant requirements, but also to adapt to most of the water restrictions mandated during drought conditions.

Because of the myriad scheduling options available, it’s a good idea to write down the entire irrigation schedule (there is often a door label or schedule card that comes with each controller). For example, if Program A is set to water on Mondays, Wednesdays and Fridays, Program B is on a once-every-three-day schedule, and Program C waters on odd dates only, a written schedule is a necessity.

Along with multiple programs, most controllers offer multiple start times per program. In some by-gone controllers, multiple start times were called "repeats," which is a good way to remember their function: they repeat the entire program with each start time. Multiple starts are ideal for keeping the top dressing damp on a new lawn or allowing soak-in time between repeats. However, three, four or more start times in use on three, four or more programs can complicate things a bit, which leads to the next feature.

Some controllers have sufficient electrical capacity to run more than one valve at a time, allowing irrigation cycles to overlap. Other controllers prevent cycle overlap with a stacking feature that defers a start time until another program in progress is finished. Still others allow the operator the choice of overlap or not. While a controller may have the capacity to allow overlap, the hydraulic capacity of the system must be considered. In other words, can the water pressure and flow capacity of the irrigation system support multiple valves running at the same time?

If the system cannot supply enough water at the pressure required, it will soon be evident by the thirsty plant material. In some cases, running a lower gallons-per-minute circuit (or a small drip irrigation station) will work well while a bigger sprinkler circuit is running. Of course the length of time the circuits run has to be coordinated in the programming.

Big controllers often come with a wide range of station running times. Whether it’s 5-minute timing for closely spaced, 2-gallon-per-minute sprayheads or timing in hours for 1-gallon-per-hour drip emitters, most controllers can meet a wide range of requirements. Typical timing ranges are from 1 minute to 4 hours, but several controllers offer 10 hours or more. Keeping track of the beginning and end of each program and all its station run times is important (especially important if program overlap could cause a problem).

Keith Shepersky, Brand Manager for Irritrol Systems, is a 30-year veteran of the irrigation industry and has 14 years of experience in controller new product development.