Wiring 101: Zones, Commons, Master, Pump, Rain Sensor, 24VAC Ports


Most standard digital controllers, including Spruce, run off of 110/120 volts AC. For indoor use, these controllers can be plugged straight into a common house electrical outlet in the United States, Canada, and any other region that uses 110V for mains electricity. The AC transformer steps-down the power from 110 to 24 volts (approximately), which is operating voltage for the Spruce Controller and most irrigation controllers.

The controller then has modules for different wires that are labeled for zones (represented by the number of the zone), common ports, master valves (required for some systems), and rain sensors (if available).

Most systems will use multi-strand wire, which is a group of single, insulated strands of wire wrapped together as one, typically in black insulation. For example, 18-5 is a group of 5, 18 gauge wires. 18 gauge wire should be used as this is the gauge that is approved for underground usage. Each wire will have its own color such as white, black, blue, green, and red.

Common Wire

Each multi-strand bundle must dedicate one wire as the common wire, which can be considered a ‘negative’ or a ‘ground’ wire.  It is called the common wire because it is connected to all the valves on that manifold.  Therefore your system may utilize more than one common wire, and it is not required to populate all of the common ports – it simply depends on how many zones and valve manifolds are on the property. Most contractors use white or green for the common wire and the other colors for the hot side.

Master Valve

On many irrigation controllers, the master valve is labeled “M” or “MV”.

  • On Spruce Gen 2, there is a dedicated master valve labeled “M”.
  • On Spruce Gen 1, the master valve can be wired into any available zone, then configured to operate as a master valve in the SmartApp settings (Zone Summary and Setup and Valve and Contact Settings).

Pump Relay

Some irrigation systems have the option of drawing water directly from a well, tank, creek or pond, rather than using a municipal source. In these situations, the water must be pumped through the system using a pump relay each time the control box turns on a valve. On many irrigation controllers, the pump relay is labeled “P” , “PV”, or “MV”.

  • On Spruce Gen 2, the pump relay can be wired into the dedicated master valve port, labeled “M”
  • On Spruce Gen 1, the pump relay can be wired into any available zone, then configured to operate as a pump relay in the SmartApp settings (Zone Summary and Setup and Valve and Contact Settings).

Rain Sensors

Rain sensors are modules that are mounted outdoors, typically on a roof or gutter, and automatically shut off watering if rain is detected. Rain sensor inputs are available for users who own a third party rain sensor accessory, and are intended for normally closed (NC) rain sensors.  The polarity of the rain sensor wires does not matter.  The rain sensor must be enabled in the Spruce Controller configuration. See this article for more information.

24VAC Port

  • On Spruce Gen 2, the 24VAC port is intended for power for external inputs only. Using the 24VAC port to power the controller (instead of the supplied AC adapter) will void the warranty.
  • On Spruce Gen 1, the 24VAC port is optional and not necessary if using the supplied AC adaptor & power input port at the bottom of the unit.
Spruce Bottom Plate and wiring layout
Spruce Gen 1 Bottom Plate with wiring layout
Spruce Gen2 Wire
Spruce Gen2 wire terminals

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