Why this duration?

Every zone’s detail view shows the inputs behind tonight’s planned minutes, because “trust me” is not a number.

Where the depth comes from. Tonight’s run length is decided by the zone’s governing model. Under the default weekly water balance: a gross weekly target per zone, settled against observed rain, water already applied, and a probability-weighted forecast credit, with the remainder split across the sessions still expected this week. Under the soil model: the zone’s replayed soil deficit divided by the capture efficiency and the throughput, capped at the run limit. Those pages hold the arithmetic that produced the minutes.

The panel is in two parts, because only two of its numbers reach the dispatch.

What sizes tonight’s run

1. Throughput (mm/hr): how fast your sprinklers actually apply water, either measured (catch cups) or the catalog default for the head type. This week’s session depth divided by this rate is where the run length starts. It then takes the seasonal adjustment and any condition rule’s multiplier, and is held to the zone’s cap, so the minutes on the panel do not have to equal depth divided by throughput.

   That seasonal adjustment is one dial for the whole yard, on the Engine settings page: 100% is the depth as computed, and you turn it down for a wet, cool stretch or up for a heat wave. It scales the depth before the zone’s cap clamps the result, so the minutes here already include it; the irrigation engine page carries the dial’s range and the rest of its behavior.

2. Scheduled: the minutes that will actually dispatch, and what the zone’s safety ceiling did to them. The ceiling is max_run_minutes, tightened further by any active watering restriction. The row reads “capped at N min” when tonight’s run is sitting on the ceiling because something asked for more than it allows: the weekly balance’s own session, the seasonal adjustment, or a condition rule’s multiplier. The zone is being shorted, so raise the ceiling, or raise sessions_per_week so each session is shorter.

   A zone with no run planned shows its minutes and nothing about a cap. There is no run for a ceiling to have shortened, and the reason the zone is not watering is on the zone card. A zone’s weekly session can outgrow the ceiling while today’s plan is zero for a separate reason (spacing, a rain defer, an Override schedule); the tuning report is where that shows up, because it is a statement about the week rather than about tonight.

   A Force override is the one case where minutes appear with no target behind them. Set Force on the zone, or globally with the zone left on Auto, and a run whose computed length came out zero waters a bounded default of five minutes instead, held down to the zone’s ceiling when that ceiling is shorter. Without the floor, a Force on an already satisfied yard flips the verdict to run and then dispatches nothing, because a zone planned for zero seconds is skipped. A zone sitting at zero for any other reason stays at zero, and so does a day an Override manual schedule already covers, so a forced run never stacks on top of the run you scheduled yourself.

Not part of tonight’s minutes

On a weekly-governed zone none of these four scales the run; they feed the ETc figure and the soil projection. On a soil-governed zone the panel moves the soil deficit and the capture efficiency above the line, because there the run length IS the deficit divided by the capture efficiency and the throughput.

3. Soil deficit (mm): how far the zone’s soil sits below full, negative when the zone needs water. The soil model’s replay of measured ET, rain and completed runs computes it for every zone with a species and a soil texture, whichever model governs; a dash appears only where no bucket can be derived (env-var zone lists). Printing a 0.00 there used to tell people their soil was full on the strength of a number nothing measured.
4. Crop coefficient (Kc): the species’ seasonal multiplier on reference ET (see the grass species catalog). Hemisphere-aware: south of the equator the curve shifts six months.
5. Heat multiplier: optional extension when the peak heat index crosses the heat-advisory threshold. Each day’s heat index pairs that day’s high temperature with that same day’s humidity (not the current, often night-time, humidity), so a cool morning’s humidity is never combined with a hot afternoon’s peak to inflate the run.
6. Capture efficiency: how much of the applied water lands in the root zone (wind drift, overspray, runoff losses). Weekly-governed zones show the fixed 0.70 the soil projection uses; soil-governed zones show the configured engine.capture_efficiency, the number each refill divides by.

The panel prints no formula. It used to print one belonging to that Home Assistant integration, which matched nothing LocalSky computes, and which multiplied the four numbers above as though they set the run length.