The Schematic tab on a twin page draws the equipment as a diagram, with live readings on each component, like the graphics in your BMS. It's drawn automatically from the twin, so every supported twin gets one without anyone setting it up. In preview it covers air handling units and terminal units, with more to come in the future. You can use it to understand how a unit operates, how air flows through it and what each of the components is currently doing. And because it's in Willow, you see live equipment status right beside everything else Willow knows about the asset: its work history, time series, insights, design parameters and more. No switching to the BMS to check one, then back to Willow for the context.
Opening the Schematic view
- Open a twin for an air handling unit, rooftop unit, VAV box or fan coil unit.
- The right panel opens on the Schematic tab by default.
If you've chosen another tab, select Schematic.
The tab only appears when the twin has enough data to draw. See "Why don't I see the Schematic tab?" in the FAQ.
Reading the drawing
Air moves along the ducts, shown by the dashed airflow line. Labels at the open ends say where the air comes from or goes, such as Outside Air, Return Air and Supply Air.
Each component sits in the duct in airflow order: dampers, filters, coils, fans, humidifiers and sensors. Its live reading sits in a tag beside it, such as a damper position, a coil valve level, a fan speed or a supply air temperature.
- Zoomed out, tags show the value only.
- Zoomed in, or when you hover a tag, they also show the name and what the value is compared against, such as a setpoint, a command or a limit.
- Scroll to zoom and drag to move around. Use + and - at the top right to zoom, and Reset View to fit the whole unit again.
A component that has no reading shows --.
Viewing a component's sensors
Select a component to open its card. The card lists every point on that component, the same way the Sensors tab does: the point name, its model, how old the reading is and the value.
Select Go to Twin to open the component's own twin page.
States and badges
The drawing shows what the unit is doing, not just what it's made of.
| What you see | What it means |
|---|---|
| Fan blades turning, airflow moving | The component is running. |
| Component greyed out | The component is off or closed, such as a stopped fan or a closed valve. Off is not a fault. |
| Damper blades at an angle | The damper's position, from fully open to closed. |
| Coloured coil | The coil is heating (orange) or cooling (green). A grey coil is off. |
| Red dot on a reading's tag | One of the component's alarm points is active. |
-- in a tag | No reading for that component. |
How the Schematic is built
Nobody draws a schematic by hand. Willow builds it from three things the twin already has:
- Components. The twin's parts, such as its fans, coils, dampers and filters.
- Relationships. How the parts connect: which component feeds which. This is the twin graph.
- Live sensor data. The points on each component, such as speeds, positions and temperatures.
Willow puts these together and lays out the unit. Because the drawing comes from the twin and not from a drawing file:
- Every supported twin gets one. There's no drawing work per building or per twin.
- It stays current. When the twin changes, the drawing changes with it.
- It looks the same everywhere. An AHU in one building reads the same as an AHU in another.
The Schematic is only as good as the twin data. Willow starts from a standard layout for the type of equipment, such as an AHU, rooftop unit, VAV box or fan coil unit. If the relationships are missing, it places components in that layout's standard order. Components still come from the twin: if one isn't modelled, it isn't drawn. See the FAQ for what to do.
Standard layouts and the component library
Every schematic is assembled from one library of components. Each component has a drawing for each of its states: running, off, open, closed, heating, cooling and fault.
Willow has standard layouts out of the box. The same components cover many arrangements, including:
- Mixing boxes with return, exhaust and outside air dampers
- 100% outside air units and dedicated outdoor air systems
- Heat recovery wheels and run-around coil loops
- Fan arrays on the supply or return side
- Hot and cold decks
- Humidifiers, UV lamps and multiple filters
- VAV boxes, fan-powered boxes and fan coil units
Preview and feedback
The Schematic is a preview and an evolving feature, with more to come. Your feedback shapes what we build next. Select Send feedback in the notice at the top of the tab, and the Contact Us form opens ready to send, with the category set to Twins and the unit named. Write what looks wrong under Feedback and send. The request includes a link to the page, so our team sees the exact unit you were looking at.
Each report helps. Most are either a twin data fix, which we make for you, or a drawing fix, which improves the Schematic for everyone.
FAQ
My unit has components in a different order, or a different orientation, than the drawing
Out of the box, Willow uses a standard layout. For example, on the supply side the order is outside air damper, filter, preheat coil, cooling coil, supply fan, then reheat coil and humidifier.
When the twin's relationships record which component feeds which (feeds and isFedBy), Willow uses them automatically to draw the components in your unit's actual order. If the order looks wrong, those relationships are missing or wrong. Use Send feedback, or contact your Willow account manager.
The Schematic always draws air the same way round: outside air in on the left, supply air out on the right, return air along the top. It's a diagram, not a scale drawing of the unit, so it doesn't change direction to match the plant room.
A component is missing from the drawing
The Schematic only draws components that are modelled in the twin. If a component isn't a part of the twin, or Willow can't tell where it sits, it's left out. Its readings are still on the Sensors tab.
Use Send feedback, or contact your Willow account manager, to tell us what's missing.
A reading is missing, shows --, or is on the wrong component
A tag shows -- when the component has no reading: the point isn't connected, has no value, or more than one point could be the reading and Willow can't tell which.
A reading on the wrong component usually means the point is attached to the wrong part of the twin. Use Send feedback, or contact your Willow account manager, and name the reading.
The drawing shows a component I can't find in the twin's relationships
Some components are drawn from the unit's own points. For example, a damper position point on the AHU itself shows as a damper in the duct, even when the damper isn't its own twin. Select it to see which twin the points belong to.
Why don't I see the Schematic tab?
- The equipment isn't supported yet. See "Which equipment is supported?" below.
- The twin has nothing to draw. If a twin has no modelled components or points, the tab doesn't appear.
Which equipment is supported?
- Air handling units, including rooftop units, dedicated outdoor air systems and energy recovery units.
- Terminal units, including VAV boxes, fan-powered boxes, chilled beams and fan coil units.
Chillers, boilers, pumps and other water-side equipment don't have a Schematic yet.
Can I edit the drawing?
No. The drawing comes from the twin, so you change it by changing the twin. Contact your Willow account manager, or use Send feedback.
Can I control equipment from the Schematic?
No. The Schematic is read-only. It shows readings and states; it doesn't send commands to your building's control system.
How current are the readings?
Readings come from the same live data as the Sensors tab. Each row in a component's card shows how old its reading is, such as 3m ago.
What does a red dot mean?
One of the component's alarm points is active. Select the component to see its points. A greyed-out component is off, which is not a fault.
Can I hide the preview notice?
Yes. Select X on the notice. It shows again the next time you open the tab.
How do I send feedback?
Select Send feedback in the notice at the top of the Schematic tab. The Contact Us form opens with the category set to Twins and the unit already named. Write what looks wrong under Feedback and send. The request includes a link to the page, so we can see the exact unit.
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