Irrigation Controllers come in a wide range of makes and models. It is important to choose your timer based on the size of the sprinkler system and any specific landscape requirements.
There are three major factors that should affect your selection of an irrigation controller:

  • Location– do you want your controller mounted indoors or outdoors?

    Irrigation controllers are available in indoor or outdoor models. Indoor controllers are not weather-resistant, so do not install an indoor controller outside. Indoor controllers are designed to be conveniently plugged directly into a 230-volt outlet; they include an external transformer as part of the plug-in cord that converts the standard 230 outlet volts to the 24 volts needed for the timer. Typical mounting locations for indoor controllers are a garage, covered patio, shed, pump house, closet, etc. 
    Outdoor irrigation controllers are weather resistant and durable, and typically need to be hard wired for power instead of plugged into a 230-volt outlet. This is because the transformer is located inside the protective weather resistant irrigation controllers casing, and it is assumed that the electrical connection will need to be weather resistant also.

  • Zone/Station Quantity – how many zones (solenoid valves) does your controller need to control? The irrigation controller you select must be able to operate at least as many zones (valves) as your sprinkler system is broken into.

    When an irrigation sprinkler system is installed, the landscape is divided into sections, called zones. Each zone is turned on and off with the help of a solenoide valve. Irrigation controllers use stations to control each zone – one station per zone. Typically, residential systems use controllers with 2-9 stations, while systems for commercial or public properties may have more. When selecting a controller, it is important to know how many zones (valves) are in your system. It is also a good idea to choose a controller with a few extra stations, in case of landscape remodeling/expansion.

  • Desired Number of Programs – irrigation controllers come in single, two, three, or four-program designs. A minimum of two programs is recommended for programming flexibility; you may want more for increased flexibility.

    Irrigation controllers typically have between one and three programs. They are usually labeled as program A, B, and C. A program is a set of watering instructions for stations that will run as a group. The more stations you wish to have running on separate schedules, the more programs you will need. An example of when you might want more than one watering program would be a landscape with both a lawn and garden – you might want your lawn to be watered every day, and your garden watered twice per week.

Additional Features

Seasonal Watering Adjustment – how detailed do you want your scheduling capabilities to be? More advanced irrigation controllers have seasonal scheduling options, in addition to daily, weekly, and monthly scheduling.
Memory – if you live in an area where power outages or brownouts are common, battery backup is highly recommended, or even non-volatile memory which will store programming indefinitely without power.
Self-Diagnostics – some irrigation controllers include short-circuit protection, or water fluctuation compensating diagnostic programs.
Rain Sensor – a great water-conserving feature for irrigation controllers is a rain sensor, which suspends watering when precipitation is detected.